Relationship between Corrected QT Intervals and QT Variability Methodologies in Subjects with and without Coronary Artery Disease

Although alterations in QT interval variability (QTV) and the clinical utility of corrected QT (QTc) intervals for risk stratification are well-documented in cardiac patients, the association between myocardial ischemia and QTc intervals remains controversial. Moreover, the relationship between QTc intervals and QTV has not been systematically investigated. Here, using QT interval time series derived from 5-minute ECG recordings of 93 patients with coronary artery disease (CAD) and 107 non-CAD controls, QTc intervals were analyzed using both traditional and individual-specific formulas, while QTV was assessed through tools from time and frequency domains, as well as nonlinear signal analysis. Our results revealed that, compared with non-CAD controls, CAD patients exhibited significantly prolonged QTc intervals and elevated QTV. However, our results indicated that QTc prolongation and QTV elevation are not strictly parallel phenomena in either group; furthermore, no strong association was found between atherosclerotic burden and either metric. Sex differences were observed in QTc intervals but not in QTV. Only weak-to-moderate correlations between QTc and QTV were observed in both groups. Significant correlations between QTc and QTV indices were more prevalent in non-CAD subjects than in CAD patients. Finally, the QTc−QTV correlation was found to be influenced by the sex difference in QTc intervals. These findings indicate ischemic pathology fundamentally disrupts intrinsic repolarization dynamics, positioning QTV as a distinct and sex-independent biomarker for cardiovascular risk assessment.