杉本 晃一

BACKGROUND: Left ventricular enlargement (LVE) is a common manifestation of cardiac remodeling that is closely associated with cardiac dysfunction, heart failure (HF), and arrhythmias. This study aimed to propose a machine learning (ML)-based strategy to identify LVE in HF patients by means of pulse wave signals. METHOD: We constructed two high-quality pulse wave datasets comprising a non-LVE group and an LVE group based on the 264 HF patients. Fourier series calculations were employed to determine if significant frequency differences existed between the two datasets, thereby ensuring their validity. Then, the ML-based identification was undertaken by means of classification and regression models: a weighted random forest model was employed for binary classification of the datasets, and a densely connected convolutional network was utilized to directly estimate the left ventricular diastolic diameter index (LVDdI) through regression. Finally, the accuracy of the two models was validated by comparing their results with clinical measurements, using accuracy and the area under the receiver operating characteristic curve (AUC-ROC) to assess their capability for identifying LVE patients. RESULTS: The classification model exhibited superior performance with an accuracy of 0.91 and an AUC-ROC of 0.93. The regression model achieved an accuracy of 0.88 and an AUC-ROC of 0.89, indicating that both models can quickly and accurately identify LVE in HF patients. CONCLUSION: The proposed ML methods are verified to achieve effective classification and regression with good performance for identifying LVE in HF patients based on pulse wave signals. This study thus demonstrates the feasibility and potential of the ML-based strategy for clinical practice while offering an effective and robust tool for diagnosing and intervening ventricular remodeling.

Abstract Objective. This study aims to accurately identify the effects of respiration on the hemodynamics of the human cardiovascular system, especially the cerebral circulation. Approach: we have developed a machine learning (ML)-integrated zero–one-dimensional (0–1D) multiscale hemodynamic model combining a lumped-parameter 0D model for the peripheral vascular bed and a one-dimensional (1D) hemodynamic model for the vascular network. In vivo measurement data of 21 patients were retrieved and partitioned into 8000 data samples in which respiratory fluctuation (RF) of intrathoracic pressure (ITP) was fitted by the Fourier series. ML-based classification and regression algorithms were used to examine the influencing factors and variation trends of the key parameters in the ITP equations and the mean arterial pressure. These parameters were employed as the initial conditions of the 0–1D model to calculate the radial artery blood pressure and the vertebral artery blood flow volume (VAFV). Main results: during stable spontaneous respiration, the VAFV can be augmented at the inhalation endpoints by approximately 0.1 ml s⁻¹ for infants and 0.5 ml s⁻¹ for adolescents or adults, compared to those without RF effects. It is verified that deep respiration can further increase the ranges up to 0.25 ml s⁻¹ and 1 ml s⁻¹, respectively. Significance. This study reveals that reasonable adjustment of respiratory patterns, i.e. in deep breathing, enhances the VAFV and promotes cerebral circulation.

Three-dimensional computational fluid dynamics (CFD) simulations were performed in the anastomotic region of the Fontan route between the venae cava and pulmonary arteries to investigate the risk of thrombosis due to blood stasis in the Fontan circulation. The finite volume method based on the time-averaged continuity and Navier–Stokes equations combined with the k-ω SST turbulent model was used in the CFD simulations. Low shear rate (SR) and SR on the wall (WSR) of <10 s−1 were used as markers to assess blood stasis as a cause of blood coagulation. Simulated blood flow velocity and both SR and WSR were reduced in the right atrium (RA) as the cavity of a flow channel in the atriopulmonary connection (APC) Fontan model, whereas the values increased in the total cavopulmonary connection (TCPC) Fontan model, which has no cavity. The volume of SR <10 s−1 and wall surface area of WSR <10 s−1 were, respectively, 4.6–261.8 cm3 and 1.2–38.3 cm2 in the APC Fontan model, and 0.1–0.3 cm3 and 0.1–0.6 cm2 in the TCPC Fontan model. The SR and WSR increased in the APC model with a normal-sized RA and the TCPC model as the flow rate of blood from the inferior vena cava increased with exercise; however, the SR and WSR in the RA decreased in the APC model with a dilated RA owing to the development of a recirculating flow. These findings suggest that the APC Fontan has a higher risk of thrombosis due to blood stasis than the TCPC Fontan and a higher RA dilation is associated with a higher risk of thrombosis from a fluid mechanics perspective.

Abstract Background: Although serum lactate levels are widely accepted markers of haemodynamic instability, an alternative method to evaluate haemodynamic stability/instability continuously and non-invasively may assist in improving the standard of patient care. We hypothesise that blood lactate in paediatric ICU patients can be predicted using machine learning applied to arterial waveforms and perioperative characteristics. Methods: Forty-eight post-operative children, median age 4 months (2.9–11.8 interquartile range), mean baseline heart rate of 131 beats per minute (range 33–197), mean lactate level at admission of 22.3 mg/dL (range 6.3–71.1), were included. Morphological arterial waveform characteristics were acquired and analysed. Predicting lactate levels was accomplished using regression-based supervised learning algorithms, evaluated with hold-out cross-validation, including, basing prediction on the currently acquired physiological measurements along with those acquired at admission, as well as adding the most recent lactate measurement and the time since that measurement as prediction parameters. Algorithms were assessed with mean absolute error, the average of the absolute differences between actual and predicted lactate concentrations. Low values represent superior model performance. Results: The best performing algorithm was the tuned random forest, which yielded a mean absolute error of 3.38 mg/dL when predicting blood lactate with updated ground truth from the most recent blood draw. Conclusions: The random forest is capable of predicting serum lactate levels by analysing perioperative variables, including the arterial pressure waveform. Thus, machine learning can predict patient blood lactate levels, a proxy for haemodynamic instability, non-invasively, continuously and with accuracy that may demonstrate clinical utility.

To explore hemodynamic interaction between the human respiratory system (RS) and cardiovascular system (CVS), here we propose an integrated computational model to predict the CVS hemodynamics with consideration of the respiratory fluctuation (RF). A submodule of the intrathoracic pressure (ITP) adjustment is developed and incorporated in a 0-1D multiscale hemodynamic model of the CVS specified for infant, adolescent, and adult individuals. The model is verified to enable reasonable estimation of the blood pressure waveforms accounting for the RF-induced pressure fluctuations in comparison with clinical data. The results show that the negative ITP caused by respiration increases the blood flow rates in superior and inferior vena cavae; the deep breathing improves the venous return in adolescents but has less influence on infants. It is found that a marked reduction in ITP under pathological conditions can excessively increase the flow rates in cavae independent of the individual ages, which may cause the hemodynamic instability and hence increase the risk of heart failure. Our results indicate that the present 0-1D multiscale CVS model incorporated with the RF effect is capable of providing a useful and effective tool to explore the physiological and pathological mechanisms in association with cardiopulmonary interactions and their clinical applications.

Total anomalous pulmonary venous connection (TAPVC) and coarctation of the aorta (CoA) rarely occur together. In affected patients, blood is supplied to the lower body by saturated ductal flow. Preoperative echocardiography may not show an acceleration of flow at the isthmus (coarctation), and the oxygen saturation (SpO2) at the feet may be satisfactory. Consequently, the severity of CoA is often underestimated before performing surgery. A 6-day-old boy weighing 2.6 kg with a diagnosis of supracardiac TAPVC was referred for surgical correction of his anomaly. The atrial septal defect (ASD) was 6.7 mm in diameter. There was a large patent ductus arteriosus (PDA) without flow acceleration at the preductal entry into the descending aorta. Only the TAPVC repair was planned, but immediately following ligation of the large PDA, the blood pressure in the lower extremity dropped to around 30 mmHg. The ligation was removed. The reason for the blood pressure discrepancy between the upper and the lower body was not clear as there was no arterial line in the upper extremity and a 6.7-mm-diameter ASD can support sufficient blood flow to the lower body without the PDA. A suspected CoA was found and repaired, followed by the TAPVC repair. Caution is necessary when repairing a TAPVC and coexisting large PDA as the severity of the CoA can easily be underestimated due to nonsignificant flow acceleration.

While bicuspid aortic valve (BAV) shows different phenotypes associated with aortic aneurysm and valvular dysfunction due to aortic stenosis (AS), hemodynamics in patients with stenotic BAVs remains poorly understood. Here we address a study of the effects of valve phenotypes on aortic hemodynamics in different configurations of AS using an image-based subject-specific left ventricle (LV)-aorta integrated computational model. The model was built up by combining both MRI images and realistic motions of aortic valve, mitral valve, and LV apex as well as its contraction and dilatation of a healthy subject. Physiological boundary conditions were given based on a parameter-adjusted 0-1D cardiovascular model. Symmetrical BAV models with mild and severe stenosis were constructed with the orientation angle varying every 15° from 0° to 165° with regards to mitral valve while within a planar disc and the orientation effects on aortic hemodynamics were systematically investigated. Our results revealed that systolic jets in aorta were dominated by a combination of valve orientation and AS. Furthermore the hemodynamic indices of maximum wall shear stress (WSS), oscillatory shear index (OSI), and axial energy loss also demonstrated a feature of phenotype-and stenosis-dependency, pointing to the importance of taking into account the valve configuration in clinical decision-making on BAV patients.

OBJECTIVES: Atrioventricular valve replacement is the last option to treat the atrioventricular valve regurgitation in single ventricle. This study investigates the mid-term outcomes of the atrioventricular valve replacement based on the Japan Cardiovascular Surgery Database registry. METHODS: From 2008 to 2014, 56 patients [34 males (61%) and 22 females (39%)] with a single ventricular circulation, underwent atrioventricular valve replacement. Questionnaires were collected to review operative data, mid-term mortality, morbidity and redo replacement. Risk factor analysis was performed by the Cox regression model for death and redo replacement. RESULTS: Heterotaxy, a right systemic ventricle and a common atrioventricular valve was present in 46% (26/56), 64% and 57% of patients, respectively. The most common timings for atrioventricular valve replacement were the interstage between the second and third palliations (34%) and after the Fontan operation (34%). Twenty died during the 3.7 ± 2.6-year follow-up. Eleven received redo atrioventricular replacement. The cumulative incidences of redo atrioventricular valve replacement and survival at 3 years were 20% [95% confidence interval (CI) 9-30] and 66% (95% CI 55-80), respectively. Univariable Cox regression analysis revealed that a tricuspid valve was a risk factor for redo valve replacement [hazard ratio (HR) 6.76, 95% CI 1.79-25.6; P = 0.005] and that young age was a risk factor for death (HR 0.77, 95% CI 0.62-0.96; P = 0.019). Fourteen patients required a pacemaker implantation. CONCLUSIONS: Valve replacement for uncontrollable atrioventricular valve regurgitation in single ventricular circulation was associated with a moderately high risk of death, redo replacement and pacemaker implantation, whereas valve replacement at a later period and with a larger prosthetic valve size was associated with low mortality.

OBJECTIVES: High-flow regional cerebral perfusion (HFRCP) provides cerebral and somatic oxygen delivery through collateral vessels during aortic arch repair in small children; however, optimal flow conditions during HFRCP have not been established. We sought to identify markers of peripheral perfusion during HFRCP. METHODS: Between 2009 and 2016, in total 20 consecutive pediatric patients undergoing aortic arch repair with HFRCP were enrolled in this prospective, observational study. Median age was 20 days (range, 6-116 days); median body weight was 2.77 kg (range, 1.8-4.98 kg). Oxygen delivery ratio (Do2R) was calculated as the oxygen delivery during HFRCP divided by the oxygen delivery before HFRCP. Regional oxygen saturations on the forehead and on the thigh (rSo2T) were monitored during HFRCP, and postoperative creatinine kinase and lactate concentrations were measured as postoperative outcomes. Multivariate analyses were performed to clarify the effectiveness of Do2R and rSo2T as markers of peripheral perfusion during HFRCP. RESULTS: No deaths or neurologic impairments occurred. Multivariate analysis showed that the lowest rSo2T (P = .005) and cardiopulmonary bypass time (P = .012) predicted postoperative creatinine kinase concentration. Do2R was the only factor to predict postoperative lactate concentration (P < .001). Receiver operating characteristic analysis showed that Do2R less than 0.66 predicted risk of high postoperative lactate concentration (>5.0 mmol/L), with area under the curve of 0.95. CONCLUSIONS: For aortic arch repair in small children, rSo2T and Do2R during HFRCP are useful markers for predicting peripheral perfusion. Maintaining higher Do2R during HFRCP minimizes postoperative increases in lactate and creatinine kinase concentrations.

Reconstruction of nonconfluent pulmonary arteries during Fontan completion is a challenging technical issue. In this case report, we describe the use of an aortic homograft, including the aortic arch, to complete a Fontan and reconstruct the pulmonary artery confluence in a child with discontinuous pulmonary arteries and bilateral superior caval veins who had undergone bilateral unidirectional Glenn palliation. The configuration of the aortic homograft was ideal to ensure laminar flow from the inferior vena cava to both pulmonary arteries and in maintaining durable elastance posterior to the native aorta.

OBJECTIVES: Although primary sutureless technique for total anomalous pulmonary venous drainage has been introduced to reduce postoperative pulmonary vein obstruction (PVO), controversy still exists about superiority of the procedure between the conventional repair and primary sutureless technique at the initial repair. In our unit, the conventional repair has been consistently used based on four important surgical policies: (1) mark incision lines between 2 chambers to gain anatomically natural alignment, (2) place precise stitches by "intima-to-intima" using monofilament suture, (3) adequate orifice size should be guaranteed in greater than expected mitral valve size, (4) do not hesitate to undertake a redo additional anastomosis by a different approach when an echocardiography shows the velocity more than 1.5 m/s. This study aims to evaluate mid-term outcome of the conventional repair for total anomalous pulmonary venous drainage. METHODS: Between 2004 and 2016, consecutive 15 patients who underwent the conventional repair without the primary sutureless technique were included in this study. Survival, Freedom from reoperation, and PVO were retrospectively reviewed. RESULTS: Mean follow-up period was 4.6 ± 3.7 years. Except for one patient who died of uncontrollable pleural effusion, all other patients survived with 5-year survival rate of 93.3%. For the 14 survivors, there was no PVO, nor reoperation. CONCLUSIONS: Following these policies, the mid-term outcome of the conventional total anomalous pulmonary venous drainage repair was excellent without the primary sutureless technique showing no obstruction. The conventional repair can be safely applied at the initial operation when the morphological condition allows for it.

OBJECTIVES: Inefficient aortic flow after the Norwood procedure is known to lead to the deterioration of ventricular function due to an increased cardiac workload. To prevent the progression of aortic arch obstruction, arch reconstruction concomitant with second-stage surgery is recommended. The aim of this study was to determine the indications for reconstruction based on numerical simulation and to reveal the morphology that affects the haemodynamic parameters. METHODS: Fifteen patients who underwent the Norwood procedure or arch repair and Damus-Kaye-Stansel anastomosis were enrolled. The pressure gradient in aortic arch was 1.6 ± 3.9 mmHg (ranged from 0 to 12 mmHg) on catheter examination. Six patients who had prominent turbulent flow accompanied with a large flow energy loss index greater than 40 mW/m2 and high wall shear stress greater than 100 Pa underwent arch reconstruction. RESULTS: After arch reconstruction, the energy loss index significantly decreased from 88.5 ± 50.0 mW/m2 to 23.1 ± 10.4 mW/m2 (P = 0.026) and wall shear stress significantly decreased from 194.5 ± 87.4 Pa to 60.3 ± 40.5 Pa (P = 0.0062). There were 3 late deaths due to heart failure caused by progressive atrioventricular valve regurgitation during the follow-up period (60 months). The systemic ventricular function was preserved in the remaining patients without any pressure gradients in the arch. CONCLUSIONS: Determining the surgical strategy for arch reconstruction based on numerical flow analysis may effectively reduce the ventricular load even if no stenosis or pressure gradients are observed on catheter examination or echocardiography.

We describe the case of a 21-year-old patient who underwent repairs for multiple lesions including aortic and pulmonary valve replacements, right ventricular outflow tract reconstruction, revision of the right pulmonary artery route, and a repair of partial anomalous pulmonary venous drainage, which was diagnosed during this fourth sternotomy. For these patients with adult CHD, it is most important to address all underlying factors as much as possible at the redo surgery.

OBJECTIVES: To study the recent trends and outcomes of congenital mitral valve surgery in children. METHODS: From 2008 to 2014, 84 procedures in 66 consecutive patients (41 procedures in 31 patients with mitral stenosis and 43 procedures in 35 patients with mitral regurgitation) were retrospectively evaluated. The mean age at surgery was 4.3 ± 5.4 years, and 27 patients (41%) were neonates or infants. RESULTS: Seven (11%) patients died during the follow-up period of 3.2 ± 2.3 years and 5 (71%) were <1 year. Ten mitral valve replacements were performed in 8 patients, including 1 pulmonary valve homograft, 3 Contegra conduits of 12 mm thickness in the intra-annular position and 6 mechanical valves. Shone's syndrome, dysplastic valve, a need for valve replacement and age <1 year were the risk factors for death or reoperation in a univariable analysis, while in a multivariable analysis of all patients, valve replacement and age <1 year remained as risk factors. In a multivariable analysis of 27 patients aged <1 year, mitral valve dysplasia was a significant risk factor for reoperation or death. The 5-year rate of freedom from death or reoperation in neonates or infants was 55% and that in patients aged >1 year was 88% (P = 0.003). CONCLUSIONS: An age of <1 year, mitral valve dysplasia and a need for mitral valve replacement were associated with a higher incidence of death or reoperation. Primary mitral valve replacement or univentricular strategy may have to be considered for symptomatic neonates with Shone's syndrome.

OBJECTIVES: There is no consensus or theoretical explanation regarding the optimal location for the fenestration during the Fontan operation. We investigated the impact of the location of the fenestration on Fontan haemodynamics using a three-dimensional Fontan model in various physiological conditions. METHODS: A three-dimensional Fontan model was constructed on the basis of CT images, and a 4-mm-diameter fenestration was located between the extracardiac Fontan conduit and the right atrium at three positions: superior, middle, and inferior part of the conduit. Haemodynamics in the Fontan route were analysed using a three-dimensional computational fluid dynamic model in realistic physiological conditions, which were predicted using a lumped parameter model of the cardiovascular system. The respiratory effect of the caval flow was taken into account. The flow rate through the fenestration, the effect of lowering the central venous pressure, and wall shear stress in the Fontan circuit were evaluated under central venous pressures of 10, 15, and 20 mmHg. The pulse power index and pulsatile energy loss index were calculated as energy loss indices. RESULTS: Under all central venous pressures, the middle-part fenestration demonstrated the most significant effect on enhancing the flow rate through the fenestration while lowering the central venous pressure. The middle-part fenestration produced the highest time-averaged wall shear stress, pressure pulse index, and pulsatile energy loss index. CONCLUSIONS: Despite slightly elevated energy loss, the middle-part fenestration most significantly increased cardiac output and lowered central venous pressure under respiration in the Fontan circulation.

Patients with mechanical aortic valves are generally contraindicated for left ventricular assist device (LVAD) insertion because the prosthetic valve often becomes fixed in closed position. A 41-year-old woman with mechanical aortic valve prosthesis experienced sudden chest pain and developed cardiogenic shock. A paracorporeal pulsatile LVAD and a monopivot centrifugal pump as a right VAD (RVAD) were implanted. The mechanical aortic valve was intentionally left in place. Soon after the operation, LVAD support was discontinued daily for few seconds to allow the mechanical aortic valve to open and to avoid thrombus formation. The patient was successfully weaned off RVAD and received anticoagulation therapy with warfarin. On postoperative day 141, she was transferred to a university hospital where a HeartMate II LVAD was implanted, and the aortic valve was successfully replaced with a bioprosthetic valve. The patient is currently awaiting heart transplantation.

OBJECTIVES: This study aimed to evaluate the outcomes of patients who did not undergo initial aortic surgery for acute Stanford type A aortic dissection with a patent false lumen of the ascending aorta. METHODS: Inpatient and outpatient records were retrospectively reviewed. RESULTS: We identified 195 patients with acute type A aortic dissection with a patent ascending false lumen between January 1998 and March 2016. Of these, 137 underwent aortic surgery, 16 died before surgery and 42 declined aortic surgery. The ages of the patients who underwent and those who declined aortic surgery were 60.0 ± 10.6 years and 72.3 ± 12.4 years, respectively. The mortality rate of those who underwent and those who declined aortic surgery was 15 and 62% at 30 days and 19% and 67 at 90 days, respectively ( P  < 0.0001). In the 58 patients who did not undergo initial aortic surgery, the maximum aortic diameter was correlated with survival ( P  = 0.0037). At follow-up (3.7 ± 4.5 years; range 0-16.4 years), survival at 1, 5 and 10 years in those who underwent and those who declined initial aortic surgery was 78, 68 and 49%, and 29, 24 and 12%, respectively ( P  < 0.0001). CONCLUSIONS: In this study of patients with acute Stanford type A aortic dissection with a patent false lumen of the ascending aorta, the mortality of those who declined initial aortic surgery was 62% at 30 days and 67% at 90 days, respectively, and a smaller aortic diameter was significantly associated with better survival.

Surgical results of Fontan operation has been improved over the decades due to the introduction of the staged operations and some modifications of Fontan route from the classical atrio-pulmonary connection to total cavo-pulmonary connection. However, issues remain because of the single ventricular physiology of Fontan circulation. This article explains about the preoperative checklist for Fontan operation and tips on the postoperative management including an early extubation, use of inhaled nitric oxide after extubation, anticoagulation therapy, and efficacy of angiotensin converting enzyme inhibitor, supported by the cutting-edge evidence. Some patients who underwent Fontan operation, however, suffer from protein-losing enteropathy, heart failure, and thus are classified as failing Fontan. Treatment for these patients with failed Fontan is an unsolved problem in the state where heart transplantation is inadequately available in Japan.

Regional cerebral oximetry using near-infrared spectroscopy device, an INVOS 5100 C (Medtronic, Minneapolis, MN, USA), during cardiac surgery aims to avoid perioperative neurological impairment, especially during cardiopulmonary bypass. However, it is not uncommon to encounter critically low initial cerebral regional oxygen saturation or a low value unresponsive to intervention. Therefore, it is important to identify factors associated with low saturation value other than true cerebral hypoxia. We investigated the relationship between preoperative regional cerebral oxygen saturation and clinical variables during cardiac surgery. From January 2013 to May 2016, 462 patients underwent elective cardiac surgery. Patient's ≤12 years of age, with acute cerebral infarction, with previous intracranial hemorrhage or neurosurgery, with concomitant aortic surgery, and having off-pump coronary artery bypass surgery were excluded. The remaining 223 patients were monitored by intraoperative regional cerebral oximetry. Univariate analysis found that scalp-cortex distance, cerebrospinal fluid thickness, left ventricular ejection fraction, hemoglobin concentration, estimated glomerular filtration rate, and hemodialysis were significantly correlated with the initial regional oxygen saturation value. Multiple regression analysis revealed that scalp-cortex distance, left ventricular ejection fraction, hemoglobin, and hemodialysis remained as significant variables. A receiver operating characteristic analysis found that for a low initial regional oxygen saturation value of 40%, the thresholds of scalp-cortex distance, left ventricular ejection fraction, and hemoglobin concentration were 17.6 mm, 45.2%, and 7.5 g/dl, respectively. In conclusion, brain atrophy, poor left ventricular function, anemia, and hemodialysis were associated with low initial cerebral regional oxygen saturation values in adult cardiac surgery patients.

We describe the implantation of an implantable cardioverter defibrillator (ICD) in a 2-month-old infant with frequent sustained ventricular tachycardia (VT) refractory to antiarrhythmic agents. An epicardial ICD shock coil lead and pacing leads were placed, as was a cumbersome device console that was stored in a pocket between the left external and internal oblique muscles. These methods were safe and feasible even for such a small infant, and possible adverse events were avoided.

Minimally invasive atrial septal defect closure and tricuspid annuloplasty in female patients are normally performed through a right submammary anterior minithoracotomy approach. However, when the aortic root is located higher, the direction of aortic cannulation becomes not ideal through the submammary incision. In such cases, transareolar approach is useful. Through this approach, aortic cannulation and tricuspid operation can be performed with endoscopic assistance, and ASD closure can be performed under direct vision.

Although abdominal aortic aneurysms (AAAs) occur mostly inferior to the renal artery, the mechanism of the development of AAA in relation to its specific location is not yet clearly understood. The objective of this study was to evaluate the hypothesis that even healthy volunteers may manifest specific flow characteristics of blood flow and alter wall shear or oscillatory shear stress in the areas where AAAs commonly develop. Eight healthy male volunteers were enrolled in this prospective study, aged from 24 to 27. Phase-contrast magnetic resonance imaging (MRI) was performed with electrocardiographic triggering. Flow-sensitive four-dimensional MR imaging of the abdominal aorta, with three-directional velocity encoding, including simple morphological image acquisition, was performed. Information on specific locations on the aortic wall was applied to the flow encodes to calculate wall shear stress (WSS) and oscillatory shear index (OSI). While time-framed WSS showed the highest peak of 1.14 ± 0.25 Pa in the juxtaposition of the renal artery, the WSS plateaued to 0.61 Pa at the anterior wall of the abdominal aorta. The OSI peaked distal to the renal arteries at the posterior wall of the abdominal aorta of 0.249 ± 0.148, and was constantly elevated in the whole abdominal aorta at more than 0.14. All subjects were found to have elevated OSI in regions where AAAs commonly occur. These findings indicate that areas of constant peaked oscillatory shear stress in the infra-renal aorta may be one of the factors that lead to morphological changes over time, even in healthy individuals.

A computer simulation was carried out for thrombus formation under the influence of blood flow after Fontan operation. Blood was modeled by computed particles assigned as normal blood or thrombus. Blood flow was calculated using a moving particle semi-implicit method. In a model of blood coagulation that causes thrombi,a normal blood particle changed to a thrombus when its shear rate was lower than a threshold. A spring force was employed to express the coagulation,and was substituted into the NS equations as the external force to couple the coagulation and the blood flow. In simulations,thrombus formation was affected by blood flow behaviors,such as stagnation and recirculation. The atrio-pulmonary connection (APC) square model showed the highest incidence for thrombus formation in the right atrium due to flow stagnation,followed by the APC round,whereas no thrombus was formed in the total cavopulmonary connection model. This result suggests that local hemodynamic behavior associated with the complex channel geometry plays a major role in thrombus formation in the Fontan route.

The classical Fontan route, namely the atriopulmonary connection (APC), continues to be associated with a risk of thrombus formation in the atrium. A conversion to a total cavopulmonary connection (TCPC) from the APC can ameliorate hemodynamics for the failed Fontan; however, the impact of these surgical operations on thrombus formation remains elusive. This study elucidates the underlying mechanism of thrombus formation in the Fontan route by using a two-dimensional computer hemodynamic simulation based on a simple blood coagulation rule. Hemodynamics in the Fontan route was simulated with Navier-Stokes equations. The blood coagulation and the hemodynamics were combined using a particle method. Three models were created: APC with a square atrium, APC with a round atrium, and TCPC. To examine the effects of the venous blood flow velocity, the velocity at rest and during exercise (0.5 and 1.0 W/kg) was measured. The total area of the thrombi increased over time. The APC square model showed the highest incidence for thrombus formation, followed by the APC round, whereas no thrombus was formed in the TCPC model. Slower blood flow at rest was associated with a higher incidence of thrombus formation. The TCPC was superior to the classical APC in terms of preventing thrombus formation, due to significant blood flow stagnation in the atrium of the APC. Thus, local hemodynamic behavior associated with the complex channel geometry plays a major role in thrombus formation in the Fontan route.

BACKGROUND: The impact of additional pulmonary forward flow (APF) through the pulmonary valve at the time of bidirectional cavopulmonary shunt (BCPS) is unknown. METHODS: Between 2000 and 2010, 276 patients had BCPS and 126 of them were selected, including 60 patients with APF via pulmonary valve and 66 patients, in whom the pulmonary valve was closed. We compared the length of hospital stay and duration of pleural drainage at BCPS and Fontan operations. We also compared the number of surgical interventions before BCPS, the number of operations between BCPS and Fontan operation, Nakata index prior to Fontan operation, grade of atrioventricular valve regurgitation (AVVR), and oxygen saturations prior to Fontan operation. RESULTS: Prior to BCPS, 20% (12 of 60) of patients with APF and none without APF had pulmonary artery (PA) banding. More patients without APF had systemic-to-PA shunts (p < 0.01). Fontan operation was completed in 58% (35 of 60) of patients with APF and in 68% (45 of 66) of patients without APF (p = 0.34). There was no difference in the length of hospital stay or duration of pleural drainage at BCPS. No significant difference was observed in the number of surgical procedures between BCPS and Fontan operation, grade of AVVR or oxygen saturations before Fontan operation. Children with APF had a higher Nakata index (p = 0.02) prior to Fontan operation, shorter duration of pleural drainage (p = 0.009) and shorter hospital stay (p = 0.009) after Fontan operation. CONCLUSIONS: Children with APF at BCPS had better developed PAs, shorter duration of pleural drainage, and shorter hospital stay after Fontan operation.

Recurrent laryngeal nerve injury is a frequent adverse event of aortic arch repair. We hereby present a technique of skeletonization of the recurrent nerve to preserve its function during the Norwood procedure and aortic arch repair.

Background:The myocardial performance index (MPI) has emerged as a Doppler-derived index for global ventricular function capable of estimating combined systolic and diastolic performance. While several studies have reported its load-dependency, responses of the MPI to various hemodynamic changes have not been fully characterized.Methods and Results:The response characteristics of the MPI were examined and compared with ejection fractions (EF) by changing hemodynamic parameters within the physiological range in a lumped parameter model of the cardiovascular system. At baseline, the MPI was 0.42 and the EF was 0.68. Heart rate increase resulted in a decrease in EF and an increase in the MPI. Reduction in end-systolic elastance decreased EF and increased the MPI. Volume overload and ventricular stiffening did not affect EF but paradoxically reduced the MPI. Increased afterload due to higher systemic resistance resulted in a decrease in EF and increase in the MPI, but afterload increase caused by reduced arterial compliance led to a decrease in both EF and MPI. These MPI characteristics caused paradoxical improvement of the MPI during disease progression of chronic heart failure in a simulation of mitral regurgitation.Conclusions:The MPI is affected by a wider variety of hemodynamic parameters than EF. In addition, it is predicted to decrease paradoxically with volume overload, reduction in arterial compliance, or ventricular diastolic stiffening. These MPI characteristics should be considered when assessing cardiovascular dynamics using this index.

Atrioventricular valve regurgitation is one of the predictors of adverse outcomes after the Fontan procedure. We describe our surgical technique of GoreTex (W. L. Gore & Associates, Inc., Flagstaff, AZ, USA) bridge to repair a common atrioventricular valve in single-ventricular circulation. The repair includes a GoreTex strip that is secured to the mid-line of both superior and inferior bridging leaflets and annulus to obtain a better coaptation of the leaflets and prevent further dilatation of the annulus. We have applied this technique for 7 consecutive patients with excellent outcomes.

The assessment of cardiovascular function is becoming increasingly important for the care of patients with single-ventricle defects. However, most measurement methods available in the clinical setting cannot provide a separate measure of cardiac function and loading conditions. In the present study, a numerical method has been proposed to compensate for the limitations of clinical measurements. The main idea was to estimate the parameters of a cardiovascular model by fitting model simulations to patient-specific clinical data via parameter optimization. Several strategies have been taken to establish a well-posed parameter optimization problem, including clinical data-matched model development, parameter selection based on an extensive sensitivity analysis, and proper choice of parameter optimization algorithm. The numerical experiments confirmed the ability of the proposed parameter optimization method to uniquely determine the model parameters given an arbitrary set of clinical data. The method was further tested in four patients undergoing the Fontan operation. Obtained results revealed a prevalence of ventricular abnormalities in the patient cohort and at the same time demonstrated the presence of marked inter-patient differences and preoperative to postoperative changes in cardiovascular function. Because the method allows a quick assessment and makes use of clinical data available in clinical practice, its clinical application is promising.

The physiological limitations of the Fontan circulation have been extensively addressed in the literature. Many studies emphasized the importance of pulmonary vascular resistance in determining cardiac output (CO) but gave little attention to other cardiovascular properties that may play considerable roles as well. The present study was aimed to systemically investigate the effects of various cardiovascular properties on clinically relevant hemodynamic variables (e.g., CO and central venous pressure). To this aim, a computational modeling method was employed. The constructed models provided a useful tool for quantifying the hemodynamic effects of any cardiovascular property of interest by varying the corresponding model parameters in model-based simulations. Herein, the Fontan circulation was studied compared with a normal biventricular circulation so as to highlight the unique characteristics of the Fontan circulation. Based on a series of numerical experiments, it was found that 1) pulmonary vascular resistance, ventricular diastolic function, and systemic vascular compliance play a major role, while heart rate, ventricular contractility, and systemic vascular resistance play a secondary role in the regulation of CO in the Fontan circulation; 2) CO is nonlinearly related to any single cardiovascular property, with their relationship being simultaneously influenced by other cardiovascular properties; and 3) the stability of central venous pressure is significantly reduced in the Fontan circulation. The findings suggest that the hemodynamic performance of the Fontan circulation is codetermined by various cardiovascular properties and hence a full understanding of patient-specific cardiovascular conditions is necessary to optimize the treatment of Fontan patients.

Aortic aneurysms may cause the turbulence of blood flow and result in the energy loss of the blood flow, while grafting of the dilated aorta may ameliorate these hemodynamic disturbances, contributing to the alleviation of the energy efficiency of blood flow delivery. However, evaluating of the energy efficiency of blood flow in an aortic aneurysm has been technically difficult to estimate and not comprehensively understood yet. We devised a multiscale computational biomechanical model, introducing novel flow indices, to investigate a single male patient with multiple aortic aneurysms. Preoperative levels of wall shear stress and oscillatory shear index (OSI) were elevated but declined after staged grafting procedures: OSI decreased from 0.280 to 0.257 (first operation) and 0.221 (second operation). Graftings may strategically counter the loss of efficient blood delivery to improve hemodynamics of the aorta. The energy efficiency of blood flow also improved postoperatively. Novel indices of pulsatile pressure index (PPI) and pulsatile energy loss index (PELI) were evaluated to characterize and quantify energy loss of pulsatile blood flow. Mean PPI decreased from 0.445 to 0.423 (first operation) and 0.359 (second operation), respectively; while the preoperative PELI of 0.986 dropped to 0.820 and 0.831. Graftings contributed not only to ameliorate wall shear stress or oscillatory shear index but also to improve efficient blood flow. This patient-specific modeling will help in analyzing the mechanism of aortic aneurysm formation and may play an important role in quantifying the energy efficiency or loss in blood delivery.

OBJECTIVE: Despite the broadened indications for Fontan procedure, there are patients who could not proceed to Fontan procedure because of the strict Fontan criteria during the early period. Some patients suffer from post-Glenn complications such as hypoxia, arrhythmia, or fatigue with exertion long after the Glenn procedure. We explored the possibility of Fontan completion for those patients. METHODS: Between 2004 and 2010, five consecutive patients aged between 13 and 31 years (median 21) underwent Fontan completion. These patients had been followed up for more than 10 years (10 to 13, median 11) after Glenn procedure as non-Fontan candidates. We summarise these patients retrospectively in terms of their pre-operative physiological condition, surgical strategy, and problems that these patients hold. RESULTS: Pre-operative catheterisation showed pulmonary vascular resistance ranging from 0.9 to 3.7 (median 2.2), pulmonary to systemic flow ratio of 0.3 to 1.6 (median 0.9), and two patients had significant aortopulmonary collaterals. Extracardiac total cavopulmonary connections were performed in three patients, lateral tunnel total cavopulmonary connection in one patient, and intracardiac total cavopulmonary connection in one patient, without a surgical fenestration. Concomitant surgeries were required including valve surgeries--atrioventricular valve plasty in three patients and tricuspid valve replacement in one patient; systemic outflow tract obstruction release--Damus-Kaye-Stansel procedure in two patients and subaortic stenosis resection in one patient; and anti-arrhythmic therapies--maze procedure in two patients, cryoablation in two patients, and pacemaker implantation in two patients. All patients are now in New York Heart Association category I. CONCLUSION: Patients often suffer from post-Glenn complications. Of those, if they are re-examined carefully, some may have a chance to undergo Fontan completion and benefit from it. Multiple lesions such as atrioventricular valve regurgitation, systemic outflow obstruction, or arrhythmia should be surgically repaired concomitantly.

OBJECTIVE: A sufficient understanding of patients' cardiovascular status is necessary for doctors to make the best decisions with regard to the treatment of cardiovascular disease; however, it is often not available because of the limitation of clinical measurements. The objective of this study was to examine whether cardiovascular function can be assessed quantitatively and for specific patients by combining clinical data with a computational model of the cardiovascular system. METHODS: Seven consecutive patients undergoing off-pump coronary artery bypass grafting were enrolled in this study. The clinical data were collected both during the preoperative diagnosis and during the operation. Sensitivity analysis was performed to select the major model parameters most relevant to the measured data. The major model parameters were then estimated through a data-fitting procedure, enabling a patient-specific quantitative assessment of various aspects of cardiovascular function. RESULTS: The results revealed the prevalence of left ventricular diastolic dysfunction in the patients, although the severity of dysfunction exhibits significant interpatient variability (the estimated left ventricular passive elastance varies from 194% to 540% of its reference value). Moreover, 4 of the 7 patients studied had impaired left ventricular systolic function. CONCLUSIONS: The current study demonstrates the feasibility of assessing cardiovascular function quantitatively by combining clinical data with a cardiovascular model. In particular, the assessment utilizes the measurements already in use or available in clinical settings, enhancing the clinical potential of the proposed method.

The clinical benefits of the Fontan operation in treating single-ventricle defects have been well documented. However, perioperative mortality or morbidity remains a critical problem. The purpose of the present study was to identify the cardiovascular factors that dominate the transient hemodynamic changes upon the change of a bidirectional cavopulmonary (Glenn) anastomosis (BCPA) into a total cavopulmonary connection (TCPC). For this purpose, two computational models were constructed to represent, respectively, a single-ventricle circulation with a BCPA and that with a TCPC. A series of model-based simulations were carried out to quantify the perioperative hemodynamic changes under various cardiovascular conditions. Obtained results indicated that the presence of a low pulmonary vascular resistance and/or a low lower-body vascular resistance is beneficial to the increase in transpulmonary flow upon the BCPA to TCPC change. Moreover, it was found that ventricular diastolic dysfunction and mitral valve regurgitation, despite being well-known risk factors for poor postoperative outcomes, do not cause a considerable perioperative reduction in transpulmonary flow. The findings may help physicians to assess the perioperative risk of the TCPC surgery based on preoperative measurement of cardiovascular function.

Although indications for a Fontan procedure have broadened, some patients, in the past, were ineligible for the Fontan completion after a Glenn procedure and thus suffered the limitations of the Glenn procedure-namely desaturation, arrhythmia and reduced quality of life. If examined more closely, however, completion may yet be feasible for such patients. We present here a complex case of asplenia, dextrocardia and total anomalous pulmonary venous return (1b) where the Fontan procedure was successfully completed 12 years after the Glenn procedure. A unique surgical strategy incorporating intra-atrial total cavopulmonary connection and atrioventricular valve repair contributed to our success.

A combination of cor triatriatum and persistent left superior vena cava without communication to the coronary sinus is uncommon. A 62-year-old male with this diagnosis in conjunction with atrial fibrillation underwent successful intracardiac repair done with a unique method. After a maze procedure and enlargement of the route from the pulmonary veins to the mitral valve, a GoreTex graft was used to reroute the left superior vena cava into the right atrium and to close two thirds of the circumference of the patient's atrial septal defect; the rest of the defect was closed with another GoreTex patch.

There have been only a few reports concerning the long-term results of a surgical procedure using a large artificial patch for patients with Williams syndrome. Twelve years have passed since a patient with William's syndrome underwent a surgery with a patch angioplasty for the diffuse supravalvular aortic stenosis and deformities of the neck branch arteries. The patient had a well-balanced aortic growth without stenotic or aneurysmal changes, which was confirmed during the time of the second surgery when replacing the mitral valve. This technique of using a large patch has proven to be safe for Williams syndrome patients with diffuse supravalvular aortic stenosis in the long term.

We describe an extremely rare form of double-outlet right ventricle in a 1-year-old boy who had l-malposition of the great arteries with the definitive conotruncal features of false Taussig-Bing heart. Extraordinary conotruncal morphology raised several surgical options, however, the definitive anatomical repair was achieved by an arterial switch operation with a baffle from a ventricular septal defect to the pulmonary artery.

BACKGROUND AND AIM OF THE STUDY: The heart produces an efficient cardiac output by repeating diastole and systole. With the evolution of three-dimensional (3D) echocardiography, it is possible to evaluate cardiac motion using detailed 3D morphologic echocardiography. The study aim was to evaluate mitral and aortic annulus excursions towards the apex of the left ventricle, using 3D echocardiography. Measurements of the angle variation between the mitral and aortic valve throughout the cardiac cycle were performed to determine the effects of annulus excursion on cardiac function. METHODS: Seven healthy adolescents (five males, two females; mean age 15.9 +/- 1.1 years; Group H) and seven patients with dilated cardiomyopathy (seven males; mean age 63.6 +/- 12.9 years; Group D) were selected. All subjects underwent 3D echocardiography between November 2007 and June 2008. Annulus excursion (AE) was defined as the annular motion towards the apex. The Ex-Ratio A (%) and Ex-Ratio M (%) were defined as the ratios of aortic or mitral excursion, respectively, to the maximal distance from the annulus to the left ventricular apex. The annulus was defined simply as a flat round disc, and the annular area calculated as the annular distance between the anterior and posterior annulus as a circle diameter. The annulus excursion volume (AEV) was calculated by multiplying the annular area by AE, and determined for each valve of each patient. The total AEV was the summation of the mitral and aortic AEVs. The ratio of AEV to left ventricular diastolic volume was expressed as AEV/EDV. Angular variation between the valves was measured during the cardiac cycle with the following values: maximal angle (Dmax), minimal angle (Dmin), and the difference between Dmax and Dmin (Dmax-min). RESULTS: In all cases, the apex was in a fixed position. The AE was significantly greater for group H than for group D. While AEV did not differ between groups, AEV/EDV(A) and AEV/EDV(M) were greater for group H than for group D. The angle between the mitral and aortic annulus changed throughout the cardiac cycle. The Dmax-min value was significantly greater for group H than for group D. CONCLUSION: Annulus excursion contributes to an efficient cardiac output. The angle variation was measured during the cardiac cycle and found to be greater in healthy adolescents. 3D echocardiography represents a useful modality for clarifying 'motional cardiac morphology'.

Aiming at establishing a simulation-based framework for predictive medicine we have developed a patient-specific aortic aneurysm model based on computational biomechanics. In this study, we construct two image-based three-dimensional patient-specific models of aortic aneurysms based on CT images of two patients. A multi-scale hemodynamic model is employed to couple these three-dimensional models with a closed-loop 0-1-dimension hemodynamic model for the whole cardiovascular system. The aortic aneurysm hemodynamics are then visualized in terms of streamlines, wall shear stresses and oscillatory shear index, and further analyzed with a specific focus on the relationship between the hemodynamics and the occurrence of the aortic aneurysm.

BACKGROUND: The physiologic goal of management after a Norwood procedure is to optimize systemic oxygen delivery, as indicated by oxygen excess factor (OEF). Factors were examined that might affect systemic oxygen delivery after the Norwood procedure with right ventricle-to-pulmonary artery (RV-PA) conduit as the pulmonary blood supply. METHODS: Hemodynamic data of 9 patients (mean age, 25.0 days; mean weight, 2.9 kg) who underwent a modified Norwood operation for hypoplastic left heart syndrome (HLHS) between April 2003 and April 2008 were retrospectively analyzed. Variables were obtained by manometry and oximetry from indwelling catheters in the systemic artery, pulmonary artery, and superior vena cava at 3- to 6-hour intervals for 72 hours postoperatively. Systemic (Qs) and pulmonary (Qp) blood flow, systemic vascular resistance (SVR), and pulmonary vascular resistance (PVR) were calculated. RESULTS: A significant increase in SVR and decrease in PVR occurred during the first 6 hours, which might be inductive to sudden cardiovascular collapse. SVR and PVR significantly decreased over time through 24 hours, followed by a lower steady increase. OEF was closely correlated with SVR (p < 0.0001). No correlation of OEF with PVR (p = 0.65) was noted among the assumed variables. Mixed venous oxygen saturation (SVO(2)) and OEF were strongly correlated. Pulmonary arterial pressure and OEF were weakly correlated. CONCLUSIONS: Postoperative management strategies to maintain a low SVR, rather than manipulating PVR, appear to be rational to achieve adequate oxygen delivery after a Norwood procedure with Sano modification. The SVO(2) provides reliable prediction of OEF during postoperative hemodynamic recovery.

A surgeon needs an innovative technique to establish a Fontan circulation for a patient who has a widely separated hepatic vein from the inferior vena cava. The inferior vena cava was redirected by placing a trimmed GoreTex baffle (W. L. Gore and Associates, Flagstaff, AZ) on the internal side of the atrium connecting the hepatic venous flow, and then directing it to the extra-atrium. Another extracardiac half-circumferential GoreTex baffle was sutured to the epicardial atrial wall and to the pulmonary artery opening. This procedure is efficacious for patients with an isolated hepatic vein and has advantages in terms of using less synthetic material in the conduit.

The surgical strategy for patients having a functionally single ventricle associated with totally anomalous pulmonary venous connection and pulmonary atresia with non-confluent pulmonary artery has yet to be agreed. We created an intraatrial tunnel to produce a total cavo-pulmonary connection in such a patient, also creating a confluence for the pulmonary arteries. By minimizing the use of the GoreTex patch, the patient was able to discontinue the use of warfarin.

A 65-year-old woman with a Hancock valve implanted 25 years earlier for Ebstein's anomaly underwent a successful second tricuspid valve replacement with a Mosaic valve because of significant tricuspid regurgitation. At surgery, it was found that the Hancock valve had a cylinder-shaped hole and had lost its entire structure. Tricuspid valve dysfunction may be tolerated for a long time before surgery is contemplated.

Bazin's disease was first reported in 1861, and is described as erythema induratum or nodular vasculitis. The condition is seen occasionally in middle-aged women on the skin of the calf, and a relationship to a tuberculosis infection has been proposed. In the present patient, valvular lesions occurred simultaneously with Bazin's disease, with granulomatous changes being demonstrated by the aortic valve pathology.