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Study examines link between peripheral artery disease and heart attack

A study confirmed that patients with peripheral artery disease have a higher risk of heart attack, and are more likely to have a rarer type of heart attack.

Heart attacks are not all the same. Researchers previously knew that people with peripheral artery disease, a condition caused by the narrowing of blood vessels in the arms and legs, were at an elevated risk of heart attack. But a new study has found that people with PAD are also more likely to have a rarer type of a heart attack — known as a type 2 or a secondary heart attack.

The researchers, led by Christoph Olivier, MD, a postdoctoral research fellow in cardiovascular medicine at the Stanford Center for Clinical Research, and Kenneth Mahaffey, MD, professor of medicine and director of SCCR, analyzed data collected during the multicenter EUCLID trial. The trial compared the efficacy of two drugs (ticagrelor and clopidogrel) for patients with PAD. But the Stanford-led team was interested in a different angle: How likely is that PAD patients will have heart attacks, and which types will they have?

The answers to these questions could help physicians provide better care for people with PAD, Olivier said. PAD affects about 8.5 million people in the U.S. and commonly involves leg pain and can lead to hard-to-heal sores or numbness in the toes and feet.

The team found that of the 14,000 patients who participated in the trial, about 5 percent of them had a heart attack within 30 months. The paper appears in JAMA Cardiology.

This finding was not particularly surprising, but serves as a good head's up to physicians that PAD patients require special care since they are at high risk for a heart attack, Olivier said.

More surprising was the type of heart attack.

Type 1 heart attacks are considered the typical heart attack, and can occur when the vessel that supplies the heart with block is blocked. It is the most common heart attack overall and was the most common among EUCLID patients (about 60 percent of their heart attacks were type 1).

Type 2 heart attacks are characterized by a mismatch between oxygen demand and supply. This type of heart attack has any number of causes and lacks a standard treatment.

Unexpectedly, the researchers found that about one third of the EUCLID patients who had a heart attack had a type 2 heart attack. Other studies that examined people with heart conditions have generally found less than 10 percent of heart attacks were type 2, the paper states.

"The rate of type 2 heart attacks seems especially high. That was a surprise," Olivier told me.

The high rate highlights the importance of developing improved evidence-based standards to manage type 2 heart attacks, which, given the variety of causes, can require a variety of therapies, Olivier said.

In addition, the researchers found that a previous heart attack was not a risk factor for a type 2 heart attack, although it was a risk factor for a type 1 heart attack.

The study participants were only followed for 30 months, but the risk of heart attack continues to climb as the patients with PAD age, Olivier said.

"More research is needed to identify therapies to reduce the risk of [heart attack] in these patients and especially to improve management of type 2 [heart attacks]," Olivier said.

Image by Spaxiax/Shutterstock

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