Cardiac output is equal to heart rate multiplied by stroke volume, or the amount of blood pumped by your ventricles with each heartbeat. Diseases effecting cardiac tissue may lead to decreases in cardiac output. This occurs because stroke volume and heart rate are directly affected by heart disease. During exercise, your body requires your heart to increase cardiac output. If the heart is unable to meet these demands you may feel short of breath, have chest pain, or feel dizzy during exercise. These symptoms may indicate a serious underlying cardiac condition and require thorough medical evaluation by a physician.
Causes of Low Cardiac Output
According to Harrison's Internal Medicine, diseases effecting heart muscle, also known as the myocardium, may result in physiologic alterations leading to low cardiac output; these changes may produce problems during exercise. For instance, a history of coronary artery disease or heart attacks could indicate a weakened heart muscle, leading to deceased cardiac output. Additionally, a history of hypertension, or high blood pressure might predispose you to low cardiac output. Chronic hypertension will weaken your heart over time as it constantly pumps against the elevated pressures in your arteries. Other causes of low cardiac output include defective heart valves and arrhythmias.
Complications of Low Cardiac Output
The heart normally pumps out as much blood into your arteries as it receives from your veins. By matching input to output the cardio-pulmonary system is able to properly function without accumulating any fluid. If your heart has a decreased cardiac output at rest, exercise may challenge the output capacity of the heart to the point that input is greater than output. In this case, fluid will accumulate in the lungs, producing symptoms of dyspnea, or shortness of breath. As your heart works hard to keep up during exercise, cardiac muscle will begin to fatigue and may produce chest pains. Additionally, if cardiac output continues to decrease, you may experience neurological symptoms such as dizziness or feeling faint; this is because the brain is not receiving enough oxygen to function properly.
Exercise with Low Cardiac Output
According to Mayo Clinic, moderate exercise will help maintain overall fitness and health throughout your body. However, it is important to discuss an exercise plan with your doctor before beginning. If your heart is too weak, your doctor may recommend light exercise such as walking to keep your heart safe.
Modifications
Depending on the severity of your heart disease, a number of options are available to approach exercise with low cardiac output. Cardiac rehabilitation programs are composed of a specialized team of exercise therapists who will advise you on how to proceed with your exercise routine. Working with your doctor, this team will be able to consider the specifics of your condition and will tailor an exercise routine that is both safe and effective for improving your cardiovascular health.
References
- "Harrison's Internal Medicine: Dyspnea and Pulmonary Edema"; Richard Schwartzstein; 2010
- MayoClinic.com: Heart Failure; Mayo Clinic Staff; December 2009
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