Background: The aim of this study was to assess the significance of ST-segment depressions (ST-SD) detected during exercise test or Holter monitoring and to determine which parameters of ST-SD are the most important prognostic factors in patients after myocardial infarction.
Methods: The study group consisted of 164 patients (126 men and 38 women) who survived their first uncomplicated myocardial infarction. Twenty-four-hour Holter monitoring on day 10 (+/- 2) after infarction and a treadmill exercise test 1 or 2 days later were performed. The following parameters of ST-SD were taken into consideration: amplitude, localization according to the area of infarction and presence or absence of concomitant angina. Patients were observed for 24 months to assess the occurrence of new cardiac events.
Results: In 78 patients (group I) ST-SD were detected in both Holter monitoring and the exercise test, and in 32 patients (group II) in the exercise test only. Fifty-four patients (group III) were without ST-SD. During follow-up there were 83 cardiac events in group I, 24 in group II and 16 in group III (P < 0.01, group I versus II; P < 0.0001, group I versus III; P < 0.05, group II versus III). In multivariate analysis the presence of ST-SD during Holter monitoring or the exercise test, or both, appeared to be of most prognostic significance (P < 0.0001). The number of new cardiac events was significantly higher in patients with painful ST-SD greater than 3 mm, detected outside the area of infarction (distant ischaemia).
Conclusions: This study shows a significant prognostic value of early post-infarction ischaemia detected by Holter monitoring and an exercise test. Distant, painful ST-SD greater than 3 mm were more powerful determinants of poor prognosis than others. Electrode placement during Holter monitoring appears to be very important, particularly in post-infarction patients.