The border zone of the early myocardial infarction in dogs; its characteristics and viability

Abstract

In open-chest dogs, the left anterior descending coronary artery was ligated for 150 min. The heart was semiserially cut on a cryomicrotome and areas of ischemic damage were visualized by means of glycogen depletion (PAS reaction) and tissue acidosis (a "sandwich" technique with pH indicator dispersed in a layer of gel). The extent of myocardial damage was determined morphometrically. The mass of the glycogen-depleted heart muscle was greater than the mass of the ischemic tissue detected by means of decreased pH (p less than 0.01). The border zone was characterized by glycogen depletion without acidosis. Circulation studies using intravital fluorescein staining have shown that perfusion is partially retained in the border zone; it is assumed that the hypoperfusion triggers glycogenolysis. Nevertheless, the level of perfusion suffices to wash out the acidic end products. Comparison of contrapulsation-treated dogs and untreated dogs shows that the amount of damaged tissue comprising the border zone can be reduced by this therapeutic intervention (p less than 0.02) - in contrast to the acidotic tissue, the amount of which is not significantly influenced. Therefore the border zone contains damaged but still viable muscle cells.

Designing Injectable, Covalently Cross‐Linked Hydrogels for Biomedical Applications

“…[ 179,180 ] However, these properties make the oxide click reaction an attractive candidate for cross-linking in regions of lower pH within the body, such as ischemic tissue following myocardial infarctions, and may be compatible with less demanding biological environments such as the subcutaneous space in which the hydrogel can form and then be titrated by buffering salts in vivo prior to inducing signifi cant tissue damage. [ 181 ] Oxime cross-linking is a relatively new approach for the synthesis of injectable hydrogels, with the fi rst example reported by Ossipov and co-workers in 2010. [ 182 ] HA was functionalized with a bi-functional dihydrazide compound with a cleavable 2,2′-dithiobis(ethoxycarbonyl) protective group using EDC chemistry.…”

Oxime Cross‐Linked Injectable Hydrogels for Catheter Delivery

“…[22] We initially envisioned that this would be a beneficial trait for in situ hydrogel injection in the heart due to the acidic environment of the ischemic tissue post-myocardial infarction. [25] …”

Three-dimensional distribution of collateral blood flow within the anatomic area at risk after circumflex coronary artery occlusion in dogs

“…This concept was supported by a number of studies which showed higher blood flow (1,2,8,10,12,21,26,28) and lesser severity of metabolic (8) and functional changes (27) at the borders, compared to the center of an ischemic region. Moreover, some investigators reported therapeutic salvage of ischemic myocardium in the lateral ischemic borderzone regions (11).…”

“…A number of investigators have mapped the distribution of coronary blood flow following coronary occlusion in dogs and have generally reported gradients of * Supported in part by NIH grants 27416 and 23138. 428 flOW in both transmural (1,19,21,29) and lateral (1,2,8,10,12,21,26,28) dimensions of the ischemic region; measured collateral flow is lowest in the central zone of the subendocardial layer of the ischemic region and higher in the subepicardial region as well as at the lateral edges of the ischemic region. The transmural gradient of blood flow has been generally accepted as reality.…”