The use of ultrasound has developed over the last 50 years into an indispensable first-line test for the cardiac evaluation of symptomatic patients. The technologic miniaturization and improvement in transducer technology, as well as the implementation of educational curriculum changes in residency training programs and specialty practice, have facilitated the integration of focused cardiac ultrasound into practice by specialties such as emergency medicine. In the emergency department, focused cardiac ultrasound has become a fundamental tool to expedite the diagnostic evaluation of the patient at the bedside and to initiate emergent treatment and triage decisions by the emergency physician.
This consensus statement by the American Society of Echocardiography (ASE) and the American College of Emergency Physicians (ACEP) delineates the important role of focused cardiac ultrasound (FOCUS) in patient care and treatment and emphasizes the complementary role of FOCUS to that of comprehensive echocardiography. We outline the clinical applications where FOCUS could be used, as part of the evolving relationship between echocardiography laboratories and emergency departments. Although cardiac ultrasound as performed by emergency physicians in emergency departments is often performed in the context of other focused ultrasound applications (examining the hypotensive patient for abdominal aortic aneurysms, ruptured ectopic pregnancy, or intraperitoneal hemorrhage as a result of trauma), the scope of this consensus statement is limited to cardiac applications of the FOCUS examination. Accordingly, the important role of comprehensive transthoracic echocardiography and transesophageal echocardiography in the emergency department will not be discussed in detail in this article.
Focused Cardiac Ultrasound Versus Comprehensive Echocardiography
The principal role for FOCUS is the time-sensitive assessment of the symptomatic patient. This evaluation primarily includes the assessment for pericardial effusion and the evaluation of relative chamber size, global cardiac function, and patient volume status ( Table 1 ). Intravascular volume status may be assessed by left ventricular (LV) size, ventricular function, and inferior vena cava (IVC) size and respiratory change. In addition, FOCUS is used to guide emergent invasive procedures, such as pericardiocentesis, or evaluate the position of transvenous pacemaker placement.
| Assessment for the presence of pericardial effusion |
| Assessment of global cardiac systolic function |
| Identification of marked right ventricular and left ventricular enlargement |
| Intravascular volume assessment |
| Guidance of pericardiocentesis |
| Confirmation of transvenous pacing wire placement |
Other pathologic diagnoses (intracardiac masses, LV thrombus, valvular dysfunction, regional wall motion abnormalities, endocarditis, aortic dissection) may be suspected on FOCUS, but additional evaluation, including referral for comprehensive echocardiography or cardiology consultation, is recommended. Further hemodynamic assessment of intracardiac pressures, valvular pathology, and diastolic function requires additional training in comprehensive echocardiography techniques.
Comprehensive echocardiographic examination or other imaging modalities are recommended in any case in which the focused findings and clinical presentations are discordant. Clinical scenarios and the information obtained from the focused use of cardiac ultrasound in emergent situations are distinctly different from those where comprehensive echocardiography are used, and both types of studies have a role in optimizing patient care as will be outlined in the following sections. The role of emergency ultrasound, including FOCUS and other core emergency ultrasound applications, also is discussed in ACEP’s Emergency Ultrasound Imaging Compendium.
Focused Cardiac Ultrasound Examination Findings
Pericardial Effusion
Studies have shown a high degree of sensitivity and specificity in the detection of pericardial effusions in both medical and trauma patients using FOCUS. Imaging in multiple views or windows provides the most accurate detection of pericardial effusion. It is important to recognize that pericardial tamponade is a clinical diagnosis that includes the visualization of pericardial fluid, blood, or thrombus, in addition to clinical signs including hypotension, tachycardia, pulsus paradoxus, and distended neck veins.
Although FOCUS may be used to visualize delayed right ventricular diastolic expansion and right atrial or ventricular diastolic collapse representing increased pericardial pressures, there are additional two-dimensional and Doppler findings obtained in a comprehensive exam that can confirm or refute the degree of suspected hemodynamic compromise and provide a means of serially monitoring its progress. In addition, small, more focal pericardial effusions can be difficult to recognize with FOCUS, and a comprehensive echocardiogram or other diagnostic imaging testing is indicated whenever the clinical suspicion for the presence of effusion is high and the FOCUS could not demonstrate it.
In trauma patients, hemodynamically significant pericardial effusions may be small or focal and the hemorrhage may exhibit evidence of clot formation, yet the degree of hemodynamic instability may be pronounced. In such hemodynamically unstable patients, a comprehensive echocardiogram will typically not be obtained before initial treatment is provided.
When emergency pericardiocentesis is indicated, ultrasound can provide guidance by first imaging the fluid collection from the subxiphoid/subcostal or other transthoracic windows to define the best trajectory for needle insertion. If the diagnosis of a pericardial effusion that could be drained percutaneously can be made at the bedside expeditiously, ultrasound-guided pericardiocentesis in these critically ill patients has been shown to have fewer complications and a higher success rate than if done without ultrasound guidance. Injection of agitated saline may be helpful in localizing needle placement during this procedure.
Global Cardiac Systolic Function
FOCUS can be used for global assessment of LV systolic function. This assessment relies on overall assessment of endocardial excursion and myocardial thickening, using multiple windows, including the parasternal, subcostal, and apical views. It is important to note that FOCUS is performed to assess global function and differentiates patients into “normal” or minimally impaired function versus “depressed” or significantly impaired function. This descriptive nomenclature when used by non-echocardiographers has good correlation with echocardiographer interpretations. The goal of the focused exam is to facilitate clinical decision-making to decide if a patient with acute shortness of breath or chest pain has impaired systolic contractility and thus would benefit from pharmacologic therapies or other interventions. Evaluation of segmental wall motion abnormalities and other causes of shortness of breath (e.g., valvular dysfunction) can be challenging and should be assessed by performing a comprehensive echocardiogram.
Right Ventricular Enlargement
In an acute massive pulmonary embolus, the right ventricle can be dilated and have reduced function or contractility. In patients with hemodynamically significant pulmonary embolus, the left ventricle can be underfilled and hyperdynamic. The presence of right ventricular (RV) enlargement and dysfunction in patients with pulmonary embolus is prognostically important and associated with significantly higher in-hospital mortality, as well as being one of the best predictors of poor early outcome. The role of FOCUS in patients with suspected pulmonary embolus is to prioritize further testing, alter differential diagnosis assessments, and assist with treatment decisions in the severely compromised patient. Because the use of thrombolytic therapy in most patients can safely be delayed, it is recommended to further assess the size and function of the RV using comprehensive echocardiography once the suspicion for the presence of pulmonary embolism is established.
FOCUS can be used to identify hemodynamically significant pulmonary emboli by observing right ventricular dilatation (>1:1 RV/LV ratio), decreased right ventricular systolic function, or occasionally by visualizing free-floating thrombus. Although an acute submassive pulmonary embolus can result in RV enlargement and dysfunction, the sensitivity of these findings even on comprehensive transthoracic echocardiography is limited (29% and 51%, respectively, 52%–56% using both criteria combined). As stated in the American College of Cardiology/ASE appropriateness criteria document, transthoracic echocardiography is not sufficiently sensitive to rule out pulmonary embolism. Likewise, FOCUS may be helpful if positive in the compromised patient but is clearly not sufficient to rule this important diagnosis out or to risk stratify patients with stable hemodynamics. Comprehensive echocardiography can be used to risk stratify patients, whereas other imaging modalities (e.g., computed tomographic angiography) should be the diagnostic modality of choice to exclude the diagnosis. In addition, emergency physicians should be aware that an increased RV:LV ratio is not specific for pulmonary embolus and that acute and chronic RV abnormalities may exist in patients with chronic obstructive pulmonary disease, obstructive sleep apnea, pulmonary hypertension, and right-sided myocardial infarction, among others.
Volume Assessment
Right atrial pressures, representing central venous pressure, can be estimated by viewing size and respiratory change in the diameter of the IVC. This is done by viewing the vena cava below the diaphragm in the sagittal plane and observing the change in the IVC diameter during the respiratory cycle. During inspiration, negative intrathoracic pressure causes negative intraluminal pressure and increases venous return to the heart. The compliance of the extrathoracic IVC causes the diameter to decrease with normal inspiration. In patients with low intravascular volume, the inspiration to expiration diameter ratios change more than in those patients who have normal or high intravascular volume, and therefore a quick assessment of intravascular volume can be made. IVC evaluation can be particularly helpful in those patients with a significant respiratory collapse during inspiration, permitting prompt identification of the hypovolemic patient.
Focused Cardiac Ultrasound Examination Findings
Pericardial Effusion
Studies have shown a high degree of sensitivity and specificity in the detection of pericardial effusions in both medical and trauma patients using FOCUS. Imaging in multiple views or windows provides the most accurate detection of pericardial effusion. It is important to recognize that pericardial tamponade is a clinical diagnosis that includes the visualization of pericardial fluid, blood, or thrombus, in addition to clinical signs including hypotension, tachycardia, pulsus paradoxus, and distended neck veins.
Although FOCUS may be used to visualize delayed right ventricular diastolic expansion and right atrial or ventricular diastolic collapse representing increased pericardial pressures, there are additional two-dimensional and Doppler findings obtained in a comprehensive exam that can confirm or refute the degree of suspected hemodynamic compromise and provide a means of serially monitoring its progress. In addition, small, more focal pericardial effusions can be difficult to recognize with FOCUS, and a comprehensive echocardiogram or other diagnostic imaging testing is indicated whenever the clinical suspicion for the presence of effusion is high and the FOCUS could not demonstrate it.
In trauma patients, hemodynamically significant pericardial effusions may be small or focal and the hemorrhage may exhibit evidence of clot formation, yet the degree of hemodynamic instability may be pronounced. In such hemodynamically unstable patients, a comprehensive echocardiogram will typically not be obtained before initial treatment is provided.
When emergency pericardiocentesis is indicated, ultrasound can provide guidance by first imaging the fluid collection from the subxiphoid/subcostal or other transthoracic windows to define the best trajectory for needle insertion. If the diagnosis of a pericardial effusion that could be drained percutaneously can be made at the bedside expeditiously, ultrasound-guided pericardiocentesis in these critically ill patients has been shown to have fewer complications and a higher success rate than if done without ultrasound guidance. Injection of agitated saline may be helpful in localizing needle placement during this procedure.
Global Cardiac Systolic Function
FOCUS can be used for global assessment of LV systolic function. This assessment relies on overall assessment of endocardial excursion and myocardial thickening, using multiple windows, including the parasternal, subcostal, and apical views. It is important to note that FOCUS is performed to assess global function and differentiates patients into “normal” or minimally impaired function versus “depressed” or significantly impaired function. This descriptive nomenclature when used by non-echocardiographers has good correlation with echocardiographer interpretations. The goal of the focused exam is to facilitate clinical decision-making to decide if a patient with acute shortness of breath or chest pain has impaired systolic contractility and thus would benefit from pharmacologic therapies or other interventions. Evaluation of segmental wall motion abnormalities and other causes of shortness of breath (e.g., valvular dysfunction) can be challenging and should be assessed by performing a comprehensive echocardiogram.
Right Ventricular Enlargement
In an acute massive pulmonary embolus, the right ventricle can be dilated and have reduced function or contractility. In patients with hemodynamically significant pulmonary embolus, the left ventricle can be underfilled and hyperdynamic. The presence of right ventricular (RV) enlargement and dysfunction in patients with pulmonary embolus is prognostically important and associated with significantly higher in-hospital mortality, as well as being one of the best predictors of poor early outcome. The role of FOCUS in patients with suspected pulmonary embolus is to prioritize further testing, alter differential diagnosis assessments, and assist with treatment decisions in the severely compromised patient. Because the use of thrombolytic therapy in most patients can safely be delayed, it is recommended to further assess the size and function of the RV using comprehensive echocardiography once the suspicion for the presence of pulmonary embolism is established.
FOCUS can be used to identify hemodynamically significant pulmonary emboli by observing right ventricular dilatation (>1:1 RV/LV ratio), decreased right ventricular systolic function, or occasionally by visualizing free-floating thrombus. Although an acute submassive pulmonary embolus can result in RV enlargement and dysfunction, the sensitivity of these findings even on comprehensive transthoracic echocardiography is limited (29% and 51%, respectively, 52%–56% using both criteria combined). As stated in the American College of Cardiology/ASE appropriateness criteria document, transthoracic echocardiography is not sufficiently sensitive to rule out pulmonary embolism. Likewise, FOCUS may be helpful if positive in the compromised patient but is clearly not sufficient to rule this important diagnosis out or to risk stratify patients with stable hemodynamics. Comprehensive echocardiography can be used to risk stratify patients, whereas other imaging modalities (e.g., computed tomographic angiography) should be the diagnostic modality of choice to exclude the diagnosis. In addition, emergency physicians should be aware that an increased RV:LV ratio is not specific for pulmonary embolus and that acute and chronic RV abnormalities may exist in patients with chronic obstructive pulmonary disease, obstructive sleep apnea, pulmonary hypertension, and right-sided myocardial infarction, among others.
Volume Assessment
Right atrial pressures, representing central venous pressure, can be estimated by viewing size and respiratory change in the diameter of the IVC. This is done by viewing the vena cava below the diaphragm in the sagittal plane and observing the change in the IVC diameter during the respiratory cycle. During inspiration, negative intrathoracic pressure causes negative intraluminal pressure and increases venous return to the heart. The compliance of the extrathoracic IVC causes the diameter to decrease with normal inspiration. In patients with low intravascular volume, the inspiration to expiration diameter ratios change more than in those patients who have normal or high intravascular volume, and therefore a quick assessment of intravascular volume can be made. IVC evaluation can be particularly helpful in those patients with a significant respiratory collapse during inspiration, permitting prompt identification of the hypovolemic patient.
Clinical Applications
Clinical Indications for Focused Cardiac Ultrasound
There are a number of common clinical scenarios where FOCUS has substantial literature support and potential to affect clinical decision making and patient care. Use will continue to evolve with technology and the changing needs of the patient. This consensus statement reflects current clinical practice. The following sections review the clinical conditions and applicable techniques of FOCUS.
Cardiac Trauma
FOCUS has been an integral part of the evaluation of the blunt and penetrating trauma patient for more than 20 years. Extensive research and literature support have led to the incorporation of FOCUS into the American Trauma Life Support training and treatment algorithm as part of the Focused Assessment with Sonography in Trauma or FAST exam. The FAST exam aims to identify active hemorrhage post-trauma by evaluating for the presence of fluid around the heart, in the thoracic cavity, and in the peritoneum. FOCUS is part of the FAST exam and is used to evaluate for the presence of pericardial effusion (and thus the identification of possible cardiac injury that may require immediate surgical attention). In addition, the presence or absence of organized ventricular contractility can be assessed. Performing emergent FOCUS as part of the FAST exam has improved outcomes by decreasing the time required to diagnose and treat traumatic cardiac and thoracic injury in those patients requiring emergent thoracotomy or laparotomy. Not only have trials shown decreased morbidity by incorporating FOCUS into trauma diagnostic evaluations, but use of FOCUS in penetrating trauma has also been shown to have a mortality benefit. The use of FOCUS in trauma patients has since become standard of care in trauma centers.
In addition to the identification of pericardial effusions, cardiac contusions can be identified by depressed wall motion and decreased myocardial contractility. This diagnosis can be difficult, however, because the trauma patient’s underlying medical condition is often not known and the evaluation of segmental wall motion abnormalities is challenging. In many cases, these patients will have follow-up comprehensive echocardiograms so that the degree of contractile dysfunction can be quantified and monitored over time.
Cardiac Arrest
The patient in cardiac arrest requires initiation of Advanced Cardiac Life Support (ACLS) treatment algorithms and rapid diagnostic evaluation for potentially treatable or reversible causes of cardiac arrest. The goal of FOCUS in the setting of cardiac arrest is to improve the outcome of cardiopulmonary resuscitation by 1) identifying organized cardiac contractility to help the clinician distinguish among asystole, pulseless electrical activity (PEA), and pseudo-PEA; 2) determining a cardiac cause of the cardiac arrest; and 3) guiding lifesaving procedures at the bedside.
In a patient with no ventricular cardiac contraction and an asystolic electrocardiogram, the survival rate is low despite aggressive ACLS resuscitation. In patients presenting to the emergency department with asystolic rhythms and no ventricular contractility by FOCUS after attempts at resuscitation with pre-hospital ACLS, survival is unlikely.
True PEA is defined as the clinical absence of ventricular contraction despite the presence of electrical activity, whereas pseudo-PEA is defined as the presence of ventricular contractility visualized on cardiac ultrasound in a patient without palpable pulses. Therefore, making the diagnosis of pseudo-PEA can be of diagnostic and prognostic importance. Patients with pseudo-PEA have some observable, although minimal, cardiac output and have a higher survival rate, in part because there are often identifiable and treatable causes of their arrest. Although there is ample literature to support that causes of PEA and pseudo-PEA can be identified with FOCUS (see “Hypotension/Shock” section), research is now focused on patient outcomes. Identification of causes of PEA arrest by FOCUS with zero or minimal interruption in cardiopulmonary resuscitation improves outcomes by decreasing time to treatment and to return of spontaneous circulation. FOCUS is only recommended in PEA and asystolic rhythms and should not delay lifesaving treatment of ventricular arrhythmias. These patients should be stabilized, and a comprehensive echocardiogram, looking for potential specific structural abnormalities such as hypertrophic cardiomyopathy or RV dysplasia, can be performed at a later point.
Hypotension/Shock
FOCUS for the hypotensive patient is a continuum from its use in cardiac arrest. For patients presenting with undifferentiated hypotension, the primary advantage of FOCUS is in determining whether the shock is cardiogenic. Shock requires aggressive early intervention to prevent organ dysfunction caused by inadequate tissue perfusion. Therefore, the distinction of cardiogenic shock from shock of other causes is extremely important. The FOCUS exam, as previously stated, should evaluate for the presence of pericardial effusion, global cardiac function, right ventricular size, and IVC size/collapsibility as a marker of central venous pressure. In the right clinical context, this evaluation can direct the clinician at the bedside in important next treatment interventions, optimize diagnostic efficiency, and assess the response to performed interventions.
FOCUS can give vital information regarding the presence, size, and functional relevance of a pericardial effusion as a cause of hemodynamic instability and can expedite pericardiocentesis with fewer complications and a higher success rate. Evaluation of right ventricular size in the peri-arrest patient may lead the clinician to consider thrombolytics if the clinical scenario and the FOCUS findings (see previous section on “Right Ventricular Enlargement”) suggest massive pulmonary embolus. It is worth reiterating that the absence of these findings cannot be used to exclude the presence of a clinically significant pulmonary embolism, although identifying an enlarged RV in an unstable patient can lead to lifesaving therapy. Studies have shown that global systolic function can be assessed accurately by FOCUS. Identification of poor but detectable LV systolic function indicates a need for further inotropes or mechanical support. In the peri-arrest patient, assessment of ventricular contraction by FOCUS can determine whether transcutaneous or transvenous pacing is capturing successfully. Finally, the finding of a hyperdynamic left ventricle can prompt evaluation for hypovolemia or suggest sepsis or massive pulmonary embolus as a diagnosis in the right clinical scenario.
In those rare but catastrophic instances when pacemaker placement results in ventricular perforation, the ability to identify pericardial effusions can expedite operative repair. In the post-resuscitation phase, however, patients can benefit from a comprehensive echocardiogram, which can provide essential information in monitoring cardiac function and in assessing the impact of resuscitative measures on a patient’s hemodynamics. In a patient with shock, a collapsed vena cava should prompt an ultrasound evaluation of the peritoneal cavity to look for abdominal hemorrhage.
Dyspnea/Shortness of Breath
Dyspnea is a Class I indication for comprehensive echocardiography. For patients presenting with acute dyspnea and shortness of breath, the three main goals for FOCUS in this instance are to rule out pericardial effusion, identify global LV systolic dysfunction, and assess the size of the right ventricle as a proxy for indicating the presence or absence of a hemodynamically significant pulmonary embolus, all discussed above.
However, complete evaluation of dyspnea in patients requires comprehensive echocardiography to evaluate diastolic function and pulmonary artery pressures, as well as to evaluate for pericardial disease and valvular heart disease. Although the presence of significantly stenotic valves or regurgitant lesions using two-dimensional and color Doppler techniques may be suggested by a FOCUS, full evaluation requires the quantitative analysis provided by a comprehensive echocardiogram.
Chest Pain
The life-threatening chest pain syndromes where FOCUS may be helpful are in the evaluation of patients with a hemodynamically significant pulmonary embolus (discussed above) or in screening patients with suspected aortic dissection.
Whereas comprehensive echocardiography could provide information about the extent of dissection and complications, the role of FOCUS in patients with suspected aortic dissection is to look for pericardial or pleural effusions and to assess the diameter of the aortic root. An aortic root greater than 4 cm is suggestive of type A dissection and should raise the clinical suspicion for disease, although it is important to state that a negative FOCUS or even a negative comprehensive transthoracic echocardiogram does not rule out aortic dissection, and further imaging and diagnostic studies should be considered for definitive diagnosis and characterization.
Chest pain is also a Class I indication for the use of comprehensive echocardiography in patients with chest pain due to suspected acute myocardial ischemia when the baseline electrocardiogram is nondiagnostic. Given that segmental wall motion and wall thickening analysis are some of the most technically demanding aspects of echocardiographic interpretation, FOCUS should not be used primarily for this purpose. Comprehensive echocardiography interpreted by experienced readers is recommended for evaluation of segmental wall motion.
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