Florida State Paramedic Practice Exam

Where do most unstable or lethal ectopic beats typically originate?

1. Atrium

2. Ventricles

3. Bundle of His

4. Purkinje Fibers

The correct answer is: Ventricles

The origin of most unstable or lethal ectopic beats is primarily in the ventricles. This is due to the fact that ventricular ectopic beats, including ventricular premature contractions (VPCs), can significantly disrupt normal cardiac rhythm and lead to potentially dangerous arrhythmias such as ventricular tachycardia or ventricular fibrillation. These ventricular ectopic beats are more concerning than those originating from the atria because they can compromise the heart's ability to effectively pump blood. When beats arise from the ventricles, they may create a scenario where the heart fails to fill appropriately, leading to a decrease in cardiac output and subsequent hemodynamic instability. In contrast, ectopic beats originating from the atria are generally less dangerous because they are less likely to disrupt the mechanical function of the heart at a critical level. While they can lead to issues like atrial fibrillation or flutter, they do not usually result in the same immediate life-threatening situations as those stemming from the ventricles. Ectopic beats from the Bundle of His or Purkinje fibers can also occur, but they are less common and typically don't have the same lethality as ventricular-origin ectopies, making them relatively more stable.