A fast pulse is called tachycardia. Tachycardia is an arrhythmia (abnormal heart rhythm) defined as a heart rate greater than 100 beats per minute. Tachycardia can be caused by a number of factors, such as exercise, pain, fear, anxiety, medications, stimulants like caffeine, fever, or problems with the heart muscle itself or the heart conduction system. The many side effects of tachycardia affect multiple body systems. The treatment for tachycardia is correction of the underlying problem that is causing the rapid heart rate.
General Side Effects
The elderly and individuals who are already ill may not tolerate prolonged tachycardia. However, most healthy individuals can tolerate tachycardia for a period of time. General side effects may include feeling anxious, sweating, feeling your heart race, shortness of breath and weakness. Unresolved and untreated tachycardia can lead to myocardial infarction (heart attack), heart failure, or sudden death.
Cardiovascular Side Effects
Prolonged tachycardia will affect the filling pressures in the heart. During normal heart function, blood returns to the heart from the venous system, emptying into the right atrium, which empties blood into the right ventricle. From here, blood is pumped into the lungs to be oxygenated and returned to the heart via the left atrium. The left atrium empties into the left ventricle. When the heart rate is rapid, there is less time for the atria and ventricles to fill, so less blood is pumped to the body with each heart beat. Over time, this causes a drop in blood pressure.
A continued tachycardia also increases the work load of the heart, increasing myocardial (heart muscle) oxygen demand. The body responds to this demand for more oxygen and the dropping blood pressure through vasoconstriction. Vasoconstriction is narrowing of blood vessels to increase the rate of blood return to the heart. Initially, this will cause an increase in blood pressure, but it also causes an increase in myocardial oxygen demand. This increases the side effects of tachycardia. Shortness of breath and chest pain may result.
Central Nervous System Side Effects
Prolonged tachycardia can cause lightheadedness, dizziness, weakness, and syncope (passing out). As the body attempts to correct the low blood pressure caused by prolonged tachycardia, blood is shunted from the extremities to vital organs. This response can cause cool extremities, numbness and tingling in the extremities.
Respiratory System Side Effects
Side effects of tachycardia on the respiratory system include shortness of breath and cough. It is possible for pulmonary edema (fluid in the lungs) to occur from prolonged tachycardia, especially if an individual has a weak heart or a history of congestive heart failure.