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ORIGINAL ARTICLE
Year : 2022 | Volume
: 32
| Issue : 4 | Page : 205-211
Utility of handheld ultrasound performed by cardiology fellows in patients presenting with suspected ST-Elevation myocardial infarction
Ravand Samaeekia1, George Jolly2, Ryan Marais3, Reza Amini2, Dmitry Abramov2, Islam Abudayyeh2
1 Department of Medicine, Division of Cardiology, Loma Linda Medical Center; Department of Internal Medicine, Loma Linda Medical Center, Loma Linda, CA, USA
2 Department of Medicine, Division of Cardiology, Loma Linda Medical Center, Loma Linda, CA, USA
3 Department of Internal Medicine, Loma Linda Medical Center, Loma Linda, CA, USA
Correspondence Address:
Islam Abudayyeh
Department of Medicine, Division of Cardiology, Loma Linda Medical Center, Loma Linda, CA
USA
Source of Support: None, Conflict of Interest: None
CheckDOI: 10.4103/jcecho.jcecho_51_22
Background: In academic hospitals, cardiology fellows may be the first point of contact for patients presenting with suspected ST-elevation myocardial infarction (STEMI) or acute coronary syndrome (ACS). In this study, we sought to determine the role of handheld ultrasound (HHU) in patients with suspected acute myocardial injury (AMI) when used by fellows in training, its association with the year of training in cardiology fellowship, and its influence on clinical care. Methods: This prospective study's sample population comprised patients who presented to the Loma Linda University Medical Center Emergency Department with suspected acute STEMI. On-call cardiology fellows performed bedside cardiac HHU at the time of AMI activation. All patients subsequently underwent standard transthoracic echocardiography (TTE). The impact of the detection of wall motion abnormalities (WMAs) on HHU in regard to clinical decision-making, including whether the patient would undergo urgent invasive angiography, was also evaluated. Results: Eighty-two patients (mean age: 65 years, 70% male) were included. The use of HHU by cardiology fellows resulted in a concordance correlation coefficient of 0.71 (95% confidence interval: 0.58–0.81) between HHU and TTE for left ventricular ejection fraction (LVEF), and a concordance correlation coefficient of 0.76 (0.65–0.84) for wall motion score index. Patients with WMA on HHU were more likely to undergo invasive angiogram during hospitalization (96% vs. 75%, P < 0.01). The time interval between the performance of HHU to initiation of cardiac catheterization (time-to-cath) was shorter in patients with abnormal versus normal HHU examinations (58 ± 32 min vs. 218 ± 388 min, P = 0.06). Finally, among patients who underwent angiography, those with WMA were more likely to undergo angiography within 90 min of presentation (96% vs. 66%, P < 0.001). Conclusion: HHU can be reliably used by cardiology fellows in training for measurement of LVEF and assessment of wall motion abnormalities, with good correlation to findings obtained via standard TTE. HHU-identified WMA at first contact was associated with higher rates of angiography as well as sooner angiography compared to patients without WMA.
Keywords: Cardiology fellow in training, handheld ultrasound, left ventricular ejection fraction, ST-elevation myocardial infarction, wall motion abnormalities
As ultrasound technology becomes more readily accessible, the use of handheld devices (HHU) is becoming increasingly prevalent in assessing most organ systems. In the high-stakes and time-sensitive field of cardiology, point-of-care ultrasound has been shown to be a valuable tool for evaluating cardiovascular status.[1],[2],[3] Examples include revealing the presence of reversible causes of cardiovascular compromise (including cardiac tamponade, hypovolemia, myocardial infarction, and pulmonary embolism), as well as estimating left ventricular ejection fraction (LVEF) and cardiac wall motion abnormalities.[4],[5],[6] These findings may play crucial roles in the clinical decision-making process in regard to whether or not a patient should be sent to the catheterization laboratory, as well as in the discernment of the etiology of acute myocardial injury (AMI). The information acquired through the use of HHU has been shown to change patient management in acute settings[7],[8],[9] by helping to direct the clinicians toward a diagnosis, such that focused ultrasound has become an important part of the evaluation of patients undergoing AMI workup.[10]
The need to rapidly diagnose and triage AMI patients makes the use of HHU appealing, particularly in patients with an equivocal diagnosis and treatment options. In these patients, the ability to estimate LVEF and identify wall motion abnormalities can often change the course of patient's management and this is the area, in which a rapid bedside HHU (as opposed to standard transthoracic echocardiography (TTE), which may not be readily available) can prove to be of significant utility. As a result, it is important to determine the reliability of the information acquired by HHU and its agreement with the gold standard TTE, as well as the possible ways in which HHU can affect care in patients presenting with suspected AMI.
As the first responders to AMI activations, the quality of images acquired by cardiology fellows and their confidence in the interpretation of HHU studies are important factors in determining the reliability and precision of the study results and in the subsequent rapid identification of cases that need urgent interventions. Furthermore, despite the proven benefits of HHU, adoption of this tool has remained heterogeneous and sporadic among both academic and community centers alike. In this study, we hypothesized that HHU, when performed and interpreted by trained cardiology fellows, provides accurate diagnostic capabilities compared with standard TTE in patients with AMI and could lead to changes in clinical management and improvement in treatment workflows.
MethodsPatient 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 the 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 two-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 manner as part of standard care. Images were then read by cardiology attendings. The cardiac HHU examination was done before obtaining the TTE and included two-dimensional images from the standard long and short parasternal, as well as apical windows. All the HHU studies were acquired by cardiology fellows and interpreted to visually estimate the LVEF, presence of left ventricular (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.
Fellows
All fellows participating in the study were enrolled in a cardiovascular diseases fellowship at different levels from PGY 4–6, and have experience in the cardiac ward at different levels commiserate to their level of training. The studies were performed by a total of 14 cardiology fellows, seven in 1st year (PGY 4) and seven in 2nd or 3rd year of training (PGY 5 and 6).
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.
Statistical analysis
Continuous variables were reported as mean ± standard deviation or median (interquartile range). Categorical variables were reported as number (%) of the total group and P values were 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 the 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.
ResultsPatient characteristics
This study enrolled 95 patients, of which 75 were included for LVEF and 82 were included for Wall Motion Abnormalities (WMA) studies. This was because some patients either did not undergo standard TTE during hospitalization or the LVEF and WMAs were not recorded by HHU users. The characteristics of the study patients are outlined in [Table 1]. The mean age was 65 ± 13 years, and 70% were male. Coronary angiography was performed on 74 (90%) patients. Index hospital treatment included percutaneous coronary intervention (PCI) in 55 (67%) patients, surgical intervention coronary artery bypass grafting in 2 (3%) patients, and medical treatment alone in 25 (30%) patients.
Table 1: Clinical and echocardiographic characteristics of the study populationAgreement on left ventricular ejection fraction and wall motion abnormalities assessed by transthoracic echocardiography and handheld ultrasound
To measure the agreement level, the concordance correlation coefficient (r) was calculated for both TTE and HHU [Figure 1]a. The r-value for LVEF between the standard TTE and HHE was 0.71 (95% confidence interval [CI]: 0.58–0.81, P < 0.0001). [Figure 1]c shows the Bland–Altman plot for agreement between HHE and TEE for assessing LVEF. The majority of measurements fell within the 95% CI indicating the high agreement between the two methods.
Figure 1: (a and b) Linear correlation between standard TTE and HHU for (a) LVEF and (b) WMSI, with a concordance correlation coefficient of 0.71 for LVEF and 0.76 for WMSI. (c and d) Bland–Altman correlation between standard TTE and HHU for (c) LVEF and (d) WMSI. The dark horizontal line in the middle represents the mean of the difference between TTE and HHU. The light dashed lines represent 2 SDs away from the mean difference. (c) For LVEF, Bland–Altman correlation demonstrates a larger difference between the TTE and HHE within the mid-range of LVEF, whereas for WMSI, largest difference between the HHU and standard TTE occurred in the mid to upper to end of the reported range, between 1.5 and 2.5. HHU = Handheld ultrasonography, LVEF = Left ventricular ejection fraction, SD = Standard deviation, TTE = Transthoracic echocardiography, WMSI = Wall motion score indexThe concordance correlation coefficient for WMSI between the standard TTE and HHE was 0.76 (95% CI: 0.65–0.84, P < 0.0001) [Figure 1]b. Similarly, a Bland–Altman graph generated from the WMSI data showed that the majority of measurements for wall motion abnormalities were seen within the range of 95% CI [Figure 1]d. The largest difference in WMSI between the HHU and standard TTE occurred in patients with more significant wall motion abnormalities and a wall motion score between 1.5-2.5.
We also calculated the agreement for the presence of segmental regional wall motion abnormalities between the HHU and standard TTE for each of the 16 segments of the left ventricle. Agreement was variable among different LV segments, with r values ranging between 0.48 and 0.80. It was highest for the mid inferoseptal wall (0.80) on the apical view and mid inferolateral wall (0.77) on the parasternal long axis, and lowest for the basal anterior (0.5) and basal inferior (0.51) walls on the parasternal short axis views [Table 2].
Table 2: LV regional wall motion abnormality agreement between HHU and standard TTE for each segmentCardiology fellows' handheld ultrasound image quality and effect of handheld ultrasound results on clinical decision-making
To describe their image quality, cardiology fellows gave a score to segmental endocardial border visualization (2 = good, 1 = poor, 0 = invisible). The mean endocardial visibility grade was 1.41 ± 0.58. When asked to rate their level of confidence in interpreting the study (2 = confident, 1 = intermediate, 0 = uncertain), the mean level of confidence was 1.30 ± 0.67. Fellows were also able to recognize pericardial effusions, identifying eight patients with small effusions on HHU of which all were confirmed with TTE.
Fellows reported that in 32% of the patients, the HHU study influenced their clinical decision-making [Table 3]. This was corroborated with several objective findings. First, patients with WMA on HHU were more likely to undergo invasive angiography during hospitalization (96% vs. 75%, P < 0.01). Second, the mean time-to-cath in a patient with abnormal HHU findings of WMA tended to be shorter than among patients without WMA (58 ± 32 min vs. 218 ± 388 min, P = 0.06). Finally, among patients undergoing angiography, those with WMA were more likely to undergo an angiogram within 90 min of presentation (96% vs. 66%, P < 0.001).
Table 3: Fellow-reported HHU image quality and reported effect of HHU results on clinical decisionsCorrelation between cardiology fellows' year of training and handheld ultrasound 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 1st-year cardiology fellows (fellow in training [FIT] = 1) or those in 2nd 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 [Figure 2]a and [Figure 2]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 [Figure 2c and d]. The higher correlation in FIT ≥2 was also reflected in recognizing WMA when comparing each wall segment separately [Table 2].
Figure 2: Stratification of linear correlation between standard TTE and HHU for LVEF (a and b) and WMSI (c and d) based on (a and c) FIT = 1 and (b and d) FIT ≥2, showing a concordance correlation coefficient of 0.64 versus 0.80 for a and b, and 0.70 versus 0.87 for c and d, respectively. FIT = Fellow in training, TTE = Transthoracic echocardiography, HHU = Handheld ultrasonography, LVEF = Left ventricular ejection fraction, WMSI = Wall motion score indexThe influence of the 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].
DiscussionAmong AMI activation cases, there is heterogeneity and uncertainty impacting whether an immediate coronary angiogram and PCI is warranted based on an equivocal electrocardiography 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 the 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 among 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 a good correlation between HHU and standard TTE for LVEF when experienced users perform the HHU exams.[13],[14],[15],[16],[17],[18],[19],[20] Liebo et 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 HHU, 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 the 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, endocardial visibility was similar to reported hand-held ultrasound studies with a visibility score (1.41 ± 0.58) equivalent to prior studies (1.60 ± 0.50).[18]
In addition to demonstrating that HHU performed by cardiology fellows is efficacious in the 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 examination, 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, and pulmonary embolism. However, even in the absence of alternative findings, the 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 the ability to defer invasive angiography, which has been shown to be safe among patients with non-STEMI[23] or considers 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 laboratory 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.
Limitations
This study represents a small cohort from a single institution. TTEs were done as part of routine care, and could have been performed several hours after HHU, as well as after coronary angiography or revascularization, by which time wall motion may have changed. This potentially could be a confounding factor, affecting the accuracy of comparing wall motion on HHU with wall motion on TTE. The HHUs in our study were performed by 14 cardiology fellows, with first-year fellows carrying out two-thirds of the studies. This increases interobserver variability, which has previously been shown to contribute to disagreement between the HHU and TTE.[15] Decision-making regarding proceeding to angiography and timing of angiography may have been made based on factors other than HHU, including patient preference and other clinical characteristics.
It should be pointed out that the influence of HHU on cardiology fellows' clinical management of each patient was a subjective report by each fellow as part of the checklist; however, other findings, including higher rates of catheterization and shorter time-to-cath timeframes, provide supporting evidence that validates the influence of HHU on fellows' better clinical decisions.
ConclusionIn summary, we found that cardiac HHU is a feasible method for cardiology fellows-in-training in rapidly determining LVEF and wall motion abnormalities in critical situations of a suspected STEMI, when timing and accuracy of clinical decision-making are paramount. We also found that cardiology fellows with a higher level of training could obtain more accurate results from HHU with higher confidence in their interpretations. In addition, the presence of WMAs on HHU was associated with higher rates of angiography and faster angiography, which may have important implications for the triage and early management of patients presenting with suspected STEMI.
Ethical clearance
This study, including the informed consent, was reviewed and approved by the Loma Linda University Institutional Review Board and ethics committees, IRB #5180250.
Financial support and sponsorship
Nil.
Conflicts of interest
There are no conflicts of interest.
References
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