Echocardiography and MRI parameters associated with exercise capacity in patients after the arterial switch operation

The arterial switch operation (ASO) for transposition of the great arteries has excellent survival, but a substantial number of patients suffer from a reduced exercise capacity. The goal of this study was to identify imaging parameters associated with a reduced exercise capacity in patients after ASO.

A retrospective analysis was performed of ASO patients who underwent cardiopulmonary exercise testing (CPET) between 2007 and 2017. Reduced exercise performance was defined as a reduced workload peak (W_peak) with Z-score <-2 or a peak oxygen uptake indexed for weight (VO_2peak/kg) with Z-score <-2. Data on echocardiography and cardiac magnetic resonance performed within 1 year of the CPET were collected for comparison.

A total of 81 ASO patients (age 17±7 years) were included. Reduced exercise performance was found in 22 patients (27%) as expressed by either a reduced W_peak and/or a reduced VO_2peak/kg. Main pulmonary artery gradient and tricuspid regurgitation gradient by echocardiography were found to be associated with reduced W_peak (p=0.031; p=0.020, respectively). The main pulmonary artery gradient and tricuspid regurgitation gradient by echocardiography were found to be associated with reduced VO_2peak/kg (p=0.009; p=0.019, respectively). No left ventricular parameters were found to be associated with abnormal exercise performance.

This study demonstrates that ASO patients frequently experience reduced exercise capacity. Echocardiographic evidence of main pulmonary artery stenosis and increased right ventricular pressure were associated with reduced exercise capacity, and are therefore key to monitor during serial follow-up of ASO patients.