PCI in Addition to Medical Therapy for Stable CAD The Debate Continues
Abstract & Commentary
By Andrew J. Boyle, MBBS, PhD, Assistant Professor of Medicine, Interventional Cardiology, University of California, San Francisco. Dr. Boyle reports no financial relationships relevant to this field of study.
Source: Hannan EL, et al. Comparative outcomes for patients who do and do not undergo percutaneous coronary intervention for stable coronary artery disease in New York. Circulation 2012;125:1870-1879.
Medical therapy is the mainstay of treatment for coronary artery disease (CAD), resulting in improved clinical outcomes. Revascularization with percutaneous coronary intervention (PCI), in addition to medical therapy, improves symptoms in patients with stable CAD. The addition of revascularization to medical therapy has not been shown to reduce the rate of myocardial infarction (MI) or death in randomized clinical trials with restrictive inclusion and exclusion criteria. However, in real-world clinical practice, physicians do not randomize patients; they employ their clinical judgment as to who would benefit from the addition of PCI to medical therapy. Whether PCI results in better clinical outcomes in this context is not known. Hannan and colleagues studied the New York State Cardiac Diagnostic Catheterization Database to identify all patients undergoing diagnostic catheterization and linked this to the state hospital discharge database, the PCI database, and the Social Security death index. They used these four linked databases to determine the percentage of patients who undergo PCI after diagnostic catheterization, and the outcomes of patients with stable CAD who undergo PCI compared to those who have routine medical therapy.
They included all patients with stable CAD, at least one coronary stenosis > 70%, and Canadian cardiovascular class 0-III symptoms. Excluded were patients with left main disease, life-threatening arrhythmia, valve disease requiring surgery, acute coronary syndromes, a negative or high-risk stress test, prior revascularization, and those who chose to undergo coronary artery bypass graft surgery (CABG) for revascularization. Over a 6-year period, they identified 9586 patients who underwent diagnostic angiography for stable CAD, of whom 1100 received routine medical treatment alone (RMT group). The remaining 8486 (89%) underwent PCI in addition to RMT (PCI/RMT group). Patients in the PCI/RMT group were younger, and were more likely to have private health insurance, a positive stress test and a larger area of viable myocardium, proximal left anterior descending disease, class III angina, and a normal injection fraction. They were less likely to have peripheral arterial disease or have had prior CABG. Because of these significant baseline differences between groups, the authors performed propensity score matching for 20 variables and identified 933 pairs of matched patients in the two groups. After propensity score matching, there were no longer any baseline differences between groups.
At 4 years of follow-up, the PCI/RMT group had lower rates of combined MI/mortality (16.5% vs 21.2%; P = 0.003), lower mortality (10.2% vs 14.5%; P = 0.02), MI (8.0% vs 11.3%; P = 0.007), and subsequent revascularization (24.1% vs 29.1%). The adjusted hazard ratio for death in the RMT group (vs PCI/RMT) was 1.46. The authors conclude that most patients in New York with stable CAD undergoing diagnostic catheterization received PCI. Patients who received PCI experienced lower mortality, mortality/MI, and revascularization rates.
Commentary
This study is at odds with the COURAGE trial, which found that there was no reduction in mortality or MI in patients who received PCI + optimal medical therapy (OMT) compared to those who received OMT alone. The present study found that there was indeed a reduction in MI and mortality in patients who received PCI + RMT compared to those who received RMT alone. Why is there such a discrepancy between the findings of these two studies? There are several important differences between the studies that may have contributed to this. First, the COURAGE trial was randomized and prospective, whereas the current study was observational and retrospective. Randomization removes selection bias and we often think of this as a more robust way to demonstrate the benefit of a specific treatment. However, randomized trials, such as the COURAGE trial, tend to have narrow inclusion criteria (more than 35,00 patients underwent diagnostic catheterization and just over 1,000 [approx 3%] were randomized to each arm). While registries like the current study may have some degree of selection bias, they include a much more general "all-comers" population. Thus, incorporating clinical judgment into an observational study of strategies of care may produce interesting results that could complement the results of randomized clinical trials. There are pros and cons to each study type, and when they are in agreement, this strengthens the evidence from each one. However, when they are discrepant, controversy will persist until a definitive trial is conducted.
Second, this trial used the term "routine medical therapy" rather than OMT, because the exact details of the medications, the blood pressures, lipid levels, medication adherence, and lifestyle factors are not known. In the COURAGE trial, OMT included training nurse managers to counsel patients on lifestyle and risk factor reduction, medications that were provided at no cost to the patients, and follow-up that was rigorous. There was a resultant very high adherence rate: In real-world clinical practice, such high rates of adherence are rarely achieved. Which of these studies more accurately represents our own practices? Perhaps one of the take-home messages from this study is that moving from RMT to OMT may make PCI unnecessary. It is interesting to note, however, that the repeat revascularization rates were very similar in this study and the COURAGE trial. The crossover from medical therapy to PCI was 29% in this study and 33% in COURAGE. The repeat revascularization rates in the PCI arms were 24% and 21%, respectively. Revascularization was symptom-driven. This suggests that the efficacy of the medical therapy at reducing angina was probably about the same in each trial.
Third, the study design here (linking databases from one state) may miss some patients who had events out of state or had data incorrectly logged. This is an inherent problem in all registry data. It is likely that this would make little impact on the overall outcome, but there may be some bias introduced in this way. The results should be interpreted with this in mind.
Finally, the evolution of PCI practice may explain some of the differences. In COURAGE, drug-eluting stents were only used in a minority of patients (3%). Since then, PCI practice has evolved to include higher rates of drug-eluting stent use, better antiplatelet agents, smaller catheters, and more transradial procedures, all of which are associated with better outcomes. It is likely that newer, better interventional techniques have improved PCI outcomes.
How should we treat our patients with stable CAD in the light of these new findings? Does this negate the COURAGE trial? Certainly not! All patients should continue to be treated with guideline-driven medical therapy to achieve targeted risk factor and lifestyle goals, as well as to minimize angina. In addition to this, PCI is known to reduce angina and continues to be a reasonable option in selected patients.
Medical therapy is the mainstay of treatment for coronary artery disease (CAD), resulting in improved clinical outcomes. Revascularization with percutaneous coronary intervention (PCI), in addition to medical therapy, improves symptoms in patients with stable CAD.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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