- Email: [email protected]
Resolution of sonographic B-lines as a measure of pulmonary decongestion in acute heart failure
Resolution of Sonographic B-Lines as a Measure of Pulmonary Decongestion in Acute Heart Failure Jennifer L. Martindale MD PII: DOI: Reference:
S0735-6757(16)00247-3 doi: 10.1016/j.ajem.2016.03.043 YAJEM 55692
To appear in:
American Journal of Emergency Medicine
Received date: Revised date: Accepted date:
20 February 2016 17 March 2016 17 March 2016
Please cite this article as: Martindale Jennifer L., Resolution of Sonographic B-Lines as a Measure of Pulmonary Decongestion in Acute Heart Failure, American Journal of Emergency Medicine (2016), doi: 10.1016/j.ajem.2016.03.043
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Title: Resolution of Sonographic B-Lines as a Measure of Pulmonary Decongestion in Acute Heart Failure
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Author: Jennifer L. Martindale, MD Department of Emergency Medicine, SUNY Downstate/Kings County Hospital, Brooklyn, NY 11203
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Corresponding Author: Jennifer L Martindale, MD SUNY Downstate Medical Center Department of Emergency Medicine 450 Clarkson Ave Brooklyn, NY 11203 Ph: 718-270-4580 Email: [email protected]
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Keywords: heart failure, pulmonary edema
ACCEPTED MANUSCRIPT Abstract Objective non-invasive measures of dyspnea in patients with acute heart failure are lacking. In this review
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we describe lung ultrasound as a tool to estimate the degree of pulmonary congestion in patients
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presenting with acute heart failure and to monitor therapeutic efficacy. Serial semi-quantitative measures of sonographic B-lines in acute heart failure patients can be converted to pulmonary edema scores
SC
obtained at admission and hospital discharge. These scores provide prognostic information for short-term
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clinical outcomes. Lung ultrasound has the potential to measure changes in pulmonary edema during
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Keywords: heart failure, pulmonary edema
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acute heart failure management and improve risk stratification.
ACCEPTED MANUSCRIPT 1. Introduction Dyspnea is the most common complaint prompting acute heart failure (AHF) patients to seek
T
emergency care [1,2]. Improvement in dyspnea is an important clinical goal in the management of AHF,
RI P
and it serves as a primary endpoint in therapeutic trials. As a surrogate marker of clinical improvement, however, change in dyspnea severity may be an inadequate measure of response to therapy for several
SC
reasons. Dyspnea is subjective and language used to describe dyspnea is subject to cultural and racial
NU
differences [3]. The most prevalent instruments used to measure dyspnea, visual analog and Likert scales, have poor inter-scale reliability [4-6]. A more objective and direct measure of the primary
MA
pathophysiologic derangement underlying dyspnea could help clinicians more accurately assess clinical improvement and readiness for discharge in AHF patients.
ED
Pulmonary congestion is most often the primary cause of dyspnea in AHF patients. The chest radiograph is the conventional tool used for identifying pulmonary congestion in acutely dyspneic
PT
patients. Radiographic signs of pulmonary congestion, however, are insensitive [7], subject to high inter-
CE
observer variability [8], and slow to improve with changes in pulmonary capillary wedge pressure. Lung ultrasound identifies pulmonary congestion with high sensitivity and is helpful in discriminating AHF
AC
from other causes of dyspnea in emergency department patients [9,10]. In the presence of extravascular pulmonary fluid, vertical hyperechoic artifacts called B-lines arise from the pleural line and extend to the bottom of the screen. When distributed diffusely, B-lines represent cardiogenic pulmonary congestion. Beyond its diagnostic value, lung ultrasound may be useful as a tool that can semi-quantitatively measure AHF severity. A higher density of B-lines has been shown to correlate with other measures of AHF severity including pulmonary capillary wedge pressure [11], echocardiographic evidence of diastolic dysfunction [12], and natriuretic peptide levels [13]. Serial measures of B-lines have also been shown to decrease in response to acute heart failure treatment [12,14,15]. This article describes current approaches to measuring sonographic pulmonary congestion and the available evidence supporting roles for lung ultrasound in monitoring response to therapy and predicting clinical outcomes.
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2. Discussion
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The potential of lung ultrasound as a tool to objectively measure the resolution of pulmonary edema in AHF patients during treatment has not been fully realized. Attributes that make lung ultrasound
SC
a potential modality for monitoring therapeutic progress include its feasibility, ease of use by novice
MA
reflect changes in pulmonary edema in real time.
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sonographers [16], the short time required for imaging and analysis (less than 5 minutes), and its ability to
2.1. Scanning Protocols
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Lung ultrasound is performed by obtaining longitudinal scans of the intercostal space with phased
PT
array or curvilinear probes set to a depth of approximately 15 cm. Scanning protocols for quantifying Blines differ by the number and designation of anatomic thoracic zones scanned. The most common and
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exhaustive protocol is based on scanning 28 lung zones (Figure 1A) [11,12,15,17-20]. The right hemithorax is scanned from the second to the fifth intercostal spaces along parasternal, midclavicular,
AC
anterior axillary, and mid-axillary lines. The left hemithorax is scanned from the second to the fourth intercostal spaces along the same vertical lines. The time required for performing this 28-zone scan has been reported to range from less than 3 minutes [12,17] to 10-15 minutes [18], but this approach may be more challenging to incorporate into routine clinical practice. A simpler protocol is based on scanning 8 thoracic lung zones (4 anterior and 4 lateral, as described by Volipicelli [21]) (Figure 1B). Anatomic zones in this protocol are defined by vertical lines through the sternum, anterior axillary line and posterior axillary line and by horizontal lines through the clavicle, third intercostal space, and the diaphragm. The presence of three or more B-lines in an intercostal space is considered pathologic and defines the corresponding anatomic zone as positive. For diagnostic purposes, a positive lung ultrasound
ACCEPTED MANUSCRIPT demonstrating diffuse pulmonary edema is defined by the presence of at least two bilateral positive lung zones [20].
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Body positioning may affect the severity and distribution of B-lines, as B-lines have shown to be
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more numerous in the supine position compared to an upright position [22]. Whether B-line scores obtained in supine patients [12,15,23,24] apply to those obtained in severely dyspneic heart failure
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patients unable tolerate recumbent positioning is unknown.
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2.2. Quantifying B-Lines
B-lines are defined as discrete hyperechoic vertical lines [25]. The most prevalent method of
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quantifying B-lines is to sum the number of discrete B-lines in an intercostal space [11,17-19]. The sum total of scores obtained from all thoracic zones yields an overall B-line score. In the setting of severe
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pulmonary edema, counting B-lines becomes less straightforward because B-lines fuse together (Figure
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2). An intercostal space may be occupied entirely by a single, wide hyperechoic B-line extending from the pleural line when coalescence is complete, producing an image described as “white lung” [26].
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Assuming that B-line fusion represents a more severe form of pulmonary edema, information is likely lost by regarding fused lines the same as discrete lines. One alternative approach discussed by Volpicelli et al [20] to quantifying the fused B-line is to estimate the percentage of intercostal space filled with confluent B-lines and dividing this percentage by 10. This number is then added to any additional discrete B-lines visualized in the intercostal space. This may be a more reliable method described for quantifying B-line severity. The interclass correlation coefficient for quantifying B-lines on lung ultrasound has been shown to be highest (ICC=0.89; 95% CI, 0.87-0.91) when confluent B-lines are counted as the percentage of rib space filled and added to any other B-lines visualized in a single static image [27].
ACCEPTED MANUSCRIPT The simplest method as described by Volpicelli et al [23] of quantifying B-line severity is based on the sum of the number of positive lung zones. A positive lung zone is defined by a minimum of three
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B-lines per intercostal space.
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2.3. Resolution of Sonographic B-Lines
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Lung ultrasound offers a real-time assessment of pulmonary congestion. Serial lung ultrasound can capture rapid changes in pulmonary congestion. Several studies performed in patients with end-stage
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renal disease have demonstrated that lung ultrasound can detect dynamic changes in B-lines in response to volume removed during a single hemodialysis session [18,28-31]. The majority of the patients in these
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studies who were found to have sonographic pulmonary congestion prior to hemodialysis [18,28,29,31] were asymptomatic, suggesting that lung ultrasound detects subclinical pulmonary congestion.
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B-lines clear in response to inpatient treatment of acute heart failure. In a cohort of 100 patients
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admitted for AHF, B-line scores obtained using the sum of individual B-lines across 28 lung zones significantly improved before hospital discharge (48 48 vs. 20 23, p<0.0001) [15]. In an earlier study
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by Frassi et al [12], a similar decrease in B-lines during AHF hospitalization was observed in a group of 70 patients whose New York Heart Association (NYHA) functional classification improved by at least 1 point (42 to 15, p<0.0001). In patients whose heart failure worsened or failed to clinically improve, B-line scores scores were not significantly (p > 0.05) different between admission (37 B-lines) and discharge (25 B-lines).
ACCEPTED MANUSCRIPT Resolution of sonographic pulmonary edema in AHF patients can be detected by scanning fewer lung zones and dichotomizing lung zones as positive or negative in place of counting individual B-lines.
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Volpicelli et al [14] showed that the total number of positive lung zones based on an 11-zone thoracic
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scanning protocol significantly decreased by 76.3% (P<0.001). In this study, lateral-basal lung zones continued to demonstrate pulmonary edema in 29% of patients at the time of discharge. Excluding these
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zones yielded a sonographic score that correlated better with clinical and radiographic improvement. Sonographic scores in this study correlated well with BNP, but the change in sonographic scores did not
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correlate with BNP changes.
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Failure of sonographic B-lines to improve during treatment targeting acute heart failure may represent suboptimal AHF treatment or point to other causes of dyspnea. Sonographic B-lines are not
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specific for cardiogenic pulmonary congestion. Other etiologies of a diffuse B-line pattern including bilateral pneumonia, pulmonary fibrosis, and acute respiratory distress syndrome (ARDS) should be
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reconsidered when B-lines persist in spite of diuretic or vasodilator therapy.
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2.4. Prognostic Value of B-Lines at Hospital Discharge Persistence of B-lines at the time of hospital discharge in patients with acute heart failure may represent subclinical pulmonary edema and predict poor clinical outcomes. Two inpatient studies by Gargani et al [15] and Coiro et al [32] have found that residual pulmonary congestion detected on ultrasound is an independent predictor of all-cause mortality and rehospitalization for acute heart failure [15,32]. In the study by Gargani et al [15] a B-line sum of 15 (using the 28-zone scanning method) was the only independent predictor of 6-month readmission in 100 patients hospitalized for acute heart failure (Hazard Ratio 11.74; 95% CI 1.30-160.16). Readmission within 3 months of discharge was best predicted with a cutoff of 20 B-lines at discharge (negative likelihood ratio of 0, positive likelihood ratio 3.96).
ACCEPTED MANUSCRIPT Coiro et al [32], demonstrated that the presence of 30 or more B-lines (using the 28-zone method) best predicted 3-month heart failure readmission (Hazard Ratio 8.12 [95% CI, 2.06-32.13]). B-lines at
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discharge improved risk stratification beyond that based on BNP results or NYHA class. A secondary
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analysis based on regrouping the video clips from 28 scanning sites into the 8 zones described by Volpicelli et al [21] was performed in this study. Patients with one or more bilateral positive lung zones
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(defined by the presence of greater than 2 B-lines in an intercostal space) were predictably at greater risk for 3-month heart failure readmission (Hazard Ratio 4.1, [95% CI 1.2-14.6]) using multivariable analysis.
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The prognostic value of pulmonary congestion in patients with chronic congestive heart failure in the
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outpatient setting has also been investigated. Patients with a greater sum of B-lines counted across 8 lung zones have been shown to be at greater risk for 6-month mortality and heart failure readmission [33].
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Thirty-day morality and hospital readmission in patients with acute heart failure are 10.7% [34] and (in Medicare patients) 27% [35], respectively. Clearly there is a need for improved risk stratification
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for patients who present to the emergency department with acute heart failure. Lung ultrasound has the
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potential to identify a low-risk group of patients that can be safely discharged from the emergency department, observation unit, or inpatient ward. Resolution of sonographic pulmonary edema has the
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potential to serve as a target for inpatient heart failure therapy. Whether clearance of B-lines improves short-term mortality and heart failure readmission rates compared to targeted improvement of dyspnea has yet to be determined.
ACCEPTED MANUSCRIPT 3. Conclusions While lung ultrasound has an established role in the diagnosis of acute heart failure, its use in
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heart failure management is undefined. Several studies have investigated the application of serial lung
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ultrasound to detect dynamic changes in pulmonary edema. Research methods vary by transducer type, number of thoracic zones scanned, and B-line scoring approaches. The ability of lung ultrasound to
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detect dynamic changes in edema severity and predict short-term clinical outcomes depends on how well
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B-lines can be semi-quantitatively measured. The sum of individual B-lines or positive lung zones may suffice as a measure to detect significant changes in pulmonary edema, but a sonographic score that
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incorporates B-line coalescence may capture more severe degrees of pulmonary edema and provide added predictive value. More research is required to develop a standardized approach to performing and
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interpreting lung ultrasound that can be readily incorporated into clinical practice. Given the current limitations inherent in our clinical assessment of pulmonary decongestion, lung ultrasound will play a
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greater role in the evaluation of patients with acute heart failure.
ACCEPTED MANUSCRIPT Figure Legends Figure 1. A. 28-zone scanning protocol. The second to fourth intercostal spaces on the left hemithorax
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and second to fifth intercostal spaces on the right hemithorax are scanned at the parasternal,
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midclavicular, anterior axillary, and midaxillary lines. B. The 8-zone scanning protocol. The third intercostal space divides upper and lower zones of the chest and the anterior axillary line divides the
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anterior and lateral zones in each hemithorax.
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Figure 2. Lung ultrasound clips showing varying degrees of pulmonary edema in a single intercostal space. A. Normal lung. B-lines are absent. Horizontal lines called A-lines run parallel to the pleural line.
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B. Pulmonary edema. Several discrete B-lines extend from the pleural line to the bottom of the screen. C. Severe pulmonary edema. B-lines have coalesced into a single hyperechoic band extending from the
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pleura.
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Fig. 2
S0735-6757(16)00247-3 doi: 10.1016/j.ajem.2016.03.043 YAJEM 55692
To appear in:
American Journal of Emergency Medicine
Received date: Revised date: Accepted date:
20 February 2016 17 March 2016 17 March 2016
Please cite this article as: Martindale Jennifer L., Resolution of Sonographic B-Lines as a Measure of Pulmonary Decongestion in Acute Heart Failure, American Journal of Emergency Medicine (2016), doi: 10.1016/j.ajem.2016.03.043
This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain.
ACCEPTED MANUSCRIPT Title: Resolution of Sonographic B-Lines as a Measure of Pulmonary Decongestion in Acute Heart Failure
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Author: Jennifer L. Martindale, MD Department of Emergency Medicine, SUNY Downstate/Kings County Hospital, Brooklyn, NY 11203
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Corresponding Author: Jennifer L Martindale, MD SUNY Downstate Medical Center Department of Emergency Medicine 450 Clarkson Ave Brooklyn, NY 11203 Ph: 718-270-4580 Email: [email protected]
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Keywords: heart failure, pulmonary edema
ACCEPTED MANUSCRIPT Abstract Objective non-invasive measures of dyspnea in patients with acute heart failure are lacking. In this review
T
we describe lung ultrasound as a tool to estimate the degree of pulmonary congestion in patients
RI P
presenting with acute heart failure and to monitor therapeutic efficacy. Serial semi-quantitative measures of sonographic B-lines in acute heart failure patients can be converted to pulmonary edema scores
SC
obtained at admission and hospital discharge. These scores provide prognostic information for short-term
NU
clinical outcomes. Lung ultrasound has the potential to measure changes in pulmonary edema during
AC
CE
PT
ED
Keywords: heart failure, pulmonary edema
MA
acute heart failure management and improve risk stratification.
ACCEPTED MANUSCRIPT 1. Introduction Dyspnea is the most common complaint prompting acute heart failure (AHF) patients to seek
T
emergency care [1,2]. Improvement in dyspnea is an important clinical goal in the management of AHF,
RI P
and it serves as a primary endpoint in therapeutic trials. As a surrogate marker of clinical improvement, however, change in dyspnea severity may be an inadequate measure of response to therapy for several
SC
reasons. Dyspnea is subjective and language used to describe dyspnea is subject to cultural and racial
NU
differences [3]. The most prevalent instruments used to measure dyspnea, visual analog and Likert scales, have poor inter-scale reliability [4-6]. A more objective and direct measure of the primary
MA
pathophysiologic derangement underlying dyspnea could help clinicians more accurately assess clinical improvement and readiness for discharge in AHF patients.
ED
Pulmonary congestion is most often the primary cause of dyspnea in AHF patients. The chest radiograph is the conventional tool used for identifying pulmonary congestion in acutely dyspneic
PT
patients. Radiographic signs of pulmonary congestion, however, are insensitive [7], subject to high inter-
CE
observer variability [8], and slow to improve with changes in pulmonary capillary wedge pressure. Lung ultrasound identifies pulmonary congestion with high sensitivity and is helpful in discriminating AHF
AC
from other causes of dyspnea in emergency department patients [9,10]. In the presence of extravascular pulmonary fluid, vertical hyperechoic artifacts called B-lines arise from the pleural line and extend to the bottom of the screen. When distributed diffusely, B-lines represent cardiogenic pulmonary congestion. Beyond its diagnostic value, lung ultrasound may be useful as a tool that can semi-quantitatively measure AHF severity. A higher density of B-lines has been shown to correlate with other measures of AHF severity including pulmonary capillary wedge pressure [11], echocardiographic evidence of diastolic dysfunction [12], and natriuretic peptide levels [13]. Serial measures of B-lines have also been shown to decrease in response to acute heart failure treatment [12,14,15]. This article describes current approaches to measuring sonographic pulmonary congestion and the available evidence supporting roles for lung ultrasound in monitoring response to therapy and predicting clinical outcomes.
ACCEPTED MANUSCRIPT
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2. Discussion
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The potential of lung ultrasound as a tool to objectively measure the resolution of pulmonary edema in AHF patients during treatment has not been fully realized. Attributes that make lung ultrasound
SC
a potential modality for monitoring therapeutic progress include its feasibility, ease of use by novice
MA
reflect changes in pulmonary edema in real time.
NU
sonographers [16], the short time required for imaging and analysis (less than 5 minutes), and its ability to
2.1. Scanning Protocols
ED
Lung ultrasound is performed by obtaining longitudinal scans of the intercostal space with phased
PT
array or curvilinear probes set to a depth of approximately 15 cm. Scanning protocols for quantifying Blines differ by the number and designation of anatomic thoracic zones scanned. The most common and
CE
exhaustive protocol is based on scanning 28 lung zones (Figure 1A) [11,12,15,17-20]. The right hemithorax is scanned from the second to the fifth intercostal spaces along parasternal, midclavicular,
AC
anterior axillary, and mid-axillary lines. The left hemithorax is scanned from the second to the fourth intercostal spaces along the same vertical lines. The time required for performing this 28-zone scan has been reported to range from less than 3 minutes [12,17] to 10-15 minutes [18], but this approach may be more challenging to incorporate into routine clinical practice. A simpler protocol is based on scanning 8 thoracic lung zones (4 anterior and 4 lateral, as described by Volipicelli [21]) (Figure 1B). Anatomic zones in this protocol are defined by vertical lines through the sternum, anterior axillary line and posterior axillary line and by horizontal lines through the clavicle, third intercostal space, and the diaphragm. The presence of three or more B-lines in an intercostal space is considered pathologic and defines the corresponding anatomic zone as positive. For diagnostic purposes, a positive lung ultrasound
ACCEPTED MANUSCRIPT demonstrating diffuse pulmonary edema is defined by the presence of at least two bilateral positive lung zones [20].
T
Body positioning may affect the severity and distribution of B-lines, as B-lines have shown to be
RI P
more numerous in the supine position compared to an upright position [22]. Whether B-line scores obtained in supine patients [12,15,23,24] apply to those obtained in severely dyspneic heart failure
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SC
patients unable tolerate recumbent positioning is unknown.
MA
2.2. Quantifying B-Lines
B-lines are defined as discrete hyperechoic vertical lines [25]. The most prevalent method of
ED
quantifying B-lines is to sum the number of discrete B-lines in an intercostal space [11,17-19]. The sum total of scores obtained from all thoracic zones yields an overall B-line score. In the setting of severe
PT
pulmonary edema, counting B-lines becomes less straightforward because B-lines fuse together (Figure
CE
2). An intercostal space may be occupied entirely by a single, wide hyperechoic B-line extending from the pleural line when coalescence is complete, producing an image described as “white lung” [26].
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Assuming that B-line fusion represents a more severe form of pulmonary edema, information is likely lost by regarding fused lines the same as discrete lines. One alternative approach discussed by Volpicelli et al [20] to quantifying the fused B-line is to estimate the percentage of intercostal space filled with confluent B-lines and dividing this percentage by 10. This number is then added to any additional discrete B-lines visualized in the intercostal space. This may be a more reliable method described for quantifying B-line severity. The interclass correlation coefficient for quantifying B-lines on lung ultrasound has been shown to be highest (ICC=0.89; 95% CI, 0.87-0.91) when confluent B-lines are counted as the percentage of rib space filled and added to any other B-lines visualized in a single static image [27].
ACCEPTED MANUSCRIPT The simplest method as described by Volpicelli et al [23] of quantifying B-line severity is based on the sum of the number of positive lung zones. A positive lung zone is defined by a minimum of three
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B-lines per intercostal space.
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2.3. Resolution of Sonographic B-Lines
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Lung ultrasound offers a real-time assessment of pulmonary congestion. Serial lung ultrasound can capture rapid changes in pulmonary congestion. Several studies performed in patients with end-stage
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renal disease have demonstrated that lung ultrasound can detect dynamic changes in B-lines in response to volume removed during a single hemodialysis session [18,28-31]. The majority of the patients in these
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studies who were found to have sonographic pulmonary congestion prior to hemodialysis [18,28,29,31] were asymptomatic, suggesting that lung ultrasound detects subclinical pulmonary congestion.
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B-lines clear in response to inpatient treatment of acute heart failure. In a cohort of 100 patients
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admitted for AHF, B-line scores obtained using the sum of individual B-lines across 28 lung zones significantly improved before hospital discharge (48 48 vs. 20 23, p<0.0001) [15]. In an earlier study
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by Frassi et al [12], a similar decrease in B-lines during AHF hospitalization was observed in a group of 70 patients whose New York Heart Association (NYHA) functional classification improved by at least 1 point (42 to 15, p<0.0001). In patients whose heart failure worsened or failed to clinically improve, B-line scores scores were not significantly (p > 0.05) different between admission (37 B-lines) and discharge (25 B-lines).
ACCEPTED MANUSCRIPT Resolution of sonographic pulmonary edema in AHF patients can be detected by scanning fewer lung zones and dichotomizing lung zones as positive or negative in place of counting individual B-lines.
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Volpicelli et al [14] showed that the total number of positive lung zones based on an 11-zone thoracic
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scanning protocol significantly decreased by 76.3% (P<0.001). In this study, lateral-basal lung zones continued to demonstrate pulmonary edema in 29% of patients at the time of discharge. Excluding these
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zones yielded a sonographic score that correlated better with clinical and radiographic improvement. Sonographic scores in this study correlated well with BNP, but the change in sonographic scores did not
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correlate with BNP changes.
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Failure of sonographic B-lines to improve during treatment targeting acute heart failure may represent suboptimal AHF treatment or point to other causes of dyspnea. Sonographic B-lines are not
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specific for cardiogenic pulmonary congestion. Other etiologies of a diffuse B-line pattern including bilateral pneumonia, pulmonary fibrosis, and acute respiratory distress syndrome (ARDS) should be
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reconsidered when B-lines persist in spite of diuretic or vasodilator therapy.
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2.4. Prognostic Value of B-Lines at Hospital Discharge Persistence of B-lines at the time of hospital discharge in patients with acute heart failure may represent subclinical pulmonary edema and predict poor clinical outcomes. Two inpatient studies by Gargani et al [15] and Coiro et al [32] have found that residual pulmonary congestion detected on ultrasound is an independent predictor of all-cause mortality and rehospitalization for acute heart failure [15,32]. In the study by Gargani et al [15] a B-line sum of 15 (using the 28-zone scanning method) was the only independent predictor of 6-month readmission in 100 patients hospitalized for acute heart failure (Hazard Ratio 11.74; 95% CI 1.30-160.16). Readmission within 3 months of discharge was best predicted with a cutoff of 20 B-lines at discharge (negative likelihood ratio of 0, positive likelihood ratio 3.96).
ACCEPTED MANUSCRIPT Coiro et al [32], demonstrated that the presence of 30 or more B-lines (using the 28-zone method) best predicted 3-month heart failure readmission (Hazard Ratio 8.12 [95% CI, 2.06-32.13]). B-lines at
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discharge improved risk stratification beyond that based on BNP results or NYHA class. A secondary
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analysis based on regrouping the video clips from 28 scanning sites into the 8 zones described by Volpicelli et al [21] was performed in this study. Patients with one or more bilateral positive lung zones
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(defined by the presence of greater than 2 B-lines in an intercostal space) were predictably at greater risk for 3-month heart failure readmission (Hazard Ratio 4.1, [95% CI 1.2-14.6]) using multivariable analysis.
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The prognostic value of pulmonary congestion in patients with chronic congestive heart failure in the
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outpatient setting has also been investigated. Patients with a greater sum of B-lines counted across 8 lung zones have been shown to be at greater risk for 6-month mortality and heart failure readmission [33].
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Thirty-day morality and hospital readmission in patients with acute heart failure are 10.7% [34] and (in Medicare patients) 27% [35], respectively. Clearly there is a need for improved risk stratification
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for patients who present to the emergency department with acute heart failure. Lung ultrasound has the
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potential to identify a low-risk group of patients that can be safely discharged from the emergency department, observation unit, or inpatient ward. Resolution of sonographic pulmonary edema has the
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potential to serve as a target for inpatient heart failure therapy. Whether clearance of B-lines improves short-term mortality and heart failure readmission rates compared to targeted improvement of dyspnea has yet to be determined.
ACCEPTED MANUSCRIPT 3. Conclusions While lung ultrasound has an established role in the diagnosis of acute heart failure, its use in
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heart failure management is undefined. Several studies have investigated the application of serial lung
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ultrasound to detect dynamic changes in pulmonary edema. Research methods vary by transducer type, number of thoracic zones scanned, and B-line scoring approaches. The ability of lung ultrasound to
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detect dynamic changes in edema severity and predict short-term clinical outcomes depends on how well
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B-lines can be semi-quantitatively measured. The sum of individual B-lines or positive lung zones may suffice as a measure to detect significant changes in pulmonary edema, but a sonographic score that
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incorporates B-line coalescence may capture more severe degrees of pulmonary edema and provide added predictive value. More research is required to develop a standardized approach to performing and
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interpreting lung ultrasound that can be readily incorporated into clinical practice. Given the current limitations inherent in our clinical assessment of pulmonary decongestion, lung ultrasound will play a
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greater role in the evaluation of patients with acute heart failure.
ACCEPTED MANUSCRIPT Figure Legends Figure 1. A. 28-zone scanning protocol. The second to fourth intercostal spaces on the left hemithorax
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and second to fifth intercostal spaces on the right hemithorax are scanned at the parasternal,
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midclavicular, anterior axillary, and midaxillary lines. B. The 8-zone scanning protocol. The third intercostal space divides upper and lower zones of the chest and the anterior axillary line divides the
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anterior and lateral zones in each hemithorax.
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Figure 2. Lung ultrasound clips showing varying degrees of pulmonary edema in a single intercostal space. A. Normal lung. B-lines are absent. Horizontal lines called A-lines run parallel to the pleural line.
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B. Pulmonary edema. Several discrete B-lines extend from the pleural line to the bottom of the screen. C. Severe pulmonary edema. B-lines have coalesced into a single hyperechoic band extending from the
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pleura.
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Fig. 2