Effect of obstructive sleep apnea on QT dispersion: a potential mechanism of sudden cardiac death.

Overview

OBJECTIVES: QT dispersion (QT(d)) measures the variability of the ventricular recovery time. QT(d) may identify patients at risk for ventricular arrhythmias and sudden cardiac death (SCD). The purpose of our study was to determine the effect of obstructive sleep apnea (OSA) on QT(d). METHODS: There were 199 patients studied: 101 patients (28 women, 73 men) with OSA diagnosed in our sleep center and 98 patients (49 women, 49 men) without OSA from the outpatient clinic, representing the control group. QT intervals (milliseconds) were measured in each of the 12 leads of a standard surface electrocardiogram during wakefulness and QT(d) calculated (QT(max) - QT(min)). QT(c)(d), which corrects for heart rate, was also calculated. RESULTS: Mean age and heart rate were similar in men and women with or without OSA. Control patients exhibited a significant difference (p < 0.001) in QT(d) between men (48 ± 19) and women (31 ± 13). Men and women with OSA had similar QT(d) (56 ± 35 vs. 54 ± 21) but higher QT(d) compared to the control group. QT(c)(d) results were similar to QT(d). CONCLUSIONS: Patients with OSA and no structural heart disease have a higher QT(d)/QT(c)(d) compared to an overtly healthy patient population, possibly serving as a marker for an increased risk of SCD.