Focus Issue: Cardiac Imaging
Clinical Research: Left Ventricular Function
Differentiation of Subendocardial and Transmural Infarction Using Two-Dimensional Strain Rate Imaging to Assess Short-Axis and Long-Axis Myocardial Function

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Objectives

This study sought to differentiate the transmural extent of infarction (TME) by assessment of the short-axis and long-axis function of the left ventricle (LV) using 2-dimensional (2D) strain.

Background

The differentiation of subendocardial infarction from transmural infarction has significant prognostic and clinical implications.

Methods

Contrast-enhanced magnetic resonance imaging (CE-MRI) and dobutamine stress echocardiography (DBE) were performed in 80 patients (age 63 ± 10 years) with chronic ischemic LV dysfunction. Myocardial function was assessed in the short axis at the midventricular level using peak strain rate (SR) and strain (S) in circumferential and radial dimensions, and was assessed in the long axis using longitudinal SR and S. Wall motion analysis was performed during DBE to assess for contractile reserve.

Results

Transmural infarct segments had lower circumferential S (−10.7 ± 6.3) and SR (−1.0 ± 0.4) than subendocardial infarcts (S: −15.4 ± 7.0, p < 0.0001; SR: −1.4 ± 0.8, p = 0.02) and normal myocardium (S: p < 0.0001; SR: p < 0.0001). Transmural and subendocardial infarct segments had similar radial S and SR. Subendocardial infarct segments showed significant reduction of longitudinal S (−13.2 ± 5.6) and SR (−0.91 ± 0.45) compared with normal myocardium (S: −17.8 ± 5.4, p < 0.0001; SR: −1.1 ± 0.41, p < 0.0001), but there were no significant differences between subendocardial and transmural infarct segments (p = 0.09). Wall motion analysis by DBE could not identify subendocardial infarction on CE-MRI (TME 1% to 50%: DBE scar 38%, DBE viable 38%, DBE ischemic 24%, p = NS).

Conclusions

The combined assessment of long-axis and short-axis function using 2D strain may be used to identify TME.

Abbreviations and Acronyms

2D
2-dimensional
AUC
area under the curve
CE-MRI
contrast-enhanced magnetic resonance imaging
DBE
dobutamine stress echocardiography
LV
left ventricle/ventricular
ROC
receiver-operating characteristic
S
peak systolic 2-dimensional strain
SR
peak systolic 2-dimensional strain rate
TME
transmural extent of infarction

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Supported in part by a project grant (210217) from the National Health and Medical Research Council, Canberra, Australia.