Silent ischaemia in post-infarction patients: a 21-month follow-up study

The purpose of this study was to determine the prevalence of silent myocardial ischaemia (SMI) in post-infarction patients and to follow its clinical evolution in the course of a 21-month follow-up period. Of the 12,500 patients treated at the Klinik Roderbirken between Jan 1980 and Jun 1983 40% had angina. Three-vessel disease was documented in 61% of the 3150 subjects who had a coronary angiography. SMI identifiable on the exercise ECG was observed in 680 patients (5.4%). Sixth-three subjects (mean age 52 +/- 5.5 years) were selected and followed on the basis of stringent criteria. Prevalence of SMI at an average of 6 weeks after MI was 1/200 or 0.5% in that sample. Prognosis was good with a low mortality rate of 3.2% during the 21-month follow-up period. Factors weighing negatively on the observed SMI prognosis are the prevalence of 3-vessel disease (74%) and of pathological ejection fractions (52%) as well as the presence of ischaemia itself. Conversely, factors weighing positively on the observed SMI prognosis are the reasonably high exercise tolerance level (102 +/- 32 W), the low arrhythmogenic potential (73% less than or equal to Lown II), and the normal chest X-ray in more than 80% of the patients. In this study, 43% of the patients were felt to require angiography and only 10% were considered for bypass surgery. Good prognosis may be seen as a contra-indication for revascularization surgery. Yet, the prevalence of 3-vessel disease and the fact that 2/3 of the SMI subjects became symptomatic during the follow-up period are arguments in favour of early angiography.