Qureshi, M. Yasir

Background— The molecular underpinnings of hypoplastic left heart are poorly understood. Staged surgical palliation has dramatically improved survival, yet eventual failure of the systemic right ventricle necessitates cardiac transplantation in a subset of patients. We sought to identify genetic determinants of hypoplastic left heart with latent right ventricular dysfunction in individuals with a Fontan circulation. Methods and Results— Evaluation of cardiac structure and function by echocardiography in patients with hypoplastic left heart and their first-degree relatives identified 5 individuals with right ventricular ejection fraction ≤40% after Fontan operation. Whole genome sequencing was performed on DNA from 21 family members, filtering for genetic variants with allele frequency <1% predicted to alter protein structure or expression. Secondary family-based filtering for de novo and recessive variants revealed rare inherited missense mutations on both paternal and maternal alleles of MYH6 , encoding myosin heavy chain 6, in 2 patients who developed right ventricular dysfunction 3 to 11 years postoperatively. Parents and siblings who were heterozygous carriers had normal echocardiograms. Protein modeling of the 4 highly conserved amino acid substitutions, residing in both head and tail domains, predicted perturbation of protein structure and function. Conclusions— In contrast to dominant MYH6 mutations with variable penetrance identified in other congenital heart defects and dilated cardiomyopathy, this study reveals compound heterozygosity for recessive MYH6 mutations in patients with hypoplastic left heart and reduced systemic right ventricular ejection fraction. These findings implicate a shared molecular basis for the developmental arrest and latent myopathy of left and right ventricles, respectively.

BackgroundTricuspid annular plane systolic excursion measured by M‐mode (MM‐TAPSE) has been validated as a marker of right ventricular systolic performance. A similar measurement by 2D imaging (2D‐TAPSE) can be obtained. We sought to determine the correlation and strength of agreement between MM‐TAPSE and 2D‐TAPSE in children.MethodsEchocardiographic studies performed for clinical indications were reviewed retrospectively. All consecutive subjects ≤18 years of age were included. The cohort was divided into those with normal echocardiographic findings and those with disorders affecting the right ventricle. Digitally recorded images were analyzed for both MM‐TAPSE and 2D‐TAPSE. Measurements of 2D‐TAPSE were made in an apical four‐chamber view, from the tricuspid valve annulus to a consistent point at the apex of the imaging sector at end‐diastole and end‐systole, with the difference representing the 2D‐TAPSE value.ResultsA total of 329 subjects (mean age 9.0 ± 6.1 years) met entry criteria. Correlation coefficient between MM‐TAPSE and 2D‐TAPSE was 0.90. Bland–Altman analysis showed agreement between the two methods to be within 1.2 ± 2.6 mm (mean percentage difference of 6.5%). About 1 mm difference between MM‐TAPSE and 2D‐TAPSE was consistently observed in all diagnostic subgroups, and across all age categories.ConclusionMM‐TAPSE and 2D‐TAPSE correlate strongly, with 2D‐TAPSE being consistently about 1 mm less than values obtained by the M‐mode technique. We conclude that 2D‐TAPSE can provide a reliable alternative to MM‐TAPSE to quantitatively measure right ventricular systolic function and may be especially useful in situations where retrospective comparisons are sought.