Multifocal atrial tachycardia

Alternative names:

atrial tachycardia

Definition:

A rapid heart rate caused by stimuli to the heart from multiple locations within the atria.

Causes, incidence, and risk factors:

Normally, electrical stimulus to contract the heart begins in the sinoatrial (sinus, SA) node, which the natural "pacemaker" for the heart. The stimulus is conducted throughout the heart and triggers the heart to contract. The normal heart rate is 60 to 100 beats per minute in adults, faster in children.

In multifocal atrial tachycardia (M.A.T.), multiple locations within the atria "fire" and initiate an electrical stimulus to contract. Most of these stimuli are conducted to the ventricles, leading to a rapid heart rate, often as high as 100 to 180 beats per minute. This very rapid rate greatly increases the heart's workload. Very rapid rates can also decrease the amount of time the heart has to fill with blood, which reduces heart function.

M.A.T. may be associated with COPD, congenital bacterial pneumonia, congestive heart failure, lung cancer, pulmonary embolus, coronary heart disease, any condition that reduces the amount of oxygen in the blood, surgery within the last 6 weeks, overdose of theophylline or digitalis, diabetes mellitus, bacterial infections, and other conditions.

M.A.T. occurs in approximately 1 out of 1,000 people. It is most common in those over 50 years old.