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 :