Systemic vascular resistance describes which concept?

Systemic vascular resistance describes which concept?

• A. Pressure the heart must overcome to pump blood into the pulmonary circulation
• B. Pressure in the left atrium during filling
• C. Pressure generated by the heart during systole
• D. Resistance the systemic vasculature offers to blood flow

Answer: (D)

Systemic vascular resistance is the resistance the systemic vasculature offers to blood flow, i.e., the afterload the left ventricle must overcome to eject blood into the aorta. It depends on arteriolar radius, blood viscosity, and vessel length; small changes in diameter have a big impact on resistance. Clinically, increasing vasoconstriction raises SVR and makes the heart work harder, while vasodilation lowers SVR. In contrast, the other descriptions refer to pressures in specific chambers or pressures of the heart during systole, or to pressures in the pulmonary circulation, not to the resistance posed by the systemic vessels.

Systemic vascular resistance is the resistance the systemic vasculature offers to blood flow, i.e., the afterload the left ventricle must overcome to eject blood into the aorta. It depends on arteriolar radius, blood viscosity, and vessel length; small changes in diameter have a big impact on resistance. Clinically, increasing vasoconstriction raises SVR and makes the heart work harder, while vasodilation lowers SVR. In contrast, the other descriptions refer to pressures in specific chambers or pressures of the heart during systole, or to pressures in the pulmonary circulation, not to the resistance posed by the systemic vessels.