Evaluation of the treadmill stress testing for risk stratification after acute myocardial infarction.

Abstract

The recent decline in postinfarction mortality reflects the success of the most recent therapeutical proposals incorporated into clinical practice . Despite this evolutional enhancement, mostly due to the use of thrombolytic agents, an increase in the recurrence of thrombotic phenomena, such as reinfarction and unstable angina, has occurred creating the need for strategies that adequately identify the patients with higher probability of an unfavorable outcome . The current evolution of acute myocardial infarction has resulted in changes in the clinical characteristics of the patients referred for the provocative tests for ischemia. These clinical characteristics were clearly identified by the professionals involved in treating acute myocardial infarction, who needed to reassess the previously existing concepts regarding these tests . This led to the spread of the routine performance of coronary angiography after acute myocardial infarction before hospital discharge . In 1987, research carried out among American cardiologists revealed that 86% of them had adopted this management in patients who had received thrombolytic agents . The TIMI II study 5 was designed to compare the routine use of coronary angiography prior to hospital discharge with the more conservative management of only those patients who had a clinical indication. All patients were treated during the acute phase with recombinant tissue plasminogen activator (r-TPA) within the first 4 hours of pain onset. In the group undergoing the invasive procedure, 1.636 patients underwent coronary angiography and prophylactic angioplasty when it was anatomically feasible 18 to 48 hours after administration of the thrombolytic agent. In the group treated conservatively, 1.626 patients were clinically followed up and only those patients with signs of ischemia during hospital stay, either spontaneous or triggered by the treadmill stress test, were referred for coronary angiography. No statistically significant difference between the two groups was observed in regard to mortality or acute myocardial infarction and the ejection fraction at rest or during exercise on the 42 postinfarction day. In the oneyear evaluation, no difference in the rate of new infarction or mortality occurred between the groups . During this period of time, a larger number of hospital admissions due to cardiac events and coronary angiography was observed in those patients undergoing the conservative treatment, but the total number of coronary angiographies was still 40% smaller than that reported for the group undergoing the invasive treatment . Evidence obtained in the TIMI II study was fundamental in defining the results obtained in both managements, reducing the impulse to use invasive techniques in all patients.