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Disease and treatment

Good news: antipsychotic drug does not increase the risk of cardiac arrest during heart attack

Doctors have been worried for some time about whether an antipsychotic drug increases the risk of cardiac arrest among people with heart disease. New Danish research refutes this concern.

Older people are often treated with antipsychotic drugs when hospitalized with an acute blood clot in the heart.

This is because older people often become confused and experience delirium in connection with hospitalization, especially if they already have some types of dementia.

One treatment option to reduce anxiety is haloperidol, an antipsychotic drug.

However, doctors are sometimes cautious about haloperidol, since it affects the electrical current in the heart, and the fear has been that it may therefore increase the risk of cardiac arrest , especially among people admitted with a blood clot in the heart.

New Danish research reveals that this is not the case.

“We have found that treating patients with acute blood clots in the heart with haloperidol to prevent delirium is not dangerous and does not increase the risk of cardiac arrest based on our experimental data. We can see that it affects the heart, but it is not dangerous,” explains a researcher behind the new study, Jacob Tfelt-Hansen, Cardiologist and Professor, Heart Centre, Rigshospitalet and Department of Forensic Medicine, University of Copenhagen.

The research has been published in the International Journal of Cardiology Heart and Vasculature.

Uncertain whether haloperidol is safe

When people with a blood clot in the heart are hospitalized and experience delirium, which could be described as transient severe confusion, the doctors can use various drugs such as haloperidol (Serenase®) and diazepam (Valium®).

Haloperidol has been linked to increased risk of death in other contexts, but it has never been studied in treating delirium among people with a blood clot in the heart.

“This means that the guidelines have been unclear, and doctors have not quite known whether it is safe to use or not. We wanted to elucidate this with this study because it could either potentially make doctors feel secure in using haloperidol or we could warn them against using it,” explains Jacob Tfelt-Hansen.

Studying pigs gives researchers unique insight into heart disease

The researchers used pigs in several studies to examine atrial fibrillation, blood clots in the heart and death from cardiac arrest.

Electrodes are applied directly to the heart to measure how its electrical impulses develop as a blood clot forms.

The researchers can simulate a blood clot by inserting and inflating a tiny balloon into one of the major arteries that oxygenates and supplies blood to the heart.

You can read more about the researchers’ model and watch a video about the research in Researchers search for the tremors that stop the heart.

Myocardial infarct in the heart in 28 pigs

In the new study, the researchers treated 17 pigs that experienced the simulated blood clot in the heart with haloperidol, while 11 pigs that also had a simulated blood clot acted as controls.

The researchers then observed how many of the pigs experienced cardiac arrest.

Five of the 17 pigs (29%) treated with haloperidol and 7 of the 11 pigs (64%) in the control group experienced cardiac arrest.

Stefan Sattler, the first author, PhD and cardiologist in training, explains that the difference between the groups was not statistically significant, so the result only means that taking haloperidol does not increase the risk of cardiac arrest.

“The main message is that haloperidol can be used for people experiencing a heart attack and delirium, and our data confirm that this is safe,” he says.

About 10–11% of the people who have an acute blood clot in the heart experience cardiac arrest.

Affects the heart’s electrical system

The researchers further divided the 17 pigs treated with haloperidol into a high-dose and a low-dose group but did not find any difference between them.

Further studies in which the researchers applied electrodes directly to the heart to measure the electrical current across the heart as it beats confirmed that haloperidol affects the electrical system in the heart, but this did not lead to harmful arrythmias.

“We thought haloperidol would affect both the electrical system and the risk of cardiac arrest, so although the heart was affected, we were pleasantly surprised that there was no increase in the risk of cardiac arrest,” says Jacob Tfelt-Hansen.

In connection with the publication of the research results, independent researchers from the Netherlands wrote an editorial about the research.

“… this comprehensive report … further adds to our understanding of the complex actions of haloperidol on [cardiac arrhythmia] …,” write the researchers.

Effect of the antipsychotic drug haloperidol on arrhythmias during acute myocardial infarction in a porcine model” has been published in International Journal of Cardiology Heart and Vasculature. In 2014, the Novo Nordisk Foundation awarded a grant to Jacob Tfelt-Hansen for the project Risk Factors for Sudden Cardiac Death during Acute Myocardial Infarction (MI-RISK).

Jacob Tfelt-Hansen
Clinical Research Associate Professor
An estimated 10% of all deaths in Europe result from sudden heart attacks. Depending on the country and the emergency services, only 5% to 20% survive a heart attack. Jacob Tfelt-Hansen was instrumental in producing previous Danish results showing that heart disease causes about two thirds of sudden deaths. The research project hopes to improve how to predict who has higher risk of a heart attack and sudden death.