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Dynamic QT-RR relationships in 12 lead ECG in patients with coronary artery disease

A computerized system for the measurement of beat to beat QT-RR intervals over a 12 leads ECG system was developed to study the dynamic change of QT interval as a function of the RR interval. The system was evaluated on 12-leads ECG recordings during the exercise and recovery phases of a treadmill exercise test from two groups of male subjects: 15 coronary arteries disease (CAD) patients and 15 healthy Israeli Air Force pilots. It was found that the relationship between the RR and QT intervals during the complete cycle of the exercise test shows different patterns of hysteresis behavior for the healthy subjects and CAD patients. In conclusion, the present study combined engineering work with an important medical application and shows that using beat-to-beat QT-RR measurements during the exercise test may contribute to identifying patients with CAD. The computerized system developed provides an accurate tool for measuring the dynamic behavior of the QT-RR relationship that can be used for testing drug treatment and effects of other interventions for cardiac disorders and arrhythmia risk.