Passage
In the event of end-stage heart failure, a left ventricular assist device (LVAD) can be used as a heart transplant bridge to keep a patient alive. The first iterations of LVADs were pulsatile and mimicked the physiological pumping action of the heart (Figure 1) .
Figure 1 A pulsatile-flow LVAD schematicA pulsatile-flow LVAD assists ventricular systole by mechanically pumping blood from a weakened left ventricle into the aorta through a pair of one-way valves. The pressure differential ΔP generated by the pump is related to cardiac output (CO) and vascular resistance (VR) :ΔP = CO × VREquation 1The efficiency and performance of the heart (or LVAD) can be determined by the patient's cardiac pressure-volume (PV) loop. A cardiac PV loop plots the pressure and volume of the blood in the left ventricle throughout a single cardiac cycle (Figure 2) .
Figure 2 Cardiac PV Loop of a pulsatile-flow LVADBlood pressure is often represented by only two numbers: arterial systolic and diastolic pressures. A more detailed representation of blood pressures is shown in a blood pressure profile, which graphs the blood pressure throughout the length of the different vessel groups (Figure 3) . Multiple pressure fluctuations are shown within a vessel because the pressure is traced across multiple cardiac cycles.
Figure 3 Blood pressure profile of the different vessels
-The area enclosed by the cardiac PV loop is:

Question

Passage
In the event of end-stage heart failure, a left ventricular assist device (LVAD) can be used as a heart transplant bridge to keep a patient alive. The first iterations of LVADs were pulsatile and mimicked the physiological pumping action of the heart (Figure 1) .

Figure 1 A pulsatile-flow LVAD schematicA pulsatile-flow LVAD assists ventricular systole by mechanically pumping blood from a weakened left ventricle into the aorta through a pair of one-way valves. The pressure differential ΔP generated by the pump is related to cardiac output (CO) and vascular resistance (VR) :ΔP = CO × VREquation 1The efficiency and performance of the heart (or LVAD) can be determined by the patient's cardiac pressure-volume (PV) loop. A cardiac PV loop plots the pressure and volume of the blood in the left ventricle throughout a single cardiac cycle (Figure 2) .

Figure 2 Cardiac PV Loop of a pulsatile-flow LVADBlood pressure is often represented by only two numbers: arterial systolic and diastolic pressures. A more detailed representation of blood pressures is shown in a blood pressure profile, which graphs the blood pressure throughout the length of the different vessel groups (Figure 3) . Multiple pressure fluctuations are shown within a vessel because the pressure is traced across multiple cardiac cycles.

Figure 3 Blood pressure profile of the different vessels
-The area enclosed by the cardiac PV loop is:

Quizplus · Accepted Answer

11ecba2d_12e7_fa81_a3bf_9d6cc44fd656_MD0008_00 The physical quantity represented by an area on a graph is equivalent to the product of the axes' quantities. Therefore, the area on a cardiac PV loop represents the physical quantity equal to pressure × volume. 11ecba2d_12e7_fa82_a3bf_4999d96d0a37_MD0008_00 Pressure is a derived quantity (P = F/A) and can be rewritten as force divided by area. 11ecba2d_12e7_fa83_a3bf_71b442e1f9b9_MD0008_00 Volume has dimensions of [length]³, and area has dimensions of [length]². Therefore, volume divided by area has dimensions of [length]³/[length]² = [length], or is distance d. 11ecba2d_12e7_fa84_a3bf_798912aeb112_MD0008_00 The amount of energy transferred by a force over a distance is the general definition of work: W= Fd. Because the product of pressure and volume is equal to the product of force and distance, the area enclosed by the cardiac PV loop is the amount of work done. (Choice A) Cardiac output is the volume of blood pumped by the heart every minute and is the product of stroke volume and heart rate. Although stroke volume is represented by the width of the PV loop, heart rate is not represented by the height of the loop. (Choice C) Power is the amount of work done over time (P = W/t). Although the area of the PV loop represents the amount of work done, time is not represented on a cardiac PV loop. (Choice D) The net pressure drop is represented by the height of the PV loop. Educational objective: An area on a graph represents the physical quantity equal to the product of the axes' quantities. On a cardiac PV loop, an area represents pressure × volume and is equal to the amount of work involved.

Passage In the Event of End-Stage Heart Failure, a Left Ventricular