High‐Frequency 4D Ultrasound Evaluation of Temporal Changes in Endocardial Surface Strain after Myocardial Infarction

Abstract

Myocardial infarction (MI) is a leading cause of death and accurate assessment of cardiac function after MI is critical for understanding mechanisms of post‐MI remodeling, recovery and treatment. Most previous studies assessed cardiac function using echocardiographic images of only one section of the heart. Newly developed high‐frequency 4D ultrasound (4DUS) may provide more accurate evaluation of cardiac function, especially after MI when geometry of the heart is abnormal. We investigated left ventricle (LV) endocardial surface peak systolic strain (SPSS) using 4DUS images (VEVO‐3100) before (baseline) and 24‐hr, 72‐hr and 1‐week post‐MI in male Sprague‐Dawley rats (n=5) subjected to left descending coronary artery ligation. Full‐length LV short‐axis ECG‐gated cine loops were acquired with ~11 µm stepwise increments. Compared to baseline, ejection fraction was significantly reduced 24‐hr, 72‐hr and 1‐week post‐MI (65±1 vs. 35±1, 34±3 and 31±2%, respectively). We also observed that SPSS showed different contractility patterns in the base, mid and apical heart regions. Among 17 myocardial segments analyzed, only septal segments were not affected by MI, with the exception of base anterior septal segment which showed reduced SPSS 72‐hr post‐MI (‐4.3 ± 2%) compared to baseline (‐26.5 ± 3%), indicating that the base is more sensitive to MI injury than mid‐LV. Since cardiac global and regional metrics are usually estimated in the mid‐LV, conventional methods may underestimate cardiac function in MI models. Thus, 4DUS with 3D‐strain analysis appears to be a valuable and sensitive tool for improved detection of cardiac disease progression.