IN-VIVO ASSESSMENT OF LEFT-VENTRICULAR REMODELING AFTER MYOCARDIAL-INFARCTION BY DIGITAL VIDEO CONTRAST ANGIOGRAPHY IN THE RAT

Objective: The aim was to develop a digital video contrast angiographi c method for assessing global left ventricular function and volume in vivo in the rat and then to apply it to a study of ventricular remodel ling after coronary occlusion, with and without reperfusion. Methods: Digital contrast angiography was performed on 29 rats, including the f ollowing groups: sham operated (n = 11), non-transmural myocardial inf arction produced by reperfusion (n = 8), and transmural infarction pro duced by permanent occlusion (n = 10). Under anaesthesia three weeks l ater, biplane fluoroscopic images were acquired following venous contr ast injection. Levophase images were digitised, and left ventricular e nd diastolic and end systolic volumes and ejection fractions were obta ined using an area-length method. Left ventricular ejection fraction d ata also were calculated by videodensitometry from video density curve s. Results: Compared to the sham operated group, the reperfused group showed a significant decrease in left ventricular ejection fraction, a t 53(SD 7) v 70(5)% (p < 0.01), and an increase in end diastolic volum e. The permanent occlusion group showed a further decrease in the ejec tion fraction [40(8)%] and a further significant increase in end diast olic volume compared to the reperfused group (p < 0.01). Left ventricu lar ejection fraction correlated inversely with percent infarct size ( r = 0.882) and showed a positive correlation with the spared epicardia l area (r = 0.721). Most haemodynamic variables, including maximum lef t ventricular dP/dt, failed to discriminate between the groups. The me thods showed reasonable accuracy when tested in vitro using contrast f illed balloons. In vivo, the left ventricular ejection fraction calcul ated by densitometry showed adequate interobserver variability (2 SD /- 8.5 percentage points), but the area-length method showed somewhat more scatter. Conclusions: Digital video contrast angiography is a fea sible method for the assessing global left ventricular function in the rat and should be useful in other small animal models. Significant di fferences in left ventricular volumes and ejection fractions were dete cted between reperfused and permanent occlusion groups, whereas haemod ynamic variables showed non-significant trends. Reperfusion after 45 m in of occlusion caused sparing of the epicardium, prevented unfavourab le remodelling, and improved the ejection fraction compared to permane nt occlusion.