What is the hallmark of a premature atrial contraction?

What is the hallmark of a premature atrial contraction?

• A. A premature beat with an early P wave
• B. A late beat with no P wave
• C. A wide QRS complex tachycardia
• D. A prolonged QT interval

Answer: (A)

Premature atrial contractions are atrial ectopic beats that fire earlier than the next expected sinus beat. The hallmark is a premature beat with an early P wave that looks different from the normal sinus P waves, indicating an atrial origin. The following QRS complex is usually normal in width because ventricular conduction is intact, and there may be a brief pause before the next normal beat as the sinus node resets. This pattern distinguishes PAC from a late beat with no P wave, which suggests a ventricular origin; a wide-complex tachycardia, which points to ventricular tachycardia; or a prolonged QT interval, which reflects repolarization abnormality rather than an atrial ectopic beat.

Premature atrial contractions are atrial ectopic beats that fire earlier than the next expected sinus beat. The hallmark is a premature beat with an early P wave that looks different from the normal sinus P waves, indicating an atrial origin. The following QRS complex is usually normal in width because ventricular conduction is intact, and there may be a brief pause before the next normal beat as the sinus node resets. This pattern distinguishes PAC from a late beat with no P wave, which suggests a ventricular origin; a wide-complex tachycardia, which points to ventricular tachycardia; or a prolonged QT interval, which reflects repolarization abnormality rather than an atrial ectopic beat.