Aim: The aim of the Multicenter Silent Ischemia Study (SMISS), co-ordinated by the Italian Working Group on Cardiac Rehabilitation, was to evaluate prospectively, the prognostic significance of silent myocardial ischemia during exercise testing in patients with proven ischemic cardiac disease.
Methods: Over a period of six months 4389 consecutive patients performing a maximal symptom-limited exercise testing, after drug withdrawal, were enrolled in the 73 ergometric laboratories. All patients were followed up after 12 months, at which time electrocardiogram, examination and clinical history were reassessed. Here we report the results of 1111 patients group with the recent myocardial infarction (inferior 3 months). The follow-up was completed in 1031 (93%) patients.
Results: The results of exercise testing were normal in 666 (64.6%) patients; angina alone in 33 (3.2%) patients; silent ischemia in 234 (22.7%) patients; symptomatic ischemia in 98 (9.5%) patients. In 270 patients (26.1%) new events occurred: angina (19.7%); myocardial infarction (3.1%; PTCA (4%); CABG (6%); cardiac death (1.4%). The total events were more common in the patients with exercise induced angina (48.5%) and in those who had exercise induced-symptomatic ischemia (48%), in respect of patients with silent ischemia (29.5%) and of those who had normal testing (20.7%) (p = 0.0001). Myocardial infarction rate was higher in patients with symptomatic ischemia (7.1%) that for those of all other groups (silent ischemia: 1.3%, angina: 3%, normal 3.2%) (p = 0.05). Moreover, the patients with symptomatic ischemia had higher incidence of CABG (p = 0.0001). The mortality rate was low among all patients and did not show differences among the groups. Only among the 31 patients (3%) with blood pressure fall was mortality higher that in patients with a normal blood pressure increase. By multivariate logistic analysis the angina induced by exercise maintained its prognostic significance for all the events, but also other variables were significant: poor exercise tolerance and, between clinical variables angina before myocardial infarction.
Conclusion: The results showed, in patients who underwent to exercise testing after drug withdrawal, a low incidence of cardiac death and of myocardial infarction on 12 month follow-up; the patients with induced-exercise symptomatic schema had a greater risk for all cardiac events, except for death.