Beat-to-beat QT interval dynamics and variability in familial dysautonomia

Familial dysautonomia (FD) is a disease characterized by dysfunction of the autonomic and sensory nervous systems. During the last five decades, the average life span of patients with FD has increased substantially. Nevertheless, sudden or unexplained death remains the most common cause of death in FD. Recently, our group reported that cardiac remodeling and hypertrophy are common in FD patients. We also described asymptomatic contractile dysfunction in some FD patients. It was speculated that repolarization abnormalities increases the risk of sudden death in patients with FD. However, data regarding repolarization dynamics in FD patients are limited. Twelve patients with FD and 12 healthy individuals (age and sex matched) underwent 5-min electrocardiograms. Time domain analysis of QT dynamics, power spectral analysis, QT variability index (QTVI), and normalized QT variance (QTVN) were computed. There was no difference in the time domain analysis of QT dynamics parameters between the two groups. QTVI((RR)) was also not statistically different. QTVI((HR)) was lower in the FD group compared to controls, but both values were low (therefore not considered pro-arrythmogenic) compared to published data. QTVN, not influenced by heart rate variability, was significantly higher in the FD group (0.39 +/- 0.1% vs. 0.3 +/- 0.05%, p = 0.032). In conclusion, most QT dynamics parameters in patients with FD are similar to that of normal controls. Nevertheless, FD patients have significantly higher QTVN, which might indicate higher risk for ventricular arrhythmias.