Ventriculoarterial Discordance Research Articles

Fetal transposition of the great arteries: 3D virtual and physical models from ultrasound datasets.

Transposition of the great arteries (TGA) is a cyanotic congenital heart disease characterized by ventriculoarterial discordance and atrioventricular concordance with the great arteries in a parallel relationship. Prenatal diagnosis of TGA has implications for postnatal outcomes, allowing for planned delivery and perinatal management. Three-dimensional virtual or physical models of fetal TGA allow better understanding of fetal cardiac anomalies by parents and interactive discussion among the multidisciplinary team (obstetricians, pediatricians, maternal-fetal specialists, pediatric cardiologists, and cardiovascular surgeons), as well as continuing medical education.

A Retrospective Observational Study in Neonates with Transposition of Great Arteries Undergoing Balloon Atrial Septostomy in a Tertiary Care Hospital

Objectives: Transposition of great arteries (TGA) is a common cause of cyanotic newborns. There is an atrioventricular concordance with ventriculoarterial discordance. This parallel circulation is incompatible with life unless communication exists for the inter-circulatory mixing of blood. Balloon atrial septostomy (BAS) is a percutaneously performed interventional procedure in catheterization laboratory, usually in patients with TGA-intact ventricular septum (IVS) to ensure admixture of oxygenated and deoxygenated blood thus improving systemic oxygen delivery, to achieve hemodynamic stability before the definitive procedure (Arterial switch operation), and to determine the risk of intraprocedural complications in neonates undergoing balloon atrial septostomy. Material and Methods: This is a retrospective observational study, which included neonatal patients during a single year. All the data were collected from the medical record section of the hospital. Results: We included 17 neonates with TGA transferred to our center for definite treatment. Six cases were done under sedation and 11 under general anesthesia. The mean age at the time of BAS was 4.8 days. Procedure-related complications occurred in 41% of patients. In one of the cases, difficult airway management made the periprocedural course daunting. Complications included intraprocedural balloon rupture (1 case), transient atrial arrhythmia (4 cases), hypotension (1 case), and pericardial tamponade due to left atrial wall puncture (1 case). Conclusion: BAS is a safe and effective palliative procedure for TGA-IVS, with good immediate results in our institution. Maintaining cardiorespiratory stability, prevention of respiratory depression in a spontaneously breathing neonate, and maintenance of normothermia in the cold temperature of the catheterization laboratory, with eternal vigilance, forms the cornerstone of a successful neonatal outcome.

Transposition of Great Vessels: Latin-American Postoperative Experience

The transposition of great vessels (TGV) is a congenital cardiac malformation where atrioventricular concordance is conserved with ventriculoarterial discordance. Regarding the management of this pathology, surgery is the cornerstone treatment. We aimed to describe the surgical characteristics of the pediatric population with transposition of great vessels surgically managed by our cardiovascular surgery group.

Incidence of coronary anomalies in patients with D-transposition of great arteries (D-TGA) after arterial switch operation (ASO)

Abstract Background and purpose D-transposition of great arteries (D-TGA) is a congenital cardiac defect defined by atrioventricular concordance and ventriculo-arterial discordance. Arterial switch operation (ASO) is currently the surgical repair and implies reimplantation of the coronary arteries from the aorta into the neo-aortic root. As such, long-term coronary anomalies and complications are possible and potentially dangerous. Recently, coronary computed tomography angiography (CCTA) has gained a prominent role for characterization of the coronary anatomy in these patients (pts) and its relationship with adjacent structures. However, routine coronary evaluation among asymptomatic pts after ASO remains controverse, as the reported incidence of coronary-related complications is low. The purpose of this study is to perform a descriptive analysis of CCTA findings in pts with D-TGA after ASO. Methods We performed a retrospective single center study that included patients with D-TGA submitted to ASO who underwent CCTA. Demographic, clinical and imaging data were collected. Results We identified 57 pts with D-TGA submitted to ASO. Of these, 39 (68%) performed a CCTA. Mean age of pts was 20.4 (± 3.8) years; 54% were male; 32% had complex D-TGA. In 35 patients (90%), CCTA was performed as part of a routine screening. In 4 (10%) pts CCTA was done due to symptoms or an abnormal non-invasive test suggestive of myocardial ischemia. Eighteen (46%) pts had coronary anomalies: 5 (13%) had an acute angulation at the coronary origin; 13 (33%) pts had anomalous origin of the coronary arteries, ranging from presence of a single coronary artery in 3 (8%) pts, common independent origin from a single sinus of Valsalva in 6 (15%) cases and anomalous origin of the circumflex artery from the right coronary artery (RCA) in 4 (10%) pts. An interarterial course was described in 2 (5%) pts and a retroaortic course was reported in 8 (21%) cases. One patient had anomalous course of the LAD into the right ventricle, a mild calcified ostial stenosis of the left main coronary artery and a chronic total occlusion of the RCA. Conclusions D-TGA patients submitted to ASO have a high incidence of coronary anomalies. Routine screening with CCTA may be justified to identify patients who may be at higher risk of coronary events.

Anaesthetic Management of Intracranial Abscess in a Patient with Surgically Uncorrected Double Outlet Right Ventricle with Transposition of Great Arteries

Double Outlet Right Ventricle (DORV) with Transposition of Great Arteries (TGA) is a rare variant. The ventriculoarterial discordance due to this anatomical defect leads to parallel circulation. The postnatal survival depends on mixing of oxygenated and deoxygenated blood at various levels by defects like Atrial Septal Defect (ASD), Ventricular Septal Defect (VSD), Patent Ductus Arteriosus (PDA). Anaesthetising children with cyanotic Congenital Heart Disease (cCHD) and brain abscess necessitates use of anaesthesia protocol appropriate to both cCHD and intracranial surgery. Anaesthetic considerations related are maintenance of intravascular volume and preload, avoidance of precursors to acidosis such as hypothermia, hypercarbia, and hypotension and challenge for anaesthesiologist is to maintain Pulmonary Vascular Resistance (PVR) and Systemic Vascular Resistance (SVR) by pharmacological and ventilatory means. This report is about a seven-year-old child who was posted for emergency craniotomy and abscess drainage, after routine preanaesthetic check-up. Induced with fentanyl, ketamine and atracurium, anaesthesia was maintained on oxygen, air and sevoflurane. Intraoperatively, normothermia was maintained, and blood pressure was maintained by noradrenaline infusion, metabolic acidosis was corrected with soda-bicarbonate. In between the procedure, the patient had an episode of Supraventricular Tachycardia (SVT), which was managed with lidocaine, metoprolal and adenosine. In such cases, it is vital to pay attention to any potential anaesthetic interactions.

Transposition of the great arteries: single center experiences

Objectives: Transposition of great arteries is the most common cyanotic congenital heart disease. It is characterized by ventriculoarterial discordance and atrioventricular concordance. The aim of the present study was to review the anatomical and embryological basis of this anomaly and to discuss the surgical outcomes of arterial switch operations. Methods: The study included a total of 61 patients who underwent arterial switch operation. Demographic, anatomical, operative data, duration of stay in intensive care unit, need of postoperative extra corporeal membrane oxigenator, need of delayed sternal closure and mortality rate were retrieved from the institutional databases and medical records. Results: The median age of the patients was 22.9±61.26 (1–455) days, and their weights ranged between 3391.97±686.6 (1900–5500) grams. Transposition of great arteries accompanied intact ventricular septum in 39 patients (63.9%) and ventricular septal defect in 22 patients (36.1%). Coronary arteries were abnormal in 11 patients (18%). Mortality was observed in 7 patients (11.5%) and was seen 5.71±2.98 (1–10) days after surgery. The incidence of coronary anomaly in patients with mortality was 28.6%. The most common coronary anomaly in patients with coronary anomaly with mortality is the anomaly in which the circumflex artery originates from the right coronary artery. Conclusion: Arterial switch operations provide anatomical and complete correction in transposition of great arteries. It can be performed with appropriate timing, good preoperative, peroperative and postoperative management with low mortality. Coronary artery anomaly is not a contraindication for arterial switch operations, and with the detailed and careful evaluation of the appropriate coronary artery anatomy, transpositions with coronary anomalies are often uneventful.

1002 A HEART BEYOND A MIRROR: WHEN CCTGA ENCOUNTERS SITUS VISCERUM INVERSUS

Abstract Background Congenitally corrected transposition of great arteries (ccTGA) is an uncommon complex congenital heart disease with atrio-ventricular and ventriculo-arterial connections discondance. ccTGA may be associated with a situs solitus or situs inversus (34% of cases). Situs inversus is a mirror image of normal with the systemic ventricle situated on the right side. Instead, dextrocardia represents 20% of cases. Case clinic and discussion Came to our observation a 61 years old female, symptomatic for dyspnea on exertion (NYHA II). She had no past medical history of cardiovascular events. In anamnesis two full-term pregnancies without complications. Transthoracic echocardiogram found atrioventricular and ventriculo-arterial discordance in absence of significant valvulopathy. Cardiac computed tomography showed pulmonary veins linked to right atrium, superior and inferior cava veins connected to the left atrium; right atrium with tricuspid valve was connected to a morphologically left ventricle and left atrium with mitral valve was linked to morphologically right ventricle; pulmonary artery was connected to morphologically left ventricle instead aorta with aortic valve was linked to morphologically right ventricle. Cardiac MRI confirmed cctga in situs viscerum inversus, mild subpulmonary stenosis, moderate dilatation of arterial pulmonary trunk, and also intramyocardial late gadolinium enhancement due to fibrosis involving anterior and inferior interventricular junctions. Cardiac Holter monitoring showed sinus rhythm with some brief phases of low atrial rhythm, monomorphic isolated ventricular extrasystoles in absence of significant hyperkinetic or hypokinetic arrhythmias. CcTGA represents approximately 0.5% of all congenital heart disease. If undiagnosed in childhood, people usually become symptomatic during the first decades of life. Dyspnea, syncope and fatigue are the most frequent symptoms detected. Cardiac conduction disorders such as atrioventricular blocks are common due to the abnormal development of cardiac structures. Quality of life and its expectancy are related to the latency of the onset of heart failure symptoms. Only few patients remain asymptomatic beyond 50 years old. Symptoms and signs are frequently due to right sided (systemic) heart dysfunction and tricuspid valve insufficiency. A particular clinical situation worthy of attention is pregnancy because of the hemodynamic imbalance occurring. In fact, cardiac output increases of 40–50% above baseline determining an augmentation of stroke volume and heart rate. For these reasons, echo surveillance is needed every 4-8 weeks because of the increased risk of acute heart failure. An accurate assessment of heart rhythm has to be done due to the known predisposition to bradyarrhythmic and tachyarrhythmic events in ccTGA. Conclusions CcTGA patients require a strict cardiological follow up with echocardiographic assessment and periodic heart rhythm monitoring, in order to early detect worsening of cardiac function and significant abnormalities of the rhythm.

Prenatal Diagnosis of Congenitally Corrected Transposition of the Great Arteries (CCTGA): A Case Report

CCTGA, also known as levo- or L-loop transposition (L-TGA), double discordance, or ventricular inversion, is a rare cardiovascular anomaly with inversion of the ventricles and great arteries. In this anomaly, the right atrium communicates with the morpho- logic left ventricle, which gives rise to the pulmonary artery, while the left atrium communicates with the morphologic right ventricle, which gives rise to the aorta. Thus, atrioventricular and ventriculoarterial discordance (double discordance) exist, and although the blood flows in the normal direction, it passes through the wrong ventricular chambers. It is a unique conotruncal anomaly, inwhich the four-chamber view is abnormal. It may be associated with other heart disorders. In most fetuses, TGA remains undiagnosed before birth. The diagnosis of TGA can be made by care- fully and appropriately evaluating the anatomic locationsof cardiac chambers and the connections between the atria, ventricles, and great arteries with high-resolution ultrasound. Patients with isolated CTGA generally present later in life with signs and symptoms related to either arrhythmias or heart failure. TGA is rarely associated with chromosomal abnormality and amniocentesis is usually not undertaken. We report a case of CTGA detected at 18 week’s gestation on screening ultrasound.

Congenitally corrected transposition of the great arteries outcomes of different surgical techniques in a paediatric population: A single-centre report.

Congenitally corrected transposition of the great arteries is a complex pathology characterised by atrioventricular and ventriculo-arterial discordance. Optimal surgical approaches are still a matter of debate. To evaluate the outcomes of different surgical treatments in a single centre. Between 1998 and 2020, 89 patients were studied. The cohort was divided into three groups: physiologic, anatomic, and univentricular repair. Physiologic correction (56.18%) was associated with significant tricuspid valve regurgitation progress (42%) and complete AV block (30%) compared to anatomic repair. Right ventricular systolic dysfunction was developed in 14%. Instead, anatomic correction (30.34%) (double switch 59% and Rastelli type 40.7%) presented moderate to severe aortic regurgitation (4%) and left ventricular systolic dysfunction (11%). Complete AV block was developed in 14.8%. Rate of reintervention was 34% for physiologic and 26% for anatomic. Univentricular palliation (13.8%) presented no complications or late mortality during the follow-up. The overall survival at 5 and 10 years, respectively, was 80% (95% CI 69, 87) and 75% (95% CI 62, 84). There was no statistically significant difference in mortality between the groups (p log-rank = 0.5752). Management of congenitally corrected transposition of the great arteries remains a challenge. In this cohort, outcomes after physiologic repair were satisfactory in spite of the progression of tricuspid regurgitation and the high incidence of AV block. Anatomic repair improved tricuspid regurgitation but increased the risk of aortic regurgitation and left ventricular systolic dysfunction. The Fontan group showed the lowest incidence of complications.

Congenitally Corrected Transposition of Great arteries with AV block -cohabitation of structural and electrical cardiac abnormality: a case report

Congenitally Corrected Transposition of Great Arteries (c-TGA) is an anomaly with atrioventricular and ventriculoarterial discordance where left atrium connects to right ventricle and right atrium to left ventricle. However in this case of double inversion, aorta carries saturated blood and pulmonary artery carries venous blood. So, normal physiological circulation is maintained. Our patient, a 38-years-old Bangladeshi male presented with palpitation, dizziness and effort intolerance (NYHAII) during exertion since childhood, which has recently become much worse. However, he had no history of central cyanosis, chest pain or syncope. We diagnosed him as a case of Corrected TGA and second-degree AV block with intermittent complete heart block. A Dual chamber permanent Pacemaker was inserted without any complications. No invasive treatment including corrective surgery was performed because patient’s cardiac function was almost normal. Patient became totally asymptomatic after pacemaker implantation Bangladesh Heart Journal 2022; 37(1): 77-80

Step-By-Step Segmental Analysis of the Fetal Heart with an Uncommon Situs Anomaly

Congenital heart diseases are the most common congenital anomalies during the fetal period. The diagnosis of complex congenital heart diseases in the fetal period is not always easy. While evaluating cardiac abnormalities, performing segmental analysis and step-by-step evaluation will facilitate the diagnosis of prenatal cardiac diseases. Here, we report a rare variant AV (atrioventricular) and VA (ventriculoarterial) discordance pattern detected in utero and identified based on step-by-step segmental analysis.

The first successful double switch operation for congenitally corrected transposition of the great arteries in Slovenia

Congenitally corrected transposition of the great arteries is a rare congenital heart defect characterized by atrioventricular and ventriculoarterial discordance and can be potentially associated with several other concomitant anomalies, such as ventricular septal defect or congenital complete atrioventricular block. Different surgical options are used for treating the condition. Anatomic repair yields the best long-term outcomes; however, it is technically the most challenging. We present a case of a 3-year old female patient who was electively admitted for complete repair after pulmonary artery banding and pacemaker implantation soon after birth. Subsequently, an anatomic repair (double switch) was performed with an uneventful postoperative course and excellent mid-term outcomes.

Abstract 11736: Anatomic Repair of Congenitally Corrected Transposition of the Great Arteries is Associated With Risk of Heart Block and ECMO, but Not Mortality

Introduction: Congenitally corrected transposition of the great arteries (CC-TGA) is characterized by atrioventricular and ventriculoarterial discordance with circulation remaining in series. The double switch operation and atrial switch with Rastelli are anatomic repairs of CC-TGA, achieving a systemic morphologic left ventricle. In contrast, physiologic repair (addressing associated lesions like ventricular septal defects and pulmonary stenosis) or no repair leave the right ventricle in the systemic position. Anatomic repair may confer superior longevity with increased upfront risk. We sought to determine if anatomic repair was associated with increased short-term risk of mortality, heart block, or extracorporeal membrane oxygenation (ECMO). Methods: Single-center retrospective cohort study of CC-TGA patients from 1990-2017. Cox proportional hazard analyses and Fisher’s exact test were performed. Results: Inclusion criteria were met by 54 patients, 21 anatomic repair and 33 physiologic/no repair. Median follow-up was 8.9 years (IQR 1.4-18.0) with no difference between cohorts (p=0.38). The anatomic repair cohort was more likely to have ventricular septal defects, 86% versus 33% (p<0.001) and pulmonary stenosis, 43% versus 15% (p=0.02). Mortality was low and did not differ significantly between cohorts (p=0.07). Probability of developing complete heart block was higher in the anatomic repair cohort (p=0.006), with no significant difference after adjusting for anatomy (HR 3.8, 95% CI 0.7-20.5). The anatomic repair cohort had an increased risk of ECMO (p=0.006). There was no difference in quantity of iterative operations (p=0.64). Conclusions: Anatomic repair of CC-TGA conferred a higher short-term risk of heart block and ECMO compared to the physiologic/no repair cohort, though risk of heart block was linked with anatomy. This upfront risk did not result in higher mortality in the anatomic repair cohort but long-term risk remains unknown.

Criss Cross Heart with Normally Related Great Arteries

The detection of rare congenital cardiac anomalies gives us an opportunity to study such infrequent conditions in greater detail. In this report we describe such an entity that has been reported in the literature extremely rarely. A six weeks old baby boy presented with respiratory distress with features of cardiac failure. The echocardiogram revealed a Criss cross heart with atrioventricular segmental discordance, with a large ventricular septal defect, atrial septal defect and pulmonary arterial hypertension. The ventricles did not have the expected supero-inferior position. There was no ventriculoarterial discordance with no atrioventricular valve straddling. This condition is a rare congenital anomaly. Absence of supero-inferior position of the ventricles, ventriculoarterial discordance and straddling of atrioventricular valves make this case most unusual. Hence such variations need to be considered while entertaining a diagnosis of Criss cross heart in future reports.

Anaesthetic management of a case of congenitally corrected transposition of great arteries for non cardiac surgery: A case report

Congenitally corrected transposition of the great arteries (CCTGA) is a rare form of congenital heart diseases, present with or without associated anomalies. It is a complex congenital heart disease with both atrioventricular and ventriculoarterial discordance. Such patients tend to develop systemic ventricular dysfuction with the stress of surgery. Patients with CCTGA are usually diagnosed at early stages of life due to associated anomalies, but they may even remain asymptomatic till later decades of their life. Literature search revealed very few reported cases of anaesthetic management of such high risk cases for non cardiac surgery. These patients have the tendency to develop cardiac dysrhythmias and left ventricular failure during intraoperative and postoperative period. We report anaesthetic management of a case of a 24 years old male with the congenitally corrected transposition of great arteries(CCTGA) who was operated for fracture left distal radius and ulna and right sided galeazzi fracture.

The choice of palliative arterial switch operation as an alternative for selected cases in a single center: Experience and mid term results.

There are various management options for newborns with single ventricle physiology, ventriculoarterial discordance and subaortic stenosis, classically involving the early pulmonary banding and aortic arch repair, the restricted bulboventriculer foramen enlargement or the Norwood and the Damus-Kaye-Stansel procedures. The aim of this study is to evaluate our preferred technique and comment on the midterm results of our clinical experience with palliative arterial switch operation (pASO) for a certain subset of patients. We hereby retrospectively evaluate the charts of patients who went through pASO, as initial palliation through Fontan pathway, starting from 2014 till today. Ten patients underwent an initial palliative arterial switch procedure. Eight of 10 patients survived the operation and discharged. Seven of 10 patients completed Stage II and 1 patient reached the Fontan completion stage and the other six of ten (6/10) patients are doing well and waiting for the next stage of palliation. There are two mortalities in the series (2/10) and one patient lost to follow-up (1/10). In our opinion, the pASO can be considered as an alternative palliation option for patients with single ventricle physiology, transposition of the great arteries and systemic outflow tract obstruction despite longer cross clamp times compared to other methods, but It not only preserves systolic and diastolic ventricular function, but also provides a superior anatomic arrangement for following stages.

Congenitally Corrected Transposition of the Great Arteries: Conduction Anomalies: A Case Report

Introduction: Congenitally corrected transposition of the great arteries (CCTGA) is a rare heart disease that encompasses an atrioventricular and ventriculoarterial discordance and accounts for less than 1 percent of congenital heart diseases. Objective: To present an atypical case of a man with complex congenital heart disease and conduction anomalies. Case Presentation: This is a case of a 34-year-old patient who came to the hospital with 1 week of dyspnea on exertion and episodes of lipothymia. The patient was referred to our hospital after an electrocardiogram from his primary care with evidence of blocked atrial fibrillation. During the initial evaluation blocked atrial fibrillation was confirmed with a rescue ventricular rate of 38 bpm. A magnetic resonance confirmed the presence of the atrioventricular and ventriculoarterial discordance, the aorta had a left anterior position, perimembranous ventricular septal defect with a right to left shunt, biventricular systolic dysfunction, moderate tricuspid, and mitral regurgitation, interventricular septal intramyocardial and biatrial fibrosis, left atrial dilation, and dilation of the pulmonary artery. After pacemaker placement, the patient has an improvement in his clinical symptoms and quality of life. Conclusions: Cardiac arrhythmias are CCTGA’s leading cause of death, mostly ventricular tachycardia, and atrial fibrillation. Right bundle branch block is a previously unreported and potentially very rare presentation of this disease. This, added to the fact that our patient was diagnosed at an advanced age, but without symptoms of heart failure, makes him an atypical case of CCTGA, with new potential treatment options.

Abstract 13323: Identifying the Culprit Lesion in a Symptomatic Patient With Physiologically Corrected Transposition of the Great Arteries

Introduction: Physiologically corrected transposition of the great arteries [(S,L,L) TGA] is a rare congenital heart disease characterized by atrioventricular and ventriculoarterial discordance. Case Presentation: A 28-year-old man with (S,L,L) TGA, pulmonary valve (PV) stenosis, ventricular septal defect (VSD), and history of Kawasaki disease who presented for a gradual decline in exercise tolerance. Oxygen saturation was 96% at rest and dropped to 86% with ambulation. Hemoglobin was 17.7 g/dl, EKG showed no bradyarrhythmias. On stress test, peak heart rate was 159 beats/minute, and peak VO 2 22.6 ml/kg/min (83%, and 57% of predicted value respectively). Spirometry was normal. Transthoracic echocardiogram revealed biventricular hypertrophy with normal systolic function, a bicuspid PV with severe stenosis (peak and mean gradient of 155 and 90 mmHg respectively), large inlet VSD with bidirectional flow and mild systemic TV regurgitation. Coronary CTA showed no coronary artery aneurysms. Cardiac catheterization suggested hypoxia due to pulmonary-to-systemic shunting across the VSD with Q p /Q s = 0.86 (Figure). Consideration should be given to performing a high-risk surgical repair versus medical management. Conclusions: Natural history, symptoms, and timing of intervention are determined by the associated cardiac anomalies and the progressive dysfunction of the systemic right ventricle (SRV). Anatomic repair to restore the left ventricle as a systemic pump is a very high-risk procedure in adults. Functional repair maintains SRV, repair the VSD, and PV stenosis has a poor late outcome. Medical management ensures iron stores are repleted, provide empirical use of pharmacological heart failure therapy, and referral to heart transplantation when SRV systolic dysfunction ensues. Clinicians need to know the potential complications in both unoperated patients and following various surgical repairs to recommend appropriate treatment options.

Atrioventricular, ventriculoarterial discordance and Ebstein malformation of the tricuspid valve with severe regurgitation resulting in aortic atresia in a neonate.

Aortic atresia is uncommonly associated with atrioventricular and ventriculoarterial discordance. Presence of severe regurgitation of Ebstein malformation of the tricuspid valve in this subset results in reduced aortic blood flow in-utero. We report here a term neonate with this anomaly detected antenatally.

Congenitally corrected transposition of the great arteries

Congenitally corrected transposition of the great arteries (cc-TGA, also known as L-transposition) is a rare condition that represents approximately 0.5% of congenital heart disease. It is characterized by atrioventricular and ventriculoarterial discordance. Patients with cc-TGA are at risk for cardiac arrhythmias due to abnormalities of the conduction system. We present an autopsy case of a 49-year-old man with cc-TGA who died unexpectedly, likely as a result of a fatal arrhythmia. This case illustrates the cardiac pathology characteristic of cc-TGA and describes how to grossly identify inversion of the atrioventricular valves.