Randomized Trial of Preventive Angioplasty in Myocardial Infarction.


Patients with acute ST-segment elevation myocardial infarction (STEMI) are effectively treated with emergency angioplasty, hereafter called percutaneous coronary intervention (PCI), to restore blood flow to the coronary artery that is judged to be causing the myocardial infarction (infarct artery, also known as culprit artery).1-5 These patients may have major stenoses in coronary arteries that were not responsible for the myocardial infarction,6 but the value of performing PCI in such arteries for the prevention of future cardiac events is not known.

Some physicians have taken the view that stenoses in noninfarct arteries may cause serious adverse cardiac events that could be avoided by performing preventive PCI during the initial procedure.7-12Others have suggested that medical therapy with antiplatelet, lipid-lowering, and blood-pressure–lowering drugs is sufficient and that the risks of preventive PCI outweigh the benefits.2-4,13-17

The aim of our single-blind, randomized study, called the Preventive Angioplasty in Acute Myocardial Infarction (PRAMI) trial, was to determine whether performing preventive PCI as part of the procedure to treat the infarct artery would reduce the combined incidence of death from cardiac causes, nonfatal myocardial infarction, or refractory angina.

DISCUSSION

The results of this trial show that in patients with acute STEMI, the use of preventive PCI to treat noninfarct coronary-artery stenoses immediately after PCI in the infarct artery conferred a substantial advantage over not performing this additional procedure. The combined rate of cardiac death, nonfatal myocardial infarction, or refractory angina was reduced by 65%, an absolute risk reduction of 14 percentage points over 23 months. The effect was similar in magnitude and remained highly significant when the analysis was limited to cardiac death and nonfatal myocardial infarction.

In this trial, all decisions regarding the treatment of patients, other than the random assignments to the two study groups, were left to the discretion of the clinicians involved. The rates of use of drug-eluting stents and medical therapy were similar in the two groups. In the group receiving no preventive PCI, ischemia testing was performed in about one third of patients: 44 tests in asymptomatic patients (usually ≤6 weeks after the myocardial infarction) and 37 tests in patients with chest pain. In the preventive-PCI group, ischemia testing was performed in about one sixth of patients: 8 tests in asymptomatic patients and 31 tests in patients with chest pain. Although such testing was not a prespecified trial outcome, these findings suggest that preventive PCI may lead to less ischemia testing and that when such testing is performed, it tends to be in patients with symptoms.

Although refractory angina is a more subjective outcome than myocardial infarction or cardiac death, it was included as a component of the primary outcome because it is a serious symptomatic condition that warrants prevention. We sought to reduce bias in the assessment of this outcome by requiring that the diagnosis be confirmed with objective evidence of ischemia. The benefit of preventive PCI was also evident when the less subjective outcomes of cardiac death and nonfatal myocardial infarction were considered alone.

We decided against using revascularization as a primary outcome, since subsequent revascularization procedures could be prompted by the identification of stenosis in a noninfarct artery in the group receiving no preventive PCI during the initial procedure. This factor would also tend to underestimate the effect of preventive PCI on primary-outcome events by reducing the treatment difference between the two study groups. However, revascularization was retained as a secondary outcome to record the number of subsequent procedures in each group.

In our study, 13 patients did not receive their assigned treatment. In the group receiving no preventive PCI, 2 patients underwent PCI in a noninfarct artery (1 for unknown reasons and 1 because the operator treated what turned out to be a noninfarct right coronary artery and then had to treat the infarct circumflex artery). In the preventive-PCI group, 11 patients underwent PCI only in the infarct artery because the preventive PCI could not be completed owing to insufficient time (because of competing emergency PCIs) in 3 patients, failure of the noninfarct-artery PCI in 5 patients, and other complications in 3 patients. These deviations from the assigned treatment mean that the intention-to-treat analysis, adopted to ensure comparability of the two study groups, will tend to underestimate the benefit of preventive PCI. However, the results of the as-treated analysis were consistent with those of the intention-to-treat analysis.

In two other randomized trials, investigators have specifically assessed the value of preventive PCI in patients with acute STEMI undergoing PCI in the infarct artery. In one study, 69 patients were randomly assigned (in a 3:1 ratio) to preventive PCI (52 patients) or no preventive PCI (17 patients).20 At 1 year, in the preventive-PCI group, there were nonsignificant reductions in the rates of repeat revascularization (17% and 35%, respectively) and cardiac death or myocardial infarction (4% and 6%, respectively). In the other trial, 214 patients were randomly assigned to one of three groups: no preventive PCI (84 patients), immediate preventive PCI (65 patients), and staged preventive PCI performed during a second procedure about 40 days later (65 patients).7 At 2.5 years, the rate of repeat revascularization was less frequent in the immediate– and staged–preventive PCI groups combined, as compared with the group receiving no preventive PCI (11% and 33%, respectively), and there was a nonsignificant decrease in the rate of cardiac death (5% and 12%, respectively). These studies were limited by a lack of statistical power and a reliance on repeat revascularization as an outcome, which, as indicated above, may be subject to bias. However, the results of these studies are consistent with those of our study.

Current guidelines on the management of STEMI recommend infarct-artery-only PCI in patients with multivessel disease, owing to a lack of evidence with respect to the value of preventive PCI.2-5 This uncertainty has led to variations in practice, with some cardiologists performing immediate preventive PCI in spite of the guidelines, some delaying preventive PCI until recovery from the acute episode, and others limiting the procedure to patients with recurrent symptoms or evidence of ischemia. The results of this trial help resolve the uncertainty by making clear that preventive PCI is a better strategy than restricting a further intervention to those patients with refractory angina or a subsequent myocardial infarction. However, our findings do not address the question of immediate versus delayed (staged) preventive PCI, which would need to be clarified in a separate trial.

Several questions remain. First, are the benefits of preventive PCI applicable to patients with non-STEMI?21 Such patients tend to be difficult to study because, unlike those with STEMI (in whom the infarct artery is invariably identifiable), there is often uncertainty over which artery is the culprit. Second, do the benefits extend to coronary-artery stenoses of less than 50%? There is uncertainty over the level of stenosis at which the risks of PCI outweigh the benefits. Third, would a physiological measure of blood flow, such as fractional flow reserve,22,23 offer an advantage over angiographic visual assessment in guiding preventive PCI? Further research is needed to answer these questions.

In conclusion, in this randomized trial, we found that in patients undergoing emergency infarct-artery PCI for acute STEMI, preventive PCI of stenoses in noninfarct arteries reduced the risk of subsequent adverse cardiovascular events, as compared with PCI limited to the infarct artery.

 

Source: NEJM

 

 

 

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