Cardiac Medicine Certification (CMC) Practice Exam

What can cause Premature Ventricular Contractions (PVCs)?

1. Hypoglycemia and hypertension

2. Electrolyte imbalances and irritability of the ventricular pacemaker cells

3. Excess Vitamin D and dehydration

4. Complete heart block and myocardial infarction

The correct answer is: Electrolyte imbalances and irritability of the ventricular pacemaker cells

Premature Ventricular Contractions (PVCs) are abnormal heartbeats that originate in the ventricles, leading to a sensation of skipped beats or palpitations. The most common causes of PVCs are related to irritability of the ventricular pacemaker cells and electrolyte imbalances. Irritable ventricular pacemaker cells can arise from various factors that affect the myocardial tissue, such as inflammation, ischemia, and increased sympathetic tone, causing the cells to discharge earlier than normal. Additionally, electrolyte imbalances—particularly involving potassium, magnesium, and calcium—can significantly influence myocardial excitability and conduction, making it a leading cause of PVCs. The other options, while they may contain elements that affect heart function or rhythm, do not specifically link to the primary mechanisms responsible for PVCs. Hypoglycemia and hypertension are less commonly associated with PVCs compared to direct irritability or electrolyte issues. Excess Vitamin D is not recognized as a typical cause of PVCs, and while dehydration can impact electrolyte levels, it does not directly stimulate ectopic ventricular contraction. Lastly, complete heart block and myocardial infarction are more likely to cause different forms of arrhythmias and conduction abnormalities rather than isolated PVCs. Thus, the connection of electrolyte imbalances and