Heart Attack Patients With Strong Legs Have Better Prognosis

The most common cause of heart failure is myocardial infarction (2), approximately 6-9% of heart attack patients will develop the condition (3,4). Having strong quadriceps has been associated with having a lower risk of death among those with coronary artery disease in previous research (5), this study set out to investigate whether or not having leg strength could lower the risk of developing heart failure after acute myocardial infarction. 

This study involved 932 patients with a median age of 66 years old who were hospitalized with acute myocardial infarction who did not have heart failure prior to admission and did not develop heart failure complications during their hospital stay. 

Quadricep strength was measured as an indicator of leg strength with the patient sitting and contracting their quadricep muscle for 5 seconds and a dynamometer attached to the ankle to record the maximum value in kgs for both legs to get the average of both values. Strength was expressed relative to body weight (strength in kg divided by body weight in kg multiplied by 100), then patients were classed as high or low strength according to if their value was above/below the median for their gender. 

Analysis revealed that the median value for women was 33% of their body weight and the median value for men was 52% of their body weight and that 451 patients had low quadriceps strength and 481 had high quadriceps strength. 67 patients were found to have developed heart failure during an average follow-up of 4.5 years, and the incidence of heart failure was 10.2 per 1,000 person-years in those with high quadriceps strength and 22.9 per 1,000 person-years in those with low quadriceps strength. 

The association between quadriceps strength and the risk of developing heart attack was analyzed next, adjusting for various factors known to be associated with the development of heart failure after myocardial infarction. Having high quadriceps strength levels was associated with a 41% lower risk of developing heart failure compared to having low quadriceps strength with a hazard ratio [HR]:0.59; 95% confidence interval [CI] 0.35–1.00; p=0.048.

The association between quadriceps strength as a continuous variable and risk of developing heart failure was also analyzed revealing that each 5% body weight increment in quadriceps strength was associated with an 11% lower likelihood of heart failure with a hazard ratio [HR]: 0.89; 95% CI 0.81–0.98; p=0.014.

“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. 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,” said study author Mr. Kensuke Ueno, a physical therapist at the Kitasato University Graduate School of Medical Sciences, Sagamihara, Japan.