AEMCA Practice Exam

Which of the following can lead to enhanced automaticity?

1. Hyperkalemia

2. Hypoxia

3. Bradycardia

4. Increased stroke volume

The correct answer is: Hypoxia

Enhanced automaticity refers to an increased ability of certain heart cells to spontaneously depolarize and generate action potentials, which is crucial in the functioning of pacemaker cells in the heart. Hypoxia, or a deficiency in the amount of oxygen reaching the tissues, can lead to enhanced automaticity primarily because it affects the ionic balance and electrical activity of cardiac cells. When cells are deprived of oxygen, they may respond by attempting to increase their activity to compensate for the lack of energy and to maintain function. As a result, the pacemaker cells may begin to depolarize more easily, demonstrating increased automaticity. This physiological response can be crucial in certain pathological conditions, as the heart may try to maintain rhythm even amid distress. In contrast, factors such as hyperkalemia and bradycardia would typically disrupt the normal functioning of the heart. Hyperkalemia can lead to depolarization disturbances and can decrease the excitability of cardiac cells. Bradycardia, which involves a slower heart rate, can also decrease the firing rate of pacemaker cells, hindering automaticity. Increased stroke volume is related to the amount of blood pumped per heartbeat and does not directly influence the automatic properties of pacemaker cells, thus it is not a factor in enhancing