Ventriculoarterial Coupling in Congenital Heart Disease – A Cardiac MRI Study

Background: The ventriculoarterial coupling ratio (VAC) is the ratio of arterial elastance and ventricular end-systolic elastance. It is a measure of cardiac efficiency, and has been shown to have prognostic significance in various clinical contexts. It can be estimated non-invasively as the ratio of end-systolic volume to stroke volume. We examined VAC in patients with various forms of congenital heart disease (CHD) undergoing cardiac MRI (CMR), and compared the results to patients found to have normal hearts on CMR.

Methods and Results: Patients with CHD who underwent clinical CMR studies between July 2016 and November 2018 were classified into 4 groups: predominantly left-sided disease, e.g. aortic stenosis (LV, n=23); predominantly right-sided disease, e.g. repaired Tetralogy of Fallot (RV, n=21); biventricular disease, e.g. repaired transposition of the great arteries (BV, n=7); and atrial shunt lesions (ASD, n=15). We calculated left and right ventricular VAC for these patients and compared to normal controls (n=13). Patients with single ventricle pathology or non-congenital heart disease were excluded. All volumes were measured by a single researcher (MEG). We found no significant difference in left and right VAC ratios between controls, RV, BV and ASD patients. However, LV patients had significantly lower median left ventricular VAC than controls (0.69 vs 0.81, p=0.02), and this finding tended towards significance for the right ventricle as well (p=0.056).

Conclusions: In this single-center study, patients with predominantly left-sided CHD had lower VAC than controls. This may be a sign of diastolic dysfunction – unlike the RV patients, most of whom are volume-loaded, many of the LV patients have experienced chronic left-sided obstruction, which may cause fibrosis. Surprisingly, this finding appears to be replicated in the right ventricle as well in these patients, which may point to ventricular interdependence. Further work is needed to elucidate these relationships more fully.