Abstract 18434: Serial Quantification of Canine Post-Infarct Left Ventricular Remodeling Using a Novel Semi-Automated 3D Echo Speckle Tracking Algorithm

Abstract

Background: Left ventricular (LV) remodeling after myocardial infarction (MI) is characterized by infarct expansion, progressive LV dilation, and hypertrophy of non-infarct zones. Global ventricular remodeling is associated with poor outcomes. Existing data on the temporal dynamics of post-MI remodeling are primarily based on 2D echo estimates of LV size. Accurate and convenient 3D echo measurements would allow more reliable tracking of LV size and function in both laboratory and clinical settings.

Methods: MI was induced in canines (N=6) with 6-hour LAD angioplasty occlusions. Transthoracic 3D B-mode echo long-axis images were obtained at baseline, 3 days, 4 weeks, and 6 weeks post-MI using a Philips iE33 system with X7-2 transducer at 41-51 fps. End-diastolic (EDV) and end-systolic (ESV) volumes were measured using a novel semi-automated 3D echo speckle tracking algorithm (4D LV-Analysis 3; TomTec Imaging Systems; Munich, Germany). ECG-gated cardiac MR images were acquired on a 1.5 T magnet at 6 weeks post-MI. Reference MRI EDV and ESV were measured using the method-of-disks with manual contours.

Results: 3D echo EDV and ESV measurements for multiple timepoints are shown in the table below. Average EDV increased from 41±14 ml at baseline to 59±12 ml at 6 weeks post-MI (p=0.02). Average ESV increased from 27±10 ml at baseline to 41±13 ml at 6 weeks post-MI (p=0.02). At 6 weeks post-MI, MRI EDV and ESV measurements were 61±6 ml and 33±7 ml, respectively, and were not significantly different from 3D echo values (p=NS for both).

Conclusions: We have used a novel 3D echo speckle tracking algorithm to obtain 3D volumes in a semiautomated fashion. This approach should prove useful in the application of 3D echo in both laboratory and clinical settings. To our knowledge, this is the first report of serial LV remodeling by 3D echo in a post-MI canine model. We documented progressive increases in EDV and ESV that were consistent with reference MRI measurements at 6 weeks post-MI.