Echocardiography and lung ultrasonography for the assessment and management of acute heart failure

Echocardiography is increasingly recommended for the diagnosis and assessment of patients with severe cardiac disease, including acute heart failure. Although previously considered to be within the realm of cardiologists, the development of ultrasonography technology has led to the adoption of echocardiography by acute care clinicians across a range of specialties. Data from echocardiography and lung ultrasonography can be used to improve diagnostic accuracy, guide and monitor the response to interventions, and communicate important prognostic information in patients with acute heart failure. However, without the appropriate skills and a good understanding of ultrasonography, its wider application to the most acutely unwell patients can have substantial pitfalls. This Consensus Statement, prepared by the Acute Heart Failure Study Group of the ESC Acute Cardiovascular Care Association, reviews the existing and potential roles of echocardiography and lung ultrasonography in the assessment and management of patients with acute heart failure, highlighting the differences from established practice where relevant.

cardiac arrest. AHF is a highly lethal condition, and studies have shown that minimizing the 'time to appropriate therapy' -the initiation of treatment as soon as possible, including in the prehospital setting -is potentially beneficial in improving outcomes 9,10 . AHF is variably defined as the rapid onset or acute worsening of symptoms and signs of heart failure that is associated with elevated plasma levels of natriuretic peptides 4,11 . However, substantial diagnostic uncertainty is inevitable when relying only on traditional clinical findings, and currently a lack of specificity exists in routine investigations for this condition. Indeed, although patients often present with a suggestive history, clinical features (such as shock, and pulmonary or peripheral congestion), and/or symptoms related to the underlying potential cause, these traditional clinical features are frequently absent; over-reliance on these factors might delay diagnosis and implementation of appropriate therapy, or contribute to a missed diagnosis in up to 20% of patients 12,13 . Furthermore, patients' clinical features might vary according to the site of initial medical contact and the management strategies employed 14,15 .
The majority of patients with AHF present to emergency departments; however, many patient are also assessed and managed in other acute care settings such as in intensive care and inpatient cardiology units. Patients with AHF usually present with symptoms of congestion and breathlessness rather than cardiac arrest or shock 16 . Symptoms of breathlessness account for 3-5% of emergency department attendances in Europe and the USA, and the major causes of breathlessness and their prevalence include AHF (50%), pneumonia or bronchitis (20%), exacerbation of chronic obstructive pulmonary disease or asthma (20%), and pulmonary embolism (5-10%) 16,17 . Current guidelines recommend that clinical examination and investigations should be integrated to form the diagnosis, including the use of electrocardiogram (ECG), chest radiograph, and biomarkers such as natriuretic peptides, troponin, and D-dimer as indicated 16,18,19 . Unfortunately, these data can be challenging to interpret, in particular in the 10-15% of patients in whom two concomitant diagnoses exist 1,4,20 . Specifically, although included in the current definition of AHF, levels of natriuretic peptides can be elevated in respiratory disease and other acute conditions such as pulmonary embolism, sepsis, and anaemia 21-24 .
Any acute condition can be further complicated by the external factors present in emergency settings, such as high ambient noise and restrictive space, limiting a clinician's ability to position the patient optimally for examination. Furthermore, the frequently atypical features of very severe pathology (in particular valvular disease), and the time pressures imposed by an acutely deteriorating patient can contribute to poor outcomes. These factors are further confounded by the presence of concomitant pathologies in the increasingly ageing patient population 25 .
Echocardiography and LUS are readily available and widely validated techniques that can be used to reveal anatomical and physiological abnormalities in patients with AHF, which when correctly applied in the acute setting, can improve patient assessment, management, and outcomes (FIGS 1,2) 26 . Unlike other biomarkers used in AHF, echocardiography and LUS can be used to identify not only inadequate cardiac output and/or the presence of congestion, but also the underlying cause, allowing the most appropriate, individualized interventions to be delivered immediately to the patient 27 . Furthermore, these imaging modalities can be used to monitor the effects of treatment (either beneficial or detrimental), as well as to guide patient disposition and interventions as indicated 28 . Pocket-sized echocardiography devices are practical for screening, and provide information to clinicians in addition to that gathered from auscultation by a stethoscope alone. When AHF is suspected, an integrative approach is recommended, including determination of cardiopulmonary instability and evaluation of congestion (pulmonary and peripheral) using a combination of techniques 4 . When image quality is inadequate, either transoesophageal echocardiography or the use of contrast should be considered.

Lung ultrasonography
Based on the interpretation of a number of artefacts, specific ultrasonography appearances, and their distribution (FIG. 1), LUS allows for a rapid point-of-care evaluation of a number of conditions, including pulmonary oedema, lung consolidation, pleural effusion, and pneumothorax 29 . High intra-rater and inter-rater reproducibility, ease of learning, short exam duration (<5 min), and the noninvasive nature of this technique makes it an advantageous point-of-care tool 30-32 . LUS is increasingly used in the acute care setting, and has improved diagnostic accuracy compared with clinical assessment and chest radiography for the identification of a cardiac aetiology in patients presenting to the emergency department with undifferentiated dyspnoea 33 .

Interstitial fluid and pulmonary oedema
Quantification of B-lines (vertical artefacts that result from an increase in interstitial density; FIG. 1b) has been shown to be useful for the diagnosis, monitoring, and risk assessment of patients with known or suspected AHF 34-36 . Either curvilinear or phased array transducers can be used, typically at an imaging depth of 18 cm. Although the assessment of eight or more anterior and lateral thoracic zones (four on each hemithorax) has been recommended in a consensus statement 29 , a subsequent study demonstrated high diagnostic accuracy with examination of only six thoracic regions 33 . The visualization of three or more B-lines in two or more intercostal spaces bilaterally should be considered diagnostic for pulmonary oedema, with sensitivity of 94% (95% CI 81-98%) and specificity of 92% (95% CI 84-96%) 33,37 . By contrast, physical examination and chest radiography have a sensitivity of only 62% (95% CI 61-64%) and 57% (95% CI 55-59%), and a specificity of 68% (95% CI 67-69%) and 89% (95% CI 88-90%) for a diagnosis of pulmonary oedema, respectively 38 . The presence of multiple bilateral B-lines in AHF has been well-correlated with natriuretic peptide levels, and only variably correlated with pulmonary capillary wedge pressure and measures of extravascular lung water 30,33,35,39-41 . Given that studies to assess the incremental diagnostic value of LUS compared with natriuretic peptides for the identification of AHF in patients with dyspnoea reported variable results in different cohorts, this topic warrants further investigation 31,33,42 . The number of B-lines is thought to decrease with treatment for AHF and, therefore, this technique is potentially useful in the monitoring of pulmonary oedema in response to therapy 35,36 . For serial assessments, patient positioning (sitting versus supine) should be kept consistent 43 . Importantly, a higher number of B-lines on LUS at the time of discharge from hospital might help to identify patients with heart failure who have a worse prognosis 36 .

Pleural effusion
Similarly to B-lines, the presence of pleural effusions can be assessed using curvilinear or phased array transducers in the posterior-axillary line 34 (FIG. 1d). Current data regarding the diagnostic utility of pleural effusions identified on ultrasonography in patients with AHF are less robust, but have been reported with sensitivities of 79-84% and specificities of 83-98% in small studies of patients with dyspnoea 44,45 .

Pneumothorax
LUS can be used to exclude pneumothorax in the area scanned with higher sensitivity than supine chest radiography by recognizing lung sliding, a slight horizontal movement of the pleural line with respiration; see Supplementary information S1 (video) 46 . In the setting of a pneumothorax, lung sliding is absent in the affected area of the chest. At the border of a pneumothorax, a transition point between normal lung surface (with lung sliding) and pneumothorax (without lung sliding) can sometimes be identified 47 . This so-called 'lung point' confirms the diagnosis. Lung sliding might be absent in several other pathological conditions (such as pleural adhesions or selective mainstem intubation) and, therefore, should not be used in isolation to make the diagnosis of pneumothorax, but rather in conjunction with the full range of sonographic features 46 .

Differential diagnosis and potential pitfalls
The major questions when using LUS for the assessment of patients with possible AHF include whether there is evidence of pulmonary oedema (such as multiple bilateral B-lines), whether there are other findings suggestive of AHF (such as pleural effusion), and finally, whether there are findings of alternate or concurrent conditions (such as pulmonary consolidation or pneumothorax). Despite its apparent simplicity, a number of caveats exist for the use of LUS. First, B-lines can resolve rapidly in response to treatment, and, therefore, LUS data must be interpreted in the context of previous interventions 35 . Second, B-lines can be seen in a number of pulmonary conditions, including pulmonary fibrosis or interstitial lung disease, acute respiratory distress syndrome, and pneumonitis 29 . The observation of Blines together with other LUS abnormalities might indicate that two pathologies coexist, or that the B-lines are an expression of pathology other than AHF (for example, acute respiratory distress syndrome, or pulmonary oedema in patients receiving haemodialysis) 48 . Third, large pleural effusions might interfere with B-line quantification in the affected thoracic zones and induce lung consolidation (FIG. 1d). Together, these considerations outline why LUS should not be used in isolation, but rather integrated into clinical and laboratory assessment 33,49,50 .

Echocardiography in AHF
Driven by progressive advances in ultrasonography technology and an expanding evidence base, the use of echocardiography has extended beyond the traditional application in stable patients to become widespread in the acute and emergency settings 51,52 . Mirroring the concept of critical care, echocardiography is increasingly used as a tool to guide management of the most acutely unwell patients wherever they present along the management pathway. Pocket-sized devices have been recommended in the emergency department, intensive care unit, and coronary units for fast initial qualitative screening of ventricular and valvular function, pericardial and pleural effusion, or extravascular lung water. However, owing to the known limitations of this technique, they are not intended as a substitution for comprehensive echocardiography 26, 53 . Remote expert review of images is now a possibility, and in the future, telemedicine will probably have an important role in guiding the assessment and management of these acutely unwell patients.
Echocardiography is used in AHF to help to confirm diagnosis, delineate potential underlying causes, identify associated pathophysiology, and monitor the response to therapy 28, 54 . Echocardiography can also be used to guide specialist interventions in the catheter laboratory or operating room [55][56][57] . Furthermore, echocardiography can address several major questions, including whether a patient has a cardiac cause for their symptoms and signs, the severity of the cardiac impairment and its physiological effect, whether there is an underlying reversible cause, what the most appropriate initial treatment is, and how the patient responds to treatment.
Guidelines recommend immediate echocardiographic assessment for patients with suspected AHF with haemodynamic instability 1,4 ; however, interpretation of echocardiographic data in these acutely unwell patients can be extremely complex (TABLE 1). First, the finding of a structurally or functionally abnormal heart does not necessarily mean the cause of dyspnoea is cardiac-related. Second, patients might be misdiagnosed as having primary respiratory disease, even in the presence of very severe cardiac pathology 27,58 . Third, substantial cardiac and respiratory disease might coexist, and determining the degree of cardiac contribution is frequently challenging in this setting 59 . These considerations are further compounded by the relative paucity of high-quality evidence to support the use of echocardiography techniques in the acute arena, as they have been predominantly validated in the outpatient clinic.

Left-sided disease and elevated LAP
Dyspnoea resulting from left-sided cardiac disease is likely to be associated with elevated left atrial pressure (LAP) and pulmonary oedema. Historically, pulmonary capillary wedge pressure has been measured using a pulmonary artery catheter as a substitute for LAP measurement [60][61][62] . The use of the pulmonary artery catheter has greatly declined over the past decade, owing to a number of studies that showed potential harm or no improved outcomes in the perioperative and critical care settings 63 . Although absolute pressure values cannot be measured using echocardiography, a drive has occurred to find an echocardiography-derived parameter that can be used to estimate the LAP noninvasively. Indices that have been proposed include interrogation of the transmitral left ventricular (LV) filling pattern (E/A ratio, E wave deceleration time, and the isovolumic relaxation time), pulmonary venous Doppler diastolic deceleration time (FIG. 2), M-mode colour Doppler propagation velocities, the time interval between the onset of early diastolic mitral inflow (E) and annular early diastolic velocity (e′) by tissue Doppler imaging, and the E/e′ ratio [64][65][66][67][68][69] . None of these measures has been well-validated in the context of emergency medicine 70,71 ; they all present technical challenges that must be carefully considered for accurate interpretation, and provide only estimates of a potential range of corresponding LAP values. Even when used in combination (as proposed in critical care), they can at best only indicate that the LAP is probably very high or normal.
LV ejection fraction has been the main parameter used for the diagnosis, treatment, and stratification of patients with heart failure. However, this parameter has several limitations that are particularly relevant in the acute setting, such as load-dependency and inotropydependency 72,73 . Even in the absence of high-quality 2D images, Doppler abnormalities in transmitral filling might provide an early indicator of important pathology 72,74-76 .
Unlike LUS, echocardiography might be challenging to perform well and interpret accurately, as a number of considerations add to the complexity of its application in the acute setting. First, in all parameters described for LAP estimation, the confounding factors imposed by critical illness (changes in heart rate, cardiac output, LV compliance, and volume and ventilatory status) have not been fully evaluated. Second, not only might patients with a relatively normal LAP have radiographic and sonographic evidence of pulmonary oedema, but conversely, patients with chronically elevated LAP might have no evidence of pulmonary oedema. Similarly to LUS, however, the echocardiographic findings should be integrated with those from clinical examination, laboratory investigations, and lung imaging data (radiographic and/or sonographic), and be assessed within the clinical context. The main value of echocardiography in this setting is to diagnose or exclude an underlying cardiac cause for dyspnoea and guide subsequent interventions.

Right-sided disease: pulmonary embolism
The diagnosis of pulmonary embolism can be challenging, because symptoms and signs are nonspecific. The transthoracic echocardiogram is normal in approximately 50% of unselected patients with acute pulmonary embolism, and has a sensitivity of 50-60% and specificity of 80-90% 77 . Therefore, other investigations are used to confirm the diagnosis, with echocardiography used as a complementary imaging technique 19 . The principal indirect echocardiographic findings are nonspecific, and include right heart dilatation, right ventricular (RV) hypokinesis (with or without apical sparing), abnormal septal motion, and inferior vena cava dilatation 78 (FIG. 3a). Secondary tricuspid regurgitation might be present, allowing estimation of pulmonary arterial systolic pressure using the simplified Bernoulli equation 79 (FIG. 3b). Given that the right ventricle can generate a pulmonary artery systolic pressure of only ≤60 mmHg acutely, a higher pressure suggests a more chronic process (either multiple repeated episodes or chronic pulmonary parenchymal disease, with or without pulmonary embolism) 80 . Although the peak tricuspid regurgitation gradient is the most commonly used parameter to assess pulmonary artery systolic pressure in clinical practice, difficulties in the detection of good tricuspid regurgitation envelope might occur. Pulsed Doppler recordings of pulmonary valve flow acceleration time, pre-ejection period, and ejection time at the RV outflow tract can also be used to estimate pulmonary artery pressure and resistance 81,82 .

Pericardial collection and tamponade
Echocardiography is pivotal for recognition of the haemodynamic consequences of a pericardial collection (FIG. 3c), allowing demonstration of features of tamponade including right atrial and/or RV diastolic collapse, in addition to guiding pericardiocentesis 83 . A number of potential pitfalls exist when interpreting the echocardiographic features of tamponade in the acute setting. These pitfalls include the effects of positive pressure ventilation (reversal of changes in transvalvular flows) and localized collections, in particular after cardiac surgery when substantial haemodynamic compromise might be present, even in the absence of echocardiographic features of tamponade 84 .

Monitoring of therapy
Echocardiography is not recommended for the monitoring of therapy in patients with AHF in the absence of cardiogenic shock 4,9,11 , given the complexity of LAP estimation using echocardiography, its lack of association with pulmonary congestion and symptoms, and superiority of natriuretic peptide levels in monitoring response to therapy. An emerging area in which echocardiography might be of use is in risk stratification before discharge from hospital. In patients with AHF with dyspnoea, persistent pulmonary congestion before discharge (demonstrated on LUS) has been shown to be an independent predictor of rehospitalization for AHF at 6 months after discharge 36 .

Cardiogenic shock
Cardiogenic shock is the most severe manifestation of AHF. Although relatively uncommon, the published prevalence (5% of patients with AHF) varies according to the point of initial contact and management (1-2% of patients with AHF in the prehospital or emergency setting versus 29% in intensive care) 4,9,10,16 . Precise definitions of cardiogenic shock can vary; however, the syndrome generally results from inadequate cardiac output for peripheral organ requirements 85,86 . Cardiogenic shock can manifest as hypotension despite adequate filling (with or without vasopressors), altered mentation, cool peripheries, oliguria, hyperlactataemia, metabolic acidaemia, and low mixed venous oxygen saturation 86 . In addition to standard evaluation of critically ill patients in parallel with resuscitation, echocardiography is mandated immediately in patients with cardiogenic shock, because without identification and treatment of the underlying cause, the outcome is usually fatal 9,85 (FIG. 3d). Additional information that should be obtained from echocardiography includes estimation of stroke volume and cardiac output levels, because these data can provide guidance on how to maximize the cardiac output at the lowest filling pressures (see Supplementary information S2 (table)). These measurements should be taken during the echocardiogram, and should be performed repeatedly to monitor the response to therapeutic interventions and minimize potentially injurious treatment. Every study must be interpreted in the context of the level of inotropic and ventilatory support, as well as metabolic and arterial blood gas status, because these variables might have profound effects on echocardiographic findings.
Assessment of volume status-The physiological basis of providing 'optimal' filling in cardiogenic shock is that a critical decrease in intravascular-stressed volume reduces the difference between mean systemic venous and right atrial pressure, thereby limiting stroke volume. Although frequently used, invasive static pressure monitoring is not helpful for determining whether an individual patient is volume-responsive 87,88 . Static echocardiographic parameters are widely used to predict volume responsiveness in critically ill patients (FIG. 4); however, their use requires that a number of strict criteria (relating to the patient, their underlying pathology, and medical interventions) are met, otherwise the investigation becomes invalid (see Supplementary information S3 (table)). Similarly, although thought to be superior, dynamic echocardiographic parameters to predict volume responsiveness are valid only in fully mechanically ventilated patients in sinus rhythm and without chronic heart disease 89 . In the presence of cardiac disease (either left-sided and/or right-sided), these measurements can be misleading and should not be used. Conversely, tolerance to volume loading among different patients is variable. The conventional teaching to increase volume in RV failure has not been upheld by findings published in the past 3 years 90,91 . Physiological models suggest that in some patients, progressive fluid loading leads to a plateauing of cardiac output, with a progressive increase in pulmonary artery occlusion pressure. In addition, higher volume is associated with worse outcome in critically ill patients [92][93][94] .
Inotropes and vasoactive agents-Although inotropes and vasopressors are commonly used to improve cardiac output and blood pressure in patients with cardiogenic shock, there is currently insufficient evidence to support the use of any particular agent in this context 9,95,96 . Dobutamine is generally the first-line inotrope of choice in the clinic 9,95,96 . The detrimental effects of positive inotropic agents have been extensively described in the literature 97,98 , and their use should, therefore, be restricted to the shortest possible duration and the lowest dose, both individualized to the patient. Although little guidance exists on how inotrope treatment should be individualized, echocardiography might be helpful in certain scenarios.
First, not all patients with cardiac disease respond to escalating doses of dobutamine by increasing their stroke volume; in some patients, dobutamine can result in an increase in the total isovolumic time (tIVT) 99 . Echocardiographic identification of an abnormally prolonged tIVT with dobutamine use, or an increase in tIVT in response to escalating inotropic support might indicate that inotropes are directly impairing myocardial performance, thereby prompting a reduction in dose or a change in treatment strategy [99][100][101] (FIG. 5). Second, the combination of LV end-diastolic pressure (LVEDP) and low aortic root pressure might result in a mismatch of coronary perfusion and myocardial oxygen demand. If untreated, this mismatch can result in type 2 myocardial infarction 102 (FIG. 3d). Echocardiographic demonstration of a dominant or isolated A wave on transmitral Doppler in combination with postejection shortening can also be diagnostic (FIG. 6a,b), and indicates that aortic root pressure should be increased and/or LVEDP reduced 103,104 . Third, physiological studies have demonstrated that the combination of RV ischaemia and increased RV afterload is particularly injurious to RV performance, resulting in a fall in systemic blood pressure and cardiac output levels 105 . Echocardiography can be used to estimate pulmonary artery systolic pressure and pulmonary vascular resistance, as well as measure RV dimensions and performance 106 . Echocardiographic identification of high pulmonary vascular resistance with or without pulmonary hypertension in combination with RV dysfunction in cardiogenic shock might necessitate the introduction of a pressor agent plus treatment to reduce RV after-load 90,107 (FIG. 6c,d). Finally, in a patient with falling cardiac output levels despite escalating inotropic support, echocardiography can help to diagnose LV outflow tract obstruction (with or without associated mitral regurgitation) 27,108 . Treatment in this context involves reduction or cessation of positive inotropic agents, in combination with volume and pressor support.
Cardiac arrest-The most extreme presentation of cardiogenic shock is cardiac arrest. International evidence-based guidelines recommend the use of echocardiography to diagnose or exclude some of the causes of arrest 109 . However, echocardiography should not affect the delivery of high-quality cardiopulmonary resuscitation, and specific training in advanced cardiovascular life support is required, even for experienced practitioners. As images are obtained and recorded only during the pulse/rhythm check, studies performed during cardiac arrest are strictly time-limited, and therefore are dissimilar to comprehensive studies that use only focused 2D imaging aimed at diagnosis or exclusion of potentially reversible causes in a simple, binary manner. The pathology leading to arrest is likely to be extreme (tamponade, massive pulmonary embolism, severe LV and/or RV dysfunction, myocardial infarction/ischaemia, hypovolaemia, or tension pneumothorax) and fairly easy to diagnose without more sophisticated echocardiographic techniques. Whether the use of echocardiography in cardiac arrest (and as part of care after resuscitation) can improve outcomes is unknown, but its application in the prehospital setting has been found to change management strategies in up to 60% of patients 110,111 .
Acute mechanical circulatory support-The indications for mechanical circulatory support (MCS) in the acute setting are constantly changing 112,113 . Intra-aortic balloon pumps are no longer routinely recommended for cardiogenic shock 114 . A range of new percutaneous ventricular assist devices are available, in addition to extracorporeal membrane oxygenation (ECMO). These techniques can be used as a bridge to recovery or for longerterm support, and differ not only in terms of their technical aspects, but the degree and type of support provided (LV and/or RV support, with or without the addition of respiratory support) [115][116][117][118][119][120] . Echocardiography is critical for successful implementation of acute MCS 121,122 (TABLE 2). MCS is not a treatment per se, but instead a supportive therapy for patients awaiting treatment or resolution of the underlying pathological process. As in all cases of AHF, the most important role of echocardiography is to diagnose the underlying cardiac cause. When the decision to institute MCS is made, echocardiography is then used to corroborate the decision regarding the type and level of support required. Although clear echocardiography parameters have been used to guide longer-term MCS for both the left and right heart 123,124 , these parameters are not yet available for devices designed for short-term use. Furthermore, clear contraindications to MCS exist that can be diagnosed only using echocardiography. Echocardiography is used in the initiation of MCS, including the use of vascular ultrasonography to guide safe vessel cannulation and steer device or cannula placement. Echocardiography is subsequently used to monitor MCS by ensuring the goals of support are met, and for detecting complications and assessing tolerance to assistance 121 . Unfortunately, peripheral ECMO can paradoxically worsen cardiac function by increasing LV afterload. Although a number of echocardiographic parameters exist that might indicate this complication (including lack of aortic valve opening, biphasic retrograde flow across the mitral valve in diastole, and retrograde systolic pulmonary venous flow ; FIG. 7), the inherent limitations of echocardiography in estimating LAP and LVEDP, especially when the heart is partially bypassed, makes this strategy particularly challenging 122 . Echocardiography can be used, however, to guide interventions to ensure that the heart is adequately offloaded. Finally, a number of echocardiographic parameters are used in conjunction with clinical and haemodynamic assessment to predict which patients might be successfully weaned off MCS 125,126 .

Other indications
Transoesophageal echocardiograpy can also be used in the acute setting in patients with dynamic mitral regurgitation (see Supplementary information S4 (figure)). Furthermore, features of infective endocarditis caused by aortic prostheses or a device can be demonstrated using transoesophageal echocardiography (see Supplementary information S5 (figure)).

Quality assurance
A detailed overview of the necessary organizational structure and processes for use of ultrasonography and echocardiography in the acute setting is beyond the scope of this Review, and has been published previously 26,127-130 . However, when used in routine clinical care, training, education, protocols, and ongoing certification of practitioners are required, which should all be performed within existing governance structures.

Conclusions
Echocardiography and LUS can assist in the rapid assessment of patients with acute dyspnoea and hypotension, and have the potential to transform the way in which clinicians assess and manage critically ill patients with AHF and cardiogenic shock (TABLE 3). The current AHF guidelines are cautious in recommendations for the widespread use of advanced echocardiography techniques in the acute care setting because robust applicability data are lacking, interpretation of findings requires highly specialized, in-depth knowledge of cardiac pathophysiology, and there is potential for harm by injudicious application in this patient population. The opportunities to improve diagnostic accuracy, reduce delays in treatment, and improve outcomes through the use of advanced echocardiography need to be further explored.

Supplementary Material
Refer to Web version on PubMed Central for supplementary material.