Rapid Heart Rate & Potassium

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Low potassium can cause shortness of breath. (Image: Elenathewise/iStock/Getty Images)

The heart is the primary organ responsible for oxygen delivery to the tissues. The heart is automatic by nature, because it can receive and pump blood without outside influences. For the heart to function adequately, it requires sufficient levels of various electrolytes, including potassium. Levels of blood potassium vary inversely with heart rate; as the levels of potassium drop below normal, the heart rate increases beyond normal.

Low Potassium

Blood potassium levels between 4.0 and 4.5 milliequivalents per liter, or mEq/L, are considered normal; blood potassium levels below 4.0 mEq/L are considered low. According to a 2010 "Experimental & Clinical Cardiology" article, in people with heart attacks, low blood potassium was associated with an increased likelihood for ventricular tachycardia or rapid beating of lower heart chambers. Also, normal levels of blood potassium was associated with no episodes of heart rhythm abnormalities.

Heart Rate

The heart rate is a component of the cardiac output or the amount of blood pumped out by the heart each minute. The cardiac output must be adjusted according to oxygen demands; as oxygen demands increase, the cardiac output must be increased to meet up with oxygen demands. Normally, increasing the heart rate is beneficial to the cardiac output, but a too-rapid heart rate compromises the cardiac output. In ventricular tachycardia, the heart rate is too fast, thereby reducing the time needed to fill the heart with blood. The heart can only pump out the blood it receives; as more blood enters the heart, more blood is pumped out.

Sources of Potassium

Normal potassium levels are maintained by diet intake of potassium and the adjustment of kidneys' excretion of potassium. According to the United States Department of Agriculture, the recommended daily intake of potassium is about 4,700 mg/day. Dietary sources of potassium include baked potatoes, yogurt, tomato paste, white beans and clams.

Symptoms of Low Potassium

In a person with normal functioning kidneys, low blood potassium may occur as a result of decreased dietary potassium intake or increased excretion of potassium from the kidneys. Severely increased release of aldosterone -- a hormone normally produced by the adrenal glands as a result of increase potassium, causes the increased excretion of potassium from the kidneys. When a person is low in potassium they may experience fatigue, muscle pain, progessive muscle weakness and shortness of breath due to weakening of the respiratory muscles.

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