Patients with non–Q-wave myocardial infarctions are generally thought to have an increased risk of early and late ischemic complications because of the presence of viable but jeopardized myocardial tissue within the zone of the initial infarction. To forestall these complications, patients are often aggressively managed, often with early coronary angiography. However, as a result of findings from several studies, the American College of Cardiology–American Heart Association guidelines on cardiac catheterization and myocardial infarction no longer advocate routine angiography in all patients with non–Q-wave infarctions. Despite this recommendation, early aggressive management is still practiced by many physicians. Boden and colleagues compared the outcomes following conservative and invasive management of patients with non–Q-wave infarctions.
This study is part of the Veterans Affairs Non–Q-Wave Infarction Strategies in Hospital Trial. The 920 patients in the study were enrolled at 15 different sites. Nearly all of them (97 percent) were men; 462 were assigned to invasive management and 458 to conservative management. Eligibility criteria included evolving myocardial infarction, a creatine kinase MB isoenzyme level of no more than 1.5 times the upper limit of normal and no new abnormal Q waves on serial electrocardiography. Patients were excluded if they had a serious coexisting condition or ischemic complications such as resting ischemia or heart failure despite intensive medical therapy.
Patients were randomly assigned to conservative or invasive management within 24 to 72 hours after the onset of symptoms. Patients assigned to early invasive strategy underwent cardiac catheterization soon after randomization. Balloon angioplasty or, rarely, atherectomy was considered for significant single-vessel disease, and bypass surgery was recommended for multivessel disease. Patients designated to conservative management underwent radionuclide ventriculography to assess left ventricular function. In addition, a symptom-limited nuclear treadmill stress test was performed before these patients were discharged from the hospital.
During hospitalization, all of the patients received 325 mg of aspirin daily and long-acting diltiazem. Other drug therapies, including beta blockers, nitroglycerin, angiotensin converting enzyme inhibitors, heparin and thrombolytic therapy, were also used, if clinically indicated. The combined primary end point was death or nonfatal myocardial infarction during 12 months of follow-up.
A total of 152 cardiac events (138 patients, 72 nonfatal infarctions and 80 deaths) occurred in the invasive management group, compared with 139 cardiac events (123 patients, 80 non-fatal infarctions and 59 deaths) in the conservative management group. Follow-up lasted an average of 23 months. Overall, a 28 percent rate of cardiac events was documented during follow-up ranging from 12 to 44 months. The frequency of cardiac events was significantly higher in the invasive management group than in the conservative management group before hospital discharge and at one-month and one-year follow-up. In no subgroup was the invasive strategy associated with a better outcome.
There were no significant differences between the two groups in the use of medications. At hospital discharge, 89 percent were receiving aspirin, 55 percent were receiving a calcium channel blocker and 52 percent were receiving a beta blocker.
The authors conclude that in this population of moderate- to high-risk patients with non–Q-wave myocardial infarction, no clinical benefit was derived from early aggressive invasive treatment. In fact, this approach was associated with an increased risk of cardiac events and death during the first year after infarction. The authors advocate a conservative initial strategy based on an ischemia-guided approach.