Session MD.2

Analysis of Regional Left Ventricular Function in the Post-Infarct Mouse by Magnetic Resonance Imaging with Retrospective Gating

EG Caiani*, M Franzosi, L Castiglioni, U Guerrini

Politecnico di Milano
Milano, Italy

Murine myocardial infarction (MMI) models are used in the evaluation of new therapies for heart failure. Cardiac MRI is the method of choice for LV volumetric quantification of cardiac function. However, rhythm disturbances and respiratory variability may result, particularly in MMI, in gating problems and long acquisition times, reducing data accuracy. Also, only evaluation of global LV function is usually performed, precluding localization of regional wall motion defects. Our aims were to: 1) test the feasibility of a new cine acquisition protocol with no ECG or respiratory gating; 2)compare normal mice versus MMI, both in terms of global and regional LV function. Methods. 4 to 6 weeks old female C57BL6 mice were studied. Ten mice constituted the control group (C). In 30 mice, MMI was created by LAD coronary ligation at mid LV level, and in the surviving 18 mice, imaging was performed after 9 days. Cine images were obtained (12 frames/cycle) using a 4.7T scanner (Bruker) with retrospective gating in 4 to 8 short axis slices(IntraGate). In each slice and frame, the LV endocardium was detected and divided into 6 segments. For each segment, regional fractional area change (RFAC) in % of regional end diastolic area was computed and used as index of regional wall motion. Also, global LV end-diastolic (EDV), -systolic (ESV) and stroke (SV) volumes, ejection fraction (EF), peak filling (PFR) and peak ejection (PER) rates were computed. Results. An increase in LV dimensions (in microL) was found in MMI compared to C (EDV: 92±25 vs 36±4, ESV: 66±27 vs 10±3, p<.05), with a significant decrease in EF (31±10 vs 72±7%), PFR(1.9±.5 vs 3.6±.4 a.u.) and PER (-1.8±.8 vs -3±.5 a.u.), while SV was unchanged (26±4 vs 26±3). RFAC in C showed etherogeneous values, with max and min in the inferior (84%) and septal (62%) segments, respectively. In MMI, RFAC decreased from LV base to apex progressively, with a min (26%) in the anterior segment, in agreement with the occluded LAD. Conclusions. In mice studies, cine MRI with retrospective gating is feasible, reducing acquisition time and trigger-related problems. Regional LV function analysis allows the localization of the induced infarction, with potential applications in MMI pre- and post-treatment studies.

(Abstract Control Number: 266)