A single irritable beat is most consistent with which arrhythmia?

• A. Atrial Flutter
• B. Sinus Tachycardia
• C. Ventricular Tachycardia
• D. Premature Ventricular Contraction

Answer: (D)

A single irritable beat is a premature ventricular contraction. This is a ventricular ectopic beat that occurs earlier than the next expected beat, producing a wide, bizarre QRS complex often without a preceding P wave and sometimes followed by a brief pause before the next normal beat. This pattern is distinct from other rhythms: atrial flutter involves rapid atrial activity with sawtooth waves; sinus tachycardia is a normal rhythm that just runs faster from the SA node; and ventricular tachycardia consists of three or more consecutive wide QRS complexes at a fast rate, not a lone premature beat. So the lone premature ventricular contraction best fits a single irritable beat.