COMMENTARY
Christopher Labos, MD CM, MSc, FRCPC
DISCLOSURES | August 08, 2024
If this is what your kitchen looks like, you may not be good with change. By the end of this video, I’m going to explain to you why carpets in your kitchen are a bad idea, and why your patient may not need that beta-blocker. This is On Second Thought.
Giving patients a beta-blocker after a myocardial infarction is standard of care. It’s in the guidelines. It’s one of the performance measures used by the American College of Cardiology (ACC) and the American Heart Association (AHA). If you aren’t putting your post–acute coronary syndrome (ACS) patients on a beta-blocker, the ACC and the AHA both think you suck.
They are very disappointed in you, just like your mother was when you told her you didn’t want to become a surgeon because you don’t like waking up early, your hands shake when you get nervous, it’s not your fault, there’s nothing you can do about it, so just leave me alone!
The data on beta-blockers are decades old. In the time before stents, statins, angiotensin-converting enzyme inhibitors, and dual antiplatelet therapy, when patients either died or got better on their own, beta-blockers showed major benefits. Studies like the Norwegian Multicenter Study Group, the BHAT trial, and the ISIS-1 trial proved the benefits of beta blockade. These studies date back to the 1980s, when you could call a study ISIS without controversy.
It was a simpler time, when all you had to worry about was the Cold War, apartheid, and the global AIDS pandemic. It was a time when doctors smoked in their offices, and patients had bigger infarcts that caused large scars and systolic dysfunction. That world is no longer our world, except for the war, the global pandemic, and the out-of-control gas prices.
The reality is that before troponins, we probably missed most small heart attacks. Now, most infarcts are small, and most patients walk away from their heart attacks with essentially normal hearts. Do beta-blockers still matter? If you’re a fan of Cochrane reviews, the answer is yes.
In 2021, Cochrane published a review of beta-blockers in patients without heart failure after myocardial infarction (MI). The authors of that analysis concluded, after the usual caveats about heterogeneity, potential bias, and the whims of a random universe, that, yes, beta-blockers do reduce mortality. The risk ratio for max all-cause mortality was 0.81.
What does that mean practically? The absolute risk was reduced from 10.9% to 8.7%, a 2.2–percentage point absolute decrease and about a 20% relative drop. A little math gives us a third number: 46. That’s the number needed to treat. If you think about how many patients you admit during a typical week of critical care unit with an MI, a number needed to treat of 46 is a pretty good tradeoff for a fairly inexpensive medication with fairly minimal side effects.
Of course, these are the same people who claim that masks don’t stop the spread of COVID-19. Sure, were they the only people who thought that handwashing was the best way to stop a respiratory virus? No. We all believed that fantasy for far longer than we should have. Not everybody can bat a thousand, if by batting a thousand, you mean reflecting on how your words will impact on a broader population primed to believe misinformation because of the increasingly toxic social media environment and worsening politicization and radicalization of our politics.
By the way, if any of you want to come to Canada, you can stay with me. Things are incrementally better here. In this day and age, incrementally better is the best we can hope for.
Here’s the wrinkle with the Cochrane beta-blocker review: Many of the studies took place before early revascularization became the norm and before our current armamentarium of drugs became standard of care.
Back in the day, bed rest and the power of positive thinking were the mainstays of cardiac treatment. Also, many of these studies mixed together ST-segment MI (STEMI) and non-STEMI patients, so you’re obviously going to see more benefits in STEMI patients who are at higher risk. Some of them used intravenous (IV) beta-blockers right away, whereas some were looking only at oral beta-blockers started days after the infarct.
We don’t use IV beta-blockers that much anymore because of the risk for shock.
Also, some studies had short-term follow-up where the benefits were less pronounced, and some studies used doses and types of beta-blockers rarely used today. Some of the studies had a mix of coronary and heart failure patients, which muddies the water because the heart failure patients would clearly benefit from being on a beta-blocker.
Basically, the data are not definitive because they are old and don’t reflect our current standard of care. The data contain a heterogeneous mix of patients that aren’t really relevant to the question that we’re asking. The question we’re asking is, should you put all your post-MI my patients on a beta-blocker routinely, even if they don’t have heart failure?
The REDUCE-AMI trial is the first of a few trials testing, or to be more accurate, retesting, whether beta-blockers are useful after an MI. BETAMI, REBOOT, DANBLOCK— you’ll be hearing these names in the next few years, either because the studies get published or because they’re the Twitter handles of people harassing you online. Either/or. (By the way, I’ll be cold in my grave before I call it X.)
For now, REDUCE-AMI is the first across the finish line, and at least in cardiology, finishing first is a good thing. This study enrolled patients with ACS, both STEMI and non-STEMI, with a post-MI ejection fraction ≥ 50%, and the result was nothing. The risk ratio for all-cause mortality was 0.94 and was not statistically significant.
In absolute terms, that’s a reduction from 4.1% to 3.9%, or a 0.2–percentage point decrease; this translates into a number needed to treat of 500, which is 10 times higher than what the Cochrane review found. That’s if you assume that there is, in fact, a small benefit amidst all the statistical noise, which there probably isn’t.
Now, studies like this can never rule out small effects, either positive or negative, so maybe there is a small benefit from using beta-blockers. If it’s there, it’s really small. Do beta-blockers work? Well, yes, obviously, for heart failure and atrial fibrillation — which, let’s face it, are not exactly rare and often coexist in patients with heart disease. They probably aren’t that great as blood pressure pills, but that’s a story for another day and another video.
Yes, beta-blockers are useful pills, and they are standard of care, just maybe not for post-MI patients with normal ejection fractions because they probably don’t really need them. They worked in the pre-stent, pre-aspirin, pre-anything era.
That’s not our world anymore. Things change. It’s not the 1980s. That’s why I don’t have a mullet, and that’s why you need to update your kitchen.
For Medscape, I’m Christopher Labos.
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