QTc dispersion measurement for risk of syncope in patients with aortic stenosis

The purposes of this study are to evaluate the clinical usefulness of maxim um QTc and QTc dispersion determination in aortic stenosis, and to compare the effects of maximum QTc and QTc dispersion on the risk of syncope in aor tic stenosis. The QT interval dispersion has long been known to be a marker of dispersion of ventricular repolarization and, hence, electrical instabi lity. Additionally, it has been shown that these patients have a propensity to ventricular tachyarrhythmic syncope. The study included 86 patients wit h aortic stenosis who underwent left-heart catheterization and coronary ang iography during investigation of syncope and 30 healthy subjects. The patie nts were characterized with regard to the presence or absence of a history of syncope and the severity of aortic stenosis (the degree of peak transval vular gradient). In addition, QT max and QT dispersion measurements were co rrected for heart rate according to Bazett's formula. The QTc max and QTc d ispersion were greater in patients with aortic stenosis than in the healthy subjects (477 +/- 49 ms vs 370 +/- 22 ms, p<0.001; 60 +/- 13 ms vs 38 +/- 1 ms, p < 0.001). Similarly, the QTc max and QTc dispersion were greater in the patients with a history of syncope than in the patients with no histor y of syncope (493 +/- 48 ms vs 459 +/- 4 ms, p < 0.001; 68 +/- 12 ms vs 53 +/- 10 ms, p < 0.001). In addition, both parameters were greater in the pat ients with a high transvalvular gradient than in the patients with a low tr ansvalvular gradient (489 +/- 49 ms vs 451 +/- 39 ms, p < 0.001; 65 +/- 12 ms vs 50 +/- 9 ms, p < 0.001). Multivariate logistic regression analysis sh owed that only a increased QTc dispersion had significant value for the ris k of syncope in aortic stenosis. An increased QTc dispersion caused a 10.4% increase in the occurrence of syncope in aortic stenosis. These results su ggest that high values of QTc dispersion are sensitive noninvasive markers to determine the risk for syncope in aortic stenosis.