Correlation between cardiology fellows’ year of training and HHU
interpretation:
To determine whether the number of years in training had any significant
influence on the HHU interpretation, all the HHU measurements were
stratified for either first year cardiology fellows (fellow in training
[FIT] = 1) or those in second year and above (FIT ≥ 2). The
correlation coefficient for LVEF between the standard TTE and HHU were
0.64 (95% CI: 0.41 – 0.79) and 0.80 (CI: 0.64 – 0.89) for FIT = 1 and
FIT ≥ 2, respectively (Fig 2A-B). A similarly significant increase in
the correlation coefficient was found when we compared the WMSI acquired
from standard TTE against HHU obtained by cardiology fellows, with r =
0.70 (CI: 0.51 – 0.82) for FIT = 1 and r = 0.87 (CI: 0.76 – 0.93) for
FIT ≥ 2 (Fig 2C-D). The higher correlation in FIT ≥ 2 was also reflected
in recognizing WMA when comparing each wall segment separately (Table
2).
The influence of number of years in training was also evident in other
factors reported by the fellows. These included higher scoring for
visualization of segmental endocardial borders (1.45 ± 0.55 in FIT ≥ 2
versus 1.39 ± 0.61 in FIT = 1, p=0.34), higher scores for level of
confidence interpreting the studies (1.47 ± 0.60 in FIT ≥ 2 versus 1.13
± 0.68 in FIT = 1, p<0.01), and a higher percentage of
fellows-reported clinical decisions being affected by HHU results: 42%
in FIT ≥ 2 group versus 24% in FIT =1, p<0.05) (Table 3).
Discussion :
Among AMI activation cases, there is heterogeneity and uncertainty
impacting whether an immediate coronary angiogram and PCI is warranted
based on an equivocal ECG and the patient’s symptoms. This is especially
challenging in most training centers where cardiology fellows in
training are the first contact provider. These may be situations in
which HHU can be of significant help in clinical decision making. Such
areas where HHU can influence next steps are estimating LVEF, evaluating
for pericardial pathology, and identifying the locations of
abnormalities in cardiac wall motion, which will help in localizing the
location of coronary artery occlusions. These findings may eventually
translate into improved diagnosis and better patient care. Thus, it is
imperative to determine 1) how reliable the information acquired by HHU
is when compared against the gold standard TTE, and 2) whether HHU is
associated with a potential change in care in terms of the need for
angiography as well as the urgency of angiography, and whether it
influences cardiovascular trainees to help make informed decisions.
In this study we found that there is a high correlation for LV function
and overall wall-motion abnormality assessment between HHU and standard
TTE (concordance correlation coefficient: 0.71 and 0.75) when performed
and interpreted by cardiovascular fellows. Furthermore, we found that
the absence of WMA on HHU was associated with an ability to defer or
delay angiography, which can have important implications for the
evaluation and triage of patients presenting with suspected STEMI.
The high degree of correlation between HHU and TTE that we demonstrated
in this study can be supported by the fact that cardiology fellows could
acquire relatively high-quality images and demonstrate a high level of
confidence in their interpretation of the studies. We also found that
the accuracy of data acquired by HHU had a positive linear correlation
with years of training amongst fellows in detecting wall motion
abnormalities, visualizing endocardial borders, and also with their
self-reported level of confidence. As a result, second- and third-year
fellows relied more heavily on the results of their HHU for making the
next clinical decisions in terms of the need for and timing of cardiac
catheterization.
Prior work has demonstrated good correlation between HHU and standard
TTE for LVEF when experienced users perform the HHU exams (13-20). Lieboet al . in their cross-sectional study of 97 patients concluded
that the rapid acquisition of images by skilled ultrasonographers who
use pocket mobile echocardiography yields accurate assessments of
ejection fraction and some, but not all, cardiac structures in many
patients (13). In another similar study, Prinz et al ., using
handheld ultrasound, showed that in relation to the basic assessment of
cardiac morphology and function, the interpretation by experienced
echocardiographers of images obtained using handheld echocardiographic
devices demonstrated a moderate to very good correlation with standard
echocardiography (r > 0.8, p < 0.01 for wall
motion abnormalities, and r > 0.6, p < 0.01 for
LVEF assessments) (14).
When compared with existing literature, our study shows comparable
findings for correlation between HHU and standard TTE measurements,
particularly for LVEF (15-16). Furthermore, there have been similar
variable discrepancies in wall motion abnormalities between HHU and TTE
in prior work, even in the hands of experienced users (17). This can be
explained by lower image resolution and the limited amount of time users
often spend optimizing images with HHU. Of note, the mean endocardial
visibility score reported in this study (1.41 ± 0.58) was almost similar
to what previously reported (1.60 ± 0.50) (18).
In addition to demonstrating that HHU performed by cardiology fellows is
efficacious in assessment of suspected STEMI, we highlighted the
possible ability of key HHU findings to affect care in this population.
Patients with suspected STEMI are a heterogenous group, with a broad
differential diagnosis (21). In addition to history, physical exam, and
laboratory values, HHU may have the ability to further risk stratify
patients. This may occur due to the finding of a competing explanatory
diagnosis, such as pericarditis, pericardial effusion, pulmonary
embolism, etc. However, even in the absence of alternative findings,
lack of WMAs on presentation may not be clinically suggestive of a STEMI
(22). We extend similar findings to HHUs performed by cardiology fellows
at the point of care in the emergency room. The ability to risk stratify
patients is potentially important due to ability to defer invasive
angiography, which has been shown to be safe among patients with non-ST
elevation MI (23) or consider alternative diagnoses. The ability to
safely determine the timing of care may be especially important in the
off-hours or in the setting of limited catheterization lab space or
requirement for decision making regarding patient transfer to a STEMI
center, especially among smaller or community hospitals. The use of HHU
for risk stratification for suspected STEMI, as well as other patient
populations presenting with suspected AMI, deserves further evaluation
in larger studies.
An important consideration in using HHU for decision making in the acute
setting is that operators should be familiar with these tools and, more
importantly, how to interpret the imaging results. Specific training in
this area, therefore, is central to effective use and improved outcomes.