Health Bulletin - September 2023

Exercise and Heart

Cardiovascular disease (CVD) is a global health challenge that accounts for more than 17.9 million deaths annually worldwide. Compared to other ethnicities, South Asians have a disproportionately higher burden of atherosclerotic CVD, which often has an early onset at age < 50 years and is more aggressive. This risk profile stems from a complex interplay of factors, including traditional risk factors of CVD, such as age, hypertension, diabetes, and dyslipidemia, where South Asians are particularly vulnerable. Genetic predisposition and lifestyle factors such as physical inactivity and unhealthy dietary habits further exacerbate susceptibility. Sedentary lifestyles and diets rich in processed foods, saturated fats, and carbohydrates have become prevalent, increasing the risk of obesity, insulin resistance, and dyslipidemia. Reduced physical activity is a strong independent predictor of mortality, whereas frequent exercise is associated with a lower cardiovascular mortality rate. Notably, the absence of obesity does not offset the mortality conferred by lack of physical activity.

Physical Activity Decreases Cardiovascular Risk Factors

Regular physical exercise is associated with numerous health benefits and reduces the progression and development of obesity, T2D, and CVD. Several randomized clinical trials have demonstrated that lifestyle interventions, including moderate exercise and a healthy diet, improve cardiovascular health in at-risk populations. Individuals with increased risk factors who participated in a 4-month program of either diet (caloric restriction) or exercise intervention had reduced fat tissue build-up, decreased blood pressure, and lower total and low-density lipoprotein (LDL) cholesterol lipid profiles compared to the control group. Both diet and exercise interventions improved these cardiovascular outcomes to a similar extent.

Importantly, several beneficial effects of exercise are independent of weight loss. Studies have shown that exercise can improve metabolic and cardiovascular health independent of changes in body weight, glucose homeostasis, endothelial function, blood pressure, and high-density lipoprotein (HDL) levels. These data indicate that exercise, independent of changes in body mass, significantly improves cardiovascular and metabolic health.

Physical Activity Improves Cardiovascular Function in Patients With CVD

Exercise is an important therapeutic strategy for patients with cardiovascular diseases. A systematic review of multiple studies found that exercise-based cardiac rehabilitation improved cardiovascular function. These studies consisted of various forms of aerobic exercise at a range of intensities over a multitude of time periods (from a month to a few years). Overall, exercise significantly reduced CVD-related mortality, decreased the risk of heart attack, and improved the quality of life. Another study examined patients with atherosclerosis after coronary artery bypass graft surgery. Patients who underwent 60 minutes of exercise per day on a cycle ergometer for 4 weeks had a 30% increase in blood flow reserve. A recent study showed that patients who underwent an exercise rehabilitation program had increased heart ejection fraction, increased exercise tolerance, and reduced cardiovascular risk factors 6 months after starting the exercise rehabilitation program.

In the 1950s, bed rest was prescribed for patients with heart failure. However, it has now been shown that a monitored rehabilitation program using moderate-intensity exercise is safe and important for patients with heart failure. More recent studies have examined the effects of high-intensity exercise in patients with heart failure and have shown benefits. Both moderate- and high-intensity exercise training improved cardiovascular function in heart failure patients, likely related to increased expansion of blood vessels and flow and improved aerobic capacity.

Mechanisms Regulating Exercise-Induced Benefits on Cardiovascular Health

Multiple mechanisms mediate the benefits of regular physical exercise on cardiovascular health (Figure 1). Exercise represents a major challenge to whole-body homeostasis and induces widespread changes in numerous cells, tissues, and organs in response to increased metabolic demand, including adaptations to the cardiovascular system.

Exercise Improves Vasculature and Myocardial Perfusion

Exercise training induces vascular adaptation in several tissues. In the heart, the increase in blood vessels protects against vascular stress and reduces the likelihood of a cardiac event. These adaptations are mediated by the increased expression of vascular endothelial nitric oxide synthase (eNOS). Exercise also induces angiogenesis (new blood vessel formation); however, the mechanisms regulating this process are unclear, thus reducing the possibility of a cardiac event.

Exercise Reduces Chronic Inflammation

Inflammation is a biological response to toxic stimuli. Chronic inflammation is associated with multiple diseases including obesity, T2D, and CVD. Excess consumption of nutrients causes cells, including fat cells, liver cells, and muscle cells, to activate inflammatory factors in the body, such as IL-6. There is robust evidence that inflammation contributes to CAD development. In this regard, several cytokines and inflammatory markers have been studied. C-reactive protein levels have a dose-response relationship with coronary artery disease independent of other major risk factors. Exercise produces a short-term inflammatory response and an overall long-term anti-inflammatory effect. Exercise also lowers the risk of HF.

Although the biology of CVD is similar in all ethnic groups, South Asians have an unfavorable risk profile, including a lack of regular exercise. Additionally, there is a knowledge gap among South Asians regarding the importance of exercise and physical activity in CVD prevention. In a survey comprising a South Asian cohort (n=270), most participants (89%) knew little or no about CAD, 53% mentioned that heart attacks were not preventable, and only 49% stated that exercise was important. This is compounded by the fact that South Asian patients have lower availability of home exercise equipment and perceived convenience of local physical activity centers. Thus, it is extremely important to raise awareness among South Asians regarding the benefits of exercise on heart health and to improve access to exercise-related education, equipment, and facilities.

Conclusion: South Asians face a heightened risk of CVD, which is characterized by early onset and increased severity. This increased risk is attributed to genetic predispositions, traditional risk factors, and prevalent modifiable risk factors such as a sedentary lifestyle and unhealthy diet. Regular physical activity offers a wide range of cardiovascular benefits and can significantly reduce the risk of cardiovascular mortality even in the absence of obesity or diabetes. Appropriate measures are needed to promote exercise and healthy lifestyle choices to combat the burden of CVD in South Asian populations.

Figure 1: Benefits of exercise on the heart

Acronyms:
CAD: Coronary artery disease
CVD: Cardiovascular disease
T2D: Type II Diabetes
HF: Heart failure

Authors:
Asim Shabbir, MD, MS, Cardiology Fellow, Omaha, NE
Sujeeth R. Punnam, MD, FACC, Interventional Cardiologist, Stockton, CA
Poonam Velagapudi, MD, MS, Interventional Cardiologist, Demarest, NJ