Antiplatelets and beta-blockers increase heart attacks in 25-59-year-olds in warm weather

Nature Cardiovascular Research recently published a study that showed that some people who take antiplatelets and beta blockers have a higher risk of a non-fatal heart attack during warm weather.

The authors were from Yale University and several prestigious institutions in Germany.

The study evaluated 2,494 heart attack cases in Augsburg, Germany, during warm seasons (May to September) from 2001 to 2014.[1]

The investigation found that the risk of heat-related non-fatal myocardial infarction was significantly elevated among users of antiplatelet medication and beta blockers compared to non-users.[1]

The grah below shows that the odds ratio of the antiplatelet and beta-blockers to have a heat effect are higher than the other cardiac medications.

Source: Triggering of myocardial infarction by heat exposure is modified by medication intake.

Antiplatelets and Beta-blockers

Antiplatelets and beta-blockers are prescribed in patients with coronary heart disease.

Antiplatelets prevent blood clotting that causes blockage in the coronary arteries. Examples of antiplatelets and their brand names in the US are:

Aspirin
Clopidogrel – Plavix
Ticagrelor – Brilinta
Ticlopidine – Ticlid
Prasugrel – Effient
Dipyridamole – Persantine
Abciximab – ReoPro
Tirofiban – Aggrastat
Cilostazol – Pletal
Vorapaxar – Zontivity

Doctors primarily use antiplatelet drugs in heart patients and people with a history of stroke or peripheral artery disease.

Beta-blockers slow down the heart rate to decrease the oxygen demand of the heart muscle. They also open the arteries and veins to lower blood pressure.

Examples of beta blockers and their common brand names are:

Acebutolol – Sectral
Atenolol – Tenormin
Bisoprolol – Zebeta
Metoprolol – Lopressor, Toprol XL
Nadolol – Corgard
Nebivolol – Bystolic
Propranolol – Inderal, InnoPran XL

Beta-blockers are used in irregular heart rhythm (arrhythmia), heart failure,
chest pain (angina), heart attacks, migraine, and certain types of tremors.

Younger age groups are more affected

Interestingly, the risk of non-fatal heart attacks was stronger among younger patients (25–59 years), who had a lower prevalence of pre-existing coronary heart disease (CHD), than among older patients (60–74 years), who had a higher prevalence of pre-existing CHD.[1]

Why is there a higher risk of heart attacks with antiplatelets and beta-blockers during warmer weather?

I did my research to find out why. A study by Bruning and colleagues showed that when people who used aspirin and clopidogrel (Plavix) were made to exercise in a warm environment, it resulted in elevated body core temperatures.[2]

A study this time on people taking beta-blockers (propranolol and atenolol) who exercise showed that both active agents produced “marked increases in the subjective perception of effort.”[3]

Elevated body temperature and higher effort when performing physical exercises lead to higher stress. I think everyone can relate to that.

A review article by Bentur et al. showed that the mediators of the stress reaction (neurotransmitters and hormones) could directly affect platelets and the coagulation cascade that eventually leads to thrombosis or clot formation.[4]

Questions and Answers

How can they have a clot and a heart attack if they are on antiplatelets and beta-blockers?

Clinical trials on medications are made under comfortable and stress-free conditions. That way, they will have good results that will pave the way for approval.

In real-life situations like physical exertion in a warm environment, the body’s response to the resulting stress increases the tendency to form blood clots.

Another thing is no doctor will say that any medication is 100% effective. That is considered unethical, unrealistic, and gives the patient false hope.

Did clots form somewhere else?

Blood clots could have formed in other organs, but they remained asymptomatic. That’s because other organs have collateral circulation. Blood can reroute if there is a blood clot in an artery.

Why was only the heart affected?

The tiny coronaries of the heart have no collaterals. Plus, with the increased activity, there is a higher oxygen demand from the heart, and coronary blockages will limit the oxygen supply.

Why did the younger group (25–59 years) have more heart attacks?

Those working-age groups tend to be more active and have to be outside in warmer weather than the 60-74 years old.

Take away message

If you are taking antiplatelets and beta-blockers, don’t stop taking them. If you plan to do outside work or exercise in hot weather, stay hydrated and don’t push yourself too hard. Make sure you have a phone in case you need to call 911.

If you are not yet on any cardiac medicines, use this article as motivation to change your lifestyle, so you don’t have to start any medications. Medications are good, but sometimes they can prevent you from doing exercise.

Physical fitness is proven to decrease all-cause mortality. Physical Activity Correlates with Life Span.

That is why: Don’t Get Sick!

Related:

References:

Chen, K., Dubrow, R., Breitner, S. et al. Triggering of myocardial infarction by heat exposure is modified by medication intake. Nat Cardiovasc Res (2022). https://doi.org/10.1038/s44161-022-00102-z
Bruning RS, Dahmus JD, Kenney WL, Alexander LM. Aspirin and clopidogrel alter core temperature and skin blood flow during heat stress. Med Sci Sports Exerc. 2013 Apr;45(4):674-82. doi: 10.1249/MSS.0b013e31827981dc. PMID: 23135368; PMCID: PMC3594134.
Gordon NF, Krüger PE, Van Rensburg JP, et al. Effect of beta-adrenoceptor blockade on thermoregulation during prolonged exercise. Journal of Applied Physiology (Bethesda, Md.: 1985). 1985 Mar;58(3):899-906. DOI: 10.1152/jappl.1985.58.3.899. PMID: 2858466.
Bentur OS, Sarig G, Brenner B, Jacob G. Effects of Acute Stress on Thrombosis. Semin Thromb Hemost. 2018 Oct;44(7):662-668. doi: 10.1055/s-0038-1660853. Epub 2018 Jun 18. PMID: 29913534.