Disrupted right ventricular force–frequency relationships in adults operated for ventricular septal defect as toddlers: Abnormal peak force predicts peak oxygen uptake during exercise

Abstract

Recent studies have shown markedly reduced functional capacity in long-term survivors of ventricular septal defect (VSD), and in order to explore possible mechanisms, we performed non-invasive assessment of ventricular force–frequency relationships during exercise in adults operated for VSD in early childhood.We conducted a prospective study at a tertiary referral center. Patients (n=23) and healthy controls (n=20) underwent continuous Doppler-echocardiographic imaging during supine bicycle ergometry. The cycling workload was individually and manually incremented during the test session in response to heart rate. The heart was imaged in an apical 4-chamber view, and color-coded myocardial velocities were recorded. Post hoc, peak systolic velocity and isovolumetric acceleration (IVA) were blindly determined in the basal ventricular segments.VSD-operated patients differed markedly in all right ventricular endpoints compared with controls. IVA was lower prior to the test, 70±30cm/s2 vs. 150±60cm/s2 among controls, and during the entire test session ending at a heart rate of 160beats/min; 140±50cm/s2 vs. 300±30cm/s2, p<0.01 at both points. A similar pattern was revealed in terms of peak right ventricular systolic velocity. Left ventricular and septal measurements showed a similar, although less significant, tendency with a clearly lower left ventricular optimum heart rate among patients: 140beats/min vs. 154beats/min among controls. In the diseased cohort biventricular force–frequency relationships were directly correlated to peak oxygen uptake.VSD repair in early childhood is associated with disruption of the right ventricular force–frequency relationship, which may contribute to the previously observed reduction in functional capacity.