Every second or so, an electrical impulse originating in the right atrium of your heart travels through the heart and triggers a single heartbeat, or contraction of the heart. A group of specialized cells in the muscle tissue, called the sinoatrial (SA) node, initiates the signal, acting as your heart’s natural pacemaker. The impulse travels through the four chambers of your heart in a carefully timed sequence to stimulate the rhythmic contractions that pump blood through your body (see pages
Any change or interruption in the electrical signal that throws off this rhythm is called an arrhythmia. The heart may beat too fast, too slow, or in an irregular pattern. Arrhythmias can occur in people with normal hearts or those with underlying disease. Throughout the course of your lifetime, your heart will occasionally skip a beat or palpitate slightly, and these brief variations are completely harmless. Some people have minor arrhythmias that never cause a problem. However, in some arrhythmias, the pumping action of the heart can be seriously affected, or it can cause symptoms of palpitation (awareness of the abnormal heartbeat), light-headedness, or fainting. If you have another heart condition, such as heart failure, an arrhythmia is more likely to cause a problem for you.
Some people are born with an irregular heartbeat. Other cardiovascular conditions, such as high blood pressure, valvular disease, heart failure, or coronary artery disease can be factors; diabetes can also con- tribute (see page 105). Substances such as caffeine, tobacco, alcohol, cocaine and prescribed medication, some over-the-counter cough and cold medications, diet pills, and some herbal remedies can affect the pattern of your heartbeat (see page 267). Stress can also cause arrhythmias in some people, as the body releases adrenaline, the stress hormone. Low levels of or an imbalance of electrolytes such as low potassium levels may cause or worsen an arrhythmia. Your doctor may order a blood test to check your electrolytes, to make sure there is no correctable problem causing your arrhythmia.
Treatment, therefore, may include lifestyle changes and control of other conditions, taking an antiarrhythmia medication, avoiding some medications, nonsurgical procedures, or surgery (for instance, implantation of a pacemaker) to restore a normal heartbeat. Your doctor may refer you to a heart rhythm specialist, called an electrophysiologist.