Review: Invasive management after unstable angina or non–ST-segment elevation MI does not reduce risk for death or MIPDF
ACP J Club. 2005 Nov-Dec;143:68. doi:10.7326/ACPJC-2005-143-3-068
Related Content in this Issue
• Companion Abstract and Commentary: Review: Routine invasive management after unstable angina or non–ST-segment elevation MI reduces risk for death or MI
Clinical Impact Ratings
Choudhry NK, Singh JM, Barolet A, Tomlinson GA, Detsky AS. How should patients with unstable angina and non-ST-segment elevation myocardial infarction be managed? A meta-analysis of randomized trials. Am J Med. 2005;118:465-74. [PubMed ID: 15866246]
In patients with unstable angina or non–ST-segment elevation myocardial infarction (NSTEMI), is initial management with an invasive strategy better than a conservative strategy?
Data sources: MEDLINE and EMBASE/Excerpta Medica (1966 to September 2003), and bibliographies of relevant articles.
Study selection and assessment: Randomized controlled trials (RCTs), published in English, that compared invasive and noninvasive strategies for early management of patients with unstable angina or NSTEMI; had ≥ 3-month follow-up; and reported mortality, reinfarction, or rehospitalization. The quality of the included trials was assessed for blinding, allocation, withdrawals, and standardization of assessment, based on the Cochrane Handbook.
Outcomes: Mortality, reinfarction, and rehospitalization.
7 RCTs (n = 9212, mean age 62 y) met the selection criteria. 6 RCTs were of high methodological quality. Meta-analysis of all 7 RCTs, using a random-effects model, showed no difference between strategies for all-cause mortality or the combined outcome of reinfarction or death (Table). Meta-analysis of 4 RCTs showed no difference between groups for nonfatal MI; 3 RCTs showed a reduction in fatal or nonfatal MI with the invasive strategy (Table). Risk for hospital readmission was also reduced with the invasive strategy (Table).
In patients with unstable angina or non–ST-segment elevation myocardial infarction (MI), an early invasive strategy reduces rates of fatal or nonfatal MI and rehospitalization more than a conservative strategy, but not all-cause mortality or the composite outcome of death or nonfatal MI.
Source of funding: Canadian Institutes of Health Research.
For correspondence: Dr. N.K. Choudhry, Harvard Medical School and Brigham and Women's Hospital, Boston, MA, USA. E-mail firstname.lastname@example.org.
Table. Invasive vs noninvasive strategies for early management of unstable angina or non–ST-segment elevation myocardial infarction (MI) at 6 to 23 months*
|Outcomes||Number of trials (n)||Weighted event rates||RRR (95% CI)||NNT (CI)|
|All-cause mortality||7 (9212)||5.2%||5.5%||3.8% (−25 to 27)†||Not significant|
|Death or nonfatal MI||7 (9212)||14%||16%||14% (−2 to 28)†||Not significant|
|Nonfatal MI||4 (3062)||8.1%||10%||19% (−14 to 44)||Not significant|
|Fatal or nonfatal MI||3 (6150)||7.5%||10%||25% (11 to 37)||41 (28 to 92)|
|Rehospitalization||5 (6482)||21%||28%||26% (4 to 44)†||14 (9 to 82)|
*Abbreviations defined in Glossary; weighted event rates, RRR, NNT, and CI calculated from odds ratio in article using
a random-effects model.
†Statistically significant heterogeneity present.
The choice of an “invasive” or “conservative” strategy for the initial management of patients with acute coronary syndromes (ACSs) has been evaluated in 7 RCTs, the results of which have been summarized by 2 groups using meta-analysis. Although it seems that the 2 meta-analyses reached different conclusions, both groups supported the invasive strategy in their respective discussion sections. Several trial limitations have confused the debate on what used to be a contentious subject, but the evidence now favors percutaneous coronary intervention (PCI) for NSTEMI.
First, the terms that describe the strategies need to be clarified. The “invasive strategy” refers to the routine use of cardiac catheterization, not coronary revascularization with PCI or coronary artery bypass graft (CABG) surgery. The “conservative strategy” limits the use of cardiac catheterization to patients with spontaneous or provokable ischemia, but the term does not convey the fact that 50% of patients allocated to this strategy also received cardiac catheterization. Therefore, these trials tested overlapping diagnostic risk-stratification strategies and did not randomize patients to cardiac catheterization versus control or coronary revascularization versus control.
Second, significant heterogeneity was present in the trials. Large differences existed among trials for men (62% to 97%), cardiac enzyme elevation (18% to 100%), electrocardiogram (ECG) ST-depression (21% to 47%), multivessel or left main disease (40% to 74%), and adjunctive drug therapy. Most important is the fact that patients with positive biomarkers or dynamic ECG changes almost always have plaque rupture, thrombosis, and vascular inflammation present, whereas a large proportion of patients with “unstable angina” in fact have noncardiac chest pain from anxiety, acid reflux, or another cause and do not really have an ACS. Therefore, the invasive strategy in many patients with “unstable angina” defines normal coronary arteries, but has no chance of changing death or MI rates.
Third, the trials were done in different eras and in different health care systems. The TIMI group did 2 of the studies in U.S. hospitals; 1 recruited patients from 1989 to 1992 and the other recruited from 1997 to 1999. 3 studies were done in Europe. VANQWISH was done in Veterans Affairs medical centers 10 years ago (1). Updated American College of Cardiology/American Heart Association guidelines on this topic have been released twice since these studies were completed. Therefore, these trials may not be applicable to the current era, in which platelet GP IIb/IIIa–receptor inhibitors and drug-eluting stents are used during PCI and clopidogrel and statins are recommended for all patients.
Fourth, the choice of revascularization strategy is important. For the past 2 decades, emergency CABG in patients with ACS has been associated with a greater mortality risk than elective CABG, whereas patients rarely die during PCI in the current era. In the VANQWISH trial, there were 2 deaths (1.3%) in the 153 patients having PCI (both in the conservative strategy group) compared with 14 deaths (7.7%) in 182 patients receiving CABG (1). Therefore, PCI should be separated from CABG as a revascularization strategy when outcomes are analyzed.
It may be time to redefine the term “ACS” because it interferes with evidence-based utilization of invasive cardiology resources. Patients with positive biomarkers (NSTEMI) or dynamic ST segments have an unstable coronary artery lesion putting them at risk for death or MI, and they should receive cardiac catheterization with the goal of proceeding to PCI. If CABG is required, it should be done electively, if possible. Patients with unstable angina can be considered for either cardiac catheterization or noninvasive stress testing, depending on the clinical assessment of risk. It is important to note that computed tomography angiography may soon replace cardiac catheterization as a noninvasive means of defining normal coronary arteries in patients with “unstable angina” who seem to be at low risk.
Eric Bates, MD
University of Michigan Medical Center
Ann Arbor, Michigan, USA
1. Boden WE, O’Rourke RA, Crawford MH, et al. Outcomes in patients with acute non-Q-wave myocardial infarction randomly assigned to an invasive as compared with a conservative management strategy. Veterans Affairs Non-Q-Wave Infarction Strategies in Hospital (VANQWISH) Trial Investigators. N Engl J Med. 1998;338:1785-92.