Influences of the alteration in aortic pressure on regional myocardial function and regional myocardial blood flow in partial coronary artery occlusion.
This study was designed to simultaneously evaluate the effects of alterations in aortic pressure (AoP) on regional myocardial function and regional myocardial blood flow (MBF) in anesthetized dogs with partial coronary occlusion. Regional myocardial function was assessed by both segment-length and tension gauges. The left circumflex coronary artery flow was reduced to 50 to 70% by a constrictor. When systolic aortic pressure (AoPS) fell from 103.6 +/- 7.4 to 72.5 +/- 4.9 mmHg following nitroprusside infusion, systolic shortening (SS) markedly depressed from 0.63 +/- 0.17 to 0.09 +/- 0.20 mm (p less than 0.01), developed tension (DT) decreased by 30% (p less than 0.01), and MBF assessed with tracer microspheres decreased from 0.61 +/- 0.13 to 0.36 +/- 0.11 ml/min/Gm (p less than 0.01) in ischemic regions. In non-ischemic regions SS was enhanced from 0.78 +/- 0.16 to 0.89 +/- 0.15 mm (p less than 0.05), but DT and MBF showed no changes. An elevation of AoPS from 106.4 +/- 5.6 to 143.3 +/- 6.9 mmHg following methoxamine infusion brought about enhanced SS from 0.42 +/- 0.15 to 0.48 +/- 0.09 mm (p less than 0.05), a 50%-increase in DT (p less than 0.01), and was associated with an increase in MBF from 0.66 +/- 0.03 to 1.19 +/- 0.07 ml/min/Gm (p less than 0.01) in ischemic regions. These results indicate that, in partial coronary occlusion, a fall of AoP induces redistribution of blood flow away from ischemic regions and aggravates the function of the ischemic myocardium, while an elevation of AoP may produce beneficial effects upon the ischemic myocardium.
D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003326:Coronary Circulation; D003327:Coronary Disease / Q000503:physiopathology*; D004285:Dogs; D006321:Heart / Q000503:physiopathology*; D006339:Heart Rate / Q000187:drug effects; D008729:Methoxamine / Q000494:pharmacology; D009599:Nitroprusside / Q000494:pharmacology; D013318:Stroke Volume / Q000187:drug effects; D014655:Vascular Resistance / Q000187:drug effects
D009599:Nitroprusside; D008729:Methoxamine