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Unformatted text preview: Question 1 of 18 The diagram above shows diastolic pressure-volume relationships for the left ventricle from three patients (X, Y, and Z), all of whom have the same cardiac output and heart rate. The black circle on each curve represents that patient’s end-diastolic pressure and volume at rest. A. End-systolic volume is greatest in patient X B. Ejection fraction is greatest in patient Z C. Left ventricular contractility is the same in all three patients D. Patient Z has the lowest left ventricular compliance at the resting end-diastolic pressure E. Patient Z probably has concentric (pressure overload) ventricular hypertrophy (e.g., due to aortic stenosis) 0 out of 1 Answer: D First, note that since all three patients have the same cardiac output and heart rate, they all have the same stroke volume (SV). Regarding choice A, patient Z has the largest end-diastolic volume (EDV); therefore, his end-systolic volume (ESV) will be the largest (ESV = EDV – SV; the SV is the same for all patients). Regarding choice B, ejection fraction (EF) equals SV/EDV. All three patients have the same SV, but patient Z has the largest EDV; therefore, his EF will be the smallest. Regarding choice C, left ventricular (LV) contractility (inotropic state) can be assessed by looking at the position and slope of the end-systolic pressure-volume relationship (ESPVR). Although that line is not shown in the figure, since all three patients have the same SV, it would be impossible for all three patients to have an end-systolic pressure- volume point on the same line (patients X and Y could have an end-systolic pressure-volume point on the same line, but not patient Z). Regarding choice D, LV compliance (ΔV/ΔP) at a given volume is the reciprocal of the slope of the diastolic pressure-volume relationship (DPVR) at that volume; therefore, patient Z has the lowest LV compliance at the resting end-diastolic pressure (patient Y has the greatest LV compliance at the resting end-diastolic pressure). Regarding choice E, patient Z probably has eccentric (volume overload) hypertrophy; note the rightward shift of the DPVR and the low filling pressures at a very large LV volume. Question 2 of 18 If an intervention decreases left ventricular (LV) end-systolic volume without changing LV end-systolic pressure, this means that the intervention: A. Decreased LV contractility B. Increased LV contractility C. Did not change LV contractility 0 out of 1 Answer: B Assume that point D in the pressure-volume (PV) loop below represents the control end-systolic volume/end-systolic pressure point. If the intervention decreases LV end-systolic volume without changing LV end-systolic pressure, the end-systolic volume/end-systolic pressure point would have to shift directly leftward, e.g., to point X on the figure below. Point X MUST lie on a different end-systolic pressure-volume relationship (ESPVR) than point D; more specifically, it must lie on an ESPVR that is left-shifted. Thus, the intervention increased LV contractility (inotropic state). left-shifted....
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- Spring '11
- ventricular depolarization, primary care practice, mean frontal qrs, transverse plane vectors