Does infarct size influence loss of embolised 15-μm microspheres from ischaemic myocardium?

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Abstract
Andersen KS, Vik-Mo H. Stangeland L. Does infarct size influence loss of embolised 15-μm microspheres from ischaemic myocardium? Scand J Clin Lab Invest 1986; 46: 71-79. The relationship between myocardial infarct size and loss of 15-μm microspheres from ischaemic tissue was investigated in anaesthetized cats. Radioactive microspheres were injected in the left atrium before and 5 h after left anterior descending coronary artery occlusion. Left ventricular hypoperfused zone (HZ) averaged 36.6% and infarct size (IS) 31.6%. Thus, 86% of HZ evolved into necrosis. Preocclusion blood flow was lower in ischaemic (1.62 ml/min per g) compared with non-ischaemic myocardium (2.09, p=0.002). indicating 22% microsphere loss. In ischaemic subendocardium, oedema (3.7%) could account for the apparent loss. In ischaemic subepicardium, oedema was less pronounced and 18% physical sphere loss occurred. Subepicardial loss increased in proportion to IS and IS/HZ ratio -(r2 = 0.71; p < 0.005). Non-entrapment of 15-μm spheres in coronary circulation averaged O.6%, and preocclusion spheres appeared in coronary sinus blood throughout the ischaemic period. In systemic circulation, non-entrapment during injection of preocclusion spheres was 7.8%, but only 1.8% 5 h later. Release of postocclusion spheres took place during KCI injection. Thus, myocardial ischaemia is associated with alterations in micro-vascular function allowing release of entrapped 15-μm spheres. Also, the magnitude of microsphere loss per gram tissue is related to infarct size.

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