ZERO FLOW PRESSURE IN HUMAN CORONARY CIRCULATION

Coronary pressure-flow (P/F) relationship has been investigated mainly from the viewpoint of coronary resistance. However, recent experiment al evidence suggests that the zero flow pressure intercept (Pzf) provi des important characteristics of coronary circulation. Although Pzf is likely to provide meaningful information about characteristics of cor onary circulation, no data are available about Pzf in humans. The auth ors attempted to determine Pzf in humans by analyzing P/F relationship during long cardiac pause. This relationship, provoked by intracorona ry adenosine triphosphate (ATP) infusion, was analyzed in 9 patients ( 8 men, 1 woman) with coronary heart disease (ages: fifty-six +/- six y ears). After the diagnostic cardiac catheterization, ATP, 0.6 mg/3 mL, was administrated by bolus intracoronary injection during measurement s of coronary blood flow velocity. Coronary blood flow velocity in the left anterior descending artery was measured with a 0.018-inch Dopple r angioplasty guide wire (FloWire, Cariometrics, Inc., Mountain View, Calif.). The dynamic P/F relationship was obtained by correlation of t he instantaneous aortic pressure and flow velocity with each other at constant intervals. The least square linear regression analysis was ap plied to the P/F data to yield the extrapolated Pzf axis. Immediately after intracoronary injection of ATP, long pause (5320 +/- 1498 msec) appeared and coronary blood flow velocity decreased to 11 +/- 8 cm/sec . Pzf calculated with P/F relationship was 14 +/-7 mmHg. Conclusions: Thus, the results clearly demonstrate that Pzf is higher than right at rial and left ventricular end-diastolic pressure in humans, indicating the complexity of the determinants of the Pzf.