Question 1

Q: A pressure-volume loop is recorded from the left ventricle of a patient before and after an intervention. The post-intervention loop is shifted rightward with a larger end-diastolic volume, a lower peak systolic pressure, and the slope of the end-systolic pressure-volume relationship (ESPVR) is unchanged. Which of the following interventions most likely produced this change?

Rapid intravenous infusion of 1 liter of normal saline. ***Rapid intravenous infusion of 1 liter of normal saline*** - Saline infusion increases **venous return** and **preload**, which shifts the pressure-volume loop rightward by increasing the **end-diastolic volume (EDV)**. - Because myocardial **contractility** remains unchanged, the slope of the **end-systolic pressure-volume relationship (ESPVR)** remains constant while the stroke volume increases. *Intravenous administration of dobutamine* - Dobutamine is a **positive inotrope** that would result in a **steepened ESPVR slope**, reflecting increased contractility. - Increased contractility typically leads to a **reduced end-systolic volume**, which contradicts the rightward shift and unchanged slope described. *Intravenous administration of phenylephrine* - Phenylephrine is an **alpha-1 agonist** that primarily increases **afterload** through systemic vasoconstriction, which would shift the loop upward. - An increase in afterload usually results in a **reduced stroke volume** and a higher end-systolic volume, but would not primarily cause an isolated rightward shift in EDV. *Administration of a loop diuretic* - Loop diuretics decrease total blood volume, leading to a **decrease in preload** and reduced venous return to the heart. - This intervention would shift the pressure-volume loop to the **left**, as the **end-diastolic volume (EDV)** would decrease. *Intravenous administration of nitroprusside* - Nitroprusside acts as a balanced **vasodilator**, reducing both **preload and afterload** simultaneously. - This would lead to a **leftward shift** of the loop due to decreased filling and a downward shift due to reduced MAP, rather than the rightward shift observed.

Question

A pressure-volume loop is recorded from the left ventricle of a patient before and after an intervention. The post-intervention loop is shifted rightward with a larger end-diastolic volume, a lower peak systolic pressure, and the slope of the end-systolic pressure-volume relationship (ESPVR) is unchanged. Which of the following interventions most likely produced this change?

Accepted Answer

Rapid intravenous infusion of 1 liter of normal saline

Answer

Intravenous administration of dobutamine

Answer

Intravenous administration of phenylephrine

Answer

Administration of a loop diuretic

Answer

Intravenous administration of nitroprusside

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