Relationship of the duration of QT interval and corrected QT interval in patients with coronary heart disease to the cause of bicycle ergometer test cessation

Aim. To comparatively study Q-T interval duration. in groups of patients with coronary heart disease (CHD) identified by the cause of exercise test cessation. Materials and methods. Bicycle ergometric test (BET) was performed in 93 males with CHD (functional class [I-III angina pectoris on exertion). During BET, ECG recorded in the leads, as described by Nebu. The QT interval was visually measured in one lead. This interval was determined as a distance between the onset of a Q wave and the end of a T wave (in mlsec). The mean value by 3 cardiac cycles was. taken as an actual value of the QT interval. To compare the duration of the QT interval at different rates of cardiac rhythm, its corrected value (QTc) was calculated. Results and conclusion. In case of positive BET (anginal attack, 1-mm or more depressed ST segment at a distance of 0.8 cm from the point J), the values of Q T and QTc measured at rest and peak exercise were greater than those if the cause of test cessation was the submaximum heart rate or a patient's fatigue. The value of QTc was higher if the cause of BR T cessation was 1-mm or more depressed ST segment preceding an anginal attack or the only cause of test cessation.