Owing to advances in medical and surgical fields, patients with single ventricle (SV) have a greatly improved life expectancy. However, progressive functional deterioration is observed over time, with a decrease in cardiopulmonary fitness.

This study aimed to identify, in patients with SV, the association between cardiac magnetic resonance imaging (CMR) parameters and change in cardiopulmonary fitness assessed by cardiopulmonary exercise test (CPET), and if certain thresholds could anticipate a decline in aerobic fitness.

Patients with an SV physiology were retrospectively screened from 2011 and 2021 in a single-centre observational study. We evaluated (1) the correlation between baseline CMR and CPET parameters, (2) the association between baseline CMR results and change in peak oxygen uptake (peak VO2), and (3) the cut-off values of end-diastolic and end-systolic volume index in patients with an impaired cardiopulmonary fitness (low peak VO2 and/or high VE/VCO2 slope).

Thirty-two patients were included in the study. End-systolic volume index (r=0.37, P=0.03), end-diastolic volume index (r=0.45, P=0.01), and cardiac index (r=0.46, P=0.01) correlated with the VE/VCO2 slope. End-systolic ventricular volume (r=–0.39, P=0.01), end-diastolic ventricular volume (r=–0.38, P=0.01), and cardiac output (r=–0.45, P<0.01) inversely correlated with the peak VO2. In multivariate analysis, the cardiac index obtained from baseline CMR was inversely associated with the change in peak VO2 (P<0.01). An end-diastolic volume index>101mL/m² and an end-systolic volume index>47mL/m² discriminated patients with impaired cardiopulmonary fitness.

CMR parameters correlate with cardiopulmonary fitness in patients with SV and can therefore be useful for follow-up and therapeutic management of these patients.