The R on T phenomenon is a dangerous pattern most associated with which arrhythmia?

The R on T phenomenon is a dangerous pattern most associated with which arrhythmia?

• A. Premature ventricular contraction
• B. Atrial flutter
• C. Sinus tachycardia
• D. Bundle branch block

Answer: (A)

R on T occurs when a premature ventricular contraction falls on the downslope of the T wave, during the ventricles’ relative refractory period. This timing can trigger dangerous ventricular activity, such as ventricular tachycardia or fibrillation, because the tissue is vulnerable to abnormal excitation during repolarization. That’s why this phenomenon is most associated with premature ventricular contractions. Atrial flutter, sinus tachycardia, and bundle branch block involve other aspects of rhythm (atrial activity, overall rate, or conduction delay) and do not specifically describe a premature beat landing during ventricular repolarization.