What are some causes of an irritable ventricular focus?

What are some causes of an irritable ventricular focus?

• A. Hypercalcemia and dehydration
• B. Hypokalemia and QT prolongating medications
• C. Ischemia and cardiac tamponade
• D. None of the above

Answer: (B)

An irritable ventricular focus refers to a situation in which a ventricular pacemaker or ectopic focus becomes overly excitable, leading to premature ventricular contractions (PVCs) or other abnormal rhythms. Hypokalemia, characterized by low potassium levels in the blood, is known to increase the irritability of cardiac cells. This can lead to abnormal electrical impulses, making it more likely for ectopic foci to fire.

Additionally, medications that prolong the QT interval can disrupt the normal depolarization and repolarization processes of the cardiac myocytes, leading to increased irritability as well. When the QT interval is lengthened, it can set the stage for potentially dangerous arrhythmias, including those originating from irritable foci in the ventricles.

In contrast, while dehydration and hypercalcemia can affect heart function and overall electrolyte balance, they aren't typically primary causes of the irritability seen in ventricular foci compared to hypokalemia and the impact of certain medications. Ischemia and cardiac tamponade may lead to other types of arrhythmias through mechanisms related to decreased perfusion and mechanical obstruction, but they do not directly cause the irritability of ventricular foci in the way that hypokalemia and QT-prolonging drugs do. Thus,