Feasibility and accuracy of speckle tracking echocardiography in emergency department patients

Speckle tracking echocardiography (STE) is a novel technology that measures regional wall-motion abnormalities that may speed diagnosis and intervention of acute coronary occlusion in Emergency Department (ED) patients with non-ST elevation ACS (NSTE-ACS). STE provides an objective measurement of myocardial strain that is superior to visual assessment of wall motion when performed as part of a point-of-care (POC) echocardiogram. We determined the feasibility and preliminary accuracy of POC STE operated by emergency providers when compared to comprehensive echocardiography or final diagnosis of ACS.

We retrospectively reviewed 187 emergency provider POC echocardiograms with STE from 7/2014-5/2016 for suspected ACS at a large academic trauma center. Feasibility of POC STE was determined by calculating the percentage of complete exams (adequate apical 4-chamber and parasternal short axis views) out of all STE exams. We then used two different criterion standards for calculating diagnostic accuracy of STE: comprehensive echocardiograms with wall motion abnormalities or formal diagnosis of ACS based on elevated cardiac troponins, unstable angina, percutaneous coronary intervention, or coronary artery stenosis >70% on catheterization.

Of 187 STE studies performed, 75 (40%) were considered complete. Ultrasound-experienced providers had higher rates of complete exams (65% vs. 35%, P = 0.01). 16 of 75 exams (21%) were positive for myocardial strain, and of these 16 (100%) were admitted, 12 (75%) had positive troponins, 6 (46%) had positive comprehensive echocardiograms, and 3 (19%) had PCI or >70% stenotic lesion on catheterization. Compared with comprehensive echocardiography, POC STE had 35% sensitivity, 70% specificity, 46% positive predictive value (PPV), and 59% negative predictive value (NPV). Compared with formal diagnosis of ACS, POC STE had 29% sensitivity, 88% specificity, 75% positive predictive value (PPV), and 51% negative predictive value (NPV).

STE is a potentially feasible adjunct to standard bedside echocardiography in ED patients with suspected ACS when operated by experienced ultrasound-trained physicians in the ED. This data shows STE performed by emergency providers is not yet sensitive enough alone to diagnose ACS, and has low accuracy when compared to comprehensive echocardiography. However, the PPV and specificity improve when performed by expert ultrasound-trained providers. STE should be considered for inclusion in the Emergency Ultrasound Fellowship curriculum.