Strain rate imaging diferentiates transmural from non-transmural myocardial infarction - A validation study using delayed-enhancement magnetic resonance Imaging

OBJECTIVES The aim of this study was to determine if strain rate imaging (SRI) correlates with the transmural extent of myocardial infarction (MI) measured by contrast-enhanced magnetic resonance imaging (Ce-MRI). BACKGROUND Identification of the transmural extent of myocardial necrosis and degree of non-viability after acute MI is clinically important. METHODS Tissue Doppler echocardiography with SRI and Ce-MRI were performed in 47 consecutive patients with a first acute MI between days 2 and 6 and compared to 60 age-matched healthy volunteers. Peak myocardial velocities and peak myocardial deformation strain rates were measured. Location and size of the infarct zone was confirmed by Ce-MRI using the delayed enhancement technique with a 16-segment model. RESULTS Contrast-enhanced MRI identified transmural infarction in 21 patients, non-transmural infarction in 15 (mean transmurality of infarct 72.3 +/- 10.6%), and another 11 patients with subendocardial infarction (< 50% transmural extent of the left ventricular wall). Peak systolic strain rate (SRs) of the transmural infarction segments was significantly lower compared to normal myocardium or with non-transmural infarction segments (both p < 0.0005). A cutoff value of SRs >-0.59 s(-1) detected a transmural infarction with high sensitivity (90.9%) and high specificity (96.4%), and -0.98 s(-1) > SRs >-1.26 s(-1) distinguished subendocardial infarction from normal myocardium with a sensitivity of 81.3% and a specificity of 83.3%. CONCLUSIONS Peak myocardial deformation by SRI can differentiate transmural from non-transmural MI, and it allows noninvasive determination of transmuratity of the scar after MI and thereby the extent of non-viable myocardium.