Potassium and heart health are inextricably linked because potassium is important for every cell in the body. With sodium, potassium is part of an electrochemical mechanism that is important for nerve impulse transmission, muscle contraction and heart function. Without enough potassium, the heart's function may be compromised both because the heart is a muscle, and because it needs electrical regulation for normal heartbeats and cardiovascular activity.
Low Potassium
Low potassium, or hypokalemia, occurs when there is less than 3.7 mEq/L of potassium in the blood as measured by a blood test. Ordinarily, people get enough potassium in their diets, but other conditions and the use of diuretics, and certain medications or supplements may lower a person's potassium level, even if he eats the suggested dietary intake of 4.7 grams per day. Excessive perspiration may also lower potassium levels, usually when the perspiration happens over an extended time.
Symptoms
Hypokalemia has long been recognized as potentially very serious. In his 1959 article in the "Archives of Internal Medicine," Chester S. Keefer, M.D., described symptoms of low potassium as he studied beriberi, a nutritional illness. Keefer described the single most striking symptom as "muscular weakness." Other symptoms he described are nausea, mental confusion, loss of reflexes, a distended abdomen, loss of appetite, fatigue and edema. Until hypokalemia is moderate to severe, a person may notice no symptoms or think symptoms are caused by something else. Usually hypokalemia is not shown on an EKG until a person is symptomatic. Even so, hypokalemia is the most common electrolyte problem in hospitalized patients.
Blood Pressure
One of the ways hypokalemia affects heart health is its possible relation to high blood pressure, which can cause weaknesses, blockages and clots affecting the heart. In cultures that eat mostly fruits and vegetables, the incidence of high blood pressure is much lower than other cultures. High blood pressure is the cause of about 1 billion cases of cardiovascular disease worldwide at any time. Addition of potassium to the diet or by supplementation may cause a drop in blood pressure.
Heart Arrhythmias
Because potassium plays an essential role in regulating electrical impulses affecting the heart, hypokalemia may cause arrhythmias, which are abnormal heart rhythms. Usually the heartbeats become too fast continuously or sporadically, causing fatigue. Arrhythmias are more likely to occur if the hypokalemia is caused by diuretics often prescribed for high blood pressure. Diuretics cause the body to urinate, lowering extra fluids in the blood and reducing pressure on blood vessel walls. If a person already has high blood pressure, the effect of the arrhythmia may be more severe.
Congestive Heart Failure
Congestive heart failure is usually a progressive disease, happening when the heart becomes unable to pump enough fluid from the heart through the blood vessels, causing fluid buildup in the lungs. Hypokalemia causes damage to both cardiac function and structure by affecting the diastolic, or resting, phase of the heartbeat, causing fibrosis of the heart and death of cardiac tissue. A University of Alabama Medicine Bulletin published in 2008 reports that long-term use of diuretics may increase chance of death in patients with chronic heart failure. For this reason, it recommended that such patients maintain a blood potassium level of 4 mEq/L or higher.
Heart Muscle
Low potassium, approaching 2.5 mEq/L or lower, causes paralysis of muscles, including the heart muscle and the lungs, which can lead to cardiac arrest and death.
Prevention
Given the potentially serious consequences of low potassium levels, it is important that the levels be checked regularly, particularly for those with cardiovascular disease or other diseases or conditions that contribute to potassium deficiency. Potassium supplementation, by diet, supplement tablets or by intravenous delivery are all effective in keeping potassium levels safe.
References
- UAB Medicine: Low Potassium Levels Linked to Increased Long-Term Mortality In Heart Failure Patients
- "Journal of the CardioMetabolic Syndrome"; Potassium, Magnesium, and Calcium: Their Role in Both the Cause and Treatment of Hypertension; Marc C. Houston, M.D., M.S., and Karen J. Harper, M.S., PharmD; August 2008
- "American Journal of Kidney Diseases"; The Cardiovascular Implications of Hypokalemia; Steven G. Coca, D.O., et al.; February 2005
- "Resuscitation"; Potassium Disorders-Clinical Spectrum and Emergency Management; Annette V. M. Alfonzo, et al.; 2006
- "Archives of Internal Medicine"; The Heart In Malnutrition and in Potassium Deficiency; Chester S. Keefer, M.D.; 1959
- Oregon State University Linus Pauling Institute: Potassium
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