Strong leg muscles may be linked with better outcomes after heart attack, study suggests

By Jacqueline Howard, CNN

(CNN) — Growing evidence shows that building muscle strength can have benefits for your heart, even leading to better outcomes after a heart attack.

Having a higher level of leg muscle strength appears to be “strongly associated” with a lower risk of developing heart failure after a heart attack, according to new research presented this month in Prague at the Heart Failure 2023 scientific congress of the European Society of Cardiology.

The findings have not been published in a peer-reviewed journal, but they highlight the importance of regular exercise and maintaining muscle strength in older age, as muscle mass can diminish with age, possibly affecting cardiovascular health, said Kensuke Ueno and Dr. Kentaro Kamiya, researchers in the Department of Rehabilitation at Kitasato University School of Allied Health Sciences in Japan and authors of the new research.

Kamiya said that after a heart attack, medically known as a myocardial infarction, the heart can go through a process called myocardial remodeling or cardiac remodeling, in which fibrous tissue accumulates, causing an enlargement of the heart. But emerging evidence suggests that exercise-based cardiac rehabilitation can alter the course of such remodeling in a way that improves heart function.

“Cardiac remodeling is the main cause of the onset of heart failure after myocardial infarction,” Kamiya said. And myokines, which are peptides or chains of amino acids released by muscle fibers, may play a role.

“Exercise could help to attenuate cardiac remodeling,” he said. “In addition, recent studies have shown that skeletal muscle itself also releases myokines, cytokines that have various effects, such as preventing the progression of atherosclerosis, stabilizing blood pressure and preventing the development of age-related diseases. Maintaining skeletal muscle itself could be associated with a reduced risk of developing heart failure via this myokine, but the detailed mechanism is unclear.”

‘Strength training … should be recommended’

The researchers analyzed the strength of the quadricep muscles – in the fronts of the thighs – of 932 people ages 57 to 74 who had been hospitalized due to heart attack between 2007 and 2020. They found that the incidence rate of subsequent heart failure was higher, at 22.9 per 1,000 person-years, among the patients whose quadriceps measured as having low strength, compared with an incidence rate of 10.2 per 1,000 person-years among those with high quadriceps strength. Person-years are a measurement that represents the number of people in a study multiplied by the years following them.

“Quadriceps strength is easy and simple to measure accurately in clinical practice. Our study indicates that quadriceps strength could help to identify patients at a higher risk of developing heart failure after myocardial infarction who could then receive more intense surveillance,” Ueno said in a news release. “The findings need to be replicated in other studies, but they do suggest that strength training involving the quadriceps muscles should be recommended for patients who have experienced a heart attack to prevent heart failure.”

This isn’t the first time scientists have studied the association between muscle strength and the prognosis for people with cardiovascular disease. In 2016, Kamiya and his colleagues said in a study published in the American Journal of Cardiology that muscle mass in the upper arms could be associated with rates of surviving heart disease.

How to prevent another heart attack

The new research on leg strength validates what’s known about managing heart disease, in that muscle strength may play a role in reducing certain risks after cardiac events. But more can be learned about why some people may be more affected after a heart attack than others, said Dr. Shaline Rao, director of heart failure services at NYU Langone Hospital-Long Island, who was not involved in the new study.

“Perhaps what this signal in the quadricep muscle is showing is that there are variations amongst people that might help us target therapies better. So I don’t think it’s a complete answer in any way. But I think it’s a helpful thing to understand,” Rao said.

“This is another added data point that may help us better understand those individuals and also make an argument for who’s going to be best served with strength training, in general, after an event or hospitalization,” she said. “These are ways to kind of mix frailty plus muscle strength and really think about how you’re going to help older adults living with chronic disease or suffering acute illness to really target their rehabilitation appropriately.”

After a heart attack, there are many steps people can take to avoid further heart problems. The American Heart Association recommends taking medications as prescribed, attending follow-up doctor appointments, participating in cardiac rehabilitation, getting support from loved ones or connecting with other heart attack survivors, and managing risk factors such as high blood pressure, high cholesterol and diabetes by staying on medications, not smoking, eating healthy and getting exercise.

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