EFFECT OF SLEEP APNEA SYNDROME ON QT DISPERSION AND QT CORRECTED INTERVAL IN PATIENTS WITH TYPE 2 DIABETES

Abstract

Objective. Prolonged QT interval and increased QT interval dispersion (QTd) are well-characterized precursor of malignant ventricular arrhythmias. The aim of the present study was to assess QT interval corrected for heart rate (QTc) and QTd in patients with type 2 diabetes and sleep apnea syndrome (SAS) comparative with patients with type 2 diabetes without sleep apnea. Methods. 52 subjects with type 2 diabetes were included in the study. According to apnea-hypopnea index (AHI) patients were divided into three groups: 1) control subjects (AHI < 5/hour of sleep); 2) patients with mild SAS (AHI=5-15/hour of sleep) and 3) patients with moderate– severe SAS (AHI≥15/hour of sleep). Bazett’s formula (QTc=QT/√RR) was used to obtain heart rate corrected values of the QT intervals and dispersions. Results. Prevalence of increased QTc interval in the whole population was 19.2% (10.5% in control group and 26.1% in moderate/severe SAS group). The mean QTd was 52.7 ms in all patients, with values increasing from 40.0 ms in controls to 64.8 ms in group with moderate-severe SAS. Statistically significant positive association was found between QTd and oxygen desaturation index (ODI) (β=0.38, p=0.006) and between QTd and AHI (β=0.29, p=0.03). In addition, a statistically significant negative association was found between QTd and mean SaO2 (β= -0.40, p=0.003) and between QTd and minimum SaO2 (β= -0.43, p=0.001). After adjustment for confounding factors, AHI, ODI, mean SaO2 and minimum SaO2 remained statistically significant associated with QTd. Conclusion. Sleep apnea is associated with changes in QT interval variability in patients with type 2 diabetes. Increased severity of SAS, as determined by AHI, may result in inhomogeneity of repolarization, favoring ventricular tachyarrhytmias.