title: Influence of tachycardia and arterial hypertension on infarct size in the pig.
abstract: To investigate the clinically important but controversial question of how hypertension during coronary occlusion affects infarct size 24 pigs underwent 1 h occlusion of the mid left anterior descending coronary artery and 24 h reperfusion and were randomised to one of three treatment groups. In group 1 blood pressure was increased during the occlusion period by an infusion of methoxamine; in group 2 tachycardia was induced by atrial pacing; and in group 3 no intervention was performed. The area at risk and infarct size were quantified by digital planimetry of slices of myocardium previously marked with fluorescein and with triphenyl-tetrazolium. Methoxamine maintained mean aortic blood pressure at 117 (SEM8) mmHg during occlusion, whereas the values were 80(6) mmHg in group 2 and 67(9) mmHg in group 3. Pacing increased heart rate to 146(1) beats.min-1 in group 2; it was 103(5) in group 1 and 99(8) in group 3. The pressure-rate product achieved was similar in groups 1 and 2 and significantly higher than in group 3. The pathological studies showed infarct size to be moderately but significantly larger in group 1 (14[3.5]% of the left ventricle) and similar in groups 2 (10.5[3.9]%) and 3 (10.1[2.2]%). The ratio of infarct size to area at risk was also significantly higher (0.743[0.057]) in group 1 with no differences between group 2 (0.604[0.055]) and group 3 (0.613[0.027]). At similar pressure-rate product, infarct size was thus greater with hypertension but not with pacing alone, showing a deleterious effect of increasing blood pressure in this experimental model with negligible collateral blood flow.
authors.affiliation: Servicio de Cardiologia, Hospital Provincial de Madrid, Spain.
authors.forename: D
authors.initials: D
authors.lastname: Garcia-Dorado
authors.forename: P
authors.initials: P
authors.lastname: Théroux
authors.forename: J
authors.initials: J
authors.lastname: Elizaga
authors.forename: F
authors.initials: F
authors.lastname: Fernandez Avilés
authors.forename: J
authors.initials: J
authors.lastname: Alonso
authors.forename: J
authors.initials: J
authors.lastname: Solares
mesh_terms: D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D002304:Cardiac Pacing, Artificial / Q000009:adverse effects; D006339:Heart Rate; D006973:Hypertension / Q000150:complications*; D008729:Methoxamine / Q000009:adverse effects; D009203:Myocardial Infarction / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000473:pathology; D013552:Swine; D013610:Tachycardia / Q000150:complications*
chemical_list: D008729:Methoxamine