Everyone takes a pharmacology class in medical school that includes a lecture on beta receptors. They're in the heart (beta-1) and lungs (beta-2), and drug compounds agonize or antagonize one or both. The professor will caution against using antagonists (beta blockade) for patients with chronic obstructive pulmonary disease (COPD) lest they further impair the patient's irreversibly narrowed airways. Obsequious students mature into obsequious doctors, intent on "doing no harm." For better or worse, you withhold beta-blockers from your patient with COPD and comorbid cardiac disease.
Perhaps because the pulmonologist isn't usually the one who decides whether a beta-blocker is prescribed, I've been napping on this topic since training. Early in fellowship, I read an American College of Physicians' Journal Club article about a Cochrane systematic review (yes, I read a review of a review) that concluded that beta-blockers are fine in patients with COPD. The summary appealed to my bias towards evidence-based medicine (EBM) supplanting physiology, medical school, and everything else. I was more apt to believe my stodgy residency attendings than the stodgy pharmacology professor. Even though COPD and cardiovascular disease share multiple risk factors, I had never reinvestigated the relationship between beta-blockers and COPD.
Turns out that while I was sleeping, the debate continued. Go figure. Just last month a prospective, observational study published in JAMA Network Open found that beta-blockers did not increase the risk for cardiovascular or respiratory events among patients with COPD being discharged after hospitalization for acute myocardial infarction. Although this could be viewed as a triumph for EBM over physiology and a validation of my decade-plus of intellectual laziness, the results are actually pretty thin. These studies, in which patients with an indication for a therapy (a beta-blocker in this case) are analyzed by whether or not they received it, are problematic. The fanciest statistics — in this case, they used propensity scores — can't control for residual confounding. What drove the physicians to prescribe in some cases but not others? We can only guess.
This might be okay if there hadn't been a randomized controlled trial (RCT) published in 2019 in The New England Journal of Medicine that found that beta-blockers increase the risk for severe COPD exacerbations. In EBM, the RCT trumps all. Ironically, this trial was designed to test whether beta-blockers reduce severe COPD exacerbations. Yes, we'd come full circle. There was enough biologic plausibility to support a positive effect, or so thought the study authors and the Department of Defense (DOD) — for reasons I can't possibly guess, the DOD funded this RCT. My pharmacology professor must be rolling over in his tenure.
The RCT did leave beta-blockers some wiggle room. The authors purposely excluded anyone with a cardiovascular indication for a beta-blocker. The intent was to ensure beneficial effects were isolated to respiratory and not cardiovascular outcomes. Of course, the reason I'm writing and you're reading this is that COPD and cardiovascular disease co-occur at a high rate. The RCT notwithstanding, we prescribe beta-blockers to patients with COPD because they have a cardiac indication, not to reduce acute COPD exacerbations. So, it's possible there'd be a net beta-blocker benefit in patients with COPD and comorbid heart disease.
That's where the JAMA Network Open study comes in, but as discussed, methodologic weaknesses preclude it being the final word. That said, I think it's unlikely we'll see a COPD with comorbid cardiac disease RCT performed to assess whether beta-blockers provide a net benefit, unless maybe the DOD wants to fund another one of these? In the meantime, I'm calling clinical equipoise and punting. Fortunately for me, I don't have to prescribe beta-blockers. I suppose I could consider stopping them in my patient with severe COPD, the one I can't keep out of the hospital, but I'm not convinced that would make much difference.
Aaron B. Holley, MD, is a professor of medicine at Uniformed Services University in Bethesda, Maryland, and a pulmonary/sleep and critical care medicine physician at MedStar Washington Hospital Center in Washington, DC. He covers a wide range of topics in pulmonary, critical care, and sleep medicine.Â
Â