Abstract 2690: Myocardial Contraction Duration is Longest in the Interventricular Septum in Patients With Long QT Syndrome With Arrhythmic Events
Background Long QT syndrome (LQTS) is due to inherited cardiac ion channel defects leading to prolonged action potential duration (APD). Purkinje cells have longer APD than cardiac myocytes and are predominantly located in the interventricular septum. Prolonged APD in LQTS may cause prolonged cardiac contraction which can be assessed by strain echocardiography. We hypothesized that myocardial contraction is inhomogeneously prolonged throughout the LV in LQTS patients.
Methods We included 88 genotyped LQT1 and LQT2 mutation carriers and 35 healthy individuals. A history of cardiac arrest or syncope was present in 42 mutations carriers and 46 were asymptomatic. Myocardial contraction duration was assessed by strain echocardiography as time from ECG Q to peak strain in 6 LV segments. Location of longest contraction duration was recorded.
Results Contraction duration in septum was longer in symptomatic compared to both asymptomatic LQTS mutation carriers and healthy individuals (475±65 vs. 435±65 vs. 385±50ms, p<0.001, respectively). Longest contraction duration was located in septum in 61% of the symptomatic mutation carriers compared to 31% of asymptomatic and 29% of healthy (p<0.001). In asymptomatic mutation carriers and healthy, longest contraction duration was evenly distributed throughout the LV (Fig⇓).
Conclusions Contraction duration in healthy indiviudals and asymptomatic LQTS mutation carriers was uniformly disseminated in LV. Contraction duration in symptomatic LQTS mutation carriers, however, was longer and more frequently located in septum. This might reflect that ion channel dysfunction in septal cells play a role in arrhythmogenesis in LQTS patients.