MI patients with nonobstructive coronary arteries should receive similar follow-up as those with CAD

Patients with myocardial infarction (MI) with nonobstructive coronary arteries appear to benefit from select secondary preventive measures, especially achieving target range low-density lipoprotein (LDL) cholesterol levels, according to a study.

“[O]ur findings emphasize the importance of structured follow-up routines in patients with MI with nonobstructive coronary arteries,” researchers said. “Although this condition may be the result of different aetiologies, our results demonstrate that much of the prognostic benefit of follow-up is associated with the modification of cardiovascular (CV) risk factors.”

The analysis included 5,830 MI patients with nonobstructive coronary arteries (group 1) and 54,637 MI patients with significant coronary artery disease (≥50 percent stenosis; group 2). Reduction in the 1-year risk of major adverse events linked to prespecified secondary preventive measures—participation in follow-up at 6–10 weeks after the hospitalization and achievement of secondary prevention targets (blood pressure and LDL cholesterol levels in the target ranges, nonsmoking, and participation in exercise training)—were evaluated using multivariable- and propensity score-adjusted statistics.

Compared with patients in group 2, those in group 1 had fewer follow-ups and less often achieved any of the secondary prevention targets. Participation in the 6–10-week follow-up correlated with a 3–20-percent risk reduction in group 1. Interaction analysis showed comparable association in group 2. [Am J Med 2018;131:524-531.e6]

Achieving target range LDL cholesterol levels (24–32-percent risk reduction) and, to a lesser extent, participating in exercise training (10–23-percent risk reduction) were the main drivers of outcome improvement in group 1.

“Achieving LDL cholesterol levels in the target range was associated with a 24–32-percent reduction in the risk of major adverse events,” researchers said. “This corresponds with recent findings from our group demonstrating that statin treatment in these patients is associated with improved outcome.” [Circulation 2017;135:1481-1489]

Additionally, previous studies have shown that physical exercise is associated with positive effects on many CV risk factors, improves cardiac function, lessens myocardial remodeling and may reduce risk across a broad range of CV conditions. [BMJ 2004;328:189; Prev Med 2007;45:169-176; Cochrane Database Syst Rev 2016;doi: 10.1002/14651858.CD001800.pub3]

“Our results for the first time extend this notion to MI patients with nonobstructive coronary arteries,” researchers said, adding that “[t]he low participation rate in exercise training among these patients from our cohort is worrisome.”

“Limitations in healthcare resources might represent a possible explanation because an additional 215 patients participated after the 6–10-week follow-up. Given the design of our study, these patients were not considered for the analyses,” they said.

However, researchers noted that overcoming the barriers behind the underuse of cardiac rehabilitation could likely lead to further outcome improvement in MI patients with nonobstructive coronary arteries.

“We also want to stress the need of further investigation, preferably using cardiac magnetic resonance, for aetiologic clarification. This will help to identify patients with undetected myocarditis or true infarction who require specific treatments,” they added.