Key result
Low-frequency oscillations of QT variability unrelated to RR variability during the first phase of exercise independently predicted coronary artery disease (OR 1.16).
Why the study?
Stress test ECG has limited accuracy for CAD diagnosis, and whether markers of low-frequency QTV oscillations unrelated to RRV could identify CAD was unknown.
Does measuring low-frequency oscillations of QT variability unrelated to RR variability during stress testing improve identification of coronary artery disease in patients referred for stress testing?
Observational (n=100)
No
Does measuring low-frequency oscillations of QT variability unrelated to RR variability during stress testing improve identification of coronary artery disease in patients referred for stress testing?
Removing the influence of RR variability when measuring QT variability during stress testing provides independent predictive value for identifying coronary artery disease.
May support adjunctive CAD risk stratification during stress testing; leaves open clinical utility pending prospective validation.
Stress test electrocardiogram (ECG) analysis is widely used for coronary artery disease (CAD) diagnosis despite its limited accuracy. Alterations in autonomic modulation of cardiac electrical activity have been reported in CAD patients during acute ischemia. We hypothesized that those alterations could be reflected in changes in ventricular repolarization dynamics during stress testing that could be measured through QT interval variability (QTV). However, QTV is largely dependent on RR interval variability (RRV), which might hinder intrinsic ventricular repolarization dynamics. In this study, we investigated whether different markers accounting for low-frequency (LF) oscillations of QTV unrelated to RRV during stress testing could be used to separate patients with and without CAD. Power spectral density of QTV unrelated to RRV was obtained based on time-frequency coherence estimation. Instantaneous LF power of QTV and QTV unrelated to RRV were obtained. LF power of QTV unrelated to RRV normalized by LF power of QTV was also studied. Stress test ECG of 100 patients were analysed. Patients referred to coronary angiography were classified into non-CAD or CAD group. LF oscillations in QTV did not show significant differences between CAD and non-CAD groups. However, LF oscillations in QTV unrelated to RRV were significantly higher in the CAD group as compared with the non-CAD group when measured during the first phases of exercise and last phases of recovery. ROC analysis of these indices revealed area under the curve values ranging from 61 to 73%. Binomial logistic regression analysis revealed LF power of QTV unrelated to RRV, both during the first phase of exercise and last phase of recovery, as independent predictors of CAD. In conclusion, this study highlights the importance of removing the influence of RRV when measuring QTV during stress testing for CAD identification and supports the added value of LF oscillations of QTV unrelated to RRV to diagnose CAD from the first minutes of exercise. This article is part of the theme issue 'Advanced computation in cardiovascular physiology: new challenges and opportunities'.
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Castillo et al. (2021) conducted an observational in Coronary artery disease (n=100). Low-frequency oscillations of QT variability unrelated to RR variability vs. Non-CAD patients was evaluated on Prediction of coronary artery disease using LF power of QTV unrelated to RRV during the first phase of exercise (PE25 QTVuRRV) (OR 1.16, 95% CI 1.02-1.32, p=0.02). Low-frequency oscillations of QT variability unrelated to RR variability during the first phase of exercise independently predicted coronary artery disease (OR 1.16).
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