Physiology: USMLE Q No. 5

[Cardiac Arrest]

You have ONLY 1 Minute :o:

A 54-year-old male is seen in clinic with complaints of palpitations and light-headedness. Physical examination is remarkable for a heart rate of greater than 200 beats per minute and a blood pressure of 75/40 mm Hg. What adjustments have probably occurred in the cardiac cycle?

A. Diastolic time has decreased and systolic time has increased

B. Diastolic time has decreased but systolic time has decreased more

C. Systolic time has decreased and diastolic time has increased

D. Systolic time has decreased but diastolic time has decreased more

E. Systolic time has decreased but diastolic time has not changed

[GoldenButterfly]

I say D

wallahu a3lam

[H@SSOOM]

Systolic time has decreased but diastolic time has decreased more

that is D


I am sure the filing time has decreased that s why the rate is increased


but I am not sure about the sys time and its relation to the BP

when tell us the right answer, please try to explain the concept so we can learn together



regards


:787: :787:

[Cardiac Arrest]

The correct answer is D. Under normal conditions, one-third of the cardiac cycle is spent in systole and two-thirds spent in diastole. As heart rate increases dramatically, the time spent in diastole falls precipitously but the time spent in systole falls only slightly.

A large increase in heart rate must produce a decrease in both diastole and systole (compare with choice A).

The major change with increased heart rate is in diastole, not systole (compare with choice B).

Heart rate cannot increase if diastolic time increases (choice C).

An increase in heart rate must be accompanied by a decrease in diastolic time (compare with choice E).

[alva]

thanks for the explanation