Myocardial contrast produced with intermittent harmonic imaging combined with wall thickening during low dose dobutamine can identify when a significant residual stenosis is present in viable myocardium following reperfusion in acute myocardial infarction

The myocardial contrast (MC) produced with intermittent harmonic imaging (IHI) following intravenous injections (IVI) of perfluorocarbon-exposed sonicated dextrose albumin (PESDA) may be an indicator of microvascular integrity following coronary reperfusion (Cor Rep) in acute myocardial infarction. The MC seen with IHI may also be affected by a significant residual stenosis (RS) after Cor Rep. Although wall thickening (WT) may improve during low dose dobutamine (LDD) in viable myocardium (VM) even if a RS is present, we hypothesized that MC intensity with IHI following IV PESDA would be abnormal, and thus differentiate jeopardized VM from VM without a RS. Accordingly, four different scenarios were created following prolonged coronary occlusion (2.1 ± 0.6 hours) in 25 dogs after Cor Rep: (1) transmural infarction (TMI) with no RS (Inf-NS) ; (2) TMI with a significant (>50% diameter) RS (Inf-S); (3) no or partial infarction with no RS (PI-NS); and (4) no or partial infarction with a significant RS (PI-S). The peak myocardial videointensily (PMVD ratio (repertused zone/normal zone) following 0.005-0.01 ml/kg IVI of PESDA and percent %WT in the reperfused zone were measured during LDD: Inf-NS Inf-S PI-NS PI-S PMVI ratio 0.55 ± 0.8 0.34 ± 0.3 0.9 ± 0.3*0.43 ± 0.13 %WT 20 ±15 18 ±14 37 ± 9 a 34 ± 10 a*p<0.05 compared to other groups; a p<0.05 compared to Inf groups. The sensitivity and specificity of a PMVI ratio <0.6 combined with WT>25% during LDD for identifying jeopardized VM was 86 and 94%, while a PMVI ratio >0.6 and WT>25% had a 100% sensitivity and 97% specified for identifying VM without a RS. PMVI obtained with IHI combined with WT responses during LDD can differentiate viable but ischemic from viable non-ischemic myocardium following Cor Rep hi acute myocardial infarction.