Methods:
Patient selection : This was a prospective study of 95 patients over 18 years of age who triggered ST elevation myocardial infarction (STEMI) activation after arrival to the emergency room at Loma Linda University Medical Center and underwent HHU by an on-call cardiology fellow as part of initial evaluation. Patients were enrolled between October 2018 and December 2020.
Equipment : Standard TTE was performed using a Philips (Bothell, WA) ultrasound device. Cardiac HHUs were done using Butterfly (Burlington, Massachusetts) or GE-V-scan (Waukesha, WI) devices. The HHU examination included 2-dimensional images from the standard long and short axis parasternal, and apical windows. The interpretations were then documented by the fellows on a standardized form to collect the data.
Echocardiographic examination : The standard echocardiograms were performed by experienced sonographers in a comprehensive a manner as part of standard care. Images were then read by cardiology attendings. The cardiac HHU examination was done prior to obtaining the TTE and included 2-dimensional images from the standard long and short parasternal, as well as apical windows. 14 cardiology fellows (seven in first year and seven in second or third year of training) performed all the HHU studies. Fellows interpreted images to visually estimate the LVEF, presence of LV regional wall-motion abnormality (based on the 16-segment model (11) for generating a wall motion score index (WMSI)), presence of pericardial effusion (graded based on the common classification), segmental endocardial border visualization, and level of confidence interpreting the data (supplemental figure 1).
Endpoint: The primary endpoint of the study was the agreement between LVEF and WMAs identified on HHU with subsequently performed clinically indicated TTE. Secondary endpoints included the role of HHU on clinical decision making, including whether angiography was performed and the timing in which it was initiated (supplemental figure 2).
Statistical analysis : Continuous variables were reported as mean +/- SD or median (interquartile range). Categorical variables were reported as number (%) of the total group and p values calculated using Chi square test. The agreement between the cardiac HHU and standard TTE was measured for LVEF which was also stratified based on cardiology fellows’ year of training. For continuous variables, Lin’s concordance correlation coefficients (r values) were estimated by variance components. Agreement was also assessed using Bland-Altman methodology (12). Results from the standard TTE were considered the gold standard for this study. Microsoft Excel was used for all of the statistical analyses.
Results :