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

Abstract

Objectives: (1) To evaluate the clinical usefulness of QTc dispersion determination in aortic stenosis and (2) to compare the effects of QTc dispersion on the occurrence risk of syncope in aortic stenosis. Background: QT interval dispersion has long been known to be a marker of dispersion of ventricular repolarization and, hence, electrical instability. Additionally, it has been shown that these patients have a propensity to ventricular tachyarrhythmic syncope. Methods: The study included 86 patients with aortic stenosis who underwent left-heart catheterization and coronary angiography during investigation of syncope, as well as 30 control subjects. The patients were characterized with regards to the presence or absence of a history of syncope and the severity of aortic stenosis (the degree of peak transvalvular gradient). In addition, QT dispersion measurements were corrected for heart rate according to Bazett's formula and both were measured. Results: QTc dispersion was greater in patients with aortic stenosis than in the control subjects (60 ± 13 msec vs 38 ± 12 msec, P < 0.001). Similarly, QTc dispersion was greater in the patients with a history of syncope than in the patients with no history of syncope (68 ± 12 msec vs 53 ± 10 msec, P < 0.001). In addition, QTc dispersion values were greater in the patients with a high transvalvular gradient than in the patients with a low transvalvular gradient (65 ± 12 msec vs 50 ± 9 reset, P < 0.001). Multivariate logistic regression analysis showed that only an increased QTc dispersion had significant value for the risk of syncope in aortic stenosis. Conclusions: An increased QTc dispersion increases the occurrence risk for syncope in aortic stenosis. These results suggest that high values of QTc dispersion are a sensitive noninvasive marker for determining the risk for syncope in aortic stenosis.