Which hemodynamic parameter is most indicative of afterload in heart failure assessment?

• A. Cardiac output
• B. Systemic vascular resistance
• C. Cardiac index
• D. Pulmonary capillary wedge pressure

Answer: (C)

Afterload is the pressure the left ventricle must overcome to eject blood. The best single surrogate for this load is systemic vascular resistance, which reflects the arterial system’s tone opposing LV ejection. When SVR is high, afterload increases and stroke volume can fall if contractility doesn’t rise, lowering cardiac output. Cardiac index (CO adjusted for body size) describes pump performance but is not a direct measure of the load on the ventricle. Pulmonary capillary wedge pressure indicates preload (left atrial filling pressure), not afterload. Cardiac output is the result of preload, afterload, and contractility, so it’s not a direct measure of afterload either. In heart failure, assessing SVR (and sometimes arterial elastance) provides the most direct sense of afterload and helps guide therapy to reduce it.