Which parameter is commonly used to assess preload in invasive hemodynamics?

Which parameter is commonly used to assess preload in invasive hemodynamics?

• A. PCWP
• B. Cardiac Output
• C. SVR
• D. SvO2

Answer: (A)

Preload is the filling pressure that determines how much the ventricle is stretched at the end of diastole. In invasive hemodynamics, the pulmonary capillary wedge pressure is used as a surrogate for left atrial pressure, and therefore left-sided preload. By advancing a pulmonary artery catheter and wedging it in a small branch, the pressure measured distal to the balloon reflects the pressure in the left atrium, giving a direct estimate of preload for the left ventricle. Elevated PCWP indicates higher left-sided preload or volume status, while a low PCWP indicates reduced preload. In contrast, cardiac output measures the amount of blood pumped per minute (volume flow), systemic vascular resistance reflects afterload, and SvO2 indicates the balance of oxygen delivery and consumption—not preload.

Preload is the filling pressure that determines how much the ventricle is stretched at the end of diastole. In invasive hemodynamics, the pulmonary capillary wedge pressure is used as a surrogate for left atrial pressure, and therefore left-sided preload. By advancing a pulmonary artery catheter and wedging it in a small branch, the pressure measured distal to the balloon reflects the pressure in the left atrium, giving a direct estimate of preload for the left ventricle.

Elevated PCWP indicates higher left-sided preload or volume status, while a low PCWP indicates reduced preload. In contrast, cardiac output measures the amount of blood pumped per minute (volume flow), systemic vascular resistance reflects afterload, and SvO2 indicates the balance of oxygen delivery and consumption—not preload.