Left ventricular outflow tract obstruction and its impact on systolic ventricular function and exercise capacity in adults with a subaortic right ventricle.

BACKGROUND

In biventricular hearts the filling and contractility of one ventricle affects the performance of the other. In this study, we compared right ventricular systolic function and exercise capacity in patients with a subaortic right ventricle (RV) in relation to the presence of a left ventricular outflow tract obstruction (LVOTO).

METHODS

Retrospective chart review of adults with congenitally corrected transposition of the great arteries (ccTGA) or with a previous atrial switch procedure for complete TGA (D-TGA). A LVOTO was defined by a peak instantaneous systolic gradient>20mmHg. Right and left ventricular ejection fraction (EF) were measured by cardiac magnetic resonance imaging (CMR), and exercise capacity as the predicted peak oxygen consumption (peak VO2) on a cycle ergometer.

RESULTS

We identified 79 clinically stable adults (age 33±10years, 70% male). Nine patients (11%) had cc-TGA and 70 patients had (89%) D-TGA. Thirteen patients (16%) had a LVOTO with a mean peak instantaneous systolic gradient of 43±22mmHg. Patients with a LVOTO had higher left (68±7% vs. 60±9%, p=0.01) and right ventricular EF (52±8 vs. 46±9%, p=0.05) by CMR compared to patients without LVOTO. In a multivariate regression analysis with left ventricular EF and LVOTO as predictors, only left ventricular EF was independently associated with right ventricular EF (correlation coefficient 0.41, p<0.01). The presence of a LVOTO was not associated with improved exercise capacity.

CONCLUSIONS

In adults with a subaortic RV, a pressure loaded subpulmonary left ventricle has a beneficial effect on systemic right ventricular EF.