Aims: This study tested the hypothesis that left ventricular (LV) contractile reserve is altered in patients after arterial switch operation (ASO) for complete transposition of the great arteries (TGA) by non-invasive determination of LV force-frequency relationship (FFR).
Methods and results: Thirty-two patients aged 16.2 ± 2.1 years and 22 healthy controls were studied. M-mode parameters, transmitral early (E) and late (A) diastolic velocities, and tissue Doppler-derived systolic (sm), early (em), and late (am) diastolic mitral annular velocities were determined at baseline and during submaximal exercise testing. The LV myocardial isovolumic acceleration (IVA) was measured at different heart rates during exercise for derivation of LV FFR and the average slope of IVA increment with heart rate. At baseline, patients had significantly greater E velocity, E/A and E/em ratios, shorter E deceleration time, and reduced mitral annular sm, em, and am velocities (all P < 0.05), but similar IVA (P = 0.29) compared with controls. During exercise, sm and em remained significantly reduced (P < 0.001), and LV IVA became lower (P < 0.001) in patients. The average FFR slope was significantly lower in patients (0.039 ± 0.019 vs. 0.070 ± 0.024 m/s(2) bpm, P < 0.001). The weighted average FFR curve of patients was flattened compared with the reported positive FFR reference curve based on a healthy paediatric cohort (P < 0.0001). Patients with variant compared with those with usual coronary arterial anatomy had significant flattening of FFR (P < 0.001) and a reduced FFR slope (P = 0.007).
Conclusion: In adolescents and young adults after ASO, exercise stress revealed reduced LV contractile reserve, which is worse in those having variant coronary arterial anatomy.