WBR1014

Author	[[PageAuthor::Rim Halaby, M.D. [1]]]
Exam Type	ExamType::USMLE Step 1
Main Category	MainCategory::Physiology
Sub Category	SubCategory::Cardiology
Prompt	[[Prompt::A 75 year old female patient complains of dyspnea and generalized fatigue. The shortness of breath is very severe when she is lying down or when she climbs the stairs. Laboratory tests and echocardiography are ordered. Echocardiography reveals abnormal filling dynamics of the left ventricle with preserved contractility which is associated with elevated left atrial filling pressures and left atrial enlargement. Which of the following most likely corresponds to the end-disatolic and end-systolic volumes respectively measured in the left ventricle of this patient?]]
Answer A	AnswerA::200 and 60 mL
Answer A Explanation	[[AnswerAExp::The ejection fraction calculated from the given end-systolic and end-diastolic volume is 70%. An ejection fraction of 70% is considered normal. Diastolic heart failure is characterized by a normal ejection fraction.]]
Answer B	AnswerB::200 and 100 mL
Answer B Explanation	[[AnswerBExp::The ejection fraction calculated from the given end-systolic and end-diastolic volume is 50%. An ejection fraction of 50% is considered low.]]
Answer C	AnswerC::180 and 100 mL
Answer C Explanation	[[AnswerCExp::The ejection fraction calculated from the given end-systolic and end-diastolic volume is 44%. An ejection fraction of 44% is considered low.]]
Answer D	AnswerD::150 and 75 mL
Answer D Explanation	[[AnswerDExp::The ejection fraction calculated from the given end-systolic and end-diastolic volume is 50%. An ejection fraction of 50% is considered low.]]
Answer E	AnswerE::110 and 70 mL
Answer E Explanation	[[AnswerEExp::The ejection fraction calculated from the given end-systolic and end-diastolic volume is 36%. An ejection fraction of 36% is considered low.]]
Right Answer	RightAnswer::A
Explanation	[[Explanation::This patients presents with symptoms of heart failure with echocardiographic findings suggestive of diastolic heart failure. Diastolic heart failure is characterized by abnormal relaxation and/or filling of the ventricles. It can be associated with left atrial enlargement due to the elevated pressures in the left heart. The ejection fraction differentiates systolic heart failure from diastolic heart failure which are two entities with different underlying pathophysiology. Systolic heart failure is characterized by a decreased ejection fraction, while diastolic heart failure is characterized by a normal ejection fraction. The ejection fraction can be calculated as follows: Ejection fraction= (end-diastolic volume -end-systolic volume)/ end-diastolic volume A normal ejection fraction ranges from 55 to 75%. Answer A corresponds to an ejection fraction of 70% which is within the normal range. Educational objective: Diastolic heart failure is characterized by a normal ejection fraction. The ejection fraction can be calculated as follows: Ejection fraction= (end-diastolic volume -end-systolic volume)/ end-diastolic volume Reference: First aid for USMLE step 1, 2014. Page 267. Educational Objective: References: ]]
Approved	Approved::No
Keyword	WBRKeyword::Ejection fraction, WBRKeyword::diastolic heart failure
Linked Question	Linked::
Order in Linked Questions	LinkedOrder::