Coronary Artery Revascularization: Interesting New Data
July 1, 2002 5 minutes read
Coronary Artery Revascularization: Interesting New Data
Abstracts & Commentary
Editor’s Note: This article reviews 3 recent studies that shed considerable light on the role of percutaneous interventions as well as coronary bypass graft surgery (CABG) in patients with coronary artery disease (CAD).
This comprehensive analysis of a swedish database of coronary care unit admissions in 75% of Swedish hospitals between 1995 and 1998 was designed to assess whether early revascularization improved long-term (1-year) survival following a first acute myocardial infarction (MI). Individuals older than 80 years of age were excluded. Data were recorded in a Swedish registry, which included detailed information about MI patients, including risk factors, prehospitalization treatments, treatment during hospitalization, procedure use, complications, and survival at 30, 60, 90 days, and 12 months. This was not a randomized trial; patients were sent for revascularization at the discretion of their physicians. A propensity score was calculated to assess the likelihood of early revascularization. The primary outcome was 1-year survival in MI patients alive at day 14 after acute MI. Approximately half of the patients had ST segment elevation MI (STEMI) and half had non-STEMI. The Swedish Registry was comprised of 36,294 patients who had a first MI during the registration period, of whom 21,912 were younger than 80, survived for 14 days after event, and had complete data. These patients represent the study cohort. Individuals who underwent revascularization included those who had primary angioplasty at admission or before 14 days, or had an acute thrombolysis. A total of 2554 patients received revascularization within 14 days of MI, 19,358 did not; thus 12% underwent revascularization by 14 days and 31% by one year. A total of 55% of the revascularization group underwent acute primary revascularization or acute thrombolysis. Data for CABG, if performed, are not provided.
Results: The revascularization cohort were a minority of the entire Swedish experience; they were younger, more often males, less frequently diabetics, and they had less congestive heart failure (CHF). Although they had more prior revascularization and in-hospital infarction and were on more medications for CAD. The conservative group had a 38% rate of acute thrombolysis. The registry demonstrates a close relationship between choice of therapy and the presence of a cath lab. The majority of hospitals did not have a cath lab, and no more than 5% of these patients had a revascularization procedure. However, in the 9 institutions that had a cath lab, the proportion of revascularized patients was approximately 25-30%. There was a 10-fold difference in the proportion of individuals between the highest and lowest hospital rates of revascularization. Other variables associated with early revascularization included younger age, ST segment elevation, absence of thrombolysis, and absence if diabetes. The 1-year mortality for individuals who did not have an early coronary intervention was 9% compared to 3% in the 12% of patients who did. After multiple adjustments, the results were similar, indicating a major significant decrease in mortality in revascularized patients at 1 year. Although data were not provided, Stenestrand and Wallentin note that "similar reductions" occurred at 30, 60, and 90 days. Early coronary intervention was associated with lower mortality regardless of gender, prior MI or CHF, or presence of diabetes. Improved survival was seen in individuals with STEMI and NSTEMI. An interesting subanalysis indicated that statin treatment at discharge resulted in even greater improvement in survival at 1 year and was additive to early revascularization; those without a statin and no revascularization had the poorest survival at 1 year. Similar results were found with beta-blocker use. Stenestrand and Wallentin concluded that their data support the benefit of early coronary intervention on survival, also suggested by the FRISC II results. The results were somewhat more robust in the NSTEMI cohort, 65% risk reduction; P = .001 vs. STEMI, 36% risk reduction; P = 0.012. They state that "the most important factor affecting the rate of early revascularization was in-house access to a catheterization laboratory." They conclude that the early procedure itself rather than patient selection was responsible for the consistent findings in this very large database (Stenestrand U, Wallentin L. Lancet. 2002;359:1805-181l).
Comment by Jonathan Abrams, MD
This observational database is persuasive because of its large size. However, this is not a randomized trial and there is a large numerical discrepancy between the minority of patients who underwent revascularization and those who did not. The results are clearly related to whether a hospital had a catheterization laboratory. There are a number of caveats. Stenestrand and Wallentin do not discuss why one quarter of the early revascularization patients received thrombolysis and then went on to have PCI. Furthermore, there is no mention of the breakdown between PCI and coronary bypass grafting, although one gets the impression that a large majority of revascularizations were percutaneous in nature. An important analysis would have been a comparison of the 38% in the "conservative group" who received thrombolytic therapy compared to the percutaneous revascularization population. These represent 7300 patients, and presumably would have had a better outcome when compared to the conservatively treated patients who did not have lytic therapy. Conservative patients in the aggregate appeared to be at high risk, due to a greater percentage of pre-existing diabetes and CHF, and on average they were 4 years older than the revascularization cohort. Furthermore, the use of angiography in this large group of individuals was only 6% in hospital, although 11% of the conservatively managed patients ultimately did receive a revascularization procedure between day 15 and 365 days post MI. A total of 55% of the revascularization cohort received their procedure nonacutely, suggesting that they had recurrent ischemia or a strongly positive stress test. No information is given about this group. Overall, the median use of angiography in the entire registry was 6% (3% in the first decile, 26% in the 10th decile)—far lower than the current practice in the United States. Nevertheless, one has to conclude that early PCI is more than likely associated with an improved outcome both early and late. The survival curves are still widening at 1 year, and the benefits of revascularization may become greater. Because these are observational data, it is possible that confounding variables that were not identified could influence the results. However, the large size and the relatively equal balance of STEMI and NSTEMI certainly support the current trend for early revascularization in acute MI. What is not clear, however, from this database, is whether individuals who received revascularization immediately on admission represented the major benefit, compared to those who got their revascularization within the next 13 days.
Dr. Abrams is Professor of Medicine, Division of Cardiology, University of New Mexico, Albuquerque.
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