Introduction: The metabolic syndrome is a matter of immense public concern for atherosclerosis prevention. Key features are visceral obesity, dyslipidemia, hyperglycemia in the non-diabetic range, and arterial hypertension. Subclinical atherosclerosis is the clinical consequence of metabolic syndrome, which may influence the QT interval. The aim was to investigate the rate corrected QT interval in subjects with metabolic syndrome in comparison to those without cardiometabolic risk factor clusters, and to explore gender differences in cardiac repolarization between the two groups.
Patients, materials and methods: Heart rate and QT interval were automatically measured from surface ECG in 1086 participants (767 men, 319 women) from the Salzburg-Atherosclerosis-Prevention-program-in-subjects-at-High-Individual-Risk (SAPHIR). To omit the QT adjustment bias inherent in Bazett's formula we used a QT adjustment method with linear scaling as described by Rautaharju.
Results: The prevalence of metabolic syndrome was 13.8% among males and 10% among females. Mean rate adjusted QT (QTa) intervals were longer in women than in men. Presence of metabolic syndrome, however, was associated with significantly prolonged QTa only in men but not in women. Adjustment for relevant confounders reduced the difference of mean QTa in men from 9.24 to 5.83 ms (95% CI 0.9-10.8), but this difference was still statistically significant (p = 0.021). The effect of metabolic syndrome on QTa was only partly mediated by hypertension and insulin resistance. In females, however, no relevant differences were detected for QTa interval between subjects categorized by presence or absence of metabolic syndrome.
Conclusions: The findings indicate a significant association between metabolic syndrome and rate-invariant QT in middle-aged men after adjustment for other risk factors. QT measurement may provide additive diagnostic and prognostic information in populations undergoing cardiovascular risk screening. However, the effect of metabolic and hormonal factors on ventricular repolarization seems to differ between the sexes.