Certified Rhythm Analysis Technician (CRAT) Practice Exam

The R-on-T phenomenon refers to a situation where a premature ventricular contraction (PVC) occurs on the T wave of a preceding heartbeat during the relative refractory period of the cardiac cycle. During this time, the myocardial cells are partially depolarized and more susceptible to stimulation, which can lead to aberrant electrical activation and potentially dangerous arrhythmias.

The relevance of this phenomenon is critical as it can precipitate more serious arrhythmias, such as ventricular tachycardia or ventricular fibrillation. Recognizing R-on-T is essential in clinical settings, especially in patients with underlying heart conditions or those on certain medications that affect cardiac conduction.

The other choices refer to different concepts in cardiology. Bigeminy describes a pattern of arrhythmia where every normal beat is followed by a PVC. A couplet consists of two consecutive PVCs, while a bundle branch block refers to a specific conduction abnormality in the heart’s electrical system and is not directly related to the timing of PVCs. Understanding these distinctions further emphasizes the significance of the R-on-T phenomenon in assessing cardiac rhythm disturbances.