INFLUENCE OF CARDIAC CONTRACTION AND CORONARY VASOMOTOR TONE ON REGIONAL MYOCARDIAL BLOOD-FLOW

We analyzed patterns of left ventricular perfusion in arrested hearts without coronary tone and in the same hearts while beating with and wi thout coronary tone. We used microspheres in anesthetized dogs to meas ure blood flow in 384 regions (averaging 140 mg wet wt) from the suben docardium, midwall, and subepicardium before and during intracoronary infusions of adenosine (beating without tone) or lidocaine and adenosi ne (arrest without tone). Mean coronary pressure was held constant at 80 mmHg. Changes in regional flow with arrest (vs. beating without ton e) were surprisingly variable (range -28 to +124%) and exhibited subst antial within-layer heterogeneity, suggesting that local differences i n contractility, stresses, or strains limit maximum coronary flow. Reg ional flows in beating hearts with tone did not correlate with flows i n the same hearts without tone, beating or not (r(2) less than or equa l to 0.03; not significant). Flow patterns during beating with tone al so demonstrated significantly shorter (i.e., the distance at which aut ocorrelation has decreased to 0.5) within-layer spatial autocorrelatio ns as well as a complete loss of radial flow correlation (e.g., betwee n corresponding subendocardial and subepicardial regions; r(2) = 0.01) . Thus neither coronary anatomy (assessed during arrest without tone) nor the mechanical effects of contraction (beating without tone) appea r to influence myocardial perfusion when vasomotor tone is present.