MONITORING CARDIAC FUNCTION BY HIGH FREQUENCY ECHOCARDIOGRAPHIC IMAGING IN RATS
B.A. Anderson*, L. Brown, C.A. Hegerty, J.L. Fawcett, B.J. Shearer, D.J. Burstow.
Echocardiographic Laboratory, The Prince Charles Hospital, Brisbane, Queensland.
Rats are commonly used for experimental studies investigating new cardiovascular drugs. We assessed the utility of high resolution ultrasound equipment in conjunction with high frequency transducers in the serial quantification of cardiac function during the development and treatment of hypertension in rats.
Methods: 24 male Wistar rats (8 weeks old) were given L-nitroarginine methyl ester (L-NAME, 400mg/l drinking water); 12 of these were supplemented for final 4 weeks of the protocol (2 mg/kg/day); 6 untreated (control) rats were also studied. Following 0, 4 and 8 weeks, left parasternal and left apical echocardiographic images were obtained using the Hewlett Packard Sonos 5500 (12 MHz frequency transducer) at an image depth of 3cm using two focal zones. Left ventricular M-mode measurements at the level of the papillary muscles included left ventricular end-diastolic dimension, left ventricular end-systolic dimension (LVESD), interventricular septum, posterior wall (PW), and fractional shortening (FS%). Pulsed-wave Doppler velocities of the ascending aorta, descending aorta, mitral valve inflow, and pulmonary veins were attempted.
Results: L-NAME treatment for 8 weeks significantly increased systolic blood pressure from 112±1 to 181±5 mmHg, PW thickness from 2.74±0.04 to 3.32±0.01mm and FS from 48.5±1.9 to 60.4±1.4% (p<0.05 vs to control). LVESD decreased from 3.39±0.02 to 2.41±0.01mm (p<0.05 vs to control). Candesartan reversed these changes.
Conclusion: High frequency echocardiographic examination demonstrated significant hypertrophic and morphologic changes in hypertensive rats. These changes were abolished in the rats on candesartan.
