P11 Effect of Aging on the Pressure Asymptote and Time Constant of Exponential Diastolic Aortic Pressure Decay in Humans

Abstract

There are few data regarding the effect of aging on pressure asymptote (Pasymptote) and time constant (Tau) of exponential diastolic aortic pressure (AoP) decay in normal human heart. To investigate this issue, we analyzed high-fidelity AoP, measured by use of a catheter-tipped manometer in 71 normal subjects who underwent diagnostic cardiac catheterization but who were found to have normal coronary artery and LV function. Subjects who had hypertension, diabetes or renal disease were excluded. There were 49 men and 22 women, ranging in age from 20 to 80 years. We analyzed diastolic AoP sampled every 5 ms from the point of minimal dP/dt to the top of ECG-R waves of the next beat, and estimated Tau and Pasymptote by the exponential best fitting with a variable Pasymptote results. Systolic AoP were significantly increased with age, but mean and diastolic AoP remained unchanged. Pasymptote was 58.5 ± 8.1 mmHg and Tau was 436 ± 105 msec. Pasymptote show no significant age-related change, but strongly and positively correlated with systolic, diastolic and mean AoP (R2 = 0.39, 0.70 and 0.66, respectively). For Tau, it was weakly and positively related with both age and AoP (Age: R2 = 0.20, AoP: R2 = 0.08–0.20).

Conclusion

We documented Pasymptote and Tau of the Windkessel with the beating heart in normal humans. Tau was associated with aging, whereas Pasymptote, which increased with the level of AoP, did not vary with aging per se, at least until the ninth decade. These data may provide insight into the understanding of AoP physiology.