Left Ventricle Radio-frequency Ablation in the Rat: A New Model of Heart Failure due to Myocardial Infarction Homogeneous in Size and Low in Mortality

Abstract 

Background

The purpose of the current study was to create a model of myocardial infarction (MI) that is homogeneous in size with a low immediate (24 hours) mortality.

Methods and Results

Male and female rats (n = 256) underwent left ventricle (LV) ablation (Ab) by a radiofrequency current (1000 kHz; 12 watts for 12 seconds) to promote a MI. A transmural MI occurred in all rats. Post-Ab complex arrhythmias were frequent (atrioventricular block, ventricular tachycardia, and fibrillation), which rapidly and spontaneously reverted to sinus rhythm. Among 66 male rats, immediate mortality occurred in 7.5%. Small MI size dispersion was characterized by smaller variability following Ab (x ± SD: 45 ± 8%) when compared with coronary occlusion (Oc; 40 ± 19%). The histopathologic evaluations identified lesions similar to those which occurred following Oc, with scarring complete at 4 weeks. The hemodynamic and Doppler echocardiograms showed comparable increases in LV dimension, end-diastolic pressure, and pulmonary water content 1 and 4 weeks post-MI. Papillary muscle mechanics 6 weeks post-MI had matched inotropic and lusitropic dysfunction.

Conclusions

LV Ab gave rise to a MI within a narrow size limit and with a low immediate mortality. LV Ab resulted in histopathologic evolution, ventricular dilation, and dysfunction, impairment in myocardial mechanics, and congestive outcome that reproduced a MI from Oc.

Key Words: Rats, myocardial infarction, radiofrequency ablation, heart failure