title: Ability of the electrocardiogram to detect myocardial lesions in isoproterenol induced rat cardiomyopathy.
abstract: Resting electrocardiograms were recorded in 18 male adult rats injected subcutaneously with two doses of isoproterenol (200 mg.kg-1 body weight) 10 days before the animals were submitted to the ajmaline test (1 mg.kg-1 body weight iv). After the ajmaline test all rats were killed and the hearts examined histologically. Electrocardiographic changes were detected at rest in 72% of the isoproterenol injected rats: pathological Q waves, lengthening of the QRS complex, and QRS abnormality were found in 50%, 44%, and 44% of these animals respectively. Ajmaline induced similar changes in both control and isoproterenol treated rats (P wave enlargement (p less than 0.01 and p less than 0.001 respectively), increased PR interval (p less than 0.003 and p less than 0.001 respectively), and increased QaT interval (p less than 0.001 in both groups]. However, ajmaline caused an increase in heart rate only in isoproterenol treated rats (p less than 0.05). A pronounced increase in PR interval, not observed in control rats, was detected in one of five isoproterenol injected rats with a normal resting ECG but showing microscopical cardiac lesions. Apical aneurysm of the left ventricle was found in 16% of isoproterenol injected rats. A mononuclear inflammatory reaction was observed in 13 (72%) of the isoproterenol injected rats and was multifocal in at least three regions of the myocardium in six (46%) and disseminated throughout the myocardium in seven (53%) of these animals. When the electrocardiographic and pathological findings were compared, the ECG changes were found to have a 91% sensitivity, 83% specificity, and 91% positive predictive value.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pathology, Faculty of Medicine of Ribeirão Preto, São Paulo University, Brazil.
authors.forename: R B
authors.initials: RB
authors.lastname: Bestetti
authors.forename: C P
authors.initials: CP
authors.lastname: Ramos
authors.forename: J
authors.initials: J
authors.lastname: Figuerêdo-Silva
authors.forename: V N
authors.initials: VN
authors.lastname: Sales-Neto
authors.forename: J S
authors.initials: JS
authors.lastname: Oliveira
mesh_terms: D000404:Ajmaline / Q000494:pharmacology; D000818:Animals; D009202:Cardiomyopathies / Q000139:chemically induced / Q000175:diagnosis* / Q000473:pathology / Q000503:physiopathology; D004562:Electrocardiography; D006321:Heart / Q000187:drug effects / Q000503:physiopathology; D007545:Isoproterenol; D008297:Male; D009206:Myocardium / Q000473:pathology*; D051381:Rats; D012680:Sensitivity and Specificity
chemical_list: D000404:Ajmaline; D007545:Isoproterenol