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QT interval prolongation during exercise has been reported in patients with coronary artery disease (CAD), mainly in those after myocardial infarction (MI). Much less is known about the behaviour of the spatial dispersion of QT. CAD-patients with three vessel disease had increased precordial SD-QT)30 ms in the resting ECG. This criterion was proposed to diagnose a critical stenosis of the left main coronary artery. Patients after MI also had increased QTc dispersion in resting ECG; however, its behaviour in response to exercise remains unclear.This study deals with the changes in measures of ventricular repolarisation induced by exercise, and later in the recovery period, in patients after myocardial infarction (MI) and in those with uncomplicated coronary artery disease (CAD). Material and methodsThe 58 patients (12 females, 46 males, mean age 53"8 years wrange 33-67x) were examined if they had angiographically proven CAD ()50% stenosis of the epicardial coronary arteries). There were 33 patients (pts) who had MI in the past (group PMI). The remaining 25 pts without a history of MI (group CAD) presented clinically with stable exertional angina.All patients were in sinus rhythm without an arrhythmia or conduction disturbances at resting ECGs. The only medications allowed were aspirin and beta-blockers (all subjects). Patients receiving other drugs, especially those which are known to influence ventricular repolar-*Corresponding author. Tel.: q48-32-2523930; fax: q48-32-2523930. isation, were not included. The purpose of the study and the methods used was explained to each patient and informed consent was obtained.An echocardiographic examination (Hewlett-Packard Sonos 1500, USA) was performed in each patient in order to obtain left ventricular diastolic diameter (LVEDD, cm), left ventricular ejection fraction (LVEF, %) and left ventricular mass index (LVMI, gym ). Only 2 LVEF was slightly, but significantly lower in post-MI patients (55.2"10.4%) as compared to CAD-pts (63.3"11.0, P-0.01). There were no patients with LVEF-35%. Other echocardiographic measures were comparable in both groups.A symptom-limited exercise treadmill test was performed on each subject in the mid-morning after a light breakfast. The Bruce protocol was used. Twelve-lead ECG recordings were obtained at rest (REST), immediately after the exercise (EXE) and after 6 min of recovery (REC). The QT interval was measured in each suitable lead from the beginning of the QRS complex to the point at which the T-wave crosses the isoelectric line. In all ECG recordings, the QT interval was suitable to determine at least eight leads. All measurements were performed by one of the co-authors in a blinded order. Measurements were repeated in 3-5 consecutive cycles and corrected to the duration of the preceding RR interval using the Bazett formula (corrected QT, QTc). The mean for each lead was calculated. The following parameters were drawn for further analysis: the maximum QTc interval (maxQTc, ms), the difference between the longest and the shortest QT in...