Abstract

Background: Microvascular perfusion is a pre-requisite for ensuring viability early after acute myocardial infarction (AMI). For adequate assessment of myocardial perfusion, both myocardial blood volume and velocity need to be evaluated. Low power continuous myocardial contrast echocardiography (MCE) can rapidly assess myocardial blood volume and velocity. Methods: Fifty patients underwent low power continuous MCE using IV Optison® 7-10 days after AMI. Myocardial perfusion (contrast opacification assessed at 15 cardiac cycles after destructive images) and wall thickening were assessed at baseline. Regional and global left ventricular (LV) function was re-assessed 12 weeks after AMI. Results: Out of the 297 dysfunctional segments, MCE detected no contrast enhancement at 15 cardiac cycles in 172 segments. Of these 160 (93%) segments failed to show improvement. MCE demonstrated homogeneous contrast opacification in 77 segments, of which 65 (84%) showed recovery of function. Furthermore, the greater the extent and intensity of contrast opacification at baseline, the better the LV function at 12 weeks (p<0.001, r = -0.91). Almost all patients with < 40% perfused, but dysfunctional myocardium failed to demonstrate functional recovery. Amongst clinical, biochemical, ECG and MCE parameters in the multiple regression analysis, only MCE (p < 0.001) and peak CK (p < 0.001) proved to be independent predictors of functional recovery. Conclusion: Low power continuous MCE is an accurate and rapid bedside technique to identify microvascular perfusion post AMI. This technique may be utilized to reliably predict late recovery of function in dysfunctional myocardium after AMI.