Lung ultrasound in acute and chronic heart failure: a clinical consensus statement of the European Association of Cardiovascular Imaging (EACVI)

Abstract

Lung ultrasound (LUS) was introduced to intensive care units and emergency departments more than 20 years ago, primarily as a tool for the assessment of patients with acute dyspnoea.1,2 Since then, it has gained popularity as a quick point-of-care examination enabling clinicians to answer crucial clinical questions. Over the last decade, the cardiology community has acknowledged the potential of LUS and expanded its use further, to assist with the diagnosis and management of patients with heart failure (HF).3–5 The importance of recognizing and treating pulmonary congestion is a cornerstone in the management of patients with HF.6 LUS is a versatile, high sensitivity point-of-care examination to detect pulmonary deaeration due to increased extravascular lung water. It has many advantages to the extent that an integrated cardiopulmonary ultrasound exam is likely to become the reference standard in HF care. This approach allows the aetiology of HF to be defined, through the assessment of cardiac structure and function by echocardiography, at the same time as the assessment of pulmonary congestion provided by LUS. In addition, it facilitates the exclusion of other highly prevalent conditions that may mimic/overlap with HF (e.g. pneumonia, acute lung injury/acute respiratory distress syndrome [ALI/ARDS], and pneumothorax). In a fully aerated lung, the only anatomical structure that can be visualized is the pleura, which appears as a smooth, hyperechoic horizontal line that moves synchronously with respiration. This line is called ‘pleural line’ and its movement is the ‘lung sliding’, providing visual assessment of lung excursion during ventilation. The sonographic pattern of the aerated lung also includes parallel, hyperechoic, horizontal lines that can be seen at regular intervals from the pleural line (A-lines, Figure 1, Supplementary data online, Video S1).7 When the air content in the lung decreases and lung density increases, vertical reverberation artefacts appear (B-lines, Figure 2, Supplementary data online, Video S2). B-lines originate from the pleural line and move synchronously with respiration, are laser-like in shape and extend towards the bottom of the US sector as displayed on the screen.8 B-lines are present in patients with HF and pulmonary oedema9 where an increasing number of visualized B-lines are associated with a decreasing air/water content ratio.10–12 B-lines are not specific for cardiogenic pulmonary oedema and can be detected in patients with non-cardiogenic pulmonary oedema, including those with end stage renal disease and in ALI/ARDS,13 but also in pulmonary fibrosis (interstitial lung disease)14 and interstitial pneumonia. Some sonographic characteristics can help differentiate these various causes of B-lines5 (Table 1). The sonographic pattern of a normally aerated lung with the pleural line (upper dotted yellow line) and A-lines (lower dotted orange lines). B-lines indicated by dotted white lines. Different LUS features in different conditions where multiple B-lines are present Different LUS features in different conditions where multiple B-lines are present Pleural effusion can be easily detected by LUS, placing the phased-array transducer on the surface of the chest wall in an intercostal space, and is displayed as an anechoic space above the diaphragm. Pleural effusion is advised to be sought at first in the dependent zones, i.e. lateral and posterior chest wall (e.g. posterior axillary line) at the level of costophrenic angles (Figure 3 and Supplementary data online, Video S3), which also allows other causes of chest X-ray radio-opacity, such as consolidation, mass, or an elevated hemidiaphragm to be ruled out (Figure 4 and Supplementary data online, Video S4). LUS is more sensitive than chest X-ray in detecting pleural effusions, when using computed tomography as the reference standard,15,16 and can determine the volume of pleural effusion and monitor its evolution. LUS can also provide information on its likely nature by differentiating between simple and complex effusions, and can help guide the optimal site for needle thoracentesis. The left costophrenic angle with pleural effusion. Pleural effusion with compression atelectasis. The pathophysiology of congestion in HF includes the different stages of haemodynamic, pulmonary, and systemic congestion,17 which can be all assessed by ultrasound. Traditional echocardiography provides indicators of haemodynamic congestion, including a dilated left atrium, a high E/e′, elevated pulmonary artery systolic pressure, and dilated inferior vena cava (IVC). B-lines on LUS are a sign of pulmonary congestion (increased extravascular lung water) due to left-sided HF, independent of—yet closely related with haemodynamic congestion. Chronically elevated left-sided filling pressures eventually result in a rise in right atrial pressures and IVC distension. An IVC smaller than 21 mm that collapses >50% during inspiration suggests normal right atrial pressures,18 although this measurement should be interpreted in the context of the overall patient’s underlying pathophysiological and haemodynamic status and integrated with other echocardiographic findings; an increased IVC diameter can identify intravascular volume expansion prior to changes in symptoms or body weight, and predicts a high risk of rehospitalization for HF or death in patients with acute or chronic HF.19,20 Using a high-frequency linear transducer, the internal jugular vein (IJV) diameter can be measured. When congestion is severe, IJV distensibility, provoked by Valsalva manoeuvre, is markedly reduced, indicating a poor prognosis.21 Congestion in other organs can be also assessed by ultrasound, such as the kidneys. A comprehensive review of these novel techniques and their potential clinical utility can be found elsewhere.22 Recently, the venous excess ultrasound (VExUS) score, including Doppler evaluation of the IVC, hepatic veins, portal vein, and renal venous flow, has been proposed to assess presence and severity of venous congestion.23 Whereas systemic venous congestion (as assessed by IVC, IJV, hepatic veins, portal veins, and renal veins) can be present in both right- and left-sided HF, LUS B-lines indicate pulmonary congestion due to left-sided HF. When the pulmonary air content is completely dissipated in areas of pulmonary consolidation, the lung parenchyma can be directly visualized (Figure 5 and Supplementary data online, Video S5) with a hypoechoic or tissue-like pattern. Different aetiologies of consolidations may have also different sonographic appearance (Figure 5). Compression atelectasis is frequent in patients with HF; here, a large cardiogenic pleural effusion causes direct compression of the pulmonary parenchyma.4 Different patterns of consolidation at LUS: A) pneumonia; B) pulmonary infarction; C) compression atelectasis; D) obstructive atelectasis. On occasion, a focal interstitial syndrome (i.e. multiple B-lines localized only in a single area of the chest) can suggest pneumonia. These are thought to represent either the very early phases of pneumonia with the partial deaeration LUS pattern (B-lines) preceding the total deaeration LUS pattern (consolidation), or the focal oedema surrounding any consolidation. Whenever possible, it is advised to perform LUS exams with a standardized approach, to facilitate interpretation and monitoring, as well as reproducibility.24 Several LUS protocols have been described, with a variable number of examination areas of the chest (‘zones’) to be examined, ranging from 4 to 2825–27 (Figure 6). Currently, the eight-zone scanning protocol is the most widely used, balancing the need for a simplified, rapid protocol, and good accuracy;8 with studies suggesting it the most appropriate approach across multiple settings, including the diagnosis of HF (with the 8-zone C-index non-inferior to the 28-zone C-index),28 and for risk stratification.29 Different LUS scanning protocols, ranging from 4 to 28 zones; the imaging protocol should be performed on both hemithoraces (in the 28-zone protocol, the left hemithorax does not include the fifth intercostal space). When integrating LUS during stress echocardiography, a simplified four-zone scanning protocol is often used, placing the probe at the third intercostal space along the anterior axillary and mid-axillary lines.30,31 In adult patients, both phased-array or convex transducers are sufficient to assess B-lines. If available, the abdominal preset (for the convex transducer) and the cardiac preset (for the phased-array transducer) usually provide adequate image quality. Some machines have also a dedicated lung preset. The transducer should be placed in the intercostal space either perpendicular (longitudinal and sagittal) or in parallel orientation (transverse) to the ribs. Imaging depth depends on the size of the patient, but is usually set at ∼15–18 cm.22 Once the transducer position and gain settings are optimized for visualization of the pleural line and B-lines, it is advised to keep the transducer in the same location for at least one respiratory cycle. When a movie clip is recorded, the suggested length is of ∼6 s.32,33 In each chest zone, the operator should scan all accessible chest surface to increase sensitivity. During the examination, patients can be positioned either sitting upright, semi-recumbent, or supine; however, it is preferred to scan patients in the same position if serial examinations are being performed.34 In those thoracic zones where a pleural effusion is visualized, B-lines cannot be assessed, and the presence of pleural effusions should be described in the LUS report instead. There are two main approaches to quantify B-lines: score- or count-based methods. Score-based methods consider a minimum number of B-lines in one thoracic zone as a ‘positive’ zone (typically at least three B-lines),8 then, the number of positive zones are added up.25 Count-based methods entail that B-lines are counted to obtain a number for each thoracic zone: B-lines can be counted one by one27,34 or, when confluent and overlapping, their number can be estimated from the percentage of space they occupy on the screen below the pleural line, divided by 10 (i.e. if ∼60% of the screen below the pleural line is occupied by B-lines, it would conventionally count as six B-lines, up to a maximum of 10 per zone) (Figure 7). It is advised to count B-lines in the worst (less aerated/with more B-lines) point of each thoracic zone, then, the number of B-lines in each zone can be summed up to obtain a total B-line count.4,8,35,36 All these methods have demonstrated good intra- and inter-observer agreement.37,38 How to quantify B-lines. Overview of select pre-discharge imaging protocols and cut-off values in acute HF Adj., adjusted; CI, confidence interval; HF, heart failure; HR, hazard ratio. Overview of select pre-discharge imaging protocols and cut-off values in acute HF Adj., adjusted; CI, confidence interval; HF, heart failure; HR, hazard ratio. Key points: To evaluate pulmonary congestion in patients with suspected or HF, using a phased-array or convex probe may be appropriate ultrasound in or perpendicular or parallel to the intercostal the eight-zone protocol and the in the same position during serial The LUS pattern of a with acute HF and pulmonary oedema is the presence of least three B-lines in one chest least two positive zones per and B-lines. It is to this pattern from the presence of a B-lines, when at the lung that can be seen in and which not as and LUS is a rapid which patients with acute LUS has demonstrated high for acute HF, with a sensitivity of and a of that has been to be to both clinical assessment (i.e. examination, and and the chest when is LUS is to chest X-ray of and a of and has than clinical assessment when integrated with (i.e. and chest to acute A number of B-lines on for an of acute HF is associated with of left and presence of HF and This suggests that B-lines be a potential for but also to monitor to in B-lines are very for those to and other the number of B-lines decreases of the aetiology of acute LUS can guide of to more rapid of congestion the length of of pulmonary congestion detected by ultrasound during HF is associated with of death or acute heart failure at the is that on B-lines can and in patients with pleural effusions are by chest X-ray in patients with acute HF, serial ultrasound are also in changes in the size of pleural effusion associated with patients to to of patients with acute HF are either for HF or of with a of congestion, including pulmonary congestion, at the time of are at high The importance of during a HF is in the with a high number of B-lines at are at risk of or death than those or with only pulmonary studies the and of B-lines at in patients with HF have or 28-zone LUS specific cut-off values for these protocols are in these suggest that LUS may detect pulmonary congestion pre-discharge in patients with acute HF, of and identify those at risk for In to B-lines, pleural effusion can be detected with ultrasound in of the patients an acute HF but it is this is associated with an increased risk of LUS in acute and chronic heart failure LUS, lung HF, heart failure; acute heart LUS in acute and chronic heart failure LUS, lung HF, heart failure; acute heart Key points: The LUS pattern of pulmonary oedema in acute left-sided HF of the presence of multiple least three (in at least two zones per and B-lines. Using LUS may be appropriate in patients with acute to in or out pulmonary oedema in suspected acute left-sided HF. Using LUS may be appropriate to detect pulmonary congestion prior to in patients with acute HF, to identify those at risk of for HF or The not serial echocardiography or assessment of B-lines in patients with HF clinical is many of those with HF clinical usually not report any and are of congestion at clinical is in most patients and is often only at a point when congestion LUS be in the clinical evaluation of to facilitate early of congestion. In a clinical a the of and death at an acute HF the also that was associated with a risk in the of HF rehospitalization for HF, and death from any by a in HF that with chronic HF demonstrated a in for acute HF at as well as decreasing and of in those patients was by A of the clinical utility of LUS in acute and chronic heart failure is in How to echocardiographic and pulmonary to assess congestion status How to echocardiographic and pulmonary to assess congestion status Key points: LUS the evaluation of patients with HF may be appropriate to and in the need for LUS can be easily performed during including stress The number of B-lines during in patients with HF more than in In patients with heart failure with B-lines are closely associated with and stress pulmonary artery systolic In patients with heart failure with the of pulmonary congestion as by B-lines with of function with and during studies suggest that the acute of pulmonary congestion during stress is related to an increase in pulmonary and systemic venous LUS during can quantify the pulmonary congestion to the in a number of B-lines at is associated with a risk of HF and death in patients with both and these suggest that LUS may standard to HF diagnosis and risk with acute may pulmonary congestion, during or an A review suggests that a high number of B-lines is a in patients with an acute syndrome and patients more likely to have and assessment of B-lines guide use of that pulmonary congestion a and and in the and to be LUS can provide information when integrated with echocardiography in the assessment of and various of with the potential of detecting the underlying and the of care to In the presence of a normal LUS pattern the presence of that has a very high in out a cardiogenic of (Figure in cardiogenic due to failure or heart disease eventually pulmonary congestion that would appear by LUS as and B-lines, associated with a regular pleural (Figure cardiopulmonary ultrasound for the diagnosis of respiratory and In patients with a LUS has sensitivity and to chest The of the of lung the sign on of B-lines, and the presence of a lung point point between a LUS pattern with lung and lung would suggest a as the of (Figure The visualization of a normal LUS pattern along with due to a would suggest pulmonary when with and consolidations with may be as the sonographic appearance of pulmonary (Figure In the are a frequent of due to pneumonia that can be with LUS with high through the visualization of consolidations often with air at the most zones of the with or pleural effusion. The presence of an pleural effusion indicate pleural The can B-lines due to of of LUS can be very in disease and in LUS can be performed also during echocardiography through dedicated of the posterior of the where lung consolidations and pleural effusions are most often with Key points: In patients with LUS can the standard clinical evaluation to echocardiography is as a in for the assessment of cardiac structure and HF on as well potential underlying aetiologies and and the of The also the use of LUS in acute settings to a diagnosis of HF, when is not pulmonary congestion is one of the main causes of in patients with cardiac and pulmonary on ultrasound can help and identify the pulmonary of or cardiac and interpretation of B-lines, with the haemodynamic that can be by echocardiography, can provide of the cardiac and pulmonary to more diagnosis and The number of B-lines is related to left to to to right and artery in patients with the same haemodynamic the of pulmonary congestion as detected by B-lines can echocardiography is to the aetiology of HF, LUS B-lines are to detect the of pulmonary congestion. The assessment of B-lines may be appropriate when either a ultrasound or the for more complex echocardiographic is not or when cardiac image is poor and diagnosis possible, these two of the patient’s congestion and pulmonary can be in an integrated ultrasound cardiopulmonary examination (Table This approach can also provide information the as a of cardiac and pulmonary congestion in a with right heart The of B-lines with IVC is also and different IVC diameter and are for right atrial pressure, but also intravascular volume B-lines extravascular lung which can be present in patients with either a normal or a dilated in the use of LUS facilitate the of that may from specific LUS imaging be to management in patients with early from the the use of LUS imaging and as of a to congestion in including of the use of LUS in patients with the use of LUS the clinical of patients with chronic HF the use of LUS facilitate the of of patients with chronic HF that can from specific the use of LUS in the management of patients with chronic HF the use of LUS the clinical of specific HF and cardiac the use of LUS facilitate the of of patients with that may from specific the use of LUS facilitate the of that may from specific LUS imaging be to management in patients with early from the the use of LUS imaging and as of a to congestion in including of the use of LUS in patients with the use of LUS the clinical of patients with chronic HF the use of LUS facilitate the of of patients with chronic HF that can from specific the use of LUS in the management of patients with chronic HF the use of LUS the clinical of specific HF and cardiac the use of LUS facilitate the of of patients with that may from specific acute heart failure; HF, heart failure; heart failure with heart failure with LUS, lung ultrasound. in the use of LUS facilitate the of that may from specific LUS imaging be to management in patients with early from the the use of LUS imaging and as of a to congestion in including of the use of LUS in patients with the use of LUS the clinical of patients with chronic HF the use of LUS facilitate the of of patients with chronic HF that can from specific the use of LUS in the management of patients with chronic HF the use of LUS the clinical of specific HF and cardiac the use of LUS facilitate the of of patients with that may from specific the use of LUS facilitate the of that may from specific LUS imaging be to management in patients with early from the the use of LUS imaging and as of a to congestion in including of the use of LUS in patients with the use of LUS the clinical of patients with chronic HF the use of LUS facilitate the of of patients with chronic HF that can from specific the use of LUS in the management of patients with chronic HF the use of LUS the clinical of specific HF and cardiac the use of LUS facilitate the of of patients with that may from specific acute heart failure; HF, heart failure; heart failure with heart failure with LUS, lung ultrasound. Key points: When patients with or suspected HF, it is advised to LUS B-lines in the echocardiographic assessment to provide information the of pulmonary congestion, in both acute and chronic cardiac ultrasound is a point-of-care cardiac ultrasound examination performed to a but scanning protocol in patients with or respiratory chest or or cardiac The scanning protocol echocardiographic sufficient for assessment of left and right size and and intravascular volume Since and pulmonary and may clinical LUS may help in the diagnosis of acute and haemodynamic and is an of the The presence of and B-lines in a with is with In the presence of left atrial and B-lines may indicate and measurement and a comprehensive echocardiography should be for the main of respiratory and where LUS integrated with can be of Key points: Whenever possible, it is advised to assessment of B-lines and pleural effusion the examination it may help in the diagnosis of acute and haemodynamic with are with LUS which should be acknowledged to this There are the of although they are related to a partial deaeration of the pulmonary LUS is an to ultrasound with a that can be to 20 but is to and the interpretation of that would and for a LUS facilitate the of this for both clinicians and other in the care of patients with HF, can assess B-lines are although have been by using different machines and settings, should be to or of Different LUS scanning protocols have been proposed and used, in and in clinical as the main is the clinical interpretation of B-lines in the of an B-lines are not specific for cardiogenic pulmonary being a sign of partial pulmonary they can be present in patients with interstitial lung such as pulmonary as well as and interstitial pneumonia in 1, are LUS features that can help differentiate these that a with clinical and other is This point the need for LUS to that not with B-lines as HF. the of pulmonary congestion on ultrasound does not HF, in the context of or HF; clinicians should not to evaluate In have been in of the utility of LUS as an imaging tool in the monitoring, and risk of patients with HF, but areas with of that to be in clinical for the clinical utility of LUS, in have data the use of this tool in clinical to either or comprehensive echocardiography in the assessment and management of patients with HF. LUS is an to and point-of-care B-lines on LUS are the sonographic sign of a lung, which can be detected in patients with HF, providing a evaluation of pulmonary interstitial B-lines are for the monitoring, and assessment of patients with HF. it would be to evaluation of B-lines and pleural effusions standard echocardiographic protocols in patients with suspected or HF, as well as in the This integrated cardiopulmonary ultrasound approach has the potential to clinical management and but is Supplementary data is at Imaging data or in of this

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