Ventricular performance before and after Fontan repair for univentricular atrioventricular connection: angiographic and radionuclide assessment

The Fontan Circulation in Pregnancy: Hemodynamic Challenges and Anesthetic Considerations

Pregnancy in patients with Fontan physiology presents unique challenges due to altered cardiovascular dynamics inherent to both conditions. The Fontan procedure reroutes venous blood directly to the pulmonary arteries, bypassing the heart, and necessitating precise regulation of pulmonary venous resistance and systemic venous pressure to maintain effective cardiac output. The significant cardiovascular adaptations required during pregnancy to meet the metabolic demands of the mother and fetus can overburden the limited preload capacity and venous compliance in Fontan patients, predisposing them to a spectrum of potential complications, including arrhythmias, heart failure, thromboembolism, and obstetric and fetal risks. This review delineates the essential physiological adaptations during pregnancy and the challenges faced by Fontan patients, advocating for a comprehensive care approach involving multidisciplinary collaboration, vigilant monitoring, tailored anesthetic management, and postpartum care. Understanding the complex dynamics between Fontan physiology and pregnancy is crucial for anesthesiologists to develop and execute individualized management strategies to minimize risks and optimize outcomes for this high-risk population.

Exercising with a Single Ventricle: Limitations and Therapies

Treatment for Hypoplastic Left Heart Syndrome (HLHS) and other single ventricle conditions requires a series of surgical interventions for long-term survival, typically culminating in the Fontan procedure. The result is an abnormal circulatory physiology with an absence of a sub-pulmonary ventricle. Exercise capacity in the Fontan circulation is often limited and is due to multiple factors, both central and peripheral. Multiple interventions, both pharmacologic and nonpharmacologic, have been studied to attempt to overcome these inherent limitations. This review will focus on the physiology of the exercising Fontan patient and on the interventions aimed at the enhancement of exercise capacity studied thus far.

Late Fontan Circulatory Failure. What Drives Systemic Venous Congestion and Low Cardiac Output in Adult Fontan Patients?

The Fontan circulation provides definite palliation for children born with a single anatomical or functional ventricle by diverting systemic venous blood directly to the pulmonary arteries, effectively rendering systemic venous return into portal vessels to the lung. Although this restores pulmonary blood flow and avoids the mixture of oxygenated and deoxygenated blood, it also results in elevated systemic venous pressures and low cardiac output. These are the two hallmarks of any Fontan circulation and the cause of Fontan circulatory failure later in life. We highlight the determinants of systemic venous return, its changed relationship with the pulmonary circulation, how it affects preload, and the changed role of the heart (myocardium, valves, and heart rate). By critically evaluating the components of the Fontan circulation, we hope to give some clues in how to optimize the Fontan circulation and avenues for future research.

Identification of high-risk Fontan candidates by intraoperative pulmonary flow study

BACKGROUND

Pre-Fontan risk stratification is still less than optimal. We aimed to evaluate the effectiveness of intraoperative pulmonary flow study (IOFS), in combination with conventional preoperative evaluation, in the identification of high-risk candidates for the Fontan operation.

METHOD

Data from 37 patients (age: 38.1 ± 4.9 months) who underwent the Fontan operation with IOFS were retrospectively reviewed. After anastomosing the Gore-Tex vascular graft to the confluent pulmonary artery, IOFS was performed through the graft at various cardiac indices (CI) (1-4 L/min/m²) generated from a roller pump. Mean pulmonary artery pressure (mPAP) and left atrial pressure (LAP) were recorded. The patients were divided into two groups: those who required Fontan circuit fenestration (group Ff) and those who did not (group Fn).

RESULTS

Eleven patients (29.7%) required fenestration, intraoperatively (n = 4) and postoperatively (n = 7), due to hemodynamic instability. Heterotaxy syndrome (P = 0.005) and atrioventricular valvar regurgitation (P = 0.04) were more frequent, and ventricle posterior wall thickness (VPWT) was higher (P = 0.024) in group Ff. On IOFS, the increase in mPAP by CI was sharper in group Ff than in group Fn (P < 0.001) owing to an increase in LAP. On multivariable analysis, mPAP at a CI of 3.0 L/min/m² from IOFS was the only predictor of fenestration and correlated with preoperative VPWT (R = 0.543, P = 0.001).

CONCLUSIONS

IOFS may be helpful to identify high-risk Fontan candidates, and high mPAP at CI of 3.0 L/min/m² on IOFS is a significant predictor of the requirement for fenestration. VPWT is an important preoperative risk factor which correlates with the IOFS results.

Patient-specific assessment of cardiovascular function by combination of clinical data and computational model with applications to patients undergoing Fontan operation

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.

Computational modeling of pathophysiologic responses to exercise in Fontan patients

Reduced exercise capacity is nearly universal among Fontan patients. Although many factors have emerged as possible contributors, the degree to which each impacts the overall hemodynamics is largely unknown. Computational modeling provides a means to test hypotheses of causes of exercise intolerance via precisely controlled virtual experiments and measurements. We quantified the physiological impacts of commonly encountered, clinically relevant dysfunctions introduced to the exercising Fontan system via a previously developed lumped-parameter model of Fontan exercise. Elevated pulmonary arterial pressure was observed in all cases of dysfunction, correlated with lowered cardiac output (CO), and often mediated by elevated atrial pressure. Pulmonary vascular resistance was not the most significant factor affecting exercise performance as measured by CO. In the absence of other dysfunctions, atrioventricular valve insufficiency alone had significant physiological impact, especially under exercise demands. The impact of isolated dysfunctions can be linearly summed to approximate the combined impact of several dysfunctions occurring in the same system. A single dominant cause of exercise intolerance was not identified, though several hypothesized dysfunctions each led to variable decreases in performance. Computational predictions of performance improvement associated with various interventions should be weighed against procedural risks and potential complications, contributing to improvements in routine patient management protocol.

Sildenafil improves exercise hemodynamics in Fontan patients

BACKGROUND

Patients with Fontan circulation have reduced exercise capacity. The absence of a presystemic pump may limit flow through the pulmonary circulation, restricting ventricular filling and cardiac output. We evaluated exercise hemodynamics and the effect of sildenafil on exercise hemodynamics in Fontan patients.

METHODS AND RESULTS

Ten Fontan patients (6 men, 20±4 years) underwent cardiac magnetic resonance imaging at rest and during supine bicycle exercise before and after sildenafil. Systemic ventricular volumes were obtained at rest and during low- (34±15 W), moderate- (69±29 W), and high-intensity (97±36 W) exercise using an ungated, free-breathing cardiac magnetic resonance sequence and analyzed correcting for cardiac phase and respiratory translation. Radial and pulmonary artery pressures and cGMP were measured. Before sildenafil, cardiac index increased throughout exercise (4.0±0.9, 5.9±1.1, 7.0±1.6, 7.4±1.7 L/(min·m(2)); P<0.0001) with 106±49% increase in heart rate. Stroke volume index (P=0.015) and end-diastolic volume index (P=0.001) decreased during exercise. End-systolic volume index remained unchanged (P=0.8). Total pulmonary resistance index (P=0.005) increased, whereas systemic vascular resistance index decreased during exercise (P<0.0001). Sildenafil increased cardiac index (P<0.0001) and stroke volume index (P=0.003), especially at high-intensity exercise (interaction P=0.004 and P=0.003, respectively). Systemic vascular resistance index was reduced (P<0.0001-interaction P=0.1), whereas total pulmonary resistance index was reduced at rest and reduced further during exercise (P=0.008-interaction P=0.029). cGMP remained unchanged before sildenafil (P=0.9), whereas it increased significantly after sildenafil (P=0.019).

CONCLUSIONS

In Fontan patients, sildenafil improved cardiac index during exercise with a decrease in total pulmonary resistance index and an increase in stroke volume index. This implies that pulmonary vasculature represents a physiological limitation, which can be attenuated by sildenafil, the clinical significance of which warrants further study.

Hemodynamic phenotype of the failing Fontan in an adult population

Fontan failure can occur even with normal systolic ventricular function and often in the context of significant liver disease. We hypothesized that Fontan failure is hemodynamically distinct from traditional heart failure and characterized by low systemic vascular resistance (SVR) index and preserved cardiac index. Twenty-seven symptomatic adult Fontan (SAF) patients who underwent catheterization from 2001 to 2011 constituted our study group. Fifty-four predominantly asymptomatic pediatric Fontan (PF) patients who underwent catheterization during the same period were randomly selected to perform a control:case cohort analysis. Clinical comparisons were made between the 2 groups. The adults were more symptomatic than the PF cohort (New York Heart Association classes I and II or III and IV: 48% or 52% [SAF] vs 94% or 6% [PF], respectively, p <0.01). SAF versus PF mean catheterization findings were central venous pressure 18 ± 6 versus 14 ± 3 mm Hg (p <0.01), SVR index 1,680 ± 368 versus 1,960 ± 550 dyn s/cm(5)/m(2) (p = 0.02), and cardiac index 2.7 ± 0.8 versus 2.8 ± 0.7 L/min/m(2) (p = 0.25). By imaging, the SAF cohort demonstrated a greater incidence of abnormal liver texture changes (96% vs 75%, p = 0.04) and nodularity (77% vs 42%, p = 0.02). In conclusion, adult patients with failing Fontan circulation had a lower SVR index and similar cardiac index compared with the pediatric cohort. Liver disease in the adults was more advanced. Our data suggest that Fontan failure is a distinct circulatory derangement with hemodynamic features similar to portal hypertension, albeit with limited ability to augment cardiac output.

Long-term results of total cavopulmonary connection with low ejection fraction

PURPOSE

The aim of this study was to investigate the surgical outcomes and change in cardiac performance after total cavopulmonary connection (TCPC) in patients with reduced ventricular ejection preoperatively.

METHODS

Among the 195 patients undergoing TCPC between 1990 and 2001 were 52 who had a preoperative ejection fraction of ≤50% (30%-50%, mean 44%). A dominant ventricle was of the morphologically right type in 81% of patients.

RESULTS

A total of 9 of the 52 patients died early. Two patients died in the intermediate term. Postoperative exercise testing showed maximum oxygen uptake of 26.4 ± 5.8 ml/kg/min (anaerobic threshold 18.3 ± 3.2 ml/kg/ min). The cardiac index was 3.1 ± 0.9 l/min/m(2) at 1 year after TCPC, with no fundamental change at 5 years (3.1 ± 0.8 l/min/m(2)). The end-diastolic volume of the dominant ventricle was 130% ± 74% of the anticipated normal value at 1 year and 93% ± 27% at 5 years after TCPC, with ejection fractions of 48% ± 13% and 49% ± 9%, respectively. When these parameters were plotted for the individual patients, the ejection fraction increased during the first postoperative year, with the percent end-diastolic volume decreasing in 31 survivors; the trend appeared atypical in the remaining 12 survivors. Even in these patients, however, the parameters eventually changed toward favorable circumstances 5 years after TCPC.

CONCLUSION

Change in ventricular function was not necessarily pessimistic after TCPC in patients with reduced ventricular contraction preoperatively.

Relation of size of secondary ventricles to exercise performance in children after fontan operation

The effects of the nondominant or secondary ventricle on the Fontan circulation are not known. The present study used cardiac magnetic resonance imaging to investigate the relations between secondary ventricular size and global cardiac performance. The Fontan cross-sectional study collected data from 7 centers participating in the Pediatric Heart Network. Subjects with complete cardiac magnetic resonance imaging data and an identifiable secondary ventricle were included in the analysis. Relationships between body surface area-adjusted parameters of the secondary ventricle (mass, end-diastolic volume, mass/volume ratio, and stroke volume) and the following measures were assessed. These measures included the percentage of predicted peak oxygen consumption and oxygen consumption at the ventilatory anaerobic threshold, ejection fraction of the main ventricular chamber, echocardiographic diastolic function grade, serum B-type natriuretic peptide, primary ventricular end-diastolic pressure, and parent-reported physical functioning summary score on the Child Health Questionnaire. Of the 546 enrolled subjects, 123 (age 12.1 ± 3.3 years, 56% male) had undergone cardiac magnetic resonance imaging, and 38 had achieved maximal aerobic capacity. A larger secondary ventricular end-diastolic volume, lower mass/volume ratio, and greater secondary/total ventricular stroke volume ratio were associated with a greater exercise capacity. No significant relationships were found between the measures of the secondary ventricle and the other outcomes. In conclusion, in children after the Fontan operation, a larger and less hypertrophied secondary ventricle with a greater contribution to stroke volume was associated with a better exercise capacity.

What Limits Cardiac Performance during Exercise in Normal Subjects and in Healthy Fontan Patients?

Exercise is an important determinant of health but is significantly reduced in the patient with a univentricular circulation. Normal exercise physiology mandates an increase in pulmonary artery pressures which places an increased work demand on the right ventricle (RV). In a biventricular circulation with pathological increases in pulmonary vascular resistance and/or reductions in RV function, exercise-induced augmentation of cardiac output is limited. Left ventricular preload reserve is dependent upon flow through the pulmonary circulation and this requires adequate RV performance. In the Fontan patient, the reasons for exercise intolerance are complex. In those patients with myocardial dysfunction or other pathologies of the circulatory components, it is likely that these abnormalities serve as a limitation to cardiac performance during exercise. However, in the healthy Fontan patient, it may be the absence of a sub-pulmonary pump which limits normal increases in pulmonary pressures, trans-pulmonary flow requirements and cardiac output. If so, performance will be exquisitely dependent on pulmonary vascular resistance. This provides a potential explanation as to why pulmonary vasodilators may improve exercise tolerance. As has recently been demonstrated, these agents may offer an important new treatment strategy which directly addresses the physiological limitations in the Fontan patient.

The Fontan circulation: who controls cardiac output?

In a Fontan circuit the mechanisms involved in control of cardiac output at rest and during exercise differ significantly from normal. The classical model presumes an unlimited preload which is not available in the Fontan circuit. This review critically analyses the role of contractility, heart rate, and afterload and highlights the importance of pulmonary vascular resistance (PVR) in determining adequate preload and, therefore, cardiac output in these patients. A conceptual model of the determinants of cardiac output in Fontan patients is presented.

Peripheral arterial function in infants and young children with one-ventricle physiology and hypoxemia

Patients with 1-ventricle (1V) physiology may be at risk for peripheral arterial dysfunction at a young age. To determine whether infants and young children with 1V physiology and hypoxemia have peripheral arterial dysfunction before undergoing the Fontan operation, we measured (1) flow-mediated vasodilation (FMD) in the brachial artery, (2) serum levels of vasoactive mediators endothelin-1 (ET-1) and metabolites of nitric oxide, and (3) arterial stiffness with pulse-wave velocity (PWV) in the aorta. Eighteen patients with 1V physiology before the Fontan procedure and hypoxemia and 19 patients with normoxemia and 2-ventricle (2V) physiology were studied. Measurements were collected during cardiac catheterization. FMD in the brachial artery was the diameter gain after 4.5 minutes of forearm occlusion measured with high-resolution ultrasound and edge-detection software. Nitric oxide and ET-1 levels were measured in venous blood. PWV between the left carotid and femoral arteries was measured using pulse Doppler ultrasound. FMD was lower (2.4 +/- 3.7% vs 11.3 +/- 6%, p <0.0005) and ET-1 levels were higher (35.5 +/- 11.3% vs 24.1 +/- 9.7%, p = 0.003) in subjects with 1V physiology versus those with 2V physiology, respectively. There were no differences in nitric oxide levels or PWV. In conclusion, infants and young children with 1V physiology and hypoxemia have blunted FMD and higher ET-1 levels before undergoing the Fontan operation compared with normoxemic subjects with 2V physiology. A further understanding of pathophysiologic mechanisms underlying peripheral arterial dysfunction, including the roles of hypoxemia, low cardiac index, and ET-1, may lead to targeted therapies and improve the long-term survival of patients with 1V physiology.

Characteristics of Doppler myocardial echocardiography in patients with tricuspid atresia after total cavopulmonary connection with preserved systolic ventricular function

BACKGROUND

Doppler myocardial echocardiography (DME) may be an excellent additional means of assessing determinants of systolic and diastolic ventricular function in patients with tricuspid atresia (TA) after total cavopulmonary connection (TCPC).

METHODS AND RESULTS

Thirty-three patients with TA and normal systolic shortening/ejection fraction (M-mode) after TCPC were studied by DME at a median age of 7.6 years (range 1.5-17 years). These results were compared to 16 age matched normal controls. Median time under a cavopulmonary shunt was 5.2 years (range 0.6-13.3 years). Isovolumic acceleration and isovolumic velocity did not differ significantly. All other systolic (S-wave acceleration-velocity and S-wave duration) and diastolic DME indices (E-deceleration-velocity, A-velocity and E/A ratio) were significantly lower in TCPC patients in comparison to normals (p<0.0001). Furthermore, isovolumic relaxation time (IRT) was significantly prolonged in the patient group (p<0.0001). Even though there was a significant correlation between the time of volume unloading and left ventricular end-diastolic diameter, exclusion of all patients with short period of volume unloading and relatively large systemic ventricles did not alter the results.

CONCLUSIONS

Patients with TA after TCPC and normal shortening and ejection fraction have normal isovolumic acceleration. Load dependent DME indices of systolic and diastolic function, however, were significantly reduced. These findings suggest that the described DME indices mirror the "normal" hemodynamics after TCPC in patients with TA. It needs to be assessed, whether this is an index of adverse prognosis in long-term surveillance of these patients.

Preserved regional atrial contractile function following extra-atrial rather than intra-atrial type Fontan operation

OBJECTIVE

To determine the univentricular and atrial function in patients following Fontan operation using tissue Doppler echocardiography (TDE).

SETTING

Hospital-based outpatient clinic and inpatient unit.

PATIENTS

Thirty-six patients (mean age 13 ys [2-34 ys]) after Fontan procedure and 30 healthy individuals matched for age and heart rate.

MAIN OUTCOME MEASURES

Pulsed wave Doppler derived Tei index was determined for global univentricular function. Tissue-Doppler derived strain rate and strain were measured for regional ventricular function. Different planimetric approaches were used to evaluate the global atrial function. Strain rate was measured for regional atrial contractile function.

RESULTS

The Tei index, reflecting global univentricular function, was significantly higher in Fontan patients than in the control group (p<0.001). The regional ventricular contractile function, which was determined by TDE derived strain and strain rate, was significantly lower in Fontan patients than in healthy controls (p<0.001). The global atrial function evaluated planimetrically, and the regional atrial function assessed using the TDE strain rate, were significantly lower in Fontan patients than in normal controls (p<0.001, p<0.001, respectively). A comparison of different types of Fontan operations with extra-atrial or intra-atrial baffle showed a better regional left atrial wall strain rate in patients with extra-atrial baffle than with intra-atrial baffle.

CONCLUSION

Patients who have undergone the Fontan procedure may present with altered ventricular and atrial performance independent of whether the extra-atrial or intraatrial type Fontan operation was performed. However, the regional atrial contractile function seems to be better preserved following the extra-atrial type Fontan operation.

Specific issues after extracardiac fontan operation: ventricular function, growth potential, arrhythmia, and thromboembolism

BACKGROUND

The purpose of this study was to define the prevalence of specific sequelae after extracardiac Fontan operation.

METHODS

Sixty-five consecutive patients undergoing extracardiac Fontan operation were studied for mortality, Fontan failure, systemic ventricular function, supraventricular arrhythmias, thromboembolism, and growth potential. Age was 3 to 31 years (mean +/- standard deviation, 9.4 +/- 1.8; median, 7 years). The conduits were constructed of polytetrafluoroethylene (n = 50), and "viable" in situ pericardium (n = 15). The patients underwent serial echocardiogram, dynamic radionuclide studies, and cardiac catheterization.

RESULTS

Operative mortality was 3%, and the incidence of conduit thrombosis was 4.6%. There was paradoxic filling of the right lung after femoral injection of the radiotracer in all cases of conduit obstruction. Perioperative and late postoperative supraventricular arrhythmias were observed in 9.2% and 4.7% of patients, respectively. Risk factors for supraventricular arrhythmias included systemic ventricular dysfunction (p = 0.000), heterotaxy syndrome (p = 0.008), systemic venous anomalies (p = 0.015), and previous bidirectional Glenn operation (p = 0.017). At a mean follow-up of 77 +/- 2 months (range, 8 to 79 months), there were no late deaths (actuarial survival at 79 months, 96.9% +/- 0.02%). Serial echocardiograms demonstrated evidence of growth of the viable tunnels. Postoperatively, there was transient depression of ejection fraction in all patients (p = 0.000).

CONCLUSIONS

Supraventricular arrhythmias after extracardiac Fontan are more common in patients with heterotaxy syndrome, bilateral superior venae cavae, systemic ventricular dysfunction, and those undergoing completion Fontan operation. The viable tunnel may emerge as an optimal alternative by virtue of reduction of supraventricular arrhythmias, elimination of the need for anticoagulation, and addressing the issue of growth potential in selected patients.

Cardiac Rest and Reserve Function in Patients With Fontan Circulation

OBJECTIVES

In the present study, we systematically tested cardiac rest and reserve function in patients with Fontan physiology to check for inherent limitations of this circulation.

BACKGROUND

Details of the mechanisms of cardiac performance that could account for adverse outcome after Fontan surgery are not well understood.

METHODS

The subjects were 17 Fontan patients with good functional status (Fontan group) and 20 patients with normal two-ventricle circulation (control group). We examined baseline ventricular contractility, diastolic function, and loading factors, and examined changes in those parameters in response to increased heart rate (HR) due to atrial pacing and in response to beta-adrenergic stimulation, using ventricular pressure-area relationships during preload reduction.

RESULTS

At baseline, the Fontan patients exhibited minimal abnormality of cardiac properties, but the significant increase in afterload resulted in decreased cardiac index. In addition, Fontan circulation was associated with limited inotropic response and worsening of diastolic filling with increased HR, leading to decreased systolic pressure and elevation of central venous pressure at higher HRs (p < 0.05 vs. control). Furthermore, beta-adrenergic reserve was markedly decreased in the Fontan group, compared with controls, owing to limited preload reserve rather than limited contractile reserve.

CONCLUSIONS

Because normal ventricular-vascular interaction and augmentation of cardiac performance during increased HR and adrenergic stimulation are important for maintaining cardiac output and exercise capacity, the present results may have important implications for the mechanisms underlying adverse outcome after Fontan surgery. Thus, improvement of long-term prognosis of patients after Fontan surgery requires the development of medical interventions that can overcome such limitations inherent in Fontan circulation.

Applying standard therapies to new targets: the use of ACE inhibitors and B-blockers for heart failure in adults with congenital heart disease

Increasingly, patients and clinicians are being confronted with congestive heart failure (CHF) as a late complication of congenital heart disease. However, medical management of heart failure in this patient group represents a challenge because of complex hemodynamics and a lack of evidence from large randomized controlled trials to guide therapy. This article will review the evidence of the use angiotensin converting enzyme inhibitors (ACEIs) and beta-blockers (BBs) in left heart failure, discuss the mechanisms of heart failure as they pertain to congenital heart disease and review the limited literature of the use of neurohormonal antagonists in congenital heart disease. Some recommendations for use of angiotensin converting enzyme inhibitors and beta-blockers in heart failure due various congenital heart lesions are offered. Well-designed clinical trials are urgently needed to extend the impressive reductions in morbidity and mortality achieved with neurohormonal blockade in left ventricular (LV) heart failure to adults with congenital heart disease.

Postoperative assessment of the univentricular repair by dynamic radionuclide studies

BACKGROUND

The purpose of this investigation was to determine the role of radionuclide studies in evaluating postoperative Fontan hemodynamics and to quantify its diagnostic accuracy.

METHODS

One hundred five patients (105), aged 11 months to 35 years old, who had undergone univentricular repair, underwent first-pass and multigated acquisition scan 1 month to 10 years after univentricular repair. Forty-five patients with evidence of Fontan failure underwent radionuclide studies using Technetium-99 m as well as cardiac catheterization (group 1). The remaining sixty randomly selected patients with excellent functional status received radionuclide studies alone (group 2). The receiver operating characteristic curve analysis was done to quantify the diagnostic accuracy of the first-pass study.

RESULTS

There was paradoxical filling of the right lung after femoral injection in all cases of tunnel or conduit obstruction. A first-pass transit time of 16 to 25 seconds (mean +/- standard deviation [SD] = 18.82 +/- 2.69) was always associated with Fontan failure and high right atrial pressure (range = 20 to 24 mm Hg, mean +/- SD = 22.02 +/- 1.58). A first-pass transit time of 16 seconds was associated with a sensitivity of 100% and a specificity of 93.33%. The predictive accuracy of a positive or negative result was 91.8% and 100% respectively. The area measured under the receiver operating characteristic curve indicates that 99.41% (SE +/- 0.0035) of the time, the value of first-pass time is higher for the Fontan failure group (group 1) compared to the normal group (group 2; p = 0.000).

CONCLUSIONS

Our data indicate that Fontan circuit can be reliably evaluated for both anatomic and functional flaws by radionuclide studies; radionuclide first-pass time may be used to predict the chances of Fontan failure postoperatively as well as its presence; and in the presence of atrial fibrillation with fast ventricular rate, analysis using first-pass radionuclide may be impossible and gated equilibrium radionuclide angiocardiography may be the preferred method. Inspection of the systemic ventricular time-activity curve is of crucial importance in this regard.

Ventricular mechanics in the bidirectional glenn procedure and total cavopulmonary connection

BACKGROUND

The time course of ventricular efficiency in Fontan candidates who underwent both the bidirectional Glenn procedure (BDG) and total cavopulmonary connection (TCPC) were analyzed in this study. We previously reported that volume-load reduction of BDG preceding TCPC allowed for any afterload mismatch to be corrected, thereby improving ventricular efficiency after staged TCPC.

METHODS

We measured percent normal systemic ventricular end-diastolic volume (%N-EDV), contractility (end-systolic elastance [Ees]), afterload (effective arterial elastance [Ea]), and ventricular efficiency (ventriculoarterial coupling [Ea/Ees]) based on cardiac catheterization data before and after both BDG and staged TCPC in 30 patients. Ees and Ea were approximated as follows: Ees = mean arterial pressure/minimal ventricular volume, and Ea = maximal ventricular pressure/(maximal ventricular volume - minimal ventricular volume), and Ea/Ees was then calculated. Ventricular volume was divided by body surface area.

RESULTS

The %N-EDV decreased both after BDG and after staged TCPC, thus resulting in an improvement of Ees. Although Ea increased both after BDG and after staged TCPC, Ea decreased during the interval between BDG and staged TCPC. These changes resulted in an improvement in Ea/Ees during the interval period and after staged TCPC, although Ea/Ees worsened after BDG.

CONCLUSIONS

Correction of afterload mismatch during the interval period between BDG and staged TCPC is considered to be one of the most important factors for obtaining excellent clinical results when selecting a staged strategy to treat high-risk Fontan candidates.

Ventricular energetics after the Fontan operation: contractility-afterload mismatch

OBJECTIVE

Fontan-type operations offer the opportunity to create pulmonary and systemic circulation in series with a single pumping chamber. The effectiveness of such a circulatory pattern determines resting and exercise hemodynamics in these patients. The present study investigated cardiac performance after the Fontan operation by using ventricular-vascular coupling framework analysis.

METHODS

In 12 anesthetized open-chest dogs, Fontan circulation was established by using a cavopulmonary anastomosis. Left ventricular hemodynamic variables were measured by using a combined pressure-volume-conductance catheter. Additionally, aortic flow and pressure were recorded continuously. Ventricular contractility was quantified by using the load-independent slope of the end-systolic pressure-volume relationship. Arterial system properties were quantified by using the end-systolic pressure/stroke volume ratio. The coupling between the left ventricle and arterial system was expressed by using the ratio of end-systolic pressure/stroke volume to slope of the end-systolic pressure-volume relationship. Additionally, external stroke work, total mechanical energy and mechanical efficiency (Mechanical efficiency = Stroke work/Total mechanical energy) were calculated. Impedance spectra were determined by means of Fourier analysis.

RESULTS

During Fontan circulation, the slope of the end-systolic pressure-volume relationship (5.3 +/- 0.6 vs 7.5 +/- 0.6 mm Hg/mL, P <.05) decreased, and the end-systolic pressure-stroke volume relationship (4.2 +/- 0.7 vs 3.3 +/- 0.5 mm Hg/mL, P =.23) increased with parallel increased characteristic impedance. Furthermore, the end-systolic pressure-stroke volume/slope of the end-systolic pressure-volume relationship ratio increased significantly (0.76 +/- 0.04 vs 0.42 +/- 0.03, P <.005). Simultaneously, stroke work (1846 +/- 146 vs 1389 +/- 60 mm Hg/mL, P <.05) and mechanical efficiency (0.82 +/- 0.09 vs 0.56 +/- 0.05, P <.05) were significantly reduced.

CONCLUSIONS

Fontan circulation leads to contractility-afterload mismatch by means of increased impedance caused by additional connection of the pulmonary vascular bed to the systemic vasculature and by means of deterioration of myocardial contractility. The increased ventriculoarterial coupling ratio and reduced mechanical efficiency predict limited cardiac functional reserve after the Fontan operation.

Fontan conversion to total cavopulmonary connection and arrhythmia ablation: clinical and functional results

OBJECTIVES

To assess the early results of conversion from atriopulmonary to total cavopulmonary connection in patients with failing Fontan operation.

DESIGN

Early clinical and instrumental evaluation of patients undergoing conversion from atriopulmonary to total cavopulmonary connection from April 1999 to November 2000.

SETTING

Tertiary referral centre for congenital heart disease.

PATIENTS

11 Fontan patients (mean (SD) age 20.9 (6.7) years) with refractory arrhythmias or ventricular dysfunction.

INTERVENTIONS

Total cavopulmonary connection, intraoperative ablation, and AAIR pacemaker implantation.

MAIN OUTCOME MEASURES

Holter monitoring, transoesophageal atrial stimulation, ergometric test, and myocardial scintigraphy at a mean (SD) follow up of 16.8 (5.6) months.

RESULTS

One early postoperative death occurred. During follow up three patients had relapse of atrial tachycardia, controlled by medical treatment, and two were pacemaker dependent. Transoesophageal stimulation did not induce atrial tachycardia in any patient. Ergometric test showed a diminished exercise tolerance in all but one patient. Mean minute ventilation and maximum oxygen consumption were 62% and 40% of their respective predicted values. Myocardial scintigraphy showed reversal of rest or exercise dysfunction in five patients and improved systemic ventricular function in seven. Mean basal ejection fraction increased from 39.4% (95% confidence interval (CI) 32% to 46%) to 46.5% (95% CI 41.7% to 51.2%) and ejection fraction on effort from 42.3% (95% CI 33.9% to 50.7%) to 50.2% (95% CI 44.5% to 55.9%).

CONCLUSIONS

Our data show that total cavopulmonary connection associated with intraoperative ablation and pacemaker implantation allows for better control of arrhythmias and improves ventricular function in the majority of patients with failing Fontan.

Ventricular afterload and ventricular work in fontan circulation: comparison with normal two-ventricle circulation and single-ventricle circulation with blalock-taussig shunts

BACKGROUND

Recent studies have indicated that there are inherent limitations associated with Fontan physiology. However, there have been no quantitative analyses of the effects of right heart bypass on ventricular afterload, hydraulic power, and resultant overall hemodynamics. Methods and Results- During routine cardiac catheterization, aortic impedance and ventricular hydraulic power were determined, both at rest and under increased ventricular work induced by dobutamine, in 17 patients with Fontan circulation, 15 patients with a single ventricle whose pulmonary circulation was maintained only by Blalock-Taussig shunts, and 13 patients who had normal 2-ventricle circulation. Both vascular resistance (nonpulsatile load on the ventricle) and pulsatile components of ventricular afterload (represented by low-frequency impedance) were significantly higher in the Fontan group than in the other groups (P<0.01), and this was associated with decreased cardiac output in the Fontan patients. In addition, hydraulic power cost per unit forward flow was 40% lower in the 2-ventricle circulation than in the single-ventricle circulation, suggesting lower ventricular efficiency in single-ventricle circulation attributable to the lack of a pulmonary ventricle. Furthermore, in the Fontan group, beta-adrenergic reserve was markedly decreased because of a limited preload reserve.

CONCLUSIONS

Fontan physiology is associated with disadvantageous ventricular power and afterload profiles and has limited ventricular reserve capacity. Thus, to improve the long-term prognosis of patients after Fontan surgery, future research should be conducted into medical interventions that can overcome these limitations inherent in Fontan circulation.

Theoretical analysis of rest and exercise hemodynamics in patients with total cavopulmonary connection

The objective of this study was to determine the impact of a total cavopulmonary connection on the main hemodynamic quantities, both at rest and during exercise, when compared with normal biventricular circulation. The analysis was performed by means of a mathematical model of the cardiovascular system. The model incorporates the main parameters of systemic and pulmonary circulation, the pulsating heart, and the action of arterial and cardiopulmonary baroreflex mechanisms. Furthermore, the effect of changes in intrathoracic pressure on venous return is also incorporated. Finally, the response to moderate dynamic exercise is simulated, including the effect of a central command, local metabolic vasodilation, and the "muscle pump" mechanism. Simulations of resting conditions indicate that the action of baroreflex regulatory mechanisms alone can only partially compensate for the absence of the right heart. Cardiac output and mean systemic arterial pressure at rest show a large decrease compared with the normal subject. More acceptable hemodynamic quantity values are obtained by combining the action of regulatory mechanisms with a chronic change in parameters affecting mean filling pressure. With such changes assumed, simulations of the response to moderate exercise show that univentricular circulation exhibits a poor capacity to increase cardiac output and to sustain aerobic metabolism, especially when the oxygen consumption rate is increased above 1.2-1.3 l/min. The model ascribes the poor response to exercise in these patients to the incapacity to sustain venous return caused by the high resistance to venous return and/or to exhaustion of volume compensation reserve.

Systolic and diastolic performance late after the Fontan procedure for a single ventricle and comparison of those undergoing operation at <12 months of age and at >12 months of age

To evaluate whether surgical history can influence systolic and diastolic properties of a functional single left ventricle after Fontan operation, we echocardiographically investigated 31 patients (mean age 93.7 months; range 21 to 276); 21 patients were >12 months of age (group A) and 10 were <12 months of age (group B) at the time of the Fontan and/or cavopulmonary procedure. In group A we found persistent abnormalities of left ventricular mass index (95.9 vs 64.1 g/m(2), p <0.05) at long-term follow-up, whereas group B had normal left ventricular mass (61.9 vs 64.1 g/m2, p = NS). In contrast, a diastolic pattern characterized by augmented late diastolic filling was present in both patient groups regardless of age at operation and length of follow-up (E/A in group A 1.3 +/- 0.4, E/A in group B 1.6 +/- 1.5, E/A in controls 1.7 +/- 0.6; A vs B, p = NS; A vs controls, p <0.05). We concluded that patients with a single left ventricle who undergo an unloading procedure performed within the first year of life have complete normalization of left ventricular mass, although a diastolic filling pattern suggestive of augmented compliance persists, regardless of the age at operation.

Bidirectional Glenn procedure improves the mechanical efficiency of a total cavopulmonary connection in high-risk fontan candidates

BACKGROUND

A total cavopulmonary connection (TCPC) is a widely performed surgical procedure for Fontan candidates. High-risk candidates who have undergone the bidirectional Glenn procedure (BDG) before TCPC have shown good results. The exact mechanism of this procedure, however, is still poorly understood. We hypothesized that a volume reduction with BDG improved ventricular contractility, thereby optimizing mechanical efficiency after TCPC.

METHODS AND RESULTS

We measured percent normal systemic ventricular end-diastolic volume (%N-EDV), contractility (end-systolic elastance; E(es)), afterload (effective arterial elastance; E(a)), and mechanical efficiency (ventriculoarterial coupling; E(a)/E(es)) on the basis of the cardiac catheterization data before and after TCPC. Eighteen patients who underwent staged TCPC after BDG (staged group) were compared with 29 patients who underwent primary TCPC (primary group). E(es) and E(a) were approximated as follows: E(es)=mean arterial pressure/minimal ventricular volume, and E(a)=maximal ventricular pressure/(maximal ventricular volume-minimal ventricular volume), and E(a)/E(es) was then calculated. The ventricular volume was normalized with the body surface area. A canine experimental model with conductance catheter was used to validate the accuracy of this approximation of E(es) and E(a). %N-EDV decreased after TCPC in both groups. In the staged group, a smaller ventricular volume resulted in better contractility (E(es)). Although afterload (E(a)) increased in both groups, the increment of E(a) was smaller in the staged group. These changes resulted in an improvement of E(a)/E(es) in the staged group, whereas E(a)/E(es) increased in the primary group.

CONCLUSIONS

The volume reduction of BDG preceding TCPC allows for any afterload mismatch to be corrected, thereby improving ventricular energetics after TCPC.

Ventricular energetics in Fontan circulation: evaluation with a theoretical model

BACKGROUND

Both pulmonary and systemic circulation must be maintained by a single pump in Fontan circulation. This unique property of Fontan circulation may be related to decreased exercise tolerance or increased instantaneous postoperative mortality rate, often observed in patients with this circulation. To better understand Fontan physiology, the present study theoretically investigated cardiac performance of Fontan circulation by using ventricular-vascular coupling framework analysis.

METHODS

End-systolic volume elastance (Ees), as a chamber contractile property, and effective arterial elastance (Ea), a lumped measure of ventricular afterload, were estimated both in normal left ventricular systemic circulation and in Fontan circulation.

RESULTS

End-systolic volume elastance was decreased and Ea was increased in Fontan circulation. Both ventricular external stroke work (SW) and mechanical efficiency (EFF) under Fontan circulation were lower compared with those under normal circulation. Furthermore, the Ees-Ea relationship in Fontan circulation predicted limited cardiac reserve in terms of SW and EFF. Such cardiac performance in Fontan circulation stemmed from increased impedance due to the additional connection of the pulmonary vascular bed to the systemic vasculature and from the lack of a compensatory increase in contractility for increased afterload.

CONCLUSIONS

Thus, it was inferred that Fontan circulation had intrinsic disadvantages and this may explain, in part, abnormal functional status and decline in survival following this procedure.

Angiotensin-converting enzyme inhibitor therapy for ventricular dysfunction in infants, children and adolescents: a review

Angiotensin-converting enzyme (ACE) inhibitors have become an important part of the pharmacologic armamentarium in the battle against treatment of ventricular dysfunction. There have been a number of large controlled, randomized trials in adults with both asymptomatic and symptomatic ventricular dysfunction, which confirm the safety and efficacy of this category of drugs for the treatment of this potentially lethal condition. ACE inhibitors may be used to treat infants, children and adolescents with asymptomatic and symptomatic ventricular dysfunction as well. The data supporting their use in children is less complete than that concerning the treatment of adults. We review here the various causes of ventricular dysfunction and congestive heart failure (CHF) in infants, children, and adolescents; the data available regarding treatment of these conditions with ACE inhibitors, and the safety and efficacy of these drugs for the various conditions. The pharmacokinetics and proposed mechanisms of action of ACE inhibitors in children are reviewed, as are speculated long-term results of ACE inhibitor use in cohorts of growing children. Recommendations are made for future studies.

New insight into left ventricular function in tricuspid atresia after total cavopulmonary connection: a three-dimensional echocardiographic study

BACKGROUND

In patients with tricuspid atresia palliated by construction of a total cavopulmonary connection, both pulmonary and systemic circulations depend on the performance of the dominant left ventricle. When estimating the volume of such ventricles using cross-sectional echocardiography, it is necessary to make assumptions concerning the geometry of the ventricular shape. This is avoided by three-dimensional echocardiography, which provides direct volumetric data. Our purpose was to apply this new method to quantify left ventricular volumes and function in patients with tricuspid atresia after construction of a total cavopulmonary connection.

METHODS

We studied ten patients (median age: 8 years) with tricuspid atresia who had undergone a total cavopulmonary connection, comparing them with 10 normal children matched for age, sex and size. The three-dimensional echocardiography was performed with electrocardiographic and respiratory gating. A new transthoracic integrated probe designed for small children was used with a rotational scanning increment of 3 degrees. The 60 slices obtained from the ventricular cavity were stored and formatted in a commercial system (TomTec). End-diastolic and end-systolic volumes, stroke volume and ejection fraction were calculated after manual tracing of the endocardial surfaces. The volumes were indexed to the body surface area.

RESULTS

As seen in the reconstructions, the dominant left ventricle in tricuspid atresia had a spherical shape, whereas the normal left ventricle is oblong. The left ventricular volumes and function in tricuspid atresia were 54+/-4 ml/m2 (end-diastolic volume), 28+/-3 ml/m2 (end-systolic volume), 26+/-7 ml/m2 (stroke volume) and 48+/-6% (ejection fraction). These volumes were not different from those obtained in the controls (p = NS). The left ventricular stroke volume and ejection fraction in 10 patients with tricuspid atresia were lower than those calculated for the controls (p < 0.05).

CONCLUSIONS

Three-dimensional echocardiography provides a quantitative insight into the pathophysiologic function of the dominant left ventricle in tricuspid atresia after construction of a total cavopulmonary connection.

Electrocardiographic ST-segment depression in children with fontan circulation

Despite successful operation, many patients palliated with a Fontan-type procedure continue to show effort limitation. We previously observed that these children showed electrocardiographic ST depression during exercise tests. The purpose of the study was to investigate whether electrocardiographic ST depression is a common finding in children with Fontan circulation. Forty-two children in two groups were examined: group A consisted of 14 patients who had all undergone a modified Fontan procedure, and group B consisted of 28 children with a structurally normal heart, matched for length, weight and gender to group A. Complete echocardiographic examinations were performed in all patients and controls. All 14 patients and all 28 healthy children underwent standard 24 h ambulatory electrocardiographic monitoring. All the recordings were analysed by a PC-based Holter system where an analysis of ST changes was performed. Seven patients and 14 matched healthy children were exercised on bicycle ergometers. Four patients and eight matched healthy children underwent exercise testing by walking/running a treadmill. Ten of 13 patients analysed had significant ST depressions on ambulatory electrocardiogram (>0.20 mV). Three of the 10 patients with ST depression were on digoxin. Three patients showed depressions of the ST segment in the electrocardiogram during exercise, with a maximal depression of 0.20-0.35 mV. None of the 28 matched healthy children showed electrocardiographic ST depression on the ambulatory 24 h ECG. These findings indicate that ST depression in daily activity is a common finding in children with Fontan circulation.

Postoperative evaluation of congenital heart disease by magnetic resonance imaging

In the last four decades the survival of patients with corrected or palliated congenital heart disease has increased dramatically. However, post-operative abnormalities frequently occur and therefore a noninvasive imaging tool is mandatory for the timely detection of morphological as well as functional abnormalities. Magnetic resonance imaging (MRI) is ideally suited for the noninvasive diagnosis and post-operative follow-up of congenital heart disease. Spin-echo MRI is able to visualize structures that may be difficult to assess with other noninvasive image modalities and is sensitive in the detection of post-interventional stenoses or aneurysms. Because the function of the ventricles may deteriorate over time after correction or palliation of a congenital cardiac malformation, the use of gradient-echo MRI is essential in the follow-up after correction or palliation, as no other conventional technique allows such detailed evaluation of ventricular function, without geometrical assumptions. Phase-contrast MRI is well suited to assess valvular function, allowing accurate measurement of regurgitation or stenosis. Shunt quantification is another application of phase-contrast MRI. J. Magn. Reson. Imaging 1999;10:656-666.

Caring for the former pediatric cardiac surgery patient

Because of marked improvements in the early diagnosis and management of patients with congenital heart defects as well as the dramatic increases in surgical survival for patients undergoing correction of these defects, a large and growing population of survivors of congenital heart surgery present themselves for care to primary care pediatricians. This article highlights the need for primary care pediatricians to understand the common clinical problems they will see in this group of patients and what surgical strategies are used in the more complex defects.

Comparison of three-dimensional echocardiographic assessment of volume, mass, and function in children with functionally single left ventricles with two-dimensional echocardiography and magnetic resonance imaging

Diminished systolic function or inappropriate hypertrophy are considered risk factors for outcome following the Fontan procedure. These parameters are difficult to assess in univentricular hearts that do not conform to the uniform shapes prescribed by conventional 2-dimensional imaging volume algorithms. Three-dimensional echocardiography requires no geometric assumptions and has been validated in both normal and distorted left ventricles. To assess the feasibility and accuracy of this technique in patients with univentricular hearts, we compared 2- and 3-dimensional echocardiographic estimates of ventricular volume, ejection fraction, and mass in patients with functionally single left ventricles with results obtained by magnetic resonance imaging (MRI). Twelve patients with functionally single left ventricles (6 months to 22 years) underwent examination by all 3 modalities. Correlation and agreement with MRI were calculated for volumes, ejection fraction, and mass. Three-dimensional echocardiographic comparison with MRI yielded a bias of 3.4 +/- 5.5 ml and 14.2 +/- 8.3 ml for systolic and diastolic volumes, respectively. Agreement analysis for mass showed a bias of 5.8 +/- 8.4 grams. Two-dimensional echocardiography showed less agreement for both volumes and mass (bias of -2.9 +/- 8.1, 2.9 +/- 10.4 ml and -8.3 +/- 12.0 g for volume and mass, respectively, p >0.05). Ejection fraction by 3-dimensional echocardiography showed significantly closer agreement with MRI (bias of 4.4 +/- 5.3%) than 2-dimensional echocardiography (bias of 8.5 +/- 10.3%, p = 0.04). Thus, 3-dimensional echocardiography provides estimates of ventricular volumes, ejection fraction, and mass that are comparable to MRI in this select group of patients with single ventricles of left ventricular morphology.

Enalapril does not enhance exercise capacity in patients after Fontan procedure

BACKGROUND

Angiotensin-converting enzyme inhibitors improve exercise capacity in adults with congestive heart failure by decreasing systemic vascular resistance and improving ventricular diastolic function. Patients who have undergone the Fontan procedure have decreased cardiac output, increased systemic vascular resistance, abnormal diastolic function, and decreased exercise capacity compared with normal people.

METHODS AND RESULTS

To test the hypothesis that afterload reduction therapy alters hemodynamic variables and augments exercise capacity in patients after a Fontan procedure, we compared the results of graded exercise with maximal effort from 18 subjects (14.5+/-6.2 years of age, 4 to 19 years after Fontan procedure) in a randomized, double-blind, placebo-controlled crossover trial using enalapril (0.2 to 0.3 mg x kg[-1] x d[-1], maximum 15 mg). Each treatment was administered for 10 weeks. Diastolic filling patterns at rest were assessed by Doppler determination of the systemic atrioventricular valve flow velocity at the conclusion of each therapy. No difference was detected in resting heart rate, blood pressure, or cardiac index. Diastolic filling patterns were also similar. Exercise duration was not different (6.4+/-2.6 [enalapril] versus 6.7+/-2.6 minutes [placebo]). The mean percent increase in cardiac index from rest to maximum exercise was slightly but significantly decreased in subjects after 10 weeks of enalapril therapy (102+/-34% [enalapril] versus 125+/-34% [placebo]; P<.02). At maximal exercise, cardiac index (3.5+/-0.9 [enalapril] versus 3.8+/-0.9 L x min[-1] x m2 [placebo]), oxygen consumption (18.3+/-9 [enalapril] versus 20.5+/-7 mL x min[-1] x kg[-1] [placebo]), minute ventilation (57.5+/-17 [enalapril] versus 55.4+/-19 L/min [placebo]), and total work (247+/-181 [enalapril] versus 261+/-197 W [placebo]) were not different.

CONCLUSIONS

We conclude that enalapril administration for 10 weeks does not alter abnormal systemic vascular resistance, resting cardiac index, diastolic function, or exercise capacity in patients who have undergone a Fontan procedure.

Acute changes in left ventricular geometry after volume reduction operation

BACKGROUND

After surgical removal of a volume load, regression of myocardial mass proceeds slowly relative to diminution in ventricular cavity size, resulting in increased wall thickness and decreased cavity dimensions, which may affect the filling properties and performance of the heart. We investigated the acute changes in ventricular geometry that occur after the Fontan operation and hemi-Fontan operation for tricuspid atresia, and compared them with closure of a ventricular septal defect in a two-ventricle heart.

METHODS

We reviewed the results of echocardiography performed before and 8 +/- 7 days after (1) Fontan operation for tricuspid atresia (n = 9), (2) hemi-Fontan operation for tricuspid atresia (n = 10), and (3) closure of a ventricular septal defect (n = 13). Measurements were made from images of the left ventricle at end-diastole: (1) apical, septal, and posterior wall thickness; and (2) long- and short-axis cavity diameters, cross-sectional areas, and ventricular volume. Posterior wall thickness to cavity dimension ratio was calculated.

RESULTS

Wall thickness increased in all groups, with the greatest degree of increase after the Fontan operation. Cavity measures decreased most dramatically after the Fontan operation, with less dramatic and equivalent changes noted after the hemi-Fontan operation and ventricular septal defect closure. Posterior wall thickness to cavity diameter ratios were equivalent in all before operation, increased after operation, and were greatest after the Fontan operation.

CONCLUSIONS

Changes in ventricular geometry identified as an increase in wall thickness and a decrease in cavity dimension are most dramatic after the Fontan operation. Changes seen after the hemi-Fontan operation are of a milder degree, which may in part explain the excellent clinical course after this operation.

Cardiopulmonary function in adult patients late after Fontan repair

OBJECTIVES

The clinical status and exercise assessment of adult patients late after the Fontan operation were reviewed to determine cardiovascular function.

BACKGROUND

The Fontan operation is the final operation for many patients with tricuspid atresia or a single ventricle. Follow-up reports describe most patients to be in Canadian Cardiovascular Society functional class I or II. Objective measures of cardiac performance in the pediatric age group have shown significant dysfunction.

METHODS

Forty-seven adult patients were seen late after the Fontan operation at the Toronto Congenital Cardiac Centre for Adults. Thirty of these underwent cycle ergometry to determine maximal exercise capacity. Maximal ventilation, maximal oxygen uptake and anaerobic threshold were determined from a ramp exercise protocol. Ejection fraction at rest and during exercise was measured with gated radionuclide angiography. Results were compared with those of eight normal volunteers. Results are given as mean +/- SD.

RESULTS

Thirty patients underwent cardiopulmonary exercise testing 6.7 +/- 3.9 years after a first Fontan operation. Clinically 93% were in functional class I or II. The Fontan group patients had a significantly lower maximal work load (548 +/- 171 vs. 1,094 +/- 190 kilopond-meters, p < 0.00001), anaerobic threshold (11.2 +/- 2.9 vs. 23.6 +/- 4.6 ml/kg per min) and maximal oxygen consumption (14.8 +/- 4.5 vs. 42.1 +/- 10.0 ml/kg per min). Systemic ventricular ejection fraction was lower at rest (38 +/- 12% vs. 58 +/- 7%) and during exercise (40 +/- 15% vs. 70 +/- 8%).

CONCLUSIONS

Despite a clinical impression of good function, by objective measures adult patients continue to have significant cardiovascular limitation late after the Fontan operation.

Influence of ventricular morphology on diastolic filling performance in double-inlet ventricle after the Fontan procedure

OBJECTIVES

The purpose of this study was to define the influence of dominant chamber morphology on ventricular performance after the Fontan procedure in patients with double-inlet ventricle.

BACKGROUND

Previous studies have reported the impact of ventricular morphology on preoperative ventricular performance and surgical outcome. However, the influence on postoperative ventricular performance has not been addressed.

METHODS

Twenty-six clinically asymptomatic patients > 1 year after repair (mean age at procedure 6.1 +/- 3.7 years) were evaluated with ventricular cineangiography and radionuclide blood pool studies (18 with a dominant left ventricular morphology [LV group], 8 with a dominant right ventricular morphology [RV group]) and compared with normal control subjects.

RESULTS

Ventricular volume, mass and systolic variables were similar between patient groups. In the LV group, however, the mass/volume ratio was significantly elevated compared with values in control subjects (1.11 +/- 0.28, 0.97 +/- 0.19, p < 0.05), whereas this ratio in the RV group (0.90 +/- 0.11) was within the normal range and significantly lower than that in the LV group (p < 0.05). Mean right atrial and pulmonary artery pressures in the RV group were significantly higher than those in the LV group (p < 0.05). Peak filling rates (2.87 +/- 0.70, 2.41 +/- 1.15 and 3.84 +/- 0.51 end-diastolic volume/s [LV and RV groups and control subjects, respectively]) were significantly lower in both groups than in control subjects (p < 0.001), without intergroup difference.

CONCLUSIONS

Ventricular filling abnormalities after atrial to pulmonary anastomosis are common regardless of the type of dominant ventricular morphology, and these abnormalities in patients with dominant right ventricular morphology do not coexist with ventricular hypertrophy. Such diastolic abnormalities may be related to either intrinsic myocardial or acquired factors, not to excessive hypertrophy alone. Those differences may become clinically more apparent with longer follow-up and may raise concerns over the long-term course.

Regional ventricular wall motion abnormalities in tricuspid atresia after the Fontan procedure

OBJECTIVES

The purpose of this study was to determine whether wall motion abnormalities are present before or after the Fontan procedure in patients with a univentricular heart of the left ventricular type with an absent right atrioventricular valve connection (tricuspid atresia) and to assess the impact of such abnormalities on ventricular performance and clinical outcome.

BACKGROUND

Normal systolic and diastolic ventricular function is critical for a successful Fontan repair. However, there have been no previous studies addressing the relation between regional ventricular function and hemodynamic factors.

METHODS

Thirty-seven pediatric patients were studied with biplane ventricular cineangiography. There were 20 male and 17 female patients whose mean age at the time of the Fontan operation was 6.5 +/- 3.5 years (range 2.5 to 15.6). Eighteen patients were studied preoperatively, 25 at > 1 year postoperatively and 6 serially. Wall motion was assessed by a centerline method. Normal ranges for wall motion and other variables were established from 25 normal subjects.

RESULTS

Wall motion abnormalities were observed in 2 of 18 patients preoperatively and in 11 of 25 patients postoperatively. Age at operation and ventricular volumes did not differ between postoperative patients who had normal (group I, 14 patients) or abnormal (group II, 11 patients) wall motion. However, ventricular mass and the mass/volume ratio were significantly greater and systolic variables and cardiac index were significantly lower in group II versus group I. Two patients in group I were considered to have a clinically poor outcome (persistent heart failure), and five in group II had heart failure, including one who died late.

CONCLUSIONS

These observations suggest that postoperative regional wall motion abnormalities in this setting are not rare, may be related to excessive hypertrophy and may contribute to cardiac dysfunction and a poor clinical outcome.

Ventriculo-coronary arterial connections in pulmonary atresia with intact ventricular septum, and their influences on ventricular performance and clinical course

To define the influence of ventriculo-coronary (VC) arterial connections on ventricular performance and late outcome, and associated wall motion abnormalities in patients with pulmonary atresia and intact ventricular septum, 21 patients aged > or = 6 months (mean 4.3 +/- 3.3 years, range 0.5 to 11.8) were reviewed. Ventricular volumes, mass, systolic functional variables and regional wall motion were measured using biplane ventricular cineangiography. Fourteen patients had VC connections, 11 of whom had coronary artery abnormalities. In comparing patients with VC connections and coronary abnormalities (group I) with those without coronary abnormalities (group II), no hemodynamic differences were observed, except the expected increased right-to-left ventricular systolic pressure ratio in group I (1.33 +/- 0.24 vs 0.72 +/- 0.50). Wall motion abnormalities were observed in 8 patients (7 in group I, and only 1 in group II [p < 0.05]). Ejection fraction in patients with abnormal wall motion was significantly lower (50 +/- 6% vs 57 +/- 7%; p < 0.05) and ventricular systolic pressure ratio significantly higher (1.46 +/- 0.16 vs 0.80 +/- 0.45; p < 0.05) than in those with normal wall motion. Five patients died during follow-up, all of whom had wall motion abnormalities. The findings suggest that patients with VC connections and coronary abnormalities have a higher incidence of wall motion abnormalities, which may reflect ongoing ischemia, and are at risk for late death.