Declining Coronary Artery Bypass‐Related Mortality: More Than Meets the Eye?

Abstract

Dr. Bhatt receives research grants from Amarin, AstraZeneca, Bristol‐Myers Squibb, Eisai, Ethicon, Medtronic, Sanofi Aventis, and The Medicines Company. The authors have no other funding, financial relationships, or conflicts of interest to disclose.

Over the last 2 decades, the United States has seen a significant fall in mortality related to coronary artery disease.1 This improvement has been attributed to better primary prevention by controlling traditional cardiovascular (CV) risk factors and to the implementation of evidence‐based secondary therapies including revascularization.

In this issue of Clinical Cardiology, Movahed et al present data from a large inpatient database highlighting the impressive decrease in age‐adjusted mortality rates after isolated coronary artery bypass grafting (CABG) in over 1.1 million patients from 1988 to 2004.2 In their article, the authors found that since 1989, the age‐adjusted rate for all CABG‐related mortality has been dropping steadily, reaching its lowest level in 2004 (300 per 100 000 in 1989 to 105 per 100 000 in 2004). They also found a decline in total death rates from 5.5% to 3.06%.

With the changing landscape of revascularization strategies and rapid improvements in percutaneous coronary intervention (PCI), the volume of CABG performed has declined, with a corresponding increase in PCI volume, including for multivessel disease. It has also been shown that the baseline risk for patients undergoing CABG has consequently risen, with a greater proportion with advanced age, diabetes, renal dysfunction, or heart failure.3 The data presented by Movahed et al are reassuring because the gains in in‐hospital mortality clearly extend to the vulnerable populations of patients with diabetes or heart failure.

Although the authors make reasonable speculations regarding reasons for better outcomes, the nature of their database precludes them from elucidating the actual causes. However, evidence comes from a recent publication from the Society of Thoracic Surgeons adult cardiac surgery database.4 In the period from 2000 to 2009, ElBardissi et al report a 6.3% increase in aspirin use and a 19.5% increase in perioperative β‐blockers, a 7.8% increase in angiotensin‐converting enzyme inhibitor use from 2004 to 2009, and a 3.8% increase in statin use from 2005 to 2009. In terms of the surgical procedure itself, they showed a 7% increase in internal thoracic artery use and a three minute decrease in the mean perfusion time.

In addition, it is almost impossible to capture the contribution of vastly improved perioperative care. Parallel data exist in the field of PCI. Holper et al showed significant reductions in death, myocardial infarction, and need for CABG in diabetic patients undergoing PCI.3 Roe et al showed improvements in outcomes for patients undergoing PCI for acute coronary syndromes in a 2‐year period from 2007 to 2009.5 Some of the improvement in mortality noted in the study by Movahed et al could be due to the observed decrease in the percentage of ST‐segment elevation myocardial infarction patients undergoing CABG, as these patients are now more often treated with PCI.

Despite increasing comorbidities, the decreasing mortality is certainly a commendable achievement and appears to be real. More difficult to measure is the potential impact of public reporting of outcomes on selection of patients by surgeons. It is conceivable—and substantial evidence supports—that public reporting, which became available in New York in 1991 and thereafter spread nationwide, has led surgeons to sometimes decline to operate on the highest‐risk patients who they think may benefit, but because of fears of the consequences of public reporting, refuse to do so.6., 7., 8. Related to this is the phenomenon of placing patients at moderate risk into high‐risk categories to favorably influence risk‐adjusted outcomes. These phenomena have been noted in the interventional cardiology literature as well.9

Additionally, the field of cardiovascular outcomes—and medicine in general—are shifting away from a focus only on in‐hospital mortality to intermediate‐ and long‐term results. If greater scrutiny of in‐hospital or even 30‐day surgical mortality led surgeons to transfer patients to other facilities so that the death occurred elsewhere and would not count against them, that too could artificially make the improvement in mortality look better than is actually the case.7

What is undeniable, however, is that there have been technical, procedural, and process‐based improvements in revascularization methods, coupled with effective medical therapies for primary and secondary prevention of CV events. Although CV surgeons, interventionalists, and noninvasive cardiologists everywhere should take a bow, we should ensure that the collaborative concept of the heart‐team approach espoused in recent times grows and spreads as we strive together toward further improvements in CV outcomes for our patients.10