Inefficient Ventriculoarterial Coupling in Fontan Patients: A Cardiac Magnetic Resonance Study

The ventriculoarterial coupling (VAC) ratio, the ratio of arterial elastance (Ea) to ventricular end-systolic elastance (Ees), reflects cardiovascular efficiency. Little is known about this ratio in patients who have undergone the Fontan procedure. Our aim was to assess the VAC ratio in a cohort of Fontan patients using a cardiac magnetic resonance (CMR) method, and to examine its relation to outcomes. We retrospectively assessed VAC from CMR data on 195 Fontan patients (age 19.6 ± 10.7 years) and 42 controls (age 15.2 ± 2.2 years). The VAC ratio was calculated as Ea/Ees (Ea = mean arterial blood pressure (MBP)/ventricular stroke volume; Ees = MBP/end-systolic volume). Compared with controls, Fontan patients had lower body surface area-adjusted median Ees (1.54 vs. 2.4, p < 0.001) and Ea (1.35 vs. 1.48, p = 0.01), and a higher median VAC ratio (0.88 vs. 0.62, p < 0.001). After a median follow-up of 4 years (range 1-10), 20 patients reached a composite endpoint of death or heart transplant listing. On multivariable modeling, being in the lowest tertile of the VAC ratio was independently associated with the composite endpoint (odds ratio 11.39, p = 0.02), and inclusion of the VAC ratio in the model improved prediction compared to traditional risk factors. In patients without ventricular dilation, the VAC ratio was the only factor predictive of the composite endpoint (p = 0.02). In conclusion, we found evidence for inefficient ventriculoarterial coupling in Fontan patients. The VAC ratio improved prediction of outcomes and was especially useful in patients without ventricular dilation. Further investigation into the clinical significance of ventriculoarterial coupling in this patient population is warranted.