Which arrhythmias may result from changes in myocardial excitability due to hypokalemia?

The focus on ventricular tachycardia and fibrillation as the correct answer highlights the significance of severe hypokalemia on myocardial excitability. When potassium levels in the blood drop, the resting membrane potential of cardiac myocytes becomes more negative, which can lead to increased automaticity and heightened susceptibility to re-entrant circuits. This altered excitability directly contributes to the development of serious arrhythmias like ventricular tachycardia and ventricular fibrillation.

Ventricular tachycardia is characterized by rapid, abnormal heartbeats originating from the ventricles, which can progress to ventricular fibrillation, a life-threatening condition where the heart quivers instead of pumping effectively due to disorganized electrical activity. Both arrhythmias can lead to significant cardiovascular instability and require immediate intervention.

In contrast, other arrhythmias such as premature atrial contractions and atrial fibrillation may occur due to changes in excitability influenced by other factors, including atrial stretch and autonomic tone, but are typically not directly precipitated by hypokalemia. Heart block involves issues with electrical conduction rather than alterations in excitability and is more related to structural conduction system problems than to electrolyte imbalances. Therefore, the link between hypokalemia and the development of life-threatening ventricular arrhythm