Reversed Apico-Basal Myocardial Relaxation Sequence During Exercise in Long QT Syndrome Mutations Carriers With History of Previous Cardiac Events

BACKGROUND: Recent echocardiography studies in inherited long QT syndrome (LQTS) have shown left ventricular (LV) myocardial relaxation disturbances to follow markedly prolonged and dispersed mechanical contraction. AIM: We used speckle-tracking echocardiography to assess disturbances in LV myocardial relaxation sequence during exercise and their relationship to symptoms. METHODS: Forty seven LQTS patients (45 ± 15 years, 25 female and 20 symptomatic, LVEF: 65 ± 6%) and 35 controls underwent exercise echocardiogram using Bruce protocol. ECG and echo parameters were recorded at rest, peak exercise (p.e.) and recovery. RESULTS: Between patients and controls there were no differences in age, gender, HR or LVEF. At p.e, patients had longer time to LV longitudinal E(SR) (tE(SR)) at all three LV segments; basal (p < 0.0001), mid- cavity (p = 0.03) and apical (p = 0.03) whereas at rest such difference was noted only at base (p = 0.0007). Patients showed reversed apico-basal relaxation sequence (ΔtE(SRbase–apex)) with early relaxation onset occurring later at base than at apex, both at rest (49 ± 43 vs. –29 ± 19 ms, p < 0.0001) and at p.e. (46 ± 38 vs. –40 ± 22 ms, p < 0.0001), particularly in symptomatic patients (69 ± 44 vs. 32 ± 26, p < 0.0007). ΔtE(SRbase–apex) correlated with longer QTc interval, lower E(SR) and attenuated LV stroke volume. CONCLUSION: LQTS patients show reversed longitudinal relaxation sequence, which worsens with exercise, particularly in those with previous cardiac events.