Mean arterial pressure is roughly the product of which two factors, and what conditions would shift it?

• A. MAP results from the product of cardiac output and systemic vascular resistance; changes in CO or SVR shift MAP accordingly.
• B. MAP ≈ HR × SV.
• C. MAP ≈ EDV × ESV.
• D. MAP ≈ Capacitance × Flow.

Answer: (A)

Mean arterial pressure reflects how hard the heart is pumping into a vascular system that offers resistance. In the usual hemodynamic model, MAP ≈ CO × SVR, where CO is the cardiac output (the amount of blood pumped per minute) and SVR is the systemic vascular resistance. Since cardiac output equals heart rate times stroke volume (CO = HR × SV), MAP can also be viewed as approximately (HR × SV) × SVR.

Shifts in MAP occur when either CO or SVR changes. An increase in heart rate or stroke volume raises CO and tends to raise MAP, while a rise in SVR from vasoconstriction increases MAP as well; decreases in either CO or SVR lower MAP.

The other ideas don’t describe MAP: HR × SV is cardiac output, not mean arterial pressure; EDV × ESV and Capacitance × Flow do not characterize MAP.