Michael D. Puchalski

Comparison of Echocardiographic and Cardiac Magnetic Resonance Imaging Measurements of Functional Single Ventricular Volumes, Mass, and Ejection Fraction (from the Pediatric Heart Network Fontan Cross-Sectional Study)

Assessment of the size and function of a functional single ventricle (FSV) is a key element in the management of patients after the Fontan procedure. Measurement variability of ventricular mass, volume, and ejection fraction (EF) among observers by echocardiography and cardiac magnetic resonance imaging (CMR) and their reproducibility among readers in these patients have not been described. From the 546 patients enrolled in the Pediatric Heart Network Fontan Cross-Sectional Study (mean age 11.9 +/- 3.4 years), 100 echocardiograms and 50 CMR studies were assessed for measurement reproducibility; 124 subjects with paired studies were selected for comparison between modalities. Interobserver agreement for qualitative grading of ventricular function by echocardiography was modest for left ventricular (LV) morphology (kappa = 0.42) and weak for right ventricular (RV) morphology (kappa = 0.12). For quantitative assessment, high intraclass correlation coefficients were found for echocardiographic interobserver agreement (LV 0.87 to 0.92, RV 0.82 to 0.85) of systolic and diastolic volumes, respectively. In contrast, intraclass correlation coefficients for LV and RV mass were moderate (LV 0.78, RV 0.72). The corresponding intraclass correlation coefficients by CMR were high (LV 0.96, RV 0.85). Volumes by echocardiography averaged 70% of CMR values. Interobserver reproducibility for the EF was similar for the 2 modalities. Although the absolute mean difference between modalities for the EF was small (<2%), 95% limits of agreement were wide. In conclusion, agreement between observers of qualitative FSV function by echocardiography is modest. Measurements of FSV volume by 2-dimensional echocardiography underestimate CMR measurements, but their reproducibility is high. Echocardiographic and CMR measurements of FSV EF demonstrate similar interobserver reproducibility, whereas measurements of FSV mass and LV diastolic volume are more reproducible by CMR.

Intermediate-term mortality and cardiac transplantation in infants with single-ventricle lesions: Risk factors and their interaction with shunt type

OBJECTIVE The study objective was to identify factors associated with death and cardiac transplantation in infants undergoing the Norwood procedure and to determine differences in associations that might favor the modified Blalock-Taussig shunt or a right ventricle-to-pulmonary artery shunt. METHODS We used competing risks methodology to analyze death without transplantation, cardiac transplantation, and survival without transplantation. Parametric time-to-event modeling and bootstrapping were used to identify independent predictors. RESULTS Data from 549 subjects (follow-up, 2.7 ± 0.9 years) were analyzed. Mortality risk was characterized by early and constant phases; transplant was characterized by only a constant phase. Early phase factors associated with death included lower socioeconomic status (P = .01), obstructed pulmonary venous return (P < .001), smaller ascending aorta (P = .02), and anatomic subtype. Constant phase factors associated with death included genetic syndrome (P < .001) and lower gestational age (P < .001). The right ventricle-to-pulmonary artery shunt demonstrated better survival in the 51% of subjects who were full term with aortic atresia (P < .001). The modified Blalock-Taussig shunt was better among the 4% of subjects who were preterm with a patent aortic valve (P = .003). Lower pre-Norwood right ventricular fractional area change, pre-Norwood surgery, and anatomy other than hypoplastic left heart syndrome were independently associated with transplantation (all P < .03), but shunt type was not (P = .43). CONCLUSIONS Independent risk factors for intermediate-term mortality include lower socioeconomic status, anatomy, genetic syndrome, and lower gestational age. Term infants with aortic atresia benefited from a right ventricle-to-pulmonary artery shunt, and preterm infants with a patent aortic valve benefited from a modified Blalock-Taussig shunt. Right ventricular function and anatomy, but not shunt type, were associated with transplantation.

Design and rationale of a randomized trial comparing the Blalock-Taussig and right ventricle-pulmonary artery shunts in the Norwood procedure

OBJECTIVE The initial palliative procedure for patients born with hypoplastic left heart syndrome and related single right ventricle anomalies, the Norwood procedure, remains among the highest risk procedures in congenital heart surgery. The classic Norwood procedure provides pulmonary blood flow with a modified Blalock-Taussig shunt. Improved outcomes have been reported in a few small, nonrandomized studies of a modification of the Norwood procedure that uses a right ventricle-pulmonary artery shunt to provide pulmonary blood flow. Other nonrandomized studies have shown no differences between the two techniques. METHODS The Pediatric Heart Network designed a randomized clinical trial to compare outcomes for subjects undergoing a Norwood procedure with either the right ventricle-pulmonary artery or modified Blalock-Taussig shunt. Infants with a diagnosis of single, morphologically right ventricle anomaly who are undergoing a Norwood procedure are eligible for inclusion in this study. The primary outcome is death or cardiac transplant 12 months after random assignment. Secondary outcomes include postoperative morbidity after Norwood and stage II palliation procedures, right ventricular function and pulmonary arterial growth at stage II palliation, and neurodevelopmental outcomes at 14 months old. Incidence of adverse events will also be compared between treatment groups. CONCLUSION This study will make an important contribution to the care of patients with hypoplastic left heart syndrome and related forms of single, morphologically right ventricle. It also establishes a model with which other operative interventions for patients with congenital cardiovascular malformations can be evaluated in the future.

Barriers to prenatal detection of congenital heart disease: a population‐based study

To evaluate the extent and determinants of missed prenatal detection of congenital heart disease (CHD) in a population‐based setting.

Factors associated with serum brain natriuretic peptide levels after the fontan procedure

OBJECTIVE Although a useful marker of heart failure in adults, the utility of brain natriuretic peptide concentration (BNP) for children after the Fontan procedure is not well studied. DESIGN BNP was measured in 510 patients who were 6-18 years old in the Pediatric Heart Network Fontan cross-sectional study at a median of 8.2 years after Fontan. Patients underwent echocardiography, exercise testing, magnetic resonance imaging (MRI) and functional health status questionnaires. Associations of BNP with baseline patient characteristics, medical history and cross-sectional assessment were examined with multivariable linear regression analyses. RESULTS The distribution of BNP was highly skewed, median 13.0 pg/mL (interquartile range: 7.1, 25.9), and was normalized with logarithmic transformation (logBNP). Among medical history variables, logBNP was greater in females (P= .02) and older patients (P < .001). Presence of pre-Fontan systolic ventricular dysfunction, greater number of post-Fontan complications, and thrombosis after Fontan were independently associated with higher logBNP (R(2) = 0.16). Age-adjusted logBNP was significantly related to Fontan connection type (lower with extracardiac conduits, higher with atriopulmonary connection; P < .001). Lower physical functioning health status (R(2) = 0.05), lower chronotropic index during exercise (R(2) = 0.17), indices of diastolic dysfunction measured by echocardiography (R(2) = 0.15), and higher total ventricular mass on MRI (R(2) = 0.33) were related to higher logBNP. CONCLUSIONS Despite a markedly abnormal circulation, BNP was variable but within a normal range in the majority of Fontan patients in this large outpatient cohort. Higher BNP was associated with several markers of suboptimal outcome, although associations were weak. The routine use of BNP as an outpatient surveillance tool in asymptomatic Fontan patients is not warranted.

Regional myocardial dysfunction following Norwood with right ventricle to pulmonary artery conduit in patients with hypoplastic left heart syndrome.

BACKGROUND Improved early survival has led many centers to use the right ventricle-to-pulmonary artery (RVPA) conduit instead of the modified Blalock-Taussig shunt for Norwood palliation of hypoplastic left-heart syndrome. However, there is concern regarding the potential deleterious effects of the required right ventriculotomy for placement of the RVPA conduit on global and regional right ventricular (RV) function. The purpose of this study was to investigate global and regional RV wall motion abnormalities after Norwood palliation with RVPA conduit using Velocity Vector Imaging (VVI). METHODS Thirty consecutive patients with hypoplastic left-heart syndrome who underwent stage 2 palliation between January 2007 and December 2009 were identified from the surgical database. VVI was performed on two-dimensional echocardiographic images obtained before second-stage palliation. Peak systolic circumferential and radial velocity, strain, and strain rate were measured from parasternal short-axis and apical four-chamber views. RV ejection fraction was measured using the biplane modified Simpsons rule. Regional RV systolic deformations were compared between different RV segments. VVI measures were also compared with RV systolic function. In a subgroup (n = 14), VVI was repeated on follow-up after stage 2 palliation to evaluate changes in regional and global RV deformation. RESULTS A total of 30 patients (20 males) were studied. The median age at the time of interstage echocardiography was 12 weeks (range, 8-18 weeks). In the short axis, average peak systolic circumferential strain values for the anterior, posterior, septal, and RV free wall segments were 3.79 ± 2.52%, 11.4 ± 5.2%, 13.3 ± 6.5%, and 11.1 ± 5.0%, respectively. From the short-axis view, the anterior RV segment (ventriculotomy site) exhibited significantly reduced circumferential velocity, peak systolic strain, and strain rate (P < .0001). Mean global VVI measurements were correlated with RV ejection fraction. On follow-up after stage 2 palliation, the ventriculotomy region showed persistently reduced velocity, peak systolic strain, and strain rate compared with all other segments. CONCLUSIONS In patients with hypoplastic left-heart syndrome after Norwood palliation with RVPA conduit, RV myocardial deformation was significantly reduced at the ventriculotomy site, which persisted after stage 2 palliation. VVI-derived measures demonstrating impairment of global systolic myocardial deformation were correlated with RV systolic function. Long-term multicenter studies to evaluate the effects of ventriculotomy scar on single systemic right ventricle are required.

Outcomes and Predictors of Perinatal Mortality in Fetuses With Ebstein Anomaly or Tricuspid Valve Dysplasia in the Current Era A Multicenter Study

Background— Ebstein anomaly and tricuspid valve dysplasia are rare congenital tricuspid valve malformations associated with high perinatal mortality. The literature consists of small, single-center case series spanning several decades. We performed a multicenter study to assess the outcomes and factors associated with mortality after fetal diagnosis in the current era. Methods and Results— Fetuses diagnosed with Ebstein anomaly and tricuspid valve dysplasia from 2005 to 2011 were included from 23 centers. The primary outcome was perinatal mortality, defined as fetal demise or death before neonatal discharge. Of 243 fetuses diagnosed at a mean gestational age of 27±6 weeks, there were 11 lost to follow-up (5%), 15 terminations (6%), and 41 demises (17%). In the live-born cohort of 176 live-born patients, 56 (32%) died before discharge, yielding an overall perinatal mortality of 45%. Independent predictors of mortality at the time of diagnosis were gestational age <32 weeks (odds ratio, 8.6; 95% confidence interval, 3.5–21.0; P<0.001), tricuspid valve annulus diameter z-score (odds ratio, 1.3; 95% confidence interval, 1.1–1.5; P<0.001), pulmonary regurgitation (odds ratio, 2.9; 95% confidence interval, 1.4–6.2; P<0.001), and a pericardial effusion (odds ratio, 2.5; 95% confidence interval, 1.1–6.0; P=0.04). Nonsurvivors were more likely to have pulmonary regurgitation at any gestational age (61% versus 34%; P<0.001), and lower gestational age and weight at birth (35 versus 37 weeks; 2.5 versus 3.0 kg; both P<0.001). Conclusion— In this large, contemporary series of fetuses with Ebstein anomaly and tricuspid valve dysplasia, perinatal mortality remained high. Fetuses with pulmonary regurgitation, indicating circular shunt physiology, are a high-risk cohort and may benefit from more innovative therapeutic approaches to improve survival.

Stentless porcine valves in the right ventricular outflow tract: improved durability?

OBJECTIVE Stentless porcine valves are commonly used for aortic valve replacement in adults, yet their long-term performance in the right ventricular (RV) outflow tract is unknown. We evaluated intermediate-term performance of stentless porcine valves in the RV outflow tract in 150 children and adults over a 10-year period. METHODS We retrospectively reviewed data on all patients undergoing placement of a pulmonary valve or RV-PA conduit with a stentless porcine prosthesis (>/=19 mm) from 1998 to 2008. Valvar function was assessed with echocardiography. Freedom from reintervention (explantation or catheter-based intervention) was determined by actuarial methods. RESULTS A stentless porcine prosthesis was placed in the pulmonary position in 150 patients with a median weight and age of 50.1 kg (range 9.8-127) and 15.8 years (range 1.4-55), respectively. There were three early deaths (2%) and no late deaths. Actuarial freedom from reintervention was 100% at 1 year and 95.5% at 5 years. Peak transvalvar gradient at 1 and 5 years was 13+/-12 mmHg and 25+/-11 mmHg, respectively. At last follow-up no patient had severe insufficiency (PI), five patients had moderate PI and the remainder mild or no PI. CONCLUSIONS Stentless porcine valves function well in the pulmonary position over the intermediate-term and are associated with low rates of reintervention in patients requiring a >19 mm valve or valved conduit. Longer-term follow-up and comparison with other alternatives will be necessary to determine if these valves are superior to commonly used allograft or bovine jugular venous valved conduits.

Functional state following the Fontan procedure

BACKGROUND Despite improvements in outcomes after completion of the Fontan circulation, long-term functional state varies. We sought to identify pre- and postoperative characteristics associated with overall function. METHODS AND RESULTS We analyzed data from 476 survivors with the Fontan circulation enrolled in the Pediatric Heart Network Fontan Cross-sectional Study. Mean age at creation of the Fontan circulation was 3.4 plus or minus 2.1 years, with a range from 0.7 to 17.5 years, and time since completion was 8.7 plus or minus 3.4 years, the range being from 1.1 to 17.3 years. We calculated a functional score for the survivors by averaging the percentile ranks of ventricular ejection fraction, maximal consumption of oxygen, the physical summary score for the Child Health Questionnaire, and a function of brain natriuretic peptide. The mean calculated score was 49.5 plus or minus 17.3, with a range from 3 to 87. After adjustment for time since completion of the circulation, we found that a lower score, and hence worse functional state, was associated with: right ventricular morphology (p less than 0.001), higher ventricular end-diastolic pressure (p equals 0.003) and lower saturations of oxygen (p equals 0.047) prior to completion of the Fontan circulation, lower income for the caregiver (p equals 0.003), and, in subjects without a prior superior cavopulmonary anastomosis, arrhythmias after completion of the circulation (p equals 0.003). The model explained almost one-fifth (18%) of the variation in the calculated scores. The score was not associated with surgical centre, sex, age, weight, fenestration, or the period of stay in hospital after completion of the Fontan circuit. A validation model, using 71 subjects randomly excluded from initial analysis, weakly correlated (R equals 0.17, p equals 0.16) with the score calculated from the dataset. CONCLUSIONS Right ventricular morphology, higher ventricular end-diastolic pressure and lower saturations of oxygen prior to completion of the Fontan circuit, lower income for the provider of care, and arrhythmias after creation of the circuit, are all associated with a worse functional state. Unmeasured factors also influence outcomes.

Pulmonary Regurgitation: Determining Severity by Echocardiography and Magnetic Resonance Imaging

OBJECTIVE Pulmonary regurgitation (PR) is common after repair of congenital heart disease involving the right ventricular outflow tract. Because PR results in chronic right ventricular volume overload and associated morbidity and mortality, accurate assessment of its severity is important. The aim of this study was to compare echocardiography with the gold standard of PR quantitation by magnetic resonance imaging (MRI) in a young population with repaired congenital heart disease. DESIGN/METHODS Patients with congenital heart disease who had undergone right ventricular outflow tract reconstruction and/or pulmonary valve replacement and had an MRI within 3 months of an echocardiogram formed the study group. Echocardiographic indices were compared with MRI-determined pulmonary regurgitant fraction (PRF) to determine the most accurate measurements to quantitate PR. RESULTS Of the 69 MRI/echocardiography pairs in 64 patients, 53 data sets were complete and used in the analysis. For the prediction of MRI PRF > or =20%, PR jet width/annulus ratio > or =0.5 demonstrated excellent sensitivity (94%), specificity (100%), positive predictive value (PPV 100%), and negative predictive value (NPV 82%). For the prediction of MRI PRF > or =40%, jet width/annulus ratio > or =0.7 and diastolic flow reversal in the branch pulmonary arteries showed useful sensitivity (92%), specificity (68%), PPV (76%), and NPV (88%). CONCLUSION Pulmonary regurgitation jet width/annulus ratio combined with diastolic flow reversal is the most valuable echocardiographic measure for assessing PR severity after right ventricular outflow tract reconstruction or pulmonary valve replacement; however, this surrogate measure does not replace the importance of MRI evaluation.