Can PVCs depolarize the SA node and reset its rhythm?

Can PVCs depolarize the SA node and reset its rhythm?

• A. No, PVCs only depolarize the ventricles
• B. Yes, PVCs can reset the SA node
• C. Yes, but only in rare cases
• D. No, PVCs also affect the atria

Answer: (A)

Premature ventricular contractions (PVCs) originate in the ventricles and result from ectopic electrical activity. When a PVC occurs, it does cause depolarization in the ventricles, allowing them to contract earlier than they normally would. However, this depolarization does not extend to the sinoatrial (SA) node, which is responsible for initiating the normal rhythm of the heart.

The SA node functions independently, generating its impulses based on intrinsic pacing capabilities that are generally not influenced by the electrical activity of the ventricles via PVCs. Therefore, while PVCs can lead to an irregular heart rhythm and potentially disrupt the overall cardiac cycle, they do not have the capacity to reset or depolarize the SA node.

Understanding the role of PVCs highlights how they primarily affect the ventricles without impacting the heart's primary pacemaker, the SA node. This distinction is vital for interpreting EKGs and understanding the implications of different arrhythmias.