What is the "R on T" phenomenon?

What is the "R on T" phenomenon?

• A. When a PVC occurs on the peak of the R wave
• B. When a PVC falls on a T wave during its vulnerable period
• C. When T waves become inverted following a PVC
• D. When two PVCs occur consecutively and cause a T wave alteration

Answer: (B)

The "R on T" phenomenon refers to a specific situation in cardiac physiology where a premature ventricular contraction (PVC) occurs during the vulnerable period of the T wave, which is the phase of the cardiac cycle when the heart muscle is particularly susceptible to arrhythmias. This vulnerability occurs because the cardiac cells are in the process of repolarization.

When a PVC lands on the T wave, it can disrupt the normal electrical activity of the heart and may lead to more dangerous arrhythmias, such as ventricular tachycardia or even ventricular fibrillation. Understanding this phenomenon is crucial in EKG interpretation, as it highlights the potential risks associated with irregular heartbeats, especially in patients who already have underlying heart conditions.

Other options represent related but distinctly different concepts. One option describes the occurrence of a PVC on the peak of the R wave, which does not align with the recognized dangers of the R on T phenomenon. Another option mentions T wave inversion following a PVC, which is a possible outcome but not the definition of the phenomenon itself. The last option implies that consecutive PVCs cause T wave changes; while this may occur, it does not specifically address the timing of the PVC in relation to the T wave that defines the R on T phenomenon.