Premature Atrial Contraction (PAC)

Premature Atrial Contraction (PAC) is a common heart rhythm irregularity where the heart's upper chambers, called atria, beat earlier than expected. This condition involves the cardiac conduction system, which controls the heartbeat. PACs can cause sensations of a skipped or extra heartbeat, often described as palpitations. While usually harmless, frequent PACs may sometimes indicate underlying heart issues. The main health effect is an irregular heartbeat that can occasionally lead to more serious arrhythmias. PACs often occur in healthy individuals but can be triggered by stress, caffeine, or other stimulants.

Premature Atrial Contraction (PAC) is defined as an early depolarization originating from an ectopic focus within the atria, outside the sinoatrial node. This premature beat disrupts the normal cardiac rhythm by causing an early atrial contraction. The core pathology involves abnormal automaticity or triggered activity in atrial myocardial cells. PACs are often caused by increased atrial irritability due to factors such as electrolyte imbalances, ischemia, or stimulants. Clinically, PACs are significant because they can precipitate more serious arrhythmias like atrial fibrillation or flutter. On electrocardiogram, PACs are characterized by an early P wave with abnormal morphology followed by a normal QRS complex. PACs may be asymptomatic or present with palpitations and are commonly detected incidentally during cardiac monitoring.