Mean aortic pressure is the geometric mean of systolic and diastolic aortic pressure in resting humans

The aim of our study was twofold: 1) to establish a mathematical link between mean aortic pressure ( MAP) and systolic ( SAP) and diastolic aortic pressures ( DAP) by testing the hypothesis that either the geometric mean or the harmonic mean of SAP and DAP were reliable MAP estimates; and 2) to critically evaluate three empirical formulas recently proposed to estimate MAP. High- fidelity pressures were recorded at rest at the aortic root level in controls ( n = 31) and in subjects with various forms of cardiovascular diseases ( n = 108). The time- averaged MAP and the pulse pressure ( PP = SAP - DAP) were calculated. The MAP ranged from 66 to 160 mmHg [ mean = 107.9 mmHg ( SD 18.2)]. The geometric mean, i. e., the square root of the product of SAP and DAP, furnished a reliable estimate of MAP [ mean bias = 0.3 mmHg ( SD 2.7)]. The harmonic mean was inaccurate. The following MAP formulas were also tested: DAP + 0.412 PP ( Meaney E, Alva F, Meaney A, Alva J, and Webel R. Heart 84: 64, 2000), DAP + 0.33 PP + 5 mmHg [ Chemla D, Hebert JL, Aptecar E, Mazoit JX, Zamani K, Frank R, Fontaine G, Nitenberg A, and Lecarpentier Y. Clin Sci ( Lond) 103: 7 - 13, 2002], and DAP + [ 0.33 + ( heart rate x 0.0012)] PP ( Razminia M, Trivedi A, Molnar J, Elbzour M, Guerrero M, Salem Y, Ahmed A, Khosla S, Lubell DL. Catheter Cardiovasc Interv 63: 419 - 425, 2004). They all provided accurate and precise estimates of MAP [ mean bias = - 0.2 ( SD 2.9), - 0.3 ( SD 2.7), and 0.1 mmHg ( SD 2.9), respectively]. The implications of the geometric mean pressure strictly pertained to the central ( not peripheral) level. It was demonstrated that the fractional systolic ( SAP/ MAP) and diastolic ( DAP/ MAP) pressures were reciprocal estimates of aortic pulsatility and that the SAP times DAP product matched the total peripheral resistance times cardiac power product. In conclusion, although the previously described thumb- rules applied, the geometric MAP appears more valuable as it established a simple mathematical link between the steady and pulsatile component of aortic pressure.