Question

1. Why is the return of venous blood to the heart impaired when heart rate is very high?

1. inotropy (contractility) is too low (i.e., heart is not contracting hard/fast enough)
2. dromotropy is too low (i.e., conduction speed in cardiac conduction system is slow)
3. lusitropy is too low (i.e., heart is not spending enough time relaxing)
4. chronotropy is too low (i.e., heart rate is too slow)

2. If afterload is high, what happens to end-systolic volume (ESV)?

1. ESV is decreased
2. ESV is increased
3. ESV stays the same

Answer 1

1. Here, the main point to be noted is that venous return to the heart is one that is directly proportional to stroke volume and end-diastolic volume. When the heart rate is high then the return of venous blood gets impaired primarily due to impaired diastolic relaxation. This is the one which is given here as option "c". Therefore , this option is the most likely answer.

2. When after load is high then we can see that there is a considerable decrease in stroke volume. This leads to an overall increase in the end systolic volume or ESV. Therefore the correct answer here is likely to be option "b".