When does the vulnerable period of a T wave occur?

When does the vulnerable period of a T wave occur?

• A. During the initial phase of the T wave
• B. The entire duration of the T wave
• C. The peak and second half of the T wave
• D. Only in the first half of the QRS complex

Answer: (C)

The vulnerable period of a T wave is most accurately described as occurring during the peak and second half of the T wave. This is significant because it represents a time when the heart is particularly susceptible to arrhythmias. During this phase, the myocardial cells are in a refractory state—they are transitioning from repolarization to readiness for the next action potential—but not yet fully repolarized. This vulnerable status reflects the potential for electrical disturbances, particularly if an additional stimulus occurs, which can lead to serious arrhythmias like Torsades de Pointes.

Understanding the timing of the vulnerable period is crucial for recognizing and managing conditions that may lead to dangerous heart rhythms. The T wave itself reflects the repolarization of the ventricles, and the peak along with the latter portion is critical for assessing risk. The timing of other options doesn't align with the established knowledge of cardiac physiology, as they either extend too early into the phase of ventricular repolarization or reference an entirely different segment of the cardiac cycle.