What phase of diastole does Bradycardia lead to a longer duration?

Bradycardia, which is a slower than normal heart rate, has a significant impact on the duration of diastole, the phase of the cardiac cycle when the heart muscle relaxes and the chambers fill with blood. Specifically, in bradycardia, the time between heartbeats increases, leading to a longer duration of the entire diastolic phase, but especially during diastasis.

Diastasis is the phase where there is minimal change in volume in the ventricles; it occurs after the rapid filling (early diastole) and just before atrial contraction (late diastole). When the heart rate decreases, the time available for all phases of diastole is extended, particularly allowing for a more pronounced diastasis since there is less urgency for the ventricles to refill.

While early diastole and late diastole both experience prolongation due to a slower heart rate, the prolongation of diastasis becomes more significant as it essentially represents a phase of inactivity between active filling periods. Consequently, bradycardia effectively extends the duration of diastasis, making it the correct choice in this context.