Abstract
Although echocardiography has been used in rats, few studies have determined its efficacy for estimating myocardial infarct size. Our objective was to estimate the myocardial infarct size, and to evaluate anatomic and functional variables of the left ventricle. Myocardial infarction was produced in 43 female Wistar rats by ligature of the left coronary artery. Echocardiography was performed 5 weeks later to measure left ventricular diameter and transverse area (mean of 3 transverse planes), infarct size (percentage of the arc with infarct on 3 transverse planes), systolic function by the change in fractional area, and diastolic function by mitral inflow parameters. The histologic measurement of myocardial infarction size was similar to the echocardiographic method. Myocardial infarct size ranged from 4.8 to 66.6% when determined by histology and from 5 to 69.8% when determined by echocardiography, with good correlation (r = 0.88; P < 0.05; Pearson correlation coefficient). Left ventricular diameter and mean diastolic transverse area correlated with myocardial infarct size by histology (r = 0.57 and r = 0.78; P < 0.0005). The fractional area change ranged from 28.5 +/- 5.6 (large-size myocardial infarction) to 53.1 +/- 1.5% (control) and correlated with myocardial infarct size by echocardiography (r = -0.87; P < 0.00001) and histology (r = -0.78; P < 00001). The E/A wave ratio of mitral inflow velocity for animals with large-size myocardial infarction (5.6 +/- 2.7) was significantly higher than for all others (control: 1.9 +/- 0.1; small-size myocardial infarction: 1.9 +/- 0.4; moderate-size myocardial infarction: 2.8 +/- 2.3). There was good agreement between echocardiographic and histologic estimates of myocardial infarct size in rats.
Highlights
The rat model of myocardial infarction has been used for decades in many research laboratories to study left ventricular function [1,2,3], remodeling [4,5], the impact of pharmacological [6,7] or surgical interventions [8], and recently, the effect of gene transfer and cell transplantation [9,10]
Some studies have dealt with the estimation of myocardial infarct size in rats by echocardiography, and usually have not directly compared the measurement obtained by echocardiography with that obtained by histology
Infarct size ranged from 4.8 to 66.6% when determined by histology and from 5.0 to 69.8% when determined by echocardiography, with good correlation between the two measurements (r = 0.88; P < 0.05; y = 0.9079x + 4.9656; Figure 1)
Summary
The rat model of myocardial infarction has been used for decades in many research laboratories to study left ventricular function [1,2,3], remodeling [4,5], the impact of pharmacological [6,7] or surgical interventions [8], and recently, the effect of gene transfer and cell transplantation [9,10]. The development of high definition echocardiographic imaging systems with high frequency transducers has permitted the study of the heart in small animal models of myocardial infarction in which Doppler echocardiography has been used to evaluate systolic and diastolic function, infarct size [12,13,14] and left ventricular remodeling [15]. Some studies have dealt with the estimation of myocardial infarct size in rats by echocardiography, and usually have not directly compared the measurement obtained by echocardiography with that obtained by histology. On this basis, the present study was undertaken to evaluate the ability of two-dimensional Doppler echocardiography to estimate the infarct size determined by histology in rats and its consequences for other anatomic and functional variables
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