The Truth About Aspirin and Heart Attack Prevention

I've seen daily aspirin save lives from heart attack — and cause fatal bleeds. As a vascular surgeon, here's my honest take on heart health.

The answer isn't yes or no — it depends entirely on who you are.

In this video I break down the three groups you need to know:

✅ Who SHOULD take daily aspirin — if you've already had a heart attack, stroke, or stent, aspirin for secondary prevention of heart disease is still one of the most evidence-backed interventions we have.

❌ Who SHOULD NOT — the 2022 USPSTF guidelines quietly changed the recommendations for primary prevention. If you haven't had a cardiovascular event, daily aspirin may be doing more harm than good.

⚠️ The gray zone — two situations where the answer gets complicated: elevated coronary artery calcium (CAC) scores and high Lp(a) (lipoprotein a). Both raise your cardiovascular risk in ways the standard guidelines don't fully account for.

This is the conversation your doctor should be having with you — but often doesn't have time for.
 
I'm a vascular surgeon teaching the prevention side of medicine — the part most doctors don't have time to cover. Subscribe for more evidence-based answers on heart disease, metabolic health, and longevity.
 
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🧬 About Dr. Lily Johnston
  
Dr. Johnston is a double board-certified vascular and general surgeon in San Diego, specializing in metabolic and cardiovascular prevention. She’s the founder of CorSight Health and a passionate advocate for reimagining how medicine approaches chronic disease.
  
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Transcript

SPEAKER_01 0:00

Are you one of the 30 million Americans taking a daily aspirin to prevent a heart attack? You might be doing the right thing, you might be wasting your time, or you might be bleeding for nothing. Let's go through the evidence and figure out which one you are. And stick around until the end where we will help you understand your own personal risks and benefits using AI. If you're new here, my name is Dr. Lily Johnston. I am a board-certified vascular surgeon, but I also specialize in cardiometabolic prevention. So hopefully you never need me as a surgeon. Now, most of my patients on the surgery side are all on aspirin. And why is that? Well, there's a whole category of people who absolutely should be taking aspirin every day for secondary prevention. What does that mean? Secondary prevention. It means they've already had either a heart attack, a stroke, or a mini stroke, or some problem with the circulation in their legs that has led to a problem or a procedure. So for most of my patients, that is what has happened. I have put a stent in their leg, or we've done a bypass operation, maybe I've cleaned out the arteries in their neck. So they're on an aspirin, or maybe even something stronger for that. And if you are in that category, you should also be on an aspirin. Don't let your primary care doctor tell you, oh, the guidelines don't support that anymore. You are not who those guidelines are talking about. We're going to get to those folks in just a bit. If you've had a bypass, a heart attack, a stroke, a stent, aspirin, or something stronger, is definitely for you. And we have good evidence to support this. We had a meta-analysis that showed a 20% reduction in serious vascular events. So if you are in this group, how many patients like you have to take an aspirin to get benefit? This is something we call number needed to treat. And it helps frame how effective these interventions are versus the number of people who would have to take it to incur harm. What's the harm associated with aspirin, by the way? It's bleeding risk. So patients who take aspirin, if we give it to enough people, some of them will have bleeding from the GI system, even like nosebleeds, or the most serious would be a bleeding episode in the brain. So there is absolutely some risk to aspirin and other antiplatelet agents, which is how aspirin works, by the way, to incur this benefit. And we want to balance the benefits versus the harms. So if you have history of heart attack, stroke, uh bypass or stenting, then we have to treat about 50 to 67 patients like you with aspirin to get one person to benefit or have a reduction in events. That's actually, it sounds like a lot, but it's pretty good in the grand scheme of medical interventions. Numbers needed to treat under 100 are pretty strong. By comparison, the number needed to harm is over 100 for aspirin in this population. So if you've had those events, aspirin is your friend, stay on it. In fact, aspirin is so effective in this group of patients who've had events that it has become the standard against which we measure new things like pelavix or burlinta, other types of medications that inhibit platelet function. We now use aspirin as the gold standard in research to compare these things to. That's how effective it is. And that's why if your cardiologist or your vascular surgeon put you on that aspirin, it's a good thing to keep taking. Next, let's talk about who should not be taking a daily aspirin anymore. But what if you have not had a heart attack or a stroke, have never needed a vascular surgeon for anything? That's awesome for you. But many people have thought, well, aspirin a day keeps the doctor away. I will just take this to ward off all of that badness because it's probably good for me, right? That used to be very common. And in fact, primary care doctors used to advise their patients to do this. However, we have new guidelines from 2022, the USPSTF or the Preventative Services Task Force in the United States. And we are now very clearly saying do not take aspirin, especially if you're over 70. But even in the younger age groups, if all you have is a wish not to have a heart attack or a stroke. But unless you've had a heart attack or an event, then it may actually hurt you and cause harm. The um best review of all of this I have seen was by Dr. Eric Topel. He runs a great Substack. Dr. Topel is one of the leaders in longevity and evidence-based medicine, and he has a great synthesis of the evidence against aspirant for primary prevention. And I actually want to take you through uh his synthesis of all of the evidence because it's really the best picture we have today about why the average person who's not had any problems should not take aspirin for primary prevention. Let's walk through the three big trials that came out in 2018 that informed these new guidelines and really showed why we all shouldn't be just taking an aspirin for the heck of it. Let's, there are these three pivotal trials. The first is the esprit trial that came out and had 19,000 patients. It enrolled healthy adults over 70 years of age, mean age was 74. They were randomized to 100 milligrams of aspirin, and they looked at the primary cardiovascular outcome, and they showed no benefit in this group of patients. However, they did show an increase in major risk for bleeding, which was increased by 38%, which ultimately also showed an increase in all-cause mortality and cancer-related mortality. Next, we have the Ascend trial. This enrolled 15,000 patients who had a diagnosis of type 2 diabetes. Average age was 63, also randomized to 100 milligrams a day of aspirin or not. And they did show a 12% reduction in vascular events, but again, we see an increase in major bleeding by about 30%. And finally, the arrived trial, another 12,000 patients. These were moderate risk individuals, so a little bit higher risk for a cardiac event, 10 to 20% based on the risk calculators, which you know how I feel about those, but best we have. And uh average age was 61 years old, again, 100 milligrams of aspirin. They did not find any difference in heart attack or stroke, but higher risk for major bleeding. So you take all of these together and you find a neutral or maybe slightly improved risk for cardiac events, but definitely a high risk for bleeding in this group. So when you take all of this together, the obvious conclusion is if you don't have a really good reason to be taking aspirin, like proven benefit in cardiac or stroke outcomes, then the risk of bleeding just isn't worth it. I'll show you these data in another way. Let's scroll down here and look at the Kaplan-Meyer curves. So looking at all-cause mortality, this was from the esprit trial again. Um, you see here that at about four years, we start to see some separation here where mortality is actually higher in the aspirin group and lower in that placebo group. And you're gonna see this same curve for different things over and over again: deaths from cancer and specifically major bleeding events, just like we talked about. And that starts quite early. That is almost immediate. You see an increased risk in the aspirin group versus the placebo group. So when you look at the Ascent trial, these are the patients who had a diagnosis of type 2 diabetes. We absolutely see that improvement here in the risk of vascular events, but that is outweighed really by the increasing risk of bleeding in these patients. All right, so that is the synthesis of all of the evidence here. And as the United Services States Preventive Services Task Force got all these guidelines together, they now have this recommendation that we'll go through here. So, taken together, we now have two major sets of recommendations. I'll start with the American College of Cardiology, American Heart Association recommendations. The first of these is shown here in this table, and it says low-dose aspirin might be considered for primary prevention of ASCBD or atherosclerotic cardiovascular disease among select adults aged 40 to 70 years of age who are at higher risk for heart attack, stroke, or PAD, but not at increased bleeding risk. And the next of these recommendations says low-dose aspirin should not be administered on a routine basis for the primary prevention of ASCVD among adults over age 70. And the third recommendation, low-dose aspirin should not be administered for primary prevention among adults of any age who are at increased risk for bleeding. The USPSTF, U.S. Preventive Services Task Force, is actually a little more stringent in their recommendations. So they have a grade C recommendation here that says adults age 40 to 59 with 10% or greater 10-year cardiovascular risk. In those patients, the decision to initiate low-dose aspirin use for primary prevention should be an individual one. Evidence indicates that the net benefit of aspirin use in this group is small. Persons who are not at increased risk for bleeding and are willing to take low-dose aspirin are more likely to benefit. And they actually bring this age cutoff down to 60. The ACC AHA said 70, but USPSTF says 60. USPSTF recommends against initiating low-dose aspirin for the use of primary prevention in adults 60 or older. So if you are in that category and you're still taking your daily aspirin, you might want to rethink that, unless you are in a couple of select groups of patients that I see every day. So of course, there are gonna be some exceptions to those rules that I just laid out for you because I see patients every day who've not yet had a heart attack or a stroke that are in my prevention practice that I recommend aspirin for. So who should get an aspirin for what we're gonna call secondary light? So patients with known disease. There have been studies that look at patients with a calcium score of greater than 100. And in those patients, there actually does seem to be some protective benefit of aspirin versus not taking it. So that is one group of patients. Now, how do you extrapolate that into the CT angiogram results or a CIMT? We don't really know. This is where the art of medicine is evolving, and we do shared decision making with uh physicians and patients because how much plaque is enough to equate to a calcium score of 100? Hard to say. But we can absolutely look at bleeding risk, like what other medications patients are on, and whether there have any other medical conditions that might make them high risk for bleeding, and take that into consideration. We certainly take age into consideration. And putting all of this together, there's some evidence that patients who have plaque, either by imaging or by some imaging mortality, might benefit from daily baby aspirin for prevention. The next group that's probably the most interesting, LP little A. You guys have heard me talk about this before on the channel. We'll put another link to that video in the show notes below. But lipoprotein little A. This is that special lipoprotein particle that looks like an APOB particle, but has that very sticky velcro tail that allows it to really get stuck in the artery wall and predisposes people to early formation and aggressive formation of plaque, also calcium deposits in the aortic valve. There have been a bunch of observational, not randomized studies yet, that show patients with elevated levels of lipoproteadil A, so greater than 50 milligrams per deciliter or 125 nanomoles per liter, will benefit or have benefited in the past in these studies from daily baby aspirin. And in particular, there is a specific gene mutation that has been shown in a couple of studies. And those patients also gain a significant reduction in events when they are taking baby aspirin. And this kind of all tracks and makes sense, right, from a pathophysiological standpoint, because LP little A is pro-thrombotic, right? It's prone to help us form clots. It has this um homology to plasminogen, which is an antifibrolytic factor. So all of this comes together. And when we see that we inhibit platelets and we get an improvement from LP little A risk, that is really exciting. Again, no randomized controlled data yet support the use of aspirin in LP little A, but I think that the preventive cardiology community is leaning pretty hard on the Mesa cohort and these other studies where we've seen benefit in patients who've been on it in the past. And by the way, that was about a 46% reduction in risk with the MESA cohort. We see about a 52% reduction in the NHANES series. So again, those are relative risk numbers. We'll talk about what the numbers needed to treat might look like for LP little A, but without randomized control data, that's a little bit uh less reliable of a statistic for us. Um, and again, what's the age cutoff here? We don't know, right? Certainly LP little A is a lifelong exposure. If you were on aspirin because of elevated LP little A through your 60s and now you turn 70, should we stop your aspirin? We don't know the answer to that. That is again part of this shared decision making and individualized, personalized conversation with your own doctor. So we've talked about who absolutely should stay on aspirin or be on aspirin, who should definitely not be on aspirin. But many of you who watch or listen to this channel are in this gray zone. You've had some positive imaging, you've not had an event yet, maybe you have elevated LP little A and you're wondering, I just don't know. Is this right for me? Should I be taking an aspirin? So I actually thought it would be fun if we walked through this kind of decision on one of the uh really high-quality medical trained large language models called open evidence. So I'm gonna share my screen here and we will walk through this together. So I have a 68-year-old woman who has a calcium score of 110 and a lipoprotein little A of 60 milligrams per deciliter. She wants to know whether she should be taking an aspirin every day. Let's see what open evidence says. So it says aspirin is generally not recommended for this patient based on current evidence, though her specific combination of risk factors creates a nuanced situation requiring individualized assessment of bleeding risk. This is interesting because I actually put this into open evidence before I started recording, and the answer was a little bit different. It actually said probably she should be taking a daily baby aspirin, so I'm a little surprised based on this, but it's going to walk us through the primary prevention literature and then talk about some of these gray zone characteristics. So again, the 2019 primary prevention guidelines represent a significant shift away from routine aspirin use driven by the trials we talked about. Okay. Let's see. Espris specifically studied adults over age 65, including 56% women, and found no reduction in cardiovascular events with aspirin but increased bleeding risk and mortality. At age 68, your patient falls into this higher risk age group where bleeding complications are more concerning. Okay, maybe I switched the age a little bit. However, her clinical profile warrants careful consideration. CAC of 110 places her in a category where some evidence suggests potential benefit. Multiple studies demonstrate that CAC greater than 100 identifies a subgroup where aspirin's cardiovascular benefits may exceed the bleeding risks, particularly in patients under 70. In the Mesa study, patients with a CAC greater than 100 had a number needed to treat of 140 to prevent one cardiovascular event, versus a number needed to harm of 518 for bleeding. So it's going to show us some figures from JAMA. Let's see what trial this is from. So PCE here is the pooled cohort equation. Value of coronary artery calcium scanning in association with net benefit of aspirin in primary prevention of atherosclerotic cardiovascular disease. Okay, so let's look at what it's showing us here. So these are panel A are patients with lower bleeding risk and the CAC category and ASCBD, these are going to be reduction in events versus bleeding events. So all patients had a very minimal change in the ASCBD versus a slight increase in the bleeding risk. But if you go increasing levels of coronary calcium score, the patients who had calcium score over 100 had a bigger reduction in events than they had an increased risk for bleeding, meaning the benefits of aspirin in this group outweighed the harms. Okay? So now we're looking at what their baseline cardiovascular risk was. And Pool Hook Cohort equation, you'll remember, does not take into consideration any of the risk-modifying factors, including your imaging, like a CAC, doesn't take into consideration LP little A, premature menopause, uh preeclampsia, any of the big other risk factors that I think about in my everyday practice. HSCRP, that's a big one, but it does take into account our lipids, our blood pressure, our diabetes, uh, history of smoking, and these types of things. So for very low-risk patients, um the CAC actually of 100 was not that helpful. As we get higher risk, then we start seeing bigger reductions in events. But I'm not sure why they didn't show us the bleeding risks here. That's interesting. Okay. Then as we get to patients with higher risks of bleeding, as you might expect, we're starting to see that the uh adverse events related to bleeding outweigh the benefit of our CAC reduction in events. So this is a complicated table. I don't think we're gonna belabor this point anymore. Um let's see what it says about her lipoprotein little A. Elevated LPA of 60 milligrams per deciliter adds another dimension. Post hoc analyses from the Women's Health Study and the Esprit trial found that aspirin-reduced cardiovascular events in individuals with genetically elevated lipoprotein little A without significantly increasing the bleeding risk. The combination of elevated LPA and CAC greater than 100 identifies particularly high-risk individuals who may derive net benefit from aspirin. These findings come from secondary analyses rather than prospective randomized control trials. The critical determining factor is bleeding risk. If she has prior GI bleeding, bleeding disorders, severe liver disease, thrombocytopenia, which is a low platelet count, concurrent anticoagulation or NSAID use, uncontrolled hypertension, aspirin would cause net harm regardless of her CAC or lipoprotein little A levels. All right. So let's take another example. What about a 50-year-old man who has not had any coronary calcium scoring or imaging, but has a lipoprotein little A of 120 milligrams per deciliter? He has not had any heart attack, stroke, or any CV event. Okay, so again, we're getting back to the post hoc analyses in other primary prevention trials. This patient faces approximately twofold higher cardiovascular risk compared to population median given the very elevated lipoprotein little A. 2019 primary prevention guidelines emphasize that aspirin use in primary prevention has become more controversial. Guidelines do not provide a specific recommendation endorsing aspirin solely based on elevated lipoprotein little A in the absence of other high-risk features. ACC emphasizes management of modifiable risk factors as early as possible. Okay, so this is pretty much a hand waving explanation. Um nuanced clinical decision and yeah, markedly elevated LP little A levels. That's why I picked that case. Use the reduction here in this post hoc analysis. So at least you'll can see the data. But what I'll say about open evidence as a as an AI tool for healthcare is that it is really anchored in our guidelines, which is appropriate, but it does not leave a lot of room for the art of medicine or the clinical nuance that we'll talk about the other components to this and doesn't um doesn't really stretch, which is how it's designed, right? That's the safest way to build this, but it is also a little limited when our guidelines tend to be a few years behind our current knowledge and understanding because the trials that the guidelines are based on are even older than that. So you can imagine guidelines tend to lag five to 10 years on our on our most current evidence. So we may have new papers, right? There's a new paper out that suggests that aspirin for patients with elevated lipoprotein little A actually reduces not only the mortality risk from ASCBD, but also valvular calcification. You'll remember that lipoprotein little A will cause calcium to deposit on that aortic valve and cause it to become very stiff and not work very well. Aspirin can also, we think, mitigate that risk. So we learn new information every day. Open evidence may not always bring us that up to speed, but it is the safest way to understand what your individual risk might be if you're curious about your own risk factors and whether a daily aspirin is right for you. Hopefully, this video has taught you whether you are in the absolutely yes aspirin category, the absolutely no aspirin category, or maybe in that gray zone and a tool that will help you understand your personal gray zone risk and how to think about that and talk about that with your physician. If you found this helpful, I would love it if you would share this video with somebody that you think needs to hear it who may also have questions about aspirin. This helps our channel grow and gets this message out to the people who need to hear it most.

SPEAKER_00 24:02

Until next time, guys, take really good care.