Pre-Clinical Investigation
Comparison of Echocardiographic Measurements of Left Ventricular Volumes to Full Volume Magnetic Resonance Imaging in Normal and Diseased Rats

https://doi.org/10.1016/j.echo.2013.04.016Get rights and content

Background

Clinical two-dimensional (2D) and clinical three-dimensional echocardiography are validated against cardiac magnetic resonance imaging (CMR), the gold standard for left ventricular (LV) volume measurement. In rodents, there is no widely accepted echocardiographic measure of whole LV volumes, and CMR measurements vary among studies. The aim of this study was to compare LV volumes by 2D echocardiography (using a hemisphere-cylinder [HC] model) with HC and full-volume (FV) CMR in normal and diseased rats to measure the impact of geometric models and imaging modalities.

Methods

Rats (n = 27) underwent ascending aortic banding, myocardial infarction induction by either permanent left anterior descending coronary artery ligation or ischemia-reperfusion, and sham thoracotomy. Subsequently, end-diastolic volume, end-systolic volume, and ejection fraction were measured using an HC 2D echocardiographic model combining parasternal short-axis and long-axis measurements, and these were compared with HC and FV CMR.

Results

Diseased groups showed LV dilatation and dysfunction. HC echocardiographic and FV CMR measures of end-diastolic volume, end-systolic volume, and ejection fraction were correlated. On Bland-Altman plots, end-diastolic volumes were concordant between both methods, while HC echocardiography underestimated end-systolic volumes, resulting in a modest overestimation of ejection fractions compared with FV CMR. Other 2D echocardiographic geometric models offered less concordance with FV CMR than HC. HC CMR overestimated LV volumes compared with FV CMR, while HC echocardiography underestimated HC CMR volumes. Echocardiography underestimated corresponding LV dimensions by CMR, particularly short axis.

Conclusions

Concordant measures of LV volume and function were obtained using (1) a relatively simple HC model of the left ventricle inclusive of two orthogonal 2D echocardiographic planes and (2) FV CMR in normal and diseased rats. The HC model appeared to compensate for the underestimation of LV dimensions by echocardiography.

Section snippets

Animal Use and Care

Animals were obtained and handled as approved by the Institutional Animal Care and Use Committee of the Icahn School of Medicine at Mount Sinai in accordance with the “Principles of Laboratory Animal Care by the National Society for Medical Research and the Guide for the Care and Use of Laboratory Animals” (National Institutes of Health Publication No. 86-23, revised 1996).

Surgical Animal Disease Models

We studied 27 rats. Male Sprague-Dawley rats (200–250 g) underwent surgery as previously described.19 Pressure-overload LV

Heart Rate During Imaging

Heart rate per animal group is shown in Table 1. It was significantly higher on echocardiography compared with CMR (394 ± 53 vs 294 ± 54 beats/min; P < .0001, paired t test).

Concordance and Correlation of LV Volumes and EF by HC Echocardiography and CMR (HC CMR and FV CMR)

Representative images of long-axis and short-axis views of the left ventricle by echocardiography and CMR are shown in Figure 2, from the same sham and post-MI animals, respectively. LV volumes (EDV and ESV) and EF measured by HC echocardiography, HC CMR, and FV CMR are shown in Table 1. Diseased groups demonstrated

Discussion

We demonstrate that an easy-to-use HC 2D echocardiographic model of whole LV volume in rats provides measurements of LV size and function that (1) are well correlated with FV CMR in both normal and diseased animals, (2) fall in the same range as FV CMR absolute measurements, particularly for EDV, and (3) compare favorably with FV CMR in their ability to discriminate between disease models of variable severity. We also show that echocardiography per se underestimates corresponding CMR

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    This work was supported by Leducq Foundation through the Caerus Network; by Centro Nacional de Investigaciones Cardiovasculares through the Cardio-Image program (Dr. Arias); and by National Institutes of Health grants R01 HL093183, HL088434, HL071763, HL080498, HL083156, and P20HL100396 (Dr. Hajjar) and NIH-T32-HL007824 (Dr. Chemaly).

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