Short QT Syndrome


Clinical EP

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Except for sporadic case reports the main information about electrophysiology studies in patients with SQTS comes from 2 studies. Hiroshi Watanabe and coworkers (2010) did not report any detailed results from programmed stimulation of 18 patients with SQTS, but stated there was no difference in inducibility of ventricular tachyarrhythmias between patients with arrhythmic events (73%) and those without arrhythmic events (72%).

In the long-term follow-up study by Carla Giustetto and coworkers (2011) 28 patients underwent an electrophysiologic study. The ventricular effective refractory periods at the right ventricular apex were shortened and varied between 140 and 200 msec (mean: 166 +/- 21 msec). No difference was found between patients with a history of cardiac arrest or syncope and those without. Ventricular fibrillation was induced in 16 patients (57%), in 7 by mechanical induction during catheter positioning.

The atrial effective refractory periods also were shortened and ranged between 120 and 200 msec (mean: 163 +/- 22 msec). Atrial fibrillation was induced in 36%. Patients with HERG mutation had shorter refractory periods than those without. From these data it is apparent that an electrophysiologic study is not useful in predicting cardiac arrest having a sensitivity of only 37%, but the mechanical induction of ventricular fibrillation by simple positioning of the electrode catheter in the right ventricle is a phenomenon rarely seen in any other clinical situation and especially not in any normal heart.

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