Longitudinal peak strain detects a smaller risk area than visual assessment of wall motion in acute myocardial infarction

Abstract

Background: Opening of an occluded infarct related artery reduces infarct size and improves survival in acute ST-elevation myocardial infarction (STEMI). In this study we performed tissue Doppler analysis (peak strain, displacement, mitral annular movement (MAM)) and compared with visual assessment for the study of the correlation of measurements of global, regional and segmental function with final infarct size and transmurality. In addition, myocardial risk area was determined and a prediction sought for the development of infarct transmurality >or=50%.

Methods: Twenty six patients with STEMI submitted for primary percutaneous coronary intervention (PCI) were examined with echocardiography on the catheterization table. Four to eight weeks later repeat echocardiography was performed for reassessment of function and magnetic resonance imaging for the determination of final infarct size and transmurality.

Results: On a global level, wall motion score index (WMSI), ejection fraction (EF), strain, and displacement all showed significant differences (p <or= 0.001, p <or= 0.001, p <or= 0.001 and p = 0.03) between the two study visits, but MAM did not (p = 0.17). On all levels (global, regional and segmental) and both pre- and post PCI, WMSI showed a higher correlation with scar transmurality compared to strain. We found that both strain and WMSI predicted the development of scar transmurality >or=50%, but strain added no significant information to that obtained with WMSI in a logistic regression analysis.

Conclusions: In patients with acute STEMI, WMSI, EF, strain, and displacement showed significant changes between the pre- and post PCI exam. In a ROC-analysis, strain had 64% sensitivity at 80% specificity and WMSI around 90% sensitivity at 80% specificity for the detection of scar with transmurality >or=50% at follow-up.

Figure 1

Strain curves from the septum at follow-up. Blue: normal longitudinal strain curve recorded from healthy myocardium in the middle septal segment. Red: reduced longitudinal strain in thinned, infarcted myocardium of the apical septal segment.

Figure 2

Segmentation of the left ventricle with determination of transmurality. Four-chamber view of the left ventricle. Red denotes the segmentation of the myocardium, yellow the scar, determined with "Segment". Transmurality is expressed as scar percentage of the area of the segment.

Figure 3

Composite display of infarct size and functional measures. Upper panel shows the distribution of scar percentage among the individual patients (no 1 to no 26). Next two panels show the number of segments with transmurality either >1% or >50% per patient. The three panels at the bottom show wall motion, ejection fraction and strain pre-PCI (black) and at follow-up (gray).

Figure 4

ROC curves for WMSI and strain vs transmurality ≥50%. ROC-curves displaying the interrelationship between sensitivity and specificity for wall motion score index and strain vs. the detection of segments with a transmurality ≥50%. Area-under-curve for WMSI is 0.92 and for strain 0.78, p < 0.0001. WMSI = Wall motion score index, SI = peak longitudinal strain