Effects of reperfusion after coronary artery occlusion on post-infarction scar tissue.

Abstract

SUMMARY. Early reperfusion after a coronary occlusion may reduce myocardial infarct size, but late reperfusion into necrotic myocardium may alter post-infarction healing. In rabbits, we compared 1-or 3-week-old scars resulting from permanent coronary occlusion to those resulting from a 1-or 3-hour occlusion followed by reperfusion. Reperfusion at 1 hour post-occlusion did not affect scar mechanical properties assessed at 1 week post-infarction, but at 3 weeks postinfarction, these scars had a tensile strength significantly lower than those not reperfused (78 ± 11 vs. 158 ± 15 g/mm 2 , P < 0.001). They also were composed of a mixture of fibrous tissue (58 ± 8%) and myocytes (43 ± 8%) with a hydroxyproline content of 23 ± 2.5 mg/g dry weight. The nonreperfused scars had a higher proportion of fibrous tissue (73 ± 3%) by histological evaluation and a 35% higher hydroxyproline content (31 ± 2 mg/g dry weight, P < 0.001) than the scars reperfused after 1 hour. In contrast, 3-week-old scars resulting from late' reperfusion at 3 hours post-occlusion were similar to nonreperfused scars in fibrous tissue composition and hydroxyproline content. Nonetheless, the tensile strength of these scars reperfused 3 hours post-occlusion was significantly less than that of the nonreperfused scars (72 ± 5 vs. 158 ± 15 g/mm 2 , P < 0.001). The lower tensile strength was associated with a lower collagen cross-link density in this reperfused group of scars. At physiological stress levels (approximately 3 g/mm 2 ), all groups of reperfused and nonreperfused scars had similar mechanical properties in terms of natural strain, stiffness, creep, and stress relaxation. Thus, although the reperfused scars ruptured more easily at high stresses, when assessed at physiological stresses their mechanical properties were not significantly different from those of nonreperfused scars. (Circ Res 57: 562-577, 1985)

Rapid expression of fibronectin in the rabbit heart after myocardial infarction with and without reperfusion.

“…Our experiments quantitated increases in the mRNA for collagen I, III, and IV. Previous studies measured hydroxyproline and demonstrated no effect of reperfusion on collagen levels at 1 wk and beyond (5,39 (53,54). Histochemical data suggested fibronectin is deposited around myocytes in the early response to infarction (I15).…”

“…Changes in the extracellular matrix comprise an important part of the wound repair process, and this topic has been studied extensively, particularly with respect to collagen content and alterations in tensile strength and compliance (1)(2)(3)(4)(5). Fibronectin is an important component of the extracellular matrix that is thought to have a functional role in diverse cellular processes, including wound healing (6)(7)(8).…”

Structural Composition of Myocardial Infarction Scar in Middle-aged Male and Female Rats

“…However, it has been previously shown that the tissue composition of a mature scar is an important determinant of its mechanical properties (Connelly et al 1985) and, thereby, can drastically influence overall ventricular performance …”

<b>Does Coronary Artery Stenting for Acute Myocardial Infarction Improve Left Ventricular Overloading at the Chronic Stage?</b>

“…However, reperfusion therapy for the infarct-related artery is the most useful method of preventing dilatation of the infarcted myocardium that occurs during the early stage of AMI. [26][27][28][29] Because the tissue-healing process is enhanced by reperfusion therapy, 30) sufficient coronary arterial blood flow should be secured from the early stage of AMI. That is, PTCA with stenting may inhibit both the formation of peripheral embolism by debris with copious platelets 31) and patency maintenance in the infarct-related artery.…”