EDUCATIONAL SERIES IN CONGENITAL HEART DISEASE: Congenital left-sided heart obstruction

Genetic Testing for Supravalvar Aortic Stenosis: What to Do When It Is Not Williams Syndrome

BACKGROUND

We aimed to describe the frequency and yield of genetic testing in supravalvar aortic stenosis (SVAS) following negative evaluation for Williams-Beuren syndrome (WS).

METHODS AND RESULTS

This retrospective cohort study included patients with SVAS at our institution who had a negative evaluation for WS from May 1991 to September 2021. SVAS was defined as (1) peak supravalvar velocity of ≥2 meters/second, (2) sinotubular junction or ascending aortic Z score <-2.0, or (3) sinotubular junction Z score <-1.5 with family history of SVAS. Patients with complex congenital heart disease, aortic valve disease as the primary condition, or only postoperative SVAS were excluded. Genetic testing and diagnoses were reported. Of 162 patients who were WS negative meeting inclusion criteria, 61 had genetic testing results available (38%). Chromosomal microarray had been performed in 44 of 61 and was nondiagnostic for non-WS causes of SVAS. Sequencing of 1 or more genes was performed in 47 of 61. Of these, 39 of 47 underwent ELN sequencing, 20 of 39 (51%) of whom had a diagnostic variant. Other diagnoses made by gene sequencing were Noonan syndrome (3 PTPN11, 1 RIT1), Alagille syndrome (3 JAG1), neurofibromatosis (1 NF1), and homozygous familial hypercholesterolemia (1 LDLR1). Overall, sequencing was diagnostic in 29 of 47 (62%).

CONCLUSIONS

When WS is excluded, gene sequencing for SVAS is high yield, with the highest yield for the ELN gene. Therefore, we recommend gene sequencing using a multigene panel or exome analysis. Hypercholesterolemia can also be considered in individuals bearing the stigmata of this disease.

A 3D scaling law for supravalvular aortic stenosis suited for stethoscopic auscultations

In this study a frequency scaling law for 3D anatomically representative supravalvular aortic stenosis (SVAS) cases is proposed. The law is uncovered for stethoscopy's preferred auscultation range (70-120 Hz). LES simulations are performed on the CFD solver Fluent, leveraging Simulia's Living Heart Human Model (LHHM), modified to feature hourglass stenoses that range between 30 to 80 percent (mild to severe) in addition to the descending aorta. For physiological hemodynamic boundary conditions the Windkessel model is implemented via a UDF subroutine. The flow-generated acoustic signal is then extracted using the FW-H model and analyzed using FFT. A preferred receiver location that matches clinical practice is confirmed (right intercostal space) and a correlation between the degree of stenosis and a corresponding acoustic frequency is obtained. Five clinical auscultation signals are tested against the scaling law, with the findings interpreted in relation to the NHS classification of stenosis and to the assessments of experienced cardiologists. The scaling law is thus shown to succeed as a potential quantitative decision-support tool for clinicians, enabling them to reliably interpret stethoscopic auscultations for all degrees of stenosis, which is especially useful for moderate degrees of SVAS. Computational investigation of more complex stenotic cases would enhance the clinical relevance of this proposed scaling law, and will be explored in future research.

Computed Tomographic Evaluation of Congenital Left Ventricular Outflow Obstruction

Congenital left ventricular outflow obstruction represents a multilevel obstruction with several morphological forms. It can involve the subvalvular, valvar, or supravalvular portion of the aortic valve complex, and may coexist. Computed tomography (CT) plays an important supplementary role in the evaluation of patients with congenital LVOT obstruction. Unlike transthoracic echocardiography and cardiovascular magnetic resonance (CMR) imaging, it is not bounded by a small acoustic window, needs for anaesthesia or sedation, and metallic devices. Current generations of CT scanners with excellent spatial and temporal resolution, high pitch scanning, wide detector system, dose reduction algorithms, and advanced 3-dimensional postprocessing techniques provide a high-quality alternative to CMR or diagnostic cardiac catheterization. Radiologists performing CT in young children should be familiar with the advantages and disadvantages of CT and with the typical morphological imaging features of congenital left ventricular outflow obstruction.

Systemic arterial hypertension but not IGF-I treatment stimulates cardiomyocyte enlargement in neonatal lambs

Although cardiomyocyte terminal differentiation is nearly complete at birth in sheep, as in humans, very limited postnatal expansion of myocyte number may occur. The capacity of newborn cardiomyocytes to respond to growth stimulation by proliferation is poorly understood. Our objective was to test this growth response in newborn lambs with two stimuli shown to be potent inducers of cardiomyocyte growth in fetuses and adults: increased systolic load (Load) and insulin-like growth factor I (IGF-I). Vascular catheters and an inflatable aortic occluder were implanted in lambs. Hearts were collected for analysis at 18 days of age after a 7-day experiment and compared with control hearts. Load hearts, but not IGF-I hearts, were heavier ( P = 0.001) because of increased mass of the left ventricle (LV), septum, and left atrium (40-50%, P = 0.004). Terminal differentiation and cell cycle activity were not different between groups. Myocyte length was 7% greater in Load lamb hearts ( P < 0.05), and binucleated myocytes, which comprise ~90% of LV cells, were 25% larger in volume ( P = 0.03). Myocyte number per gram of myocardium was decreased in all ventricles of Load lambs ( P = 0.01). Cells from the IGF-I group were not different by any comparison. These results suggest that the newborn sheep LV responds to systolic stress with cardiomyocyte hypertrophy, not proliferation. Furthermore, IGF-I is ineffective at stimulating cardiomyocyte proliferation at this age (despite effectiveness when administered before birth). Thus, to expand cardiomyocyte number in the newborn heart, therapies other than systolic pressure load and IGF-I treatment need to be developed.