Secondary prevention is poor following revascularization—particularly for CABG

Compliance with guideline-directed medical therapy (GDMT) is low following coronary revascularization—but especially low after coronary artery bypass grafting (CABG), possibly influencing the common comparisons between CABG and percutaneous coronary intervention (PCI).

Lead author Ana-Catarina Pinho-Gomes, MSc, and colleagues reported these findings in the Journal of the American College of Cardiology.

There are numerous clinical trials comparing outcomes between PCI and CABG, but they rarely account for medical therapy following the intervention, according to the authors. To address this issue, Pinho-Gomes et al. pulled data from five randomized trials with follow-up information on medical therapy comparing CABG to PCI with drug-eluting stents.

GDMT was broken into two categories: any antiplatelet agent plus beta-blocker plus statin (GDMT1), or any antiplatelet agent plus beta-blocker plus statin plus angiotensin-converting enzyme inhibitor/angiotensin receptor blocker (ACE inhibitor/ARB) (GDMT2).

The researchers found:

• Compliance with GDMT1 was 67 percent at one year and 53 percent at five years.
• Compliance for GDMT2 was 40 percent at one year and 38 percent at five years.
• For both categories, compliance was higher in PCI than in CABG at all time points.
• Compliance with statins and aspirins was relatively high, ranging from 75 to 95 percent. But ACE inhibitors/ARBs were only used 28 to 79 percent of the time, while beta-blockers were used 43 to 80 percent of the time.

“Despite the compelling benefits demonstrated by GDMT as secondary prevention after coronary revascularization, compliance remains low even in the tightly controlled environment of clinical trials,” Pinho-Gomes et al. wrote. “Furthermore, in our study, compliance with GDMT was higher in patients undergoing PCI compared with patients undergoing CABG, which may skew the comparison of clinical endpoints between those revascularization strategies.”

To that point, the authors noted as compliance in GDMT increased in the PCI group relative to the CABG group, better outcomes with CABG became less marked. There was no difference in clinical outcomes—mortality, MI or a composite of mortality, MI and stroke—when compliance for PCI was roughly 8 percent higher than CABG.

“The underuse of GDMT, particularly after CABG, is likely multifactorial,” the researchers wrote. “It may be related to underestimation of the importance of GDMT and the misconception that the value of maintaining GDMT is reduced once diseased coronary arteries have been mechanically revascularized with either PCI or CABG. In keeping with this, medical therapy is often neglected in coronary revascularization trials and hence poorly reported or not even collected at all.”

The researchers suggested the cost of the cardiovascular medications may have played a role in the poor adherence to guidelines, as the studies were conducted in multiple countries with varying drug costs. Also, medication adherence was likely overestimated in the study because the researchers used prescriptions as a substitute for adherence; in reality, patients may not have taken all of their prescribed drugs.

Despite varying drug recommendations following PCI or CABG, Pinho-Gomes et al. reiterated a true comparison between the strategies couldn’t take place unless medical therapies are equal with both techniques.

In an accompanying editorial, Marc Ruel, MD, MPH and Alexander Kulik, MD, MPH, pointed out the analysis was limited because it only contained a few studies and lacked individual patient-level data on clinical outcomes. However, the unique design of the study was a strength, they wrote, and the researchers’ work should serve as a reminder to track secondary prevention data in future trials.

“Going forward, clinical investigators must direct their energy toward collecting prescription data in CAD trials and strive to implement GDMT for nearly all study subjects,” Ruel and Kulik wrote. “As leaders in the field and frequent co-authors of guideline statements, revascularization trialists have a responsibility to serve as role models in improving GDMT prescription rates.”