Transmural coronary blood flow distribution in the left ventricular wall perfused by the by-passed left circumflex artery was assessed by labelled microspheres (15±5 μ diameter) during maximal vasodilatation induced by intracoronary adenosine infusion. The study was performed in a group of 8 anesthetized mongrel dogs with systolic (PVS) and diastolic (PAS) left ventricular pressure of 109±17 and 2±1.4 mmHg, respectively. For each experiment flow/g of tissue was obtained at 3 or 4 levels of coronary perfusion pressure for the internal (ENDO) middle (MID) and external (EPI) third of the perfused left ventricular wall. Linear pressure-flow relatonships were obtained for the entire wall and for each of the three layers of the left ventrical using the diastolic coronary perfusing pressure (PPD) and regional flows. The slopes (P/F) of the ENDO were in each instance statistically lower than those of the EPI (but not significantly different from those of the MID), indicating a value of vascular resistance in the EPI almost double than in the ENDO. The extrpolation of the regional pressure-flow relationships on the pressure axis indicated the highest value of intercept for the ENDO, the lowest for the EPI, suggesting a transmural gradient of intramyocardial pressure. Results of this study fit with a model of coronary circulation, based on the waterfall principle, in which the extravascular pressure decreases from the ENDO to the EPI in contrast to the vascular resistance which decreases from the EPI to the ENDO. This model explains why the subendocardial layer receives an equal or higher blood flow relative to the subepicardium in normal haemodynamic conditions even in absence of autoregulation and in spite of higher extravascular pressure, and why it becomes selectively ischemic in the presence of a low perfusing pressure as produced by a coronary stenosis.
|Translated title of the contribution||A model of coronary circulation suggested by the study of transmural myocardial perfusion|
|Number of pages||11|
|Journal||Giornale Italiano di Cardiologia|
|Publication status||Published - 1979|
ASJC Scopus subject areas
- Cardiology and Cardiovascular Medicine