Peak longitudinal strain most accurately reflects myocardial segmental viability following acute myocardial infarction - an experimental study in open-chest pigs.

BACKGROUND: The extension and the transmurality of the myocardial infarction are of high predictive value for clinical outcome. The aim of the study was to characterize the ability of longitudinal, circumferential and radial strain measured by 2-dimensional speckle tracking echocardiography (2D-STE) to predict the extent of necrosis in myocardial segments following acute myocardial infarction and to separate transmural necrotic segments from non-transmural necrotic segments in a full 18-segment porcine model. METHODS: 2D-STE strain was assessed in long- and short-axis following myocardial infarction in ten open-chest anesthetized pigs. Strain was defined according to systolic peak values. In segments displaying both negative and positive peaks, only the peak with the highest absolute value was utilized. Necrosis was measured by 2,3,5-triphenyltetrazolium chloride (TTC) staining and expressed as percent of each myocardial segment. RESULTS: Significant correlations were found between the extension of necrosis and all measured parameters of myocardial deformation (p < 0.001), but was stronger for longitudinal strain (r(2) = 0.52) than circumferential strain (r(2) = 0.38) and radial strain (r(2) = 0.23). The area under the receiver operator characteristic curve (AUC) for separating transmural necrotic segments (>50% necrosis) from predominantly viable segments (0-50% necrosis) was significantly larger for longitudinal strain (AUC = 0.98, CI = 0.97-1.00) when compared with circumferential strain (AUC = 0.91, CI = 0.84-0.97, p < 0.05) and radial strain (AUC = 0.90, CI = 0.83 - 0.96, p < 0.01), indicating a stronger ability of longitudinal strain to identify segments with transmural necrosis. CONCLUSION: Peak strain values derived from 2D-STE correlate well with the extent of necrosis in myocardial segments following acute myocardial infarction. Longitudinal strain most accurately reflects myocardial segmental viability in this setting.

Oral ß-glucan reduces infarction size and improves regional contractile function in a porcine ischaemia/reperfusion model.

OBJECTIVES: We previously reported a cardioprotective effect of oral ß-glucan in patients who underwent coronary artery bypass grafting. The present study was conducted to determine whether oral ß-glucan could reduce myocardial infarction size and whether these changes would be reflected by better preservation of contractile indices measured by speckle tracking echocardiography (STE). METHODS: Fourteen pigs were randomized to receive oral ß-glucan 50 mg/kg (n = 7) or placebo (control, n = 7) 10 days before they were anaesthetized and subjected to 1 h clamping of the left anterior descending coronary artery followed by reperfusion for 3 h. Longitudinal strain, circumferential strain and radial strain were assessed by STE after 3 h of reperfusion. Infarction size and area at risk were determined by Evans blue and 2,3,5-triphenyltetrazolium chloride staining. RESULTS: Pretreatment with ß-glucan reduced the infarct area/area at risk ratio by 36% (P < 0.05) and the total necrotic area of the left ventricle by 37% (P < 0.05) compared with controls. Viable myocardium at risk was 30% higher in the ß-glucan vs. control group (P < 0.05). Anterior apical strain values for ß-glucan vs. control were -4.7 ± 9.4 vs. 5.9 ± 6.1% (P < 0.05) for longitudinal strain, -14.7 ± 6.6 vs. -7.7 ± 4.3 (P < 0.05) for circumferential strain, 15.1 ± 7.7 vs. 7.1 ± 11.8 (ns) for radial strain. CONCLUSIONS: Oral ß-glucan pretreatment reduces infarction size and improves regional contractile function in a porcine ischaemia/reperfusion model.