A 62-year-old man with a 10-year history of hypertension presents with dyspnea on exertion and orthopnea. Echocardiography shows an ejection fraction of 35% with global hypokinesis. His left ventricular pressure-volume loop is plotted, and the line marked **C** (End-Systolic Pressure-Volume Relation, ESPVR) is compared to that of a healthy control. Which of the following best describes the expected change in the structure marked **C** in this patient?

Explanation

## Why "The slope of ESPVR (Emax) is decreased, reflecting reduced myocardial contractility and explaining the reduced ejection fraction" is right The End-Systolic Pressure-Volume Relation (ESPVR) is the gold-standard load-independent measure of myocardial contractility. In heart failure with reduced ejection fraction (HFrEF), the primary pathophysiology is loss of contractile function. This manifests as a DECREASED slope of the ESPVR line (lower Emax). A flatter ESPVR slope means the ventricle generates less pressure at any given end-systolic volume, which directly explains why this patient's ejection fraction is reduced—the failing myocardium cannot contract as forcefully. This is the textbook hallmark of systolic heart failure on the pressure-volume diagram (Guyton & Hall 14e, Ch 9). ## Why each distractor is wrong - **"The slope of ESPVR (Emax) is increased due to compensatory sympathetic activation..."**: While sympathetic activation does occur in heart failure as a compensatory mechanism, it cannot overcome the fundamental loss of myocardial contractility. The ESPVR slope still decreases in HFrEF. Increased catecholamines may temporarily improve contractility in acute decompensation, but chronic HFrEF is defined by a persistently flattened ESPVR. This confuses acute compensation with the underlying pathology. - **"The ESPVR line shifts rightward, indicating that the heart requires greater volumes..."**: A rightward shift of the entire P-V loop occurs with increased preload (volume loading), not with reduced contractility. In HFrEF, the loop is typically shifted rightward AND upward (higher filling pressures), but the ESPVR line itself (the upper-left boundary) becomes flatter. This distractor conflates loop position with ESPVR slope. - **"The ESPVR line becomes horizontal, indicating complete loss of pressure-generating capacity..."**: While ESPVR does flatten in HFrEF, it does not become truly horizontal (zero slope). The ventricle retains some contractile function; it is simply reduced. A completely horizontal line would imply no pressure generation at any volume, which would be incompatible with life. This is an extreme misinterpretation. **High-Yield:** ESPVR slope (Emax) is the load-independent contractility index—decreased slope = reduced contractility (HF), increased slope = positive inotropes (epinephrine, digoxin, dobutamine, calcium). [cite: Guyton & Hall Textbook of Medical Physiology, 14th Edition, Chapter 9: Cardiac Output, Venous Return, and Their Regulation]