A 58-year-old man in the ICU has a pulmonary capillary wedge pressure of 24 mmHg and a cardiac output of 3.1 L/min. His systemic vascular resistance is calculated to be elevated. According to the Frank-Starling mechanism, which of the following best describes the state of his left ventricle?
- A Operating on the ascending limb with reserve contractility
- B Operating on the descending limb; increasing preload will improve output
- C Operating near the peak of the Frank-Starling curve with limited further preload reserve ✓
- D Preload is insufficient; afterload is the dominant determinant of dysfunction
Correct answer: C. Operating near the peak of the Frank-Starling curve with limited further preload reserve
Explanation
Elevated PCWP (24 mmHg) with reduced cardiac output and high SVR indicates a failing ventricle operating near or beyond the flat peak of its Frank-Starling curve. Adding more preload yields little additional output (preload reserve exhausted). The descending limb concept exists theoretically but is rarely observed clinically. Afterload reduction (vasodilators) and inotropes, not fluid boluses, are appropriate here.
Reference: Guyton & Hall, Textbook of Medical Physiology, 14th ed.
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Written and medically reviewed by the StethoPrep medical team.