Ultrasound Perfusion Improves Microvascular Flow in STEMI

Study Questions:

What is the impact of high mechanical index (HMI) impulses applied using a diagnostic ultrasound transducer to patients with ST-segment elevation myocardial infarction (STEMI) treated with intravenous microbubble infusion?


Prior studies suggest that HMI impulses might enhance myocardial perfusion in patients with STEMI. The authors randomized patients undergoing primary percutaneous coronary intervention (PCI) to HMI before and for 30 minutes after primary PCI (n = 20) versus diagnostic ultrasound only (n = 10) using 5% Definity contrast. Initial epicardial flow and final microvascular flow were compared between the two groups. Another 70 patients who presented for primary PCI during a time window when ultrasound was not available served as controls.


The median door-to-balloon time was 82 minutes in the diagnostic scan group, 72 minutes in the HMI group, and 103 minutes in the control group. Angiographic recanalization was present in 60% of the HMI group versus 10% of the diagnostic scan and 23% of the control group. HMI was associated with reduced microvascular obstruction and improved left ventricular function at 30 days.


HMI impulses applied using commercial ultrasound equipment combined with commercial microbubbles result in improved myocardial salvage in patients undergoing primary PCI.


This small pilot study suggests that using microbubbles and HMI ultrasound can significantly enhance myocardial reperfusion and preserve ejection fraction in patients undergoing primary PCI. Larger studies are needed to corroborate these findings and to assess if these changes translate into a clinical benefit.

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