Heparin potentiates collateral growth but not growth of intramyocardial endarteries in dogs with repeated coronary occlusion

Heparin accelerates coronary collateral development in various animal model s of myocardial ischemia, The purpose of this study was to clarify the bene ficial effect of heparin on canine collateral development. Seventeen adult mongrel dogs were instrumented for measurements of a subendocardial segment length in the central area perfused by the left circumflex coronary artery , its flow, and left ventricular pressure. A pulsed Doppler flow probe and an externally inflatable pneumatic occluder were placed around the proximal circumflex artery. After the recovery from surgery, 2-min circumflex coron ary artery occlusions were repeated eight times at 58-min intervals daily. After excluding seven dogs with well-developed preexisting collateral circu lation, ten dogs were randomized into two groups with (n = 5) and without ( n = 5) heparin treatment. The total occlusion time until adequate collatera l development, (an index of collateral growth) was 164+/-34 (SD) min in dog s with heparin treatment, being significantly less than 289+/-49 min in dog s without heparin (p<0.01). In contrast, the extent of the reduction in res ting blood flow of the repeatedly occluded circumflex artery (an index of n eovascularization toward the ischemic area) was comparable in dogs with and without heparin (15.4+/-12.4% vs. 21.1+/-13.6%, p=NS). Heparin promotes no nsprouting angiogenesis (arteriogenesis) of preformed collateral vessels bu t not neovascularization toward the ischemic area in dogs with brief repeti tive coronary occlusions. (C) 1999 Elsevier Science Ireland Ltd. All rights reserved.