What type of PVCs typically indicates an irritable focus?

What type of PVCs typically indicates an irritable focus?

• A. Isolated PVCs
• B. Frequent unifocal PVCs
• C. Frequent multifocal PVCs
• D. Ventricular bigeminy

Answer: (B)

Frequent unifocal PVCs indicate an irritable focus due to their consistent morphological appearance, which suggests that a single ectopic focus in the ventricles is responsible for their occurrence. The term "unifocal" means that all the PVCs originate from the same site in the ventricles, producing identical QRS complexes on the EKG. This uniformity indicates that a specific area of cardiac tissue is irritable and firing repeatedly, which is characteristic of an irritative process.

In contrast, other types of PVCs can suggest different underlying mechanisms. For instance, isolated PVCs may not indicate significant irritability, as they occur sporadically and do not imply a continuous abnormal focus. Frequent multifocal PVCs would suggest multiple ectopic foci, indicating broader irritability across different areas of the myocardium, which is often more concerning regarding underlying heart disease. Ventricular bigeminy, which involves alternating between normal beats and PVCs, may also indicate irritability, but the consistent nature of frequent unifocal PVCs more clearly points to a single active focus that is persistently firing.

Thus, in interpreting EKGs, recognizing the pattern of frequent unifocal PVCs is crucial in identifying isolated foci of irrit