Cardiac Cycle Adjustments! - USMLE Forums
USMLE Forums Logo
USMLE Forums         Your Reliable USMLE Online Community     Members     Posts
USMLE Articles
Go Back   USMLE Forums > USMLE Step 1 Forum

USMLE Step 1 Forum USMLE Step 1 Discussion Forum: Let's talk about anything related to USMLE Step 1 exam

Thread Tools Search this Thread Display Modes
Old 10-15-2010
USMLE Forums Guru
Steps History: 1 + CS
Posts: 405
Threads: 55
Thanked 556 Times in 168 Posts
Reputation: 566
Heart Cardiac Cycle Adjustments!

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

Please answer with reasoning written.
Reply With Quote Quick reply to this message
The above post was thanked by:
Haisook (10-15-2010)

Old 10-15-2010
Haisook's Avatar
USMLE Forums Master
Steps History: 1+CK+CS+3
Posts: 752
Threads: 124
Thanked 633 Times in 266 Posts
Reputation: 653

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

Tachycardia will decrease both systole and diastole times, but because the diastole constitutes two thirds of the cardiac cycle, the decrease will be more pronounced. Systole time is already small, being one third of the cycle, so further reduction of time would not make a large difference, not as much as that of the diastole.
Reply With Quote Quick reply to this message
Old 10-15-2010
USMLE Forums Scout
Steps History: CS Only
Posts: 24
Threads: 4
Thanked 17 Times in 8 Posts
Reputation: 27
Post confounding reason

My answer is D as well...with rapid heart rates there is not enough time to relax and fill the ventricles. Systole would be decreased as well but since it is the contract and eject phase it is not as reduced as diastolic phase. Not 100% sure though!
Reply With Quote Quick reply to this message


Cardiovascular-, Physiology-, Step-1-Questions

Quick Reply

Register Now

In order to be able to post messages on the USMLE Forums forums, you must first register.
Please enter your desired user name, your email address and other required details in the form below.
User Name:
Please enter a password for your user account. Note that passwords are case-sensitive.
Confirm Password:
Email Address
Please enter a valid email address for yourself.
Email Address:
Medical School
Choose "---" if you don't want to tell. AMG for US & Canadian medical schools. IMG for all other medical schools.
USMLE Steps History
What steps finished! Example: 1+CK+CS+3 = Passed Step 1, Step 2 CK, Step 2 CS, and Step 3.

Choose "---" if you don't want to tell.

Favorite USMLE Books
What USMLE books you really think are useful. Leave blank if you don't want to tell.
Where you live. Leave blank if you don't want to tell.


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Similar Threads
Thread Thread Starter Forum Replies Last Post
abdominal pain during her menstrual cycle doctorF USMLE Step 1 Forum 13 09-22-2013 07:10 AM
cardiac muscle contraction Pixie USMLE Step 1 Forum 3 05-21-2012 03:41 PM
Cardiac Innervation aungawa USMLE Step 1 Forum 8 02-22-2012 02:36 AM
Cardiac Bruise ecgram USMLE Step 1 Forum 2 05-22-2010 11:55 AM
Krebs Cycle Mnemonic aalous USMLE Step 1 Mnemonics 1 04-06-2010 05:57 AM

Find Us on Facebook
Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2020, vBulletin Solutions, Inc.
vBulletin Security provided by vBSecurity v2.2.2 (Pro) - vBulletin Mods & Addons Copyright © 2020 DragonByte Technologies Ltd.

USMLE® & other trade marks belong to their respective owners, read full disclaimer
USMLE Forums created under Creative Commons 3.0 License. (2009-2019)