How does a PVC affect the cardiac cycle?

How does a PVC affect the cardiac cycle?

• A. It normalizes heart rhythm
• B. It causes an early ventricular contraction
• C. It slows down the heart rate
• D. It has no effect on the cycle

Answer: (B)

A premature ventricular contraction (PVC) affects the cardiac cycle by causing an early ventricular contraction. This occurs when an electrical impulse originates in the ventricles instead of the usual pacemaker, the sinoatrial (SA) node. As a result, the ventricles contract before the atria have finished contracting, leading to an early beat in the rhythm. In the normal cardiac cycle, the atria contract first, allowing for optimal filling of the ventricles before they contract. When a PVC occurs, it disrupts this sequence. The early contraction leads to a premature heartbeat, which can sometimes be followed by a compensatory pause, allowing the heart to reset before the next normal beat. This is significant because while it may not always lead to symptoms or hemodynamic instability, it represents a disruption in the normal rhythm and can indicate underlying cardiac issues if frequent PVCs occur. The other potential choices do not accurately describe the impact of a PVC on the cardiac cycle. A PVC does not stabilize the heart rhythm, as it introduces irregularity. It also does not inherently slow down the heart rate, and while the heart may have moments of altered timing due to the PVC, the cycle itself is indeed affected in terms of contraction timing.

A premature ventricular contraction (PVC) affects the cardiac cycle by causing an early ventricular contraction. This occurs when an electrical impulse originates in the ventricles instead of the usual pacemaker, the sinoatrial (SA) node. As a result, the ventricles contract before the atria have finished contracting, leading to an early beat in the rhythm.

In the normal cardiac cycle, the atria contract first, allowing for optimal filling of the ventricles before they contract. When a PVC occurs, it disrupts this sequence. The early contraction leads to a premature heartbeat, which can sometimes be followed by a compensatory pause, allowing the heart to reset before the next normal beat. This is significant because while it may not always lead to symptoms or hemodynamic instability, it represents a disruption in the normal rhythm and can indicate underlying cardiac issues if frequent PVCs occur.

The other potential choices do not accurately describe the impact of a PVC on the cardiac cycle. A PVC does not stabilize the heart rhythm, as it introduces irregularity. It also does not inherently slow down the heart rate, and while the heart may have moments of altered timing due to the PVC, the cycle itself is indeed affected in terms of contraction timing.