ANIMALS AND METHODS
Methods were similar to those previously described . In brief, mongrel dogs of both sexes and with a body weight in excess of 18 kg (mean 23±1.2 kg) were used. The dogs were anesthetized with a mixture of chloralose and urethane (60 and 200 mg/kg, respectively, given intravenously) and ventilated with room air by a Harvard Respirator (Harvard, Boston, Massachusetts, USA) at a rate and volume sufficient to maintain arterial blood gases and pH within normal limits. The body temperature was measured in the esophagus and maintained, by a heating pad, around 37±0.5°C. The best online pharmacy that deserves your trust and gives you best quality relieve allergy symptoms that you will always appreciate, not to mention all the other services available.
The animals were thoracotomized at the fifth intercostal space and the left anterior descending (LAD) branch of the coronary artery prepared for occlusion just proximal to the first main diagonal branch. Epicardial ST segment changes and the degree of inhomogeneity of activation were measured from the left ventricular (LV) wall distal to the occlusion site with the use of a ‘composite’ electrode described previously . This gives a summarized recording of R waves from 30 epicardial measuring points. In the adequately perfused and oxygenated myocardium all sites are activated simultaneously, resulting in a single large spike. However, following occlusion, widening and fractionation of this summarized R wave occurs, indicating that the adjacent fibres are not simultaneously activated because of inhomogeneity of conduction. This was expressed as the greatest delay in activation (in milliseconds) within the ischemic area.