An echocardiogram records an EDV of 150 mL and an ESV of 90 mL. What is the stroke volume?
The Correct Answer is {"dropdown-group-1":"C","dropdown-group-2":"A"}
Correct answer:
- Stroke volume (SV) = 60 mL
- This stroke volume is within the normal expected range.
Stroke volume represents the amount of blood ejected from the ventricle with each heartbeat and is calculated using the formula:
SV = EDV – ESV
EDV (end-diastolic volume) = 150 mL
ESV (end-systolic volume) = 90 mL
SV = 150 mL – 90 mL
= 60 mL
An anatomically and physiologically normal adult stroke volume ranges from approximately 60–100 mL per beat. This measurement indicates that the ventricles are ejecting an adequate volume of blood during systole. The calculation reflects effective ventricular filling and contractility, suggesting that the patient’s heart is pumping a normal volume of blood per beat.
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Related Questions
Correct Answer is B
Explanation
Correct answer: False
Afterload refers to the resistance the ventricles must overcome to eject blood into the aorta and pulmonary artery during systole. Vasoconstriction of blood vessels increases systemic vascular resistance, which raises afterload and makes it more difficult for the heart to pump blood effectively. Conversely, vasodilation decreases vascular resistance, lowering afterload and reducing cardiac workload. Anatomically, the aorta and systemic arteries are the primary sites where afterload is influenced, and physiologically, increased afterload can lead to higher ventricular pressure, reduced stroke volume, and increased myocardial oxygen demand.
Correct Answer is C
Explanation
A. Contractile force increases to compensate for the reduced cardiac output: In early compensatory phases, the heart may attempt to increase contractility via sympathetic stimulation, but in true heart failure, the myocardium is unable to generate sufficient force due to structural or functional impairment.
B. Contractile force increases, leading to an increased end systolic volume: Increased contractility would reduce, not increase, end-systolic volume because more blood is ejected per beat. In heart failure, contractile weakness leads to higher end-systolic volumes, reflecting incomplete emptying of the ventricles.
C. Contractile force is diminished due to damaged cardiomyocytes or cardiomyopathies: Heart failure results from conditions such as myocardial infarction, chronic hypertension, or dilated cardiomyopathy that impair cardiomyocyte function. This reduces the strength of ventricular contraction, decreasing stroke volume and overall cardiac output.
D. Contractile force is not affected in heart failure: Contractile force is significantly affected in heart failure. The weakened myocardium cannot generate sufficient pressure to maintain normal stroke volume, making this statement inaccurate.
E. Contractile force remains the same, but the heart becomes larger: While ventricular dilation can occur in chronic heart failure as a compensatory mechanism (eccentric hypertrophy), the contractile force per myocyte is reduced. Increased chamber size alone does not preserve effective contraction.
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