Curr Emerg Hosp Med Rep (2015) 3:16–22 DOI 10.1007/s40138-014-0063-5
ACUTE CORONARY SYNDROME (J. HOLLANDER, SECTION EDITOR)
Cardiac Ultrasound in Patients with Chest Pain J. Matthew Fields • Pablo Aguilera
Published online: 21 January 2015 Springer Science+Business Media New York 2015
Abstract Chest pain is a frequent presenting complaint with a broad differential diagnosis. Emergency physicians routinely train in point-of-care cardiac ultrasound, which has the ability to rapidly and noninvasively assist in the diagnosis of many life-threatening causes of chest pain including acute coronary syndrome, cardiac tamponade, pulmonary embolism, and aortic dissection. In addition, the physician may quickly utilize other bedside ultrasound modalities, such as lung and musculoskeletal ultrasound, to diagnose pneumothorax, pneumonia, rib or sternal fractures, or soft tissue abnormalities. The article reviews the current literature and discusses the utility and performance of ultrasound in patients presenting with chest pain to the emergency department. Keywords Chest pain Ultrasound Pulmonary embolism Acute coronary syndrome Aortic dissection Pericardial effusion Cardiac tamponade Echocardiography Introduction Chest pain is a common cause for presentation to the emergency department (ED) accounting for 7 million visits This article is part of the Topical collection on Acute Coronary Syndrome. J. M. Fields (&) Department of Emergency Medicine, Thomas Jefferson University, Thompson 239, 1020 Sansom Street, Philadelphia, PA 19107, USA e-mail:
[email protected] P. Aguilera Emergency Medicine Residency Program, Pontificia Universidad Cato´lica de Chile, Lira 63, Santiago, Chile e-mail:
[email protected]
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in the US in 2010 [1]. The work-up is variable based on the history, physical and differential diagnosis, but often includes electrocardiogram, biomarkers, and imaging studies, such as chest X-ray or computed tomography (CT). Cardiac ultrasound, also referred to as trans-thoracic echocardiography (TTE), is a non-invasive, non-radiating bedside test that can be useful in diagnosing certain causes of chest pain. Traditionally, cardiac ultrasound was a limited resource in the ED. It was only performed by cardiologists and technicians, with availability varying by institution. Now, emergency physicians (EPs) routinely train in cardiac ultrasound and its utility in chest pain deserves consideration. In 2010, the American College of Emergency Physicians (ACEP) and the American Society of Echocardiography formed a consensus statement on the use of focused cardiac ultrasound as appropriate timesensitive evaluation for pericardial effusions, evaluation of left ventricular function, left and right ventricular chamber size, intravascular volume assessment, and guidance of pericardiocentesis and transvenous wire placement [2••]. The differential of chest pain is broad and there is no evidence supporting the routine use of cardiac ultrasound in every patient. However, when the differential includes specific diagnoses, ultrasound may provide valuable information (Table 1). The current article will review causes of chest pain in which cardiac ultrasound can aid in diagnosis including aortic dissection, cardiac tamponade, pulmonary embolism (PE), and acute coronary syndrome. Causes of chest pain that can be potentially diagnosed with an alternative point-of-care ultrasound modality will also be discussed. Pulmonary Embolism Nearly 50 % of patients with PE present with chest pain [3]. While pleuritic chest pain is common, presentations
Curr Emerg Hosp Med Rep (2015) 3:16–22 Table 1 Conditions potentially diagnosed by ultrasound in patients with chest pain Cardiac ultrasound
Other point-of-care ultrasound modalities
Acute coronary syndrome
Pneumothorax
Aortic dissection
Pneumonia
Pericardial effusion/cardiac tamponade
Rib/sternal fracture
Pulmonary embolism
Muscular hematoma Chest wall cellulitis or abscess Foreign body Pacemaker/AICD infection/hematoma
may vary. The diagnostic approach in the ED typically involves the use of decision rules, D-dimer testing, lower extremity ultrasound, and CT angiography or ventilation– perfusion scan (VQ). Studies of PE typically define three different stages reflecting a continuum of hemodynamic compromise: PE with normal blood pressure and no evidence of right heart strain, PE with normal blood pressure and evidence of right heart strain (referred to as submassive PE), and PE with hypotension and evidence of right heart strain (referred to as massive PE). By definition, cardiac ultrasound will only show an abnormality if a patient either has submassive or massive PE. Findings may include right ventricular (RV) dilation (Fig. 1), paradoxical septal motion, RV hypokinesis, McConnell’s sign (a distinct contractile pattern with akinesia of the mid RV wall with normal contraction at the apex), and right atrial or ventricular thrombus [4–6]. A number of studies have evaluated the test characteristics of RV dilation on cardiac ultrasound for the diagnosis of PE. Given that approximately 50 % of patients with PE have either massive or submassive PE, it is not surprising that echo has only a sensitivity of 40–50 %, but high specificity (85–98 %) for diagnosing PE [7–9, 10•]. The sensitivity is increased to 87–89 % when lower extremity deep vein thrombosis evaluation is combined with echocardiographic findings but with a lower specificity of 69–74 % [7–9, 11]. Additional findings of RV hypokinesis, paradoxical septal motion, and McConnell’s sign increase the specificity to 100 %, but with significant drops in sensitivity, making these additional features less useful than RV dilation alone when determining the probability of PE [10•]. In addition to aiding in the diagnosis, bedside echo may assist in the decision to give thrombolysis. Frequently, an unstable patient may have a high clinical concern for a massive PE (a potential indication for thrombolysis), but the provider is unable to obtain radiographic confirmation with CT or VQ scan due to patient instability or inability to give contrast material secondary to contrast allergy or renal failure. In this scenario, the presence of RV dilation on bedside
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cardiac ultrasound should be used as indirect evidence of PE and help guide the decision to initiate thrombolysis [12]. Acute Coronary Syndrome The utility of echocardiography to visualize regional wall motion abnormalities (RWMA) in acute coronary syndrome (ACS) has been studied since the 1980s [13]. Studies have shown varying test characteristics [14–20]. When applied to a high-risk population for ACS, RWMA detected by echocardiography has sensitivities in the 90 % range for the diagnosis of myocardial infarction [13, 16–18]. However, when studies include a larger or consecutive sample size including low-risk patients, sensitivity is much lower in the 50 % range [14, 15, 19]. The major limitation to TTE in evaluating ACS is many patients with unstable angina or non-ST elevation myocardial infarction (MI) may not have RWMAs or they may be transient, but still of clinical importance. For example, in one study by Weston et al., the incidence of MI was significantly higher in patients with abnormal versus normal TTE (20 vs 2.5 %), but the incidence of ischemia was not significantly different (14.6 vs 7.6 %), making bedside echo an ineffective rule out method overall for ACS [21]. Despite this, TTE does yield prognostic information with the absence of RWMA having a 91 % sensitivity for predicting MI or revascularization and outperforming EKG [15]. In certain scenarios, TTE may be a useful adjunct in risk-stratifying a patient with a history concerning for ACS. One caveat is that a previous MI may cause a fixed defect leading the clinician to believe ACS is occurring when it is not (false positive). In the study by Kontos et al., exclusion of patients with historical or EKG evidence of previous MI improved sensitivity from 91 to 97 % and specificity from 75 to 84 % for diagnosis of ACS [15]. A few different studies have evaluated the use of bedside ultrasound for evaluation of chest pain in the ED. A study by Atar et al. found 100 % sensitivity when evaluating 70 consecutive ED patients with chest pain (10 of whom had ACS) [22]. Another study found that use of hand-carried ultrasound by medical students with basic cardiac ultrasound training yielded a NPV of 91 % for ACS. While it may be useful as a diagnostic tool, it is unclear how cardiac ultrasound truly affects the management of patients with chest pain. One study by Kansal et al. found that hand-held ultrasound performed by cardiology fellows did not affect the triage of ED patients presenting with chest pain; however, the study was severely limited by small sample size and may have had selection bias [23]. The utility of cardiac ultrasound in chest pain should be further studied with a larger group of patients to better determine how it affects the immediate work-up. Overall, the evidence suggests that, regardless of ultrasound machinery, the presence of a new RWMA in a high-risk patient with chest pain is highly predictive of MI; however,
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Fig. 1 Ultrasound in the evaluation of chest pain. Top left—right ventricular dilation (double headed arrow) seen in submassive and massive pulmonary embolus. Top right—dilated aortic root (double headed arrow) in a case of ascending aortic dissection. Bottom
left—M-mode ultrasound demonstrating the stratosphere or bar code sign indicative of pneumothorax. Bottom right—musculoskeletal ultrasound of a rib fracture with overlying periosteal hematoma (arrow)
the absence of a new RWMA cannot be used to safely exclude ACS [15].
dissections by visualization and measurement of a dilated aortic root over 4 cm (Fig. 1) or detecting the presence of an ascending aortic dissection flap. Bedside cardiac ultrasound may be used to accurately measure proximal aortic dimensions [28]. The inability to image the entire aorta makes TTE unable to rule out AAD in many patients with chest pain. It has a reported sensitivity of 59–83 % and a specificity of 63–93 % for the diagnosis of AAD [29]. Despite this, the immediate availability of bedside ultrasound may make it extremely useful in some cases, especially when patients are critically ill [30]. In addition, bedside ultrasound has excellent diagnostic accuracy for the diagnosis of pericardial effusions (discussed below), which may be a common secondary sign of aortic root involvement of proximal AADs [31, 32]. Employment of abdominal aorta ultrasound assessment may reveal a dissection flip in cases where AAD involves the descending aorta. A more accurate sonographic test for the diagnosis of AAD is the use of transesophageal echocardiography (TEE). It has a demonstrated sensitivity from 86 to 100 % and specificity from 75 to 100 %, with a diagnostic
Aortic Dissection Acute aortic dissection (AAD) is one of the acute aortic syndromes along with aortic intramural hematoma, penetrating atherosclerotic ulcers, and traumatic transection. AAD is an uncommon diagnosis and is missed in 16–38 % of cases [24]. It carries a high mortality rate estimated at 40 % immediately, with an increasing mortality rate of 1 %/hour making early diagnosis essential [25]. Patients with AAD may have similar clinical presentations, severe acute chest pain radiating to neck or the back [26]. There are two types of AAD according to the Stanford classification; type A that involves the aortic root and aortic arch and type B which corresponds to dissections distal to the left subclavian artery. Overall, 65 % of dissections arise in the ascending aorta, 20 % in the descending, 10 % in the aortic arch, and fewer than 5 % are isolated to the abdominal aorta [27]. Cardiac ultrasound has the ability to diagnose Type A
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accuracy comparable with angio CT and MRI [33]. TEE is similar to TTE in that it is rapid and able to be performed at the bedside, but it is invasive and not commonly practiced by EPs. One study has demonstrated its feasibility and it may become a more common test in the future [34]. Pericardial Effusion and Cardiac Tamponade Pericardial effusions are common and may be caused by pericarditis, autoimmune disease, malignancy, trauma, uremia, aortic dissection, medications, or as a result of a procedure. When pericardial effusions expand rapidly, or when they expand gradually and reach a critical volume, the intrapericardial pressure becomes higher than the pressure in the cardiac chambers leading to chamber collapse, reduced filling and cardiac tamponade. Patients may present with shortness of breath, chest discomfort, distended neck veins, syncope, hypotension, and shock [35]. Bedside cardiac ultrasound performs well for the diagnosis of pericardial effusion and cardiac tamponade. When compared to formal echocardiography, bedside cardiac ultrasound has a 96 % sensitivity and 98 % specificity for detecting a pericardial effusion [32]. The most useful echocardiographic finding for diagnosing cardiac tamponade is diastolic RV collapse which has a sensitivity of 93 % and specificity of 100 % [36]. It has been shown to outperform the traditional pulsus paradoxus physical examination, which only has a sensitivity of 79 % and specificity of 40 % and may be dependent on the patient’s volume status. [36, 37] Other findings that may be seen include collapse of any cardiac chamber, a plethoric noncollapsing IVC, and a greater than 25 % respiratory variation in mitral valve inflow velocity [38, 39]. In addition to diagnosing cardiac tamponade, cardiac ultrasound can guide pericardiocentesis [40]. Prior to the use of ultrasound, pericardiocentesis was often performed by inserting a needle into the subxiphoid space, traversing the liver, toward the right ventricle. Studies have shown that the actual best location is more often the apex or parasternal position [35]. Ultrasound will allow the provider to find the point closest to the effusion that does not encounter lung tissue in these regions. In addition, ultrasound can be used to dynamically visualize the needle and guidewire entering the pericardium [41]. Contrast material, such as agitated saline, can also be used as an adjunct to determine that the drainage catheter has been appropriately placed [42]. Finally, serial cardiac ultrasounds can be performed to determine adequate fluid drainage [35]. Other (Non-cardiac) Ultrasound Modalities in the Evaluation of Chest Pain When considering the differential diagnosis of chest pain, the utility of ultrasound as a bedside test can be greatly
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increased by evaluation of the soft tissue, ribs, sternum, and pleura. Historically, ultrasound was not believed to be useful for evaluation of pleura because sound waves are reflected by the air present in alveoli. Over the last two decades, sonologists have discovered that the presence or absence of specific ultrasound artifacts, related to the liquid-gas interface in the lungs, can be utilized to diagnose pulmonary conditions [43]. Two common causes of chest pain that can accurately be diagnosed by lung ultrasound are pneumothorax and pneumonia. Ultrasound can reliably detect pneumothorax in trauma and non-trauma patients with chest pain and is more accurate than portable chest X-ray [44, 45•]. In addition, approximately 40–50 % of pneumothoraces can be misdiagnosed using only chest radiography [46, 47]. Pneumothorax is defined by the interposition of gas between the parietal and visceral pleura, which creates specific findings on ultrasound including loss of lung sliding and disappearance of comet tails. Although lung sliding disappears in 100 % of patients with pneumothorax, lung conditions that limit pulmonary expansion such as acute respiratory distress syndrome, atelectasis, pulmonary fibrosis, or mainstem intubation can create false positives making a more variable specificity between 60 and 91 % [48]. When considered together, the absence of both signs gives pointof-care ultrasound a sensitivity of 90.9 % and specificity of 98.2 % in the diagnosis of pneumothorax [49]. Evaluation of lung sliding can be enhanced by use of M-mode, which will demonstrate a lack of motion below the pleural line, known as the ‘‘bar code’’ or ‘‘strasophere sign’’ (Fig. 1). The point where the visceral pleura and parietal pleura separate is called the lung point or leading edge, which is 100 % specific and considered pathognomonic for pneumothorax [50]. When evaluating the patient’s chest pain, lung ultrasound may also reveal findings consistent with pneumonia including presence of B-lines, consolidation of lung tissue causing an appearance similar to liver (known as ‘‘hepatization’’), and visualization of dynamic air bronchograms [51]. Lung ultrasound for the diagnosis of pneumonia has been demonstrated in adults and pediatrics. In one metaanalysis of adults, it had a pooled sensitivity of 94 % and specificity of 96 % [52]. In children, it has similar test characteristics [53]. Studies have shown that lung sonography is as sensitive and specific as CT for pneumonia diagnosis, without the downside of having to move the patient to the radiology suite and without the associated radiation risk [54, 55]. Ultrasound can assist in the diagnosis of soft tissue and musculoskeletal injuries on the chest. A unique characteristic of ultrasound is the ability to perform a dynamic examination. The sonographer can apply focused pressure
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with the probe to determine whether reproducibility of pain is over a region of visualized abnormality. In addition, in some cases, the sonographer can perform a contralateral examination to compare sides. In a study of 88 patients with chest trauma, ultrasound was found to be superior to clinical gestalt and radiography for detecting rib and sternal fractures (Fig. 1) [56]. Another study showed that ultrasound was six times more sensible diagnosing rib fractures compared with chest X-ray [57]. Ultrasound is very reliable to determine the presence or absence of abscesses, cellulitis, or chest wall hematomas, which may be related to the cause of the patient’s chest pain.
Curr Emerg Hosp Med Rep (2015) 3:16–22
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Conclusion 7.
Evaluation of patients that presents to the ED with chest pain presents a large differential diagnosis and may require a significant amount of resources. Cardiac ultrasound is an inexpensive, non-radiating tool that may provide a rapid diagnosis or affect the probability of disease in cases of ACS, cardiac tamponade, PE, or AAD. In addition, use of lung and musculoskeletal ultrasound may further assist in diagnosis. In critically ill patients, ultrasound may be one of the few imaging modalities available to the practitioner. As research continues in the era of point-of-care ultrasound, the applications of ultrasound in chest pain may expand.
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Compliance with Ethics Guidelines Conflict of Interest Dr. Fields and Dr. Aguilera both state they have no disclosures to declare.
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Human and Animal Rights and Informed Consent This article does not contain any studies with human or animal subjects performed by any of the authors.
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References Papers of particular interest, published recently, have been highlighted as: • Of importance •• Of major importance
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