Electrocardiographic repolarization abnormalities in familial dysautonomia: an indicator of cardiac autonomic dysfunction

Objective: Electrocardiographic repolarization intervals were evaluated to determine the extent of cardiac autonomic dysfunction in patients with fami lial dysautonomia (FD) and to determine if any of these intervals could ser ve as a possible predictor of clinical symptoms. Methods: Thirty-seven electrocardiograms of patients with FD were retrospec tively evaluated. QT, JT, rate-corrected QT and JT intervals were calculate d as well as QT and QTC dispersion. Results were compared to normative data and electrocardiograms of 20 age-matched control subjects. Observations: In the FD group, prolongation of QTC (>450 msec) was noted in 5/37 (13.5%) patients, as compared to 0/20 normal controls (p = NS), and p rolongation of JTc (>340 msec) in 16/37 (43.3%) patients, as compared to 0/ 20 normal controls (p < 0.001). QT and QTC dispersion were abnormal in 3/37 (8.1%) and 5/37 (13.5%), respectively. In the 16 FD patients with prolonge d JTc, six had a positive history of syncope, whereas none of the 21 with n ormal JTc had syncope or symptoms suggesting arrhythmia (p < 0.003). The po sitive predictive value of having syncope or symptoms suggestive of arrhyth mia with an abnormal JTc is 37.5% (95% CI [15%, 65%]). The negative predict ive value is 100% (95% CI [87%, 100%]). Conclusion: In the FD population, the electrocardiographic measure of repol arization that was most frequently abnormal was the JTc interval. Prolongat ion of the JTc interval was significantly more frequent than prolongation o f the QTC interval (p < 0.001) QT and QTC dispersions were less significant ly affected in the FD population, indicating uniform ventricular recovery t ime. These results suggest that a prolonged JTc interval may be a more sens itive indicator of abnormal ventricular repolarization and cardiac autonomi c dysfunction. Due to the known sympathetic denervation inherent in patient s with FD, they are at risk for unopposed parasympathetic predominance. FD patients, therefore, are more likely to have brady arrhythmias and asystole rather than polymorphic ventricular tachycardia. The increased incidence o f syncope in patients with prolonged JTc suggests that this measure may ser ve as a helpful marker to predict which FD patients are at increased risk o f serious clinical sequelae including bradyarrhythmias with asystole or sud den death.