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Open Access Thoracic Massage Permits Use of Echocardiography in Unanesthetized Rats

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Purpose: The objective of the study reported here was to investigate whether massage-like stroking of the thorax and cranial portion of the abdomen might relax unanesthetized rats sufficiently to permit in vivo echocardiography.

Methods: Nine-month-old spontaneously hypertensive rats (SHR) were first conditioned to being held by hand for 10 to 15 min twice a day for seven to 10 days. During each session, the animal was placed in supine position, and the thorax and cranial abdominal area were gently stroked (approx. 5 cm/s, 12 to 14 times/min). After the conditioning period, echocardiography was initiated. We obtained serial transthoracic two-dimensional (2-D) and M-mode echocardiograms from nine-month-old SHR that were treated with isoproterenol (60 mg/kg of body weight, s.c., x 1, followed by 30 mg/kg/d x3), and from old (20 to 24 months old) SHR, studied when labored breathing, suggestive of heart failure, was evident (SHR-F). Measurements included end-diastolic volume (EDV) and end-systolic volume (ESV).

Results: In the isoproterenol-treated SHR, mean ± SD echocardiographically derived EDV (2-D, 0.29 ± 0.05; M-mode, 0.28 ± 0.01 ml) was not significantly different from volume at necropsy (0.33 ± 0.04 ml). Measurements of EDV and ESV by use of M-mode and 2-D echocardiography were significantly correlated (EDV R 2 = 0.48, P = 0.05; ESV R 2 = 0.39, P = 0.02). Echocardiography revealed pleuropericardial effusions (4/6), atrial thrombi (5/6), and left and right ventricular enlargement (6/6). The EDV and ESV were increased fivefold (P < 0.01) and threefold (P < 0.05), respectively, versus values for SHR not in heart failure (SHR-NF). Left ventricular ejection fraction of hearts from SHR-F was markedly decreased, compared with that in SHR-NF (44 ± 7 versus 74 ± 2%, respectively; P < 0.05). The presence or absence of left atrial thrombi and fluid in the thoracic cavity was confirmed at necropsy in SHR-F and SHR-NF.

Conclusion: Thoracic massage permits use of echocardiography in unanesthetized rats, thereby providing a simple, non-invasive technique for assessment of cardiac structure and function in rats without the potentially adverse effects of anesthesia.

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Document Type: Research Article

Affiliations: From the VA Boston Healthcare System, Boston Massachusetts 02130 and Department of Medicine, Boston University School of Medicine, Boston, Massachusetts 02118

Publication date: June 1, 2003

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  • Comparative Medicine (CM), an international journal of comparative and experimental medicine, is the leading English-language publication in the field and is ranked by the Science Citation Index in the upper third of all scientific journals. The mission of CM is to disseminate high-quality, peer-reviewed information that expands biomedical knowledge and promotes human and animal health through the study of laboratory animal disease, animal models of disease, and basic biologic mechanisms related to disease in people and animals.

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