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Differentiation of dysfunctional but viable myocardium from irreversibly damaged scar tissue has important clinical implications for patients’ ischemic heart disease and impaired left ventricular function.
We studied 27 male patients with ischemic cardiomyopathy (Age: 60±7 years) before and after low dose dobutamine echocardiography (LDDE). Mitral annular isovolumic contraction velocity (IVV) was obtained from septal, lateral, anterior and inferior mitral annuli. Wall motion score index (WMSI) was averaged from 18 segments in apical views. Global viability was considered if enhanced motion occurred in ≥2 segments. Difference between post and pre-LDDE IVV and WMSI were calculated as d-IVV and d-WMSI.
486 segments were assessed. 14 segments were normal, and 472 were abnormal, of which 67 (14%, 33 basal, 22 mid, and 12 apical) had enhanced motion post-LDDE. Global WMSI decreased post compared to pre-LDDE (2.33±0.36 vs. 2.46±0.21, p=0.07). IVV increased post-LDDE (6.1±4.7 vs. 3.7±1.6 cm/s, p=0.01). IVV of different annular positions increased similarly. IVV correlated after LDDE with global WMSI (r= -0.43, p=0.028), and d-SWMI correlated with d-IVV (-0.43, p=0.02). 12 patients (44%) showed global viability, for whom d-IVV was higher than patients without viability (4.1±SE 1.17 vs. 1.16±SE 0.59 cm/s, p=0.02). Walls with enhanced motion had higher d-IVV from the corresponding mitral annular position (4.7±SE0.84 vs. 1.9±SE0.33 cm/s, p=0.002) and wall specific d-WMSI correlated with the d-IVV of the corresponding mitral annular position (r=0.43, p<0.001). Post LDDE IVV showed no significant difference when only basal segments showed enhanced motion post LDDE compared to those who did not (p=0.134). While, post LDDE IVV was higher when enhanced motion occurred in mid or apical segments than when they did not (p=0.01, 0.005, respectively). d-IVV correlated with d-WMSI of the mid and apical levels (r=0.48, 0.42, p=0.01, 0.03), while it did not for the basal level (r=0.21, p=0.3). ROC-curve showed that d-IVV detects global viability effectively (AUC=0.761), however, sensitivity and specificity increased for mid and apical levels (AUC=0.790, 0.868).
Mitral annular longitudinal motion during isovolumic contraction, represented by IVV and d-IVV, increase after LDDE in the presence of viable myocardium. Changes that occur in the mid and apical segments of the LV seem to contribute more to this effect than the basal segments.