heartbeat

A heartbeat is the rhythmic contraction and relaxation of the heart that sustains blood circulation throughout the body. Each beat involves a sequence of electrical and mechanical events that coordinate the heart’s four chambers to fill with blood and then eject it into the lungs and the systemic circulation. The audible sounds produced by the closure of heart valves, known as S1 and S2, are often used to assess rhythm and rate during clinical examination.

The heartbeat is governed by the heart’s electrical conduction system. An electrical impulse originates in the sinoatrial node, the natural pacemaker, and spreads through the atrioventricular node to the ventricles via the bundle of His and Purkinje fibers. On an electrocardiogram, this sequence corresponds to the P wave, the QRS complex, and the T wave. Mechanically, the atria contract first (atrial systole), followed by the ventricles (ventricular systole); between contractions, the heart muscle relaxes (diastole) to refill with blood.

Heart rate, the number of beats per minute, is a common measure of cardiac activity. In healthy adults at rest, the typical range is about 60 to 100 bpm, varying with age, fitness, and autonomic tone. A heartbeat can be regular or irregular; sustained irregularities may indicate an arrhythmia. The rate and rhythm can be influenced by sleep, activity, temperature, medications, and illnesses.

Clinically, persistent abnormalities of heartbeat can signal cardiovascular disease. Arrhythmias, heart block, and myocardial ischemia may be detected by pulse checks and electrocardiography, and evaluated with imaging and blood tests. Management depends on cause and may include lifestyle changes, medications such as beta blockers, or devices like pacemakers for certain conduction disorders.