A cardiologist uses a conductance catheter to construct pressure-volume loops in a patient. The slope and position of the end-systolic pressure-volume relationship (ESPVR) is used as a load-independent index of which parameter?
- A Preload
- B Afterload
- C Contractility (inotropy) ✓
- D Ventricular compliance
Correct answer: C. Contractility (inotropy)
Explanation
The ESPVR is the line connecting the end-systolic points of pressure-volume loops at varying loading conditions. Its slope (Ees, end-systolic elastance) reflects myocardial contractility and is relatively independent of preload and afterload. Increased inotropy shifts the ESPVR upward and leftward; decreased inotropy shifts it downward and rightward. Preload is assessed by end-diastolic volume; afterload by arterial elastance.
Reference: Guyton and Hall Textbook of Medical Physiology, 14th ed.
High-yield for: NEET PGINI-CETNExTFMGEUSMLEPLABMRCP
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