Low zero-flow pressure and minimal capacitance effect on diastolic coronary arterial pressure-flow relationships during maximum vasodilation in swine.

Abstract

During maximum dilation with adenosine in dogs, the diastolic coronary pressure at which flow ceases (Pzf) has been observed to be up to 27 mm Hg above coronary sinus and right atrial pressures. We studied swine to measure the Pzf and to determine the effects of interventions that change collateral flow and coronary capacitance. In 44 swine, the left anterior descending coronary artery (LAD)

End-Diastolic Fractional Flow Reserve

“…Our findings, as summarized in the Table, corroborate the findings of Pantely et al 10,12 relating to the hemodynamic stability of instantaneous hyperemic end-diastolic measurements. This is evident in minimal fluctuations in coronary resistance and wedge pressure despite substantially reduced impedance to coronary blood flow, as opposed to full-cardiac cycle measurements that include the effects of systole.…”

“…For end-diastolic FFR, the same 3 cardiac cycles were analyzed, respectively, except that instantaneous values at 60 ms before R-wave of the ECG were averaged. This was a slightly modified technique from a large animal study by Pantely et al 10 who also sampled the end-diastolic phase 60 ms before onset of the QRS complex of the ECG. We chose the R-wave to simplify and automate ECG-gating.…”

“…The decision to examine end-diastolic FFR was motivated by a large animal study by Pantely et al 10,12 who was first to identify the instantaneous hyperemic end-diastolic phase as a dynamic equilibrium state with minimal fluctuations in zero-flow pressure and microvascular resistance along with decreased residual effects of intramyocardial capacitance and ventricular contraction. Subsequent physiological studies also found a good correlation between end-diastolic left-ventricular pressure and zero-flow intracoronary pressure in normal as well as pathological states where increased heart chamber pressure can cause a right shift in the intracoronary pressure-flow curve via increases in physiological back pressure.…”

“…Previous physiological studies during the diastolic phase of the cardiac cycle have also shown promise for instantaneous pressure measurements at end-diastole where both zero-flow pressure (finite back pressure above right atrial or sinus pressure) and capacitance effects on coronary pressure-flow relation have been observed to be minimal. [10][11][12] Our present hypothesis was that decreased residual effects of contraction on intracoronary pressure measurement, as well as lower and more constant zero-flow pressure at end-diastole, would result in reduced variability in combined subject data during comparison of pressure-based FFR with actual reductions in coronary blood flow. As such, the goal of this study was to compare the relation between FFR acquired at end-diastole with conventional FFR performed at full-cardiac cycle using flow-probe measured FFR as a gold standard.…”

Effects of pressure gradients between branches of the left coronary artery on the pressure axis intercept and the shape of steady state circumflex pressure-flow relations in dogs.

“…Finally, support comes also from studies in swine which normally have very little collateral coronary flow (Fedor et al, 1978;Millard, 1980;Sjoquist et al, 1984). If our hypothesis about the influence of collateral flow on pressure axis intercept is correct, there should be little difference between pressure axis intercepts or peripheral coronary pressures in the left main coronary artery or in one of its branches in swine; Bellamy and O'Benar (1984) noted that flow stopped at a left main coronary arterial pressure of 13 ± 5 mm Hg, whereas Pantely et al (1984) observed a pressure axis intercept of 12.1 ± 3.1 mm Hg in the left anterior descending coronary artery.…”