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

BackgroundRecent echocardiography studies in inherited long QT syndrome (LQTS) have shown left ventricular (LV) myocardial relaxation disturbances to follow markedly prolonged and dispersed mechanical contraction. AimWe used speckle-tracking echocardiography to assess disturbances in LV myocardial relaxation sequence during exercise and their relationship to symptoms. MethodsForty 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. ResultsBetween 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 (Delta tE(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). Delta tE(SRbase-apex) correlated with longer QTc interval, lower E-SR and attenuated LV stroke volume. ConclusionLQTS patients show reversed longitudinal relaxation sequence, which worsens with exercise, particularly in those with previous cardiac events.