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A Modified Lung and Cardiac Ultrasound Protocol Saves Time and Rules in the Diagnosis of Acute Heart Failure
The Journal of Emergency Medicine, Vol. -, No. -, pp. 1–7, 2017 Published by Elsevier Inc. 0736-4679/$ - see front matter
http://dx.doi.org/10.1016/j.jemermed.2017.02.003
Ultrasound in Emergency Medicine
A MODIFIED LUNG AND CARDIAC ULTRASOUND PROTOCOL SAVES TIME AND RULES IN THE DIAGNOSIS OF ACUTE HEART FAILURE Frances M. Russell, MD*† and Robert R. Ehrman, MD*‡ *Department of Emergency Medicine, Cook County Hospital, Chicago, Illinois, †Department of Emergency Medicine, Indiana University School of Medicine, Indianapolis, Indiana, and ‡Department of Emergency Medicine, Wayne State University, Detroit, Michigan Corresponding Address: Frances M. Russell, MD, Department of Emergency Medicine, Indiana University School of Medicine, 720 Eskenazi Avenue, Fifth Third Faculty Office Building, 3rd Floor, Emergency Medicine Office, Indianapolis, IN 46202
, Abstract—Background: Multiorgan ultrasound (US), which includes evaluation of the lungs and heart, is an accurate method that outperforms clinical gestalt for diagnosing acutely decompensated heart failure (ADHF). A known barrier to ultrasound use is the time needed to perform these examinations. Objective: The primary goal of this study was to determine the test characteristics of a modified lung and cardiac US (LuCUS) protocol for the accurate diagnosis of ADHF. Methods: This was a secondary analysis of a prospective observational study that enrolled adult patients presenting to the emergency department with undifferentiated dyspnea. Intervention consisted of a modified LuCUS protocol performed by experienced emergency physician sonographers. A positive modified LuCUS protocol was defined as the presence of B+ lines in both the left and right anterosuperior lung zones, plus a left ventricular ejection fraction <45%. If all three of these findings were not present, the modified LuCUS result was interpreted as negative for ADHF. The primary objective was measured by comparing US findings to final diagnosis independently determined by two physicians, both blinded to US findings and each other’s final diagnosis. Results: We analyzed data on 99 patients; 36% had a final diagnosis of ADHF. The sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of the modified LuCUS protocol are 25% (95% confidence interval [CI] 14–41%), 100% (95% CI 94–100%), undefined, and 0.75 (95% CI 0.62–0.91%), respectively. This modified protocol takes on average 1 min and 32 sec to com-
plete. Conclusion: The point estimate for the specificity of the modified LuCUS protocol in this pilot study, accomplished by a reanalysis of data collected for a previously reported investigation of the full LuCUS protocol, was 100% for the diagnosis of ADHF. Published by Elsevier Inc. , Keywords—acute heart failure; bedside ultrasound; cardiac ultrasound; clinical ultrasound; diagnosis; emergency ultrasound; lung ultrasound; multiorgan ultrasound; undifferentiated dyspnea
INTRODUCTION Millions of Americans are evaluated in the emergency department (ED) for acute dyspnea (1). Determining the etiology of dyspnea can be challenging. Acute decompensated heart failure (ADHF) accounts for many of these presentations (2). A prompt and accurate diagnosis is imperative to guide acute management, avoid unnecessary medications, and avoid delays in care (3). The traditional work-up for ADHF, including physical examination findings, chest radiography, and serum brain natriuretic peptide, is not always diagnostic or helpful in determining the cause of dyspnea (4–9). Multiorgan ultrasound (US), including lung and cardiac sonography, is accurate for differentiating ADHF from other etiologies of acute dyspnea (10–12). Russell
Reprints are not available from the authors.
RECEIVED: 26 November 2016; FINAL SUBMISSION RECEIVED: 1 February 2017; ACCEPTED: 2 February 2017 1
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et al. found that the lung and cardiac US (LuCUS) protocol was more accurate for the diagnosis of ADHF when compared to clinical gestalt (10). In addition, they found that multiorgan US improved acute clinical management in approximately 50% of their patients—an impactful change, because disease-specific therapy may lead to improved outcomes (3). Multiorgan US may also identify alternative causes of dyspnea requiring different treatment than that required for ADHF. Despite knowing that bedside US may be the best modality for ruling in ADHF, many clinicians fail to perform US in the initial diagnostic evaluation of patients with undifferentiated dyspnea (4). One of the biggest barriers to implementation is the perceived amount of time it takes to perform a bedside sonographic examination (13). Multiorgan US, including a full lung and cardiac examination, can take anywhere from 10–15 min, which may not be ideal for a fast-paced and busy ED (10,14,15). Lung US alone, to detect pulmonary edema, is highly sensitive for ADHF, but lacks specificity, because diffuse B-lines can be seen in many other conditions (5,16–19). The addition of cardiac US greatly improves the specificity (10–12). The primary aim of this study was to determine the sensitivity, specificity, and likelihood ratios for diagnosing ADHF in patients in the ED with undifferentiated dyspnea using a modified LuCUS protocol. A positive modified LuCUS protocol scan was defined as B+ lines in both the left and right anterosuperior lung zones, plus an estimated left ventricular ejection fraction (LVEF) <45%. A scan was determined to be negative if all three of these criteria were not present. METHODS This study was a secondary analysis of the LuCUS protocol, a prospective, observational, single-center study that enrolled ED patients with acute undifferentiated dyspnea (10). This study of the LuCUS protocol was conducted at an urban tertiary care teaching hospital with >120,000 annual ED visits, from December 2012 to July 2013, and was approved by the institutional review board. The methods from that study have been published previously (10). A convenience sample of patients meeting the following inclusion criteria were enrolled: adult patients >18 years of age and a primary complaint of undifferentiated dyspnea according to their treating clinician. Undifferentiated dyspnea was defined as at least two possible etiologies in the differential diagnosis, and this did not have to include ADHF as a potential diagnosis. Patients were excluded if the treating clinician was confident in their diagnosis after initial assessment, if patients had an electrocardiogram showing ST segment elevation
myocardial infarction, if patients had been treated for ADHF for >30 min prior to US, if patients refused consent, or if patients had been previously enrolled in the study. The LuCUS protocol was performed and interpreted by three investigators; an emergency medicine US director and two emergency medicine US fellows. All sonographers had previously performed >1000 bedside sonograms, including lung and cardiac examinations. All investigators were required to scan five patients at bedside under the direct supervision of the principal investigator to ensure a standardized method of acquiring and interpreting images. Sonographers were blinded to the treating clinician’s initial assessment, medical comorbidities, and the results of laboratory tests or imaging studies performed during the ED encounter. The full LuCUS protocol interrogated four anterolateral lung zones in each hemithorax with a curvilinear probe to assess for the presence of B-lines. The costophrenic recess was examined bilaterally to assess for the presence of pleural effusion. The cardiac portion of the examination included parasternal long- and shortaxis views to assess ejection fraction, the subcostal view was used to assess inferior vena cava diameter and collapsibility, and the apical four-chamber view was used for assessment of diastolic function. The full protocol took an average of 12 min to complete (10). The Modified LuCUS Protocol Each sonographer conducted the scanning protocol using a Mindray M7 US machine (Mindray Bio-Medical Electronics Co., Shenzhen, China). The lung portion of the modified LuCUS examination interrogated the anterosuperior lung zones in each hemithorax with a curvilinear probe. Sonographers recorded the number of B-lines seen between two ribs in each lung zone. Three or more B-lines in a rib space were considered B+ lines. The cardiac portion of the modified LuCUS examination assessed the parasternal long axis view for LVEF. This was estimated qualitatively by assessing wall contraction and thickening (20,21). If EF could not be determined in the parasternal long axis view, it was assessed in the parasternal short, apical, or subxiphoid view. We defined a positive modified LuCUS protocol as B+ lines in both the left and right anterosuperior lung zones, plus an LVEF <45%. All three of these criteria had to be met for a positive study. A scan was determined to be modified LuCUS–negative if any or all three of these criteria were not met. The time to complete the modified LuCUS protocol was obtained by reviewing the time stamps on each US image included as part of the protocol. Timing started when the sonographer began recording the right
Modified LuCUS Protocol Saves Time in Diagnosis of AHF
anterosuperior lung zone and ended when they completed the parasternal long axis view of the examination. Total scan time included time to store all three images, and time to find the right windows for scanning the left anterosuperior lung zone and cardiac view for EF. Findings from the modified LuCUS protocol were documented on a standardized data collection form in real time. Demographic information, initial vital signs, admission diagnosis, and ED interventions were collected. This information was abstracted by research assistants who were trained in data abstraction according to recommendations from a previously published study (22). Abstractors were blinded to US results and final discharge diagnosis. Final diagnosis was determined independently by two emergency physicians (EPs) through a rigorous chart review, which served as our criterion standard. Chart reviewers followed previously published methods and determined each patient’s final diagnosis after reviewing laboratory results, imaging studies, medications administered, consults obtained, comprehensive echocardiography results, and discharge summaries (22). Each review was performed independently, and neither reviewer performed any of the US examinations for this study. If the reviewers disagreed, a third blinded reviewer served as the adjudicator.
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Data Analysis Sensitivity, specificity, positive likelihood ratios, and negative likelihood ratios were calculated and 95% confidence intervals (CIs) were derived using Microsoft Excel (Microsoft, Redmond, WA) and VassarStats software (available at http://vassarstats.net). Kappa and observed agreement were used to assess inter-rater reliability between coinvestigators’ interpretations of images. RESULTS We performed the complete LuCUS protocol on 104 patients who presented to the ED with undifferentiated dyspnea, and analyzed data on 99 patients. Five patients were excluded because of poor scanning windows and one patient dropped out of the study prior to completion. Patient characteristics are listed in Table 1. The flow of the study is presented in Figure 1. Thirty-six of 99 patients had a criterion standard diagnosis of ADHF. Of these 36, 25% (n = 9) were modified LuCUS–positive. All 63 patients who had an alternative final diagnosis were modified LuCUS–negative. The sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of the modified LuCUS protocol was 25% (95% CI 14–41%), 100% (95% CI 94–100%),
Table 1. Patient Characteristics, Dispositions, and Final Diagnoses
Age (years) 6 SD (range) Male, n (%) Medical comorbidities, n (%) Congestive heart failure COPD Coronary artery disease Hypertension Diabetes Smoking Vital signs, n (%) Hypotension (SBP <100 mm Hg) Tachycardia (HR >100 beats/min) Tachypnea (RR >20 breaths/min) Hypoxia (<92%) Disposition, n (%) ICU Floor Observation unit Home Final diagnosis, n (%) ADHF COPD Pneumonia Lung cancer Other
Modified LuCUS–Positive
ADHF
Total
n=9
n = 36
n = 99
53 6 12 (38–79) 8 (89)
57 6 14 (34–91) 23 (63.9)
56 6 13 (22–91) 55 (55.6)
6 (67) 2 (22) 2 (22) 7 (78) 2 (22) 3 (33)
23 (63.9) 12 (33.3) 6 (16.7) 30 (83) 11 (30.6) 6 (16.7)
40 (40.4) 43 (43.4) 16 (16.2) 68 (68.7) 29 (29.3) 21 (21.2)
0 (0) 4 (44) 7 (78) 2 (22)
3 (8.3) 15 (41.7) 16 (44.4) 4 (11.1)
5 (5.0) 36 (36.3) 44 (44.4) 12 (33.3)
1 (11) 6 (67) 2 (22) 0
3 (8.3) 26 (72.2) 4 (11.1) 3 (8.3)
9 (9.1) 64 (64.6) 9 (9.1) 16 (16.2)
36 (36) 24 (24) 10 (10) 7 (7) 23 (23)
ADHF = acutely decompensated heart failure; COPD = chronic obstructive pulmonary disease; ICU = intensive care unit; HR = heart rate; RR = respiratory rate; SBP = systolic blood pressure; LuCUS = lung and cardiac ultrasound protocol; SD = standard deviation.
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F. M. Russell and R. R. Ehrman
Figure 1. Flow diagram of enrolled patients, final diagnosis, and modified lung and cardiac ultrasound (LuCUS) findings. ADHF = acutely decompensated heart failure; ED = emergency department.
infinite, and 0.75 (95% CI 0.62–0.91%), respectively. This modified protocol took on average 1 min and 32 sec ( 6 23 sec) to complete. Secondarily, we evaluated sensitivity, specificity, and likelihood ratios of lung US alone, using the anterosuperior lung zones in each hemithorax. When both the left and right anterosuperior lung zones were positive for B+ lines, we found a sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 31% (95% CI 17–48%), 95% (95% CI 86–98%), 6.4 (95% CI 1.9–21), and 0.73 (95% CI 0.59–90), respectively. Observed agreement for the modified LuCUS protocol was 98% between coinvestigators, and kappa was 0.87 (95% CI 0.72–1). DISCUSSION Differentiating ADHF from other causes of acute dyspnea remains a challenge. Reliance on history, physical examination, and chest radiography can be misleading (4,23–25). US has been shown to outperform physical examination, chest radiography, brain natriuretic peptide, and bioimpedance in the diagnosis of ADHF, but may be limited by the time it takes to acquire images (4,26). In this secondary analysis, we found the modified LuCUS protocol to have 100% specificity for the diagnosis of ADHF. This protocol assessed for the presence of multiple B-lines in both the left and right anterosuperior lung zones, in combination with a poor to moderately reduced LVEF. In this study, all patients with a positive modified LuCUS scan had a final diagnosis of ADHF. When positive, these findings on bedside US can accurately guide acute disease-specific management without additional diagnostic imaging or laboratory studies. Numerous studies have assessed the accuracy of lung US alone for the diagnosis of ADHF, with sensitivities ranging from 58–100% and specificities ranging from 79–97% (7,16–18,27–30). However, these test characteristics are only obtained after interrogating all
eight lung zones or 26 intercostal spaces. The modified LuCUS protocol, in contrast, requires only three views, and is completed in a fraction of the time. Furthermore, the addition of a single cardiac view to the lung views would allow for identification of other, unanticipated causes of dyspnea, such as cardiac tamponade or signs of right ventricular dysfunction that may be suggestive of pulmonary embolism (10). Multiorgan US is sensitive and specific for the diagnosis of ADHF, but protocols entail performing a full lung and cardiac examination. In addition, some advocate for assessment for pleural effusion, valvular pathology, and diastolic dysfunction; while in certain clinical presentations these additional assessments may improve diagnostic accuracy, they also markedly increase the time required to complete the examination (10,11). The full LuCUS protocol, with 12 views (four intercostal spaces and the costophrenic recess in each hemithorax, plus four cardiac views) took an average of 12 6 4 min to complete. The modified LuCUS protocol can be completed in a more rapid manner. This is because the modified protocol not only requires only one quarter of the number of views, but it also omits the most timeintensive portions of the lung (costophrenic recesses) and cardiac (apical four-chamber view) examinations. Barriers to US implementation in a busy clinical environment include a lack of training and the length of time it takes to perform and interpret US examinations (13). In addition, some clinicians believe that the time or skill needed to become proficient in these US modalities is prohibitive. However, lung US is one of the easiest US examinations to perform with high feasibility and inter-rater reliability (28,31,32). While cardiac US can be more challenging, it is considered a core US modality, well within the scope and ability of all EPs (33). Prior studies have found that even with limited training, EPs can quickly obtain a parasternal long-axis view and reliably estimate LVEF(34,35). A benefit of point-of-care US that is often unrecognized by novice users is that incorporation early in the diagnostic process often saves a great deal of time. Using the modified LuCUS protocol for rapid identification of ADHF could allow clinicians to begin treatment and disposition patients within a few minutes of the initial evaluation rather than waiting for additional information, such as radiology and laboratory studies. The time not spent pondering a differential diagnosis could be used for other duties. This, in fact, could save clinicians time for other responsibilities. In addition, the cognitive unloading associated with arriving at a diagnosis and disposition may be beneficial to other patients in the ED concurrently, because multiple studies have shown a relationship between increased cognitive load and medical errors and treatment delays (36).
Modified LuCUS Protocol Saves Time in Diagnosis of AHF
The modified LuCUS protocol lacks sensitivity, meaning that if a patient did not have B+ lines in both of the anterosuperior lung zones, plus an LVEF <45%, ADHF could not be ruled out. This is similar to prior studies by Chiem et al. and Liteplo et al. finding 31% (95% CI 24-40%) and 40% (95% CI 21–61%) sensitivity for the diagnosis of ADHF using the anterosuperior lung zones alone, respectively (27,28). They concluded that if these lung zones were negative for B+ lines, additional assessment of the remaining lung zones would increase sensitivity. This additional assessment, evaluating LVEF plus these additional six lung zones, would take, on average, 6 min to complete (5,10,14). This stepwise approach would improve the sensitivity of this multiorgan protocol while being less time- and labor-intensive than the full LuCUS protocol. Only 9 of 36 patients with a final diagnosis of ADHF were correctly identified with the modified LuCUS protocol; the remaining 75% required additional testing. Thus, it could be argued that performing the modified LuCUS results in a net ‘‘waste’’ of time, because it will only be useful in 25% of patients with ADHF. We disagree with this proposition. The amount of time required to perform this protocol is minimal in comparison with the time required to obtain results of nearly any other diagnostic test used in the ED, and it can be performed at the bedside. Thus, we feel that it is time well spent, because it allows those patients with a positive study to rapidly receive diseasespecific therapy. Another reason the modified LuCUS protocol had decreased sensitivity is that two patients in our study had heart failure with preserved ejection fraction. Bedside US interpretations should be applied within the clinical context of the patient being evaluated, so if there remains high suspicion for ADHF and the patient has a normal ejection fraction, assessment of diastolic function should be considered. Isolated evaluation of the anterosuperior lung zones yielded a sensitivity and specificity of 31% and 95%, respectively, similar to prior literature (27,28). We found that the addition of a single cardiac view to the lung windows achieved a specificity of 100%, compared to 96–97% found in other studies (27,28). This means that, for a subset of patients presenting with undifferentiated dyspnea (nearly 10% in our study), the final diagnosis can be correctly identified almost immediately upon arrival to the ED; targeted therapy can be rapidly initiated. Given the prevalence of heart failure and the ease and rapidity of performance of the modified LuCUS protocol, we feel that its use is a critical, high-yield step in the evaluation of dyspnea.
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Limitations This study has several important limitations that may impact its validity or generalizability. This was a secondary analysis of data from a prospective observational study of a more in-depth US protocol. As such, the results—while promising—are meant to be hypothesisgenerating rather than interpreted as fact. Also, because this was a secondary analysis, we did not perform a sample size calculation. In addition, our study used a convenience sample of patients during daytime hours at a single, tertiary care, academic ED. Therefore, because of the potential for selection bias, it is possible, although unlikely, that our results may not be generalizable to other practice settings. US examinations in our study were performed by experienced sonographers. However, prior studies have found that performance and interpretation of lung and cardiac US is feasible and accurate even in novice learners (28,31,32,34,35). Despite being within the scope of practice for all EPs, sonographers in this study all had advanced US training (33). It is probable that many practicing physicians lack the training, comfort, or confidence to rapidly perform and interpret these examinations, thereby limiting the external validity of our results. Finally, our study is limited by its small sample size and the small number of patients with a final diagnosis of ADHF. Nevertheless, our finding of ADHF in approximately one-third of patients evaluated with undifferentiated dyspnea is consistent with prior studies (27,28). CONCLUSIONS The modified LuCUS protocol appeared in this pilot study to be 100% specific for the diagnosis of ADHF. This finding provides strong support for further testing of this modified protocol in a larger cohort of patients being evaluated in the ED to determine the cause of their undifferentiated dyspnea. Only if our findings are confirmed in a larger, adequately powered study would we advocate making clinical decisions based upon these results.
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Modified LuCUS Protocol Saves Time in Diagnosis of AHF
ARTICLE SUMMARY 1. Why is this topic important? Differentiating acutely decompensated heart failure (ADHF) from other causes of dyspnea can be challenging. Multiorgan ultrasound is accurate for differentiating ADHF from other etiologies of acute dyspnea, but many clinicians fail to perform ultrasound because of the perceived amount of time it takes to perform the examination. 2. What does this study attempt to show? In this study, we found the modified lung and cardiac ultrasound (LuCUS) protocol, defined as B+ lines in both the left and right anterosuperior lung zones, plus an left ventricular ejection fraction <45%, was 100% specific for the diagnosis of ADHF. 3. What are the key findings? In this study, the specificity of the modified LuCUS protocol was 100% (95% confidence interval 94–100%). This modified protocol takes on average 1 min and 32 sec to complete. 4. How is patient care impacted? When positive, these findings on clinical ultrasound can accurately and rapidly guide acute disease-specific management in patients with ADHF.
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http://dx.doi.org/10.1016/j.jemermed.2017.02.003
Ultrasound in Emergency Medicine
A MODIFIED LUNG AND CARDIAC ULTRASOUND PROTOCOL SAVES TIME AND RULES IN THE DIAGNOSIS OF ACUTE HEART FAILURE Frances M. Russell, MD*† and Robert R. Ehrman, MD*‡ *Department of Emergency Medicine, Cook County Hospital, Chicago, Illinois, †Department of Emergency Medicine, Indiana University School of Medicine, Indianapolis, Indiana, and ‡Department of Emergency Medicine, Wayne State University, Detroit, Michigan Corresponding Address: Frances M. Russell, MD, Department of Emergency Medicine, Indiana University School of Medicine, 720 Eskenazi Avenue, Fifth Third Faculty Office Building, 3rd Floor, Emergency Medicine Office, Indianapolis, IN 46202
, Abstract—Background: Multiorgan ultrasound (US), which includes evaluation of the lungs and heart, is an accurate method that outperforms clinical gestalt for diagnosing acutely decompensated heart failure (ADHF). A known barrier to ultrasound use is the time needed to perform these examinations. Objective: The primary goal of this study was to determine the test characteristics of a modified lung and cardiac US (LuCUS) protocol for the accurate diagnosis of ADHF. Methods: This was a secondary analysis of a prospective observational study that enrolled adult patients presenting to the emergency department with undifferentiated dyspnea. Intervention consisted of a modified LuCUS protocol performed by experienced emergency physician sonographers. A positive modified LuCUS protocol was defined as the presence of B+ lines in both the left and right anterosuperior lung zones, plus a left ventricular ejection fraction <45%. If all three of these findings were not present, the modified LuCUS result was interpreted as negative for ADHF. The primary objective was measured by comparing US findings to final diagnosis independently determined by two physicians, both blinded to US findings and each other’s final diagnosis. Results: We analyzed data on 99 patients; 36% had a final diagnosis of ADHF. The sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of the modified LuCUS protocol are 25% (95% confidence interval [CI] 14–41%), 100% (95% CI 94–100%), undefined, and 0.75 (95% CI 0.62–0.91%), respectively. This modified protocol takes on average 1 min and 32 sec to com-
plete. Conclusion: The point estimate for the specificity of the modified LuCUS protocol in this pilot study, accomplished by a reanalysis of data collected for a previously reported investigation of the full LuCUS protocol, was 100% for the diagnosis of ADHF. Published by Elsevier Inc. , Keywords—acute heart failure; bedside ultrasound; cardiac ultrasound; clinical ultrasound; diagnosis; emergency ultrasound; lung ultrasound; multiorgan ultrasound; undifferentiated dyspnea
INTRODUCTION Millions of Americans are evaluated in the emergency department (ED) for acute dyspnea (1). Determining the etiology of dyspnea can be challenging. Acute decompensated heart failure (ADHF) accounts for many of these presentations (2). A prompt and accurate diagnosis is imperative to guide acute management, avoid unnecessary medications, and avoid delays in care (3). The traditional work-up for ADHF, including physical examination findings, chest radiography, and serum brain natriuretic peptide, is not always diagnostic or helpful in determining the cause of dyspnea (4–9). Multiorgan ultrasound (US), including lung and cardiac sonography, is accurate for differentiating ADHF from other etiologies of acute dyspnea (10–12). Russell
Reprints are not available from the authors.
RECEIVED: 26 November 2016; FINAL SUBMISSION RECEIVED: 1 February 2017; ACCEPTED: 2 February 2017 1
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F. M. Russell and R. R. Ehrman
et al. found that the lung and cardiac US (LuCUS) protocol was more accurate for the diagnosis of ADHF when compared to clinical gestalt (10). In addition, they found that multiorgan US improved acute clinical management in approximately 50% of their patients—an impactful change, because disease-specific therapy may lead to improved outcomes (3). Multiorgan US may also identify alternative causes of dyspnea requiring different treatment than that required for ADHF. Despite knowing that bedside US may be the best modality for ruling in ADHF, many clinicians fail to perform US in the initial diagnostic evaluation of patients with undifferentiated dyspnea (4). One of the biggest barriers to implementation is the perceived amount of time it takes to perform a bedside sonographic examination (13). Multiorgan US, including a full lung and cardiac examination, can take anywhere from 10–15 min, which may not be ideal for a fast-paced and busy ED (10,14,15). Lung US alone, to detect pulmonary edema, is highly sensitive for ADHF, but lacks specificity, because diffuse B-lines can be seen in many other conditions (5,16–19). The addition of cardiac US greatly improves the specificity (10–12). The primary aim of this study was to determine the sensitivity, specificity, and likelihood ratios for diagnosing ADHF in patients in the ED with undifferentiated dyspnea using a modified LuCUS protocol. A positive modified LuCUS protocol scan was defined as B+ lines in both the left and right anterosuperior lung zones, plus an estimated left ventricular ejection fraction (LVEF) <45%. A scan was determined to be negative if all three of these criteria were not present. METHODS This study was a secondary analysis of the LuCUS protocol, a prospective, observational, single-center study that enrolled ED patients with acute undifferentiated dyspnea (10). This study of the LuCUS protocol was conducted at an urban tertiary care teaching hospital with >120,000 annual ED visits, from December 2012 to July 2013, and was approved by the institutional review board. The methods from that study have been published previously (10). A convenience sample of patients meeting the following inclusion criteria were enrolled: adult patients >18 years of age and a primary complaint of undifferentiated dyspnea according to their treating clinician. Undifferentiated dyspnea was defined as at least two possible etiologies in the differential diagnosis, and this did not have to include ADHF as a potential diagnosis. Patients were excluded if the treating clinician was confident in their diagnosis after initial assessment, if patients had an electrocardiogram showing ST segment elevation
myocardial infarction, if patients had been treated for ADHF for >30 min prior to US, if patients refused consent, or if patients had been previously enrolled in the study. The LuCUS protocol was performed and interpreted by three investigators; an emergency medicine US director and two emergency medicine US fellows. All sonographers had previously performed >1000 bedside sonograms, including lung and cardiac examinations. All investigators were required to scan five patients at bedside under the direct supervision of the principal investigator to ensure a standardized method of acquiring and interpreting images. Sonographers were blinded to the treating clinician’s initial assessment, medical comorbidities, and the results of laboratory tests or imaging studies performed during the ED encounter. The full LuCUS protocol interrogated four anterolateral lung zones in each hemithorax with a curvilinear probe to assess for the presence of B-lines. The costophrenic recess was examined bilaterally to assess for the presence of pleural effusion. The cardiac portion of the examination included parasternal long- and shortaxis views to assess ejection fraction, the subcostal view was used to assess inferior vena cava diameter and collapsibility, and the apical four-chamber view was used for assessment of diastolic function. The full protocol took an average of 12 min to complete (10). The Modified LuCUS Protocol Each sonographer conducted the scanning protocol using a Mindray M7 US machine (Mindray Bio-Medical Electronics Co., Shenzhen, China). The lung portion of the modified LuCUS examination interrogated the anterosuperior lung zones in each hemithorax with a curvilinear probe. Sonographers recorded the number of B-lines seen between two ribs in each lung zone. Three or more B-lines in a rib space were considered B+ lines. The cardiac portion of the modified LuCUS examination assessed the parasternal long axis view for LVEF. This was estimated qualitatively by assessing wall contraction and thickening (20,21). If EF could not be determined in the parasternal long axis view, it was assessed in the parasternal short, apical, or subxiphoid view. We defined a positive modified LuCUS protocol as B+ lines in both the left and right anterosuperior lung zones, plus an LVEF <45%. All three of these criteria had to be met for a positive study. A scan was determined to be modified LuCUS–negative if any or all three of these criteria were not met. The time to complete the modified LuCUS protocol was obtained by reviewing the time stamps on each US image included as part of the protocol. Timing started when the sonographer began recording the right
Modified LuCUS Protocol Saves Time in Diagnosis of AHF
anterosuperior lung zone and ended when they completed the parasternal long axis view of the examination. Total scan time included time to store all three images, and time to find the right windows for scanning the left anterosuperior lung zone and cardiac view for EF. Findings from the modified LuCUS protocol were documented on a standardized data collection form in real time. Demographic information, initial vital signs, admission diagnosis, and ED interventions were collected. This information was abstracted by research assistants who were trained in data abstraction according to recommendations from a previously published study (22). Abstractors were blinded to US results and final discharge diagnosis. Final diagnosis was determined independently by two emergency physicians (EPs) through a rigorous chart review, which served as our criterion standard. Chart reviewers followed previously published methods and determined each patient’s final diagnosis after reviewing laboratory results, imaging studies, medications administered, consults obtained, comprehensive echocardiography results, and discharge summaries (22). Each review was performed independently, and neither reviewer performed any of the US examinations for this study. If the reviewers disagreed, a third blinded reviewer served as the adjudicator.
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Data Analysis Sensitivity, specificity, positive likelihood ratios, and negative likelihood ratios were calculated and 95% confidence intervals (CIs) were derived using Microsoft Excel (Microsoft, Redmond, WA) and VassarStats software (available at http://vassarstats.net). Kappa and observed agreement were used to assess inter-rater reliability between coinvestigators’ interpretations of images. RESULTS We performed the complete LuCUS protocol on 104 patients who presented to the ED with undifferentiated dyspnea, and analyzed data on 99 patients. Five patients were excluded because of poor scanning windows and one patient dropped out of the study prior to completion. Patient characteristics are listed in Table 1. The flow of the study is presented in Figure 1. Thirty-six of 99 patients had a criterion standard diagnosis of ADHF. Of these 36, 25% (n = 9) were modified LuCUS–positive. All 63 patients who had an alternative final diagnosis were modified LuCUS–negative. The sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of the modified LuCUS protocol was 25% (95% CI 14–41%), 100% (95% CI 94–100%),
Table 1. Patient Characteristics, Dispositions, and Final Diagnoses
Age (years) 6 SD (range) Male, n (%) Medical comorbidities, n (%) Congestive heart failure COPD Coronary artery disease Hypertension Diabetes Smoking Vital signs, n (%) Hypotension (SBP <100 mm Hg) Tachycardia (HR >100 beats/min) Tachypnea (RR >20 breaths/min) Hypoxia (<92%) Disposition, n (%) ICU Floor Observation unit Home Final diagnosis, n (%) ADHF COPD Pneumonia Lung cancer Other
Modified LuCUS–Positive
ADHF
Total
n=9
n = 36
n = 99
53 6 12 (38–79) 8 (89)
57 6 14 (34–91) 23 (63.9)
56 6 13 (22–91) 55 (55.6)
6 (67) 2 (22) 2 (22) 7 (78) 2 (22) 3 (33)
23 (63.9) 12 (33.3) 6 (16.7) 30 (83) 11 (30.6) 6 (16.7)
40 (40.4) 43 (43.4) 16 (16.2) 68 (68.7) 29 (29.3) 21 (21.2)
0 (0) 4 (44) 7 (78) 2 (22)
3 (8.3) 15 (41.7) 16 (44.4) 4 (11.1)
5 (5.0) 36 (36.3) 44 (44.4) 12 (33.3)
1 (11) 6 (67) 2 (22) 0
3 (8.3) 26 (72.2) 4 (11.1) 3 (8.3)
9 (9.1) 64 (64.6) 9 (9.1) 16 (16.2)
36 (36) 24 (24) 10 (10) 7 (7) 23 (23)
ADHF = acutely decompensated heart failure; COPD = chronic obstructive pulmonary disease; ICU = intensive care unit; HR = heart rate; RR = respiratory rate; SBP = systolic blood pressure; LuCUS = lung and cardiac ultrasound protocol; SD = standard deviation.
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F. M. Russell and R. R. Ehrman
Figure 1. Flow diagram of enrolled patients, final diagnosis, and modified lung and cardiac ultrasound (LuCUS) findings. ADHF = acutely decompensated heart failure; ED = emergency department.
infinite, and 0.75 (95% CI 0.62–0.91%), respectively. This modified protocol took on average 1 min and 32 sec ( 6 23 sec) to complete. Secondarily, we evaluated sensitivity, specificity, and likelihood ratios of lung US alone, using the anterosuperior lung zones in each hemithorax. When both the left and right anterosuperior lung zones were positive for B+ lines, we found a sensitivity, specificity, positive likelihood ratio, and negative likelihood ratio of 31% (95% CI 17–48%), 95% (95% CI 86–98%), 6.4 (95% CI 1.9–21), and 0.73 (95% CI 0.59–90), respectively. Observed agreement for the modified LuCUS protocol was 98% between coinvestigators, and kappa was 0.87 (95% CI 0.72–1). DISCUSSION Differentiating ADHF from other causes of acute dyspnea remains a challenge. Reliance on history, physical examination, and chest radiography can be misleading (4,23–25). US has been shown to outperform physical examination, chest radiography, brain natriuretic peptide, and bioimpedance in the diagnosis of ADHF, but may be limited by the time it takes to acquire images (4,26). In this secondary analysis, we found the modified LuCUS protocol to have 100% specificity for the diagnosis of ADHF. This protocol assessed for the presence of multiple B-lines in both the left and right anterosuperior lung zones, in combination with a poor to moderately reduced LVEF. In this study, all patients with a positive modified LuCUS scan had a final diagnosis of ADHF. When positive, these findings on bedside US can accurately guide acute disease-specific management without additional diagnostic imaging or laboratory studies. Numerous studies have assessed the accuracy of lung US alone for the diagnosis of ADHF, with sensitivities ranging from 58–100% and specificities ranging from 79–97% (7,16–18,27–30). However, these test characteristics are only obtained after interrogating all
eight lung zones or 26 intercostal spaces. The modified LuCUS protocol, in contrast, requires only three views, and is completed in a fraction of the time. Furthermore, the addition of a single cardiac view to the lung views would allow for identification of other, unanticipated causes of dyspnea, such as cardiac tamponade or signs of right ventricular dysfunction that may be suggestive of pulmonary embolism (10). Multiorgan US is sensitive and specific for the diagnosis of ADHF, but protocols entail performing a full lung and cardiac examination. In addition, some advocate for assessment for pleural effusion, valvular pathology, and diastolic dysfunction; while in certain clinical presentations these additional assessments may improve diagnostic accuracy, they also markedly increase the time required to complete the examination (10,11). The full LuCUS protocol, with 12 views (four intercostal spaces and the costophrenic recess in each hemithorax, plus four cardiac views) took an average of 12 6 4 min to complete. The modified LuCUS protocol can be completed in a more rapid manner. This is because the modified protocol not only requires only one quarter of the number of views, but it also omits the most timeintensive portions of the lung (costophrenic recesses) and cardiac (apical four-chamber view) examinations. Barriers to US implementation in a busy clinical environment include a lack of training and the length of time it takes to perform and interpret US examinations (13). In addition, some clinicians believe that the time or skill needed to become proficient in these US modalities is prohibitive. However, lung US is one of the easiest US examinations to perform with high feasibility and inter-rater reliability (28,31,32). While cardiac US can be more challenging, it is considered a core US modality, well within the scope and ability of all EPs (33). Prior studies have found that even with limited training, EPs can quickly obtain a parasternal long-axis view and reliably estimate LVEF(34,35). A benefit of point-of-care US that is often unrecognized by novice users is that incorporation early in the diagnostic process often saves a great deal of time. Using the modified LuCUS protocol for rapid identification of ADHF could allow clinicians to begin treatment and disposition patients within a few minutes of the initial evaluation rather than waiting for additional information, such as radiology and laboratory studies. The time not spent pondering a differential diagnosis could be used for other duties. This, in fact, could save clinicians time for other responsibilities. In addition, the cognitive unloading associated with arriving at a diagnosis and disposition may be beneficial to other patients in the ED concurrently, because multiple studies have shown a relationship between increased cognitive load and medical errors and treatment delays (36).
Modified LuCUS Protocol Saves Time in Diagnosis of AHF
The modified LuCUS protocol lacks sensitivity, meaning that if a patient did not have B+ lines in both of the anterosuperior lung zones, plus an LVEF <45%, ADHF could not be ruled out. This is similar to prior studies by Chiem et al. and Liteplo et al. finding 31% (95% CI 24-40%) and 40% (95% CI 21–61%) sensitivity for the diagnosis of ADHF using the anterosuperior lung zones alone, respectively (27,28). They concluded that if these lung zones were negative for B+ lines, additional assessment of the remaining lung zones would increase sensitivity. This additional assessment, evaluating LVEF plus these additional six lung zones, would take, on average, 6 min to complete (5,10,14). This stepwise approach would improve the sensitivity of this multiorgan protocol while being less time- and labor-intensive than the full LuCUS protocol. Only 9 of 36 patients with a final diagnosis of ADHF were correctly identified with the modified LuCUS protocol; the remaining 75% required additional testing. Thus, it could be argued that performing the modified LuCUS results in a net ‘‘waste’’ of time, because it will only be useful in 25% of patients with ADHF. We disagree with this proposition. The amount of time required to perform this protocol is minimal in comparison with the time required to obtain results of nearly any other diagnostic test used in the ED, and it can be performed at the bedside. Thus, we feel that it is time well spent, because it allows those patients with a positive study to rapidly receive diseasespecific therapy. Another reason the modified LuCUS protocol had decreased sensitivity is that two patients in our study had heart failure with preserved ejection fraction. Bedside US interpretations should be applied within the clinical context of the patient being evaluated, so if there remains high suspicion for ADHF and the patient has a normal ejection fraction, assessment of diastolic function should be considered. Isolated evaluation of the anterosuperior lung zones yielded a sensitivity and specificity of 31% and 95%, respectively, similar to prior literature (27,28). We found that the addition of a single cardiac view to the lung windows achieved a specificity of 100%, compared to 96–97% found in other studies (27,28). This means that, for a subset of patients presenting with undifferentiated dyspnea (nearly 10% in our study), the final diagnosis can be correctly identified almost immediately upon arrival to the ED; targeted therapy can be rapidly initiated. Given the prevalence of heart failure and the ease and rapidity of performance of the modified LuCUS protocol, we feel that its use is a critical, high-yield step in the evaluation of dyspnea.
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Limitations This study has several important limitations that may impact its validity or generalizability. This was a secondary analysis of data from a prospective observational study of a more in-depth US protocol. As such, the results—while promising—are meant to be hypothesisgenerating rather than interpreted as fact. Also, because this was a secondary analysis, we did not perform a sample size calculation. In addition, our study used a convenience sample of patients during daytime hours at a single, tertiary care, academic ED. Therefore, because of the potential for selection bias, it is possible, although unlikely, that our results may not be generalizable to other practice settings. US examinations in our study were performed by experienced sonographers. However, prior studies have found that performance and interpretation of lung and cardiac US is feasible and accurate even in novice learners (28,31,32,34,35). Despite being within the scope of practice for all EPs, sonographers in this study all had advanced US training (33). It is probable that many practicing physicians lack the training, comfort, or confidence to rapidly perform and interpret these examinations, thereby limiting the external validity of our results. Finally, our study is limited by its small sample size and the small number of patients with a final diagnosis of ADHF. Nevertheless, our finding of ADHF in approximately one-third of patients evaluated with undifferentiated dyspnea is consistent with prior studies (27,28). CONCLUSIONS The modified LuCUS protocol appeared in this pilot study to be 100% specific for the diagnosis of ADHF. This finding provides strong support for further testing of this modified protocol in a larger cohort of patients being evaluated in the ED to determine the cause of their undifferentiated dyspnea. Only if our findings are confirmed in a larger, adequately powered study would we advocate making clinical decisions based upon these results.
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Modified LuCUS Protocol Saves Time in Diagnosis of AHF
ARTICLE SUMMARY 1. Why is this topic important? Differentiating acutely decompensated heart failure (ADHF) from other causes of dyspnea can be challenging. Multiorgan ultrasound is accurate for differentiating ADHF from other etiologies of acute dyspnea, but many clinicians fail to perform ultrasound because of the perceived amount of time it takes to perform the examination. 2. What does this study attempt to show? In this study, we found the modified lung and cardiac ultrasound (LuCUS) protocol, defined as B+ lines in both the left and right anterosuperior lung zones, plus an left ventricular ejection fraction <45%, was 100% specific for the diagnosis of ADHF. 3. What are the key findings? In this study, the specificity of the modified LuCUS protocol was 100% (95% confidence interval 94–100%). This modified protocol takes on average 1 min and 32 sec to complete. 4. How is patient care impacted? When positive, these findings on clinical ultrasound can accurately and rapidly guide acute disease-specific management in patients with ADHF.
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