Hourglass-shaped stent could ease severe chest pain from microvascular disease

ROCHESTER, Minn. — A study at Mayo Clinic suggests that an hourglass-shaped stent could improve blood flow and ease severe and reoccurring chest pain in people with microvascular disease. Of 30 participants in a phase 2 clinical trial, 76% saw improvement in their day-to-day life. For example, some participants who reported not being able to walk around the block or up a flight of stairs without chest pain were able to do these ordinary physical activities at the end of a 120-day period. Clinical measures of blood flow related to the microvasculature of the heart significantly improved during follow-up, according to findings published in the Journal of the American College of Cardiology: Cardiovascular Interventions.

Microvascular disease is a condition in which tiny blood vessels in the heart are not working properly, resulting in reduced blood flow to the heart. The resulting chest pains, or angina, can be debilitating, limiting a person's ability to exercise, do household chores or even walk to the mailbox. About 40% of patients receiving a diagnostic coronary angiogram for chest pain do not have blocked arteries that also can cause angina. However, up to 66% of these patients do have coronary microvascular disease, which is more common in women overall and found in people with conditions such as diabetes, high blood pressure and obesity.

For decades, there have been few viable treatment options to improve blood flow through the tiny vessels of the heart. At most, doctors have treated symptoms of angina with several medications and cardiovascular disease prevention methods, including healthy eating, weight loss and regular exercise. The use of a stent could target the issue behind the chest pain — the severe reduction in blood flow affecting the heart muscle.

Unlike tube-shaped stents used to open clogged arteries, the hourglass-shaped stent narrows in the middle. The different design is thought to increase back pressure, redistributing blood flow more fully through small vessels in the heart that were not working at capacity.

"The patients with heart-related microvascular dysfunction in this study had little ability to control their chronic angina, which severely limited their day-to-day activities," says Amir Lerman, M.D., a cardiologist at Mayo Clinic and senior author of the study. "Beyond reductions in chest pain and being able to comfortably handle more physical activity, the majority of patients in the study also showed a connection between the changes in their coronary flow reserve, which is a measure of maximum blood flow, and changes in their quality-of-life responses on the survey. This points to the link between the physiological measurement and angina symptoms."

Dr. Lerman notes that more studies are needed to better understand how the reducer stent works and its long-term effects on blood flow. The stent did not improve chest pain symptoms in 20%-30% of the participants, so future research studies will need to better identify which patients respond best to this therapy.   

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