* Your assessment is very important for improving the workof artificial intelligence, which forms the content of this project
Download Michael P. Mallin and Christine Butts
Survey
Document related concepts
Coronary artery disease wikipedia , lookup
Heart failure wikipedia , lookup
Management of acute coronary syndrome wikipedia , lookup
Electrocardiography wikipedia , lookup
Cardiothoracic surgery wikipedia , lookup
Cardiac contractility modulation wikipedia , lookup
Myocardial infarction wikipedia , lookup
Lutembacher's syndrome wikipedia , lookup
Cardiac surgery wikipedia , lookup
Hypertrophic cardiomyopathy wikipedia , lookup
Jatene procedure wikipedia , lookup
Mitral insufficiency wikipedia , lookup
Cardiac arrest wikipedia , lookup
Quantium Medical Cardiac Output wikipedia , lookup
Arrhythmogenic right ventricular dysplasia wikipedia , lookup
Transcript
Emergency Cardiac Ultrasound: Evaluation for Pericardial Effusion and Cardiac Activity 5 Michael P. Mallin and Christine Butts KEY POINTS • Emergency cardiac ultrasound is performed by the emergency physician to assess for the presence of cardiac activity, determine whether a pericardial effusion is present, and answer other specific questions. • Echocardiography can be used during cardiac arrest to guide resuscitation decisions. • Emergency use of echocardiography is indicated for assessment of cardiac ejection fraction, wall motion abnormalities, and other critical findings that will direct acute diagnostic decision making. INTRODUCTION Echocardiography has been the “gold standard” for cardiologists for decades. Over the past 20 years, emergency physicians have adopted point-of-care (POC) cardiac ultrasound to answer specific questions on the management of critical patients. Assessment for pericardial effusion and for cardiac activity have traditionally been the principal indications for emergency physicians, but indications for bedside echocardiography are growing rapidly.1 physicians were found to have a correlation coefficient of 0.86 with cardiologists when assessing ejection fraction. Cardiologists had a similar coefficient of 0.84 among themselves. DIAGNOSIS OF PERICARDIAL EFFUSION Emergency physicians have proved to be accurate in the diagnosis of pericardial effusion. Previous research has shown that emergency physicians have a sensitivity of 96%5 to 100%6 as compared with formal overreading by trained echocardiographers. HOW TO SCAN/SCANNING PROTOCOLS PROBE SELECTION Classic echocardiography requires the use of a phased-array probe, sometimes referred to as the thoracic probe. These probes have a small footprint and are ideal for achieving visualization with a small acoustic window between ribs. WHAT WE ARE LOOKING FOR ACOUSTIC WINDOWS Bedside cardiac ultrasound is typically taught with the use of three separate acoustic windows and multiple orthogonal views within the windows. These acoustic windows include the parasternal, apical, and subcostal. Each window is then broken down into orthogonal views, including the parasternal long-axis, parasternal short-axis, apical four-chamber, apical two-chamber, apical long-axis, subcostal four-chamber, and subcostal long-axis views. The initial and best evidence-based indications include applications for tamponade, cardiac arrest, and acute heart failure. Rapidly developing areas of cardiac ultrasound include evaluation of hypotension, pulmonary embolism (PE), acute myocardial infarction, diastolic heart failure, and echocardiographically guided resuscitation (Box 5.1).1,2 PROBE ORIENTATION Echocardiography places the probe marker on the right side of the ultrasound screen so that when the ultrasound machine is in the cardiac mode, the right-hand side of the screen indicates the side of the probe with the marker on it (this is opposite any other scanning mode). LITERATURE REVIEW ESTIMATION OF GLOBAL CARDIAC FUNCTION AND EJECTION FRACTION Multiple studies have shown the ability of emergency physicians to accurately evaluate cardiac function and ejection fraction.3,4 When compared with cardiologists, emergency SPECIFIC VIEWS Parasternal Long Axis The parasternal long-axis view seen in Figure 5.1 is obtained by placing the probe in the third to fourth intercostal space with the probe marker pointed toward the patient’s right shoulder (Figs. 5.2 and 5.3). The long axis of the heart should be horizontal on the screen with the apex pointed to the left. If the apex is pointed up, the probe is too low and should be 43 SECTION I RESUSCITATION SKILLS AND TECHNIQUES BOX 5.1 Traditional and Emerging Point-of-Care Cardiac Ultrasound Indications Traditional Indications Tamponade Cardiac standstill during cardiac arrest Acute heart failure Emerging Indications Echocardiographically guided resuscitation Undifferentiated hypotension Pulmonary embolism Acute myocardial infarction Diastolic heart failure Fig. 5.3 Probe orientation for the parasternal long-axis view. RV LV Fig. 5.1 Parasternal long-axis view of a normal-appearing heart. Fig. 5.4 Parasternal short-axis diagram. LV, Left ventricle; RV, right ventricle. moved up an interspace. This view allows visualization of the left ventricle, mitral valve, left atrium, right ventricular outflow tract, aortic valve, and aorta. The descending thoracic aorta is often visualized posterior to the left ventricle in transection. RVOT LV Ao LA Fig. 5.2 Parasternal long-axis diagram. Ao, Aorta; LA, left atrium; LV, left ventricle; RVOT, right ventricular outflow tract. 44 Parasternal Short Axis The parasternal short-axis view is obtained by rotating the probe 90 degrees from the parasternal long-axis position so that the probe marker is pointed to the patient’s left shoulder (Figs. 5.4 and 5.5). The ultrasound beam is now transecting the heart in its short axis. If the physician tilts the probe so that it is pointing to the base of the heart, the aortic valve is visualized along with the “inflow and outflow” of the right heart. This view includes the right atrium, right ventricular outflow tract, and pulmonic valve. As the probe is tilted more apically, the aortic valve is lost and a cross-sectional view of the mitral valve is obtained (Fig. 5.6). At this point the right ventricle becomes more apparent and takes a position as a CHAPTER 5 EMERGENCY CARDIAC ULTRASOUND Fig. 5.7 Parasternal short-axis view at the level of the papillary muscles. This is an athletic heart with an enlarged right ventricle. Fig. 5.5 Probe orientation for the parasternal short-axis view. LV RV RA LA Fig. 5.6 Parasternal short-axis view at the level of the mitral valve: the “fish mouth” view. Fig. 5.8 Diagram of the apical four-chamber view. LA, Left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. crescentic ventricle to the left and superficial to the mitral valve and left ventricle. Finally, as the probe is tilted more toward the apex, the mitral valve is lost and the muscular portion of the left ventricle is visualized. The posterior medial and anterior papillary muscles are visualized at this point, and the circular nature of the left ventricle can be appreciated (Fig. 5.7). often impossible. The window is obtained by placing the probe at the location of maximal impulse with the probe marker pointed to the left axilla. The probe must be tilted so that the probe is pointed to the patient’s right shoulder (Fig. 5.11). The apical two-chamber view allows further evaluation of the left ventricle and mitral valve. The left atrial appendage can sometimes be see on the right side of the screen on the anterior side of the basal left ventricle. Apical Four- and Two-Chamber Views The apical window allows visualization of either all four chambers (Figs. 5.8 and 5.9) or just two chambers (the left atrium and ventricle) (Fig. 5.10). The apical windows are difficult to obtain in the emergency setting and often require the patient to be in the left lateral decubitus position, which is Subcostal Four-Chamber View The subcostal four-chamber view (Figs. 5.12 to 5.14) is obtained by placing the probe just inferior to the xiphoid and applying pressure downward on the abdomen with the probe 45 SECTION I RESUSCITATION SKILLS AND TECHNIQUES Fig. 5.9 Probe orientation for the apical four-chamber view. Fig. 5.11 Apical four-chamber view. Notice the size of the left ventricle in comparison with the right ventricle in this normal heart. Liver RV LV RA LV LA LA Fig. 5.10 Diagram of the apical two-chamber view. LA, Left atrium; LV, left ventricle. horizontal. This view can be performed with either the curvilinear abdominal probe or the phased-array thoracic probe. The probe marker should be toward the patient’s left in cardiac mode and toward the patient’s right when using focused abdominal sonography for trauma (FAST) or abdominal protocols. NORMAL AND ABNORMAL FINDINGS PERICARDIAL EFFUSION Evaluation of pericardial effusion is one of the first indications for cardiac ultrasound.6 Identification of pericardial effusion (Fig. 5.15) is achieved by visualization of the heart in multiple views. The subcostal window is the most commonly taught site because of the FAST examination. An effusion will appear 46 Fig. 5.12 Subcostal four-chamber window. Note the liver at the top of the ultrasound imaging window. LA, Left atrium; LV, left ventricle; RA, right atrium; RV, right ventricle. as an anechoic stripe of fluid surrounding the heart. This stripe is most commonly located between the right ventricle and the liver. Ideally, all three acoustic windows should be used when attempting to rule out pericardial effusion. The critical complication of pericardial effusion is cardiac tamponade (Fig. 5.16). Physiologically, cardiac tamponade occurs when the pressure inside the pericardial sac becomes elevated above right ventricular diastolic filling pressure. This leads to decreased filling of the right ventricle in diastole and reduced preload and cardiac output. Echocardiographic signs of cardiac tamponade are the presence of right ventricular free wall collapse as seen in Figure 5.16. Alternatively, a more sensitive, but less specific finding is the presence of right atrial collapse during ventricular systole (atrial diastole). CARDIAC ARREST POC cardiac echocardiography can be invaluable during cardiac arrest. Typical uses include evaluation for tamponade, hypovolemia, and suggestions of PE (clot, right ventricular CHAPTER 5 Fig. 5.13 Probe orientation for the subcostal four-chamber window. The probe is placed in the subxiphoid space with the probe marker oriented to the patient’s left (cardiac mode) or to the patient’s right (abdomen/focused abdominal sonography for trauma mode). The apex of the heart should be pointing to the right of the screen as seen in Figures 5.8 and 5.7. Fig. 5.14 Subcostal four-chamber window. dilation); detection of aortic dissection; monitoring for pacer capture and the adequacy of compressions; and most important, evaluation for cardiac activity in patients with pulseless electrical activity (PEA) and asystole. Studies have shown cardiac standstill during arrest to be 100% predictive of mortality.7 Furthermore, cardiac ultrasound has been used in place of a pulse check in pediatric populations because of the inherent difficulty of finding a pulse.8 Typical algorithms use cardiac ultrasound to evaluate PEA and asystolic rhythms.9 If cardiac standstill is present, further resuscitation is futile.7 EMERGENCY CARDIAC ULTRASOUND Fig. 5.15 Pericardial effusion noted in the parasternal long-axis view. Notice the location in reference to the descending thoracic aorta. Pericardial effusions track between the heart and the descending aorta, whereas pleural effusions can be seen posterior to the descending aorta. Fig. 5.16 Pericardial effusion with tamponade. Note the right ventricular free wall collapse in diastole (arrow). ACUTE HEART FAILURE Emergency physicians have been shown to be accurate in estimating left ventricular ejection fraction (LVEF).3 LVEF is most easily separated into three categories: reduced, normal, and hyperdynamic. Although echocardiographers often report actual percentages, we can think of normal LVEF as 55% to 75%, reduced as less than 55%, and hyperdynamic as greater than 75%. Some authors add a fourth category in which severely reduced LVEF is less than 30%. This distinction can be useful when discussing cardiac function with consultants. 47 SECTION I RESUSCITATION SKILLS AND TECHNIQUES The ejection fraction is typically estimated by visual inspection of the “squeeze” of the left ventricle, although it can also be measured with algorithms in the cardiac package of many emergency ultrasound machines. Pitfalls Emergency cardiac ultrasound involves the use of clear indications and directed ultrasound of the heart to answer specific questions, as described in the “Introduction.” Apart from these questions, a cardiologist should be consulted to aid in complex diagnosis and clinical decision making. Normal systolic function does not rule out acute heart failure. Diastolic heart failure can occur in patients with a normal LVEF. Diagnosis of cardiac tamponade by echocardiography can be complicated, and advanced echocardiographic techniques may be required, including Doppler evaluation. Stable patients may benefit from evaluation by a trained echocardiographer. Technically, the bedside sonographer may encounter difficulty obtaining the full series of views as described earlier. Patient habitus or artifact from the lungs or ribs may present challenges. Placing the patient on the left side in a left lateral decubitus position may aid in better viewing the parasternal and apical windows. This position moves the heart closer to the anterior chest wall. In the subcostal window, asking the patient to breathe in deeply may move the heart closer to the transducer. Additionally, moving the transducer toward the patient’s right, while still pointing toward the left side of the chest, may overcome artifact caused by the stomach or bowel by using the left lobe of the liver as an acoustic window. PULMONARY EMBOLISM Although cardiac ultrasound cannot identify a pulmonary embolus,10 several findings are suggestive of this diagnosis. Right ventricular dysfunction and dilation are typically visualized in the apical four-chamber window. Right ventricular dilation has been described in reference to the relative areas of the right and left ventricles at end-diastole. A right-to-left ventricular area ratio of greater than 0.66 has been shown to be 85% specific for PE.11 Another finding is described as retained apical function in the setting of right ventricular free wall hypokinesis. This is called the McConnell sign and can be fairly specific for PE. McConnell et al. described this particular finding as being 94% specific for PE11 (Fig. 5.17). An additional finding in acute PE is flattening of the interventricular septum. This is seen in the parasternal short-axis view and is due to either volume or pressure overload of the right heart (Fig. 5.18).12 VOLUME STATUS Assessment of the patient’s condition and the presence of hypervolemia or hypovolemia can be complicated. Through direct visualization of chamber size and evaluation of the great vessels, this clinical conundrum can often be overcome. Echocardiographic evaluation of volume status starts with global assessment of the ejection fraction and filling of the right and left sides of the heart. Reduced filling of both the right and left heart chambers implies reduced preload and hypovolemia. Conversely, the presence of dilated right and left heart chambers with a poor ejection fraction suggests hypervolemia. Finally, a dilated right ventricle with a contracted left 48 ventricle and an elevated LVEF suggests a forward flow problem of the right heart, such as PE, right-sided myocardial infarction, or cor pulmonale. Additionally, a body of research has led to evaluation of the inferior vena cava as a surrogate marker for central venous pressure and thus volume status.13 The current recommendations are summarized in Table 5.1. The inferior vena cava should measured during both inspiration and expiration from the subcostal long-axis view as seen in Figure 5.19. Fig. 5.17 McConnell sign. The apical contraction is denoted by the arrow. Fig. 5.18 Parasternal short-axis view showing septal flattening associated with right-sided pressure or volume overload. CHAPTER 5 EMERGENCY CARDIAC ULTRASOUND Fig. 5.19 Subcostal long axis of the inferior vena cava used to estimate central venous pressure. Table 5.1 IVC Diameters and Respective Collapse Associated with CVP Estimates Normal In between High IVC (CM) COLLAPSE CVP <2.1 >50% 3 (0-5) <2.1/>2.1 <50%/>50% 8 (5-10) >2.1 <50% 15 (10-20) Labovitz AJ, Noble VE, Bierig M, et al. Focused cardiac ultrasound in the emergent setting: a consensus statement of the American Society of Echocardiography and the American College of Emergency Physicians. J Am Soc Echocardiogr 2010;23:1225-30. Mandavia D, Hoffner R, Mahaney K, et al. Bedside echocardiography by emergency physicians. Ann Emerg Med 2001;38:377-82. Moore C, Rose GA, Tayal VS, et al. Determination of left ventricular function by emergency physician echocardiography of hypotensive patients. Acad Emerg Med 2002;9:186-93. Perera P, Mailhot D, Riley D, et al. The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically ill. Emerg Med Clin North Am 2010;28:29-56. CVP, Central venous pressure; IVC, inferior vena cava. SUGGESTED READINGS Blaivas M, Fox J. Outcome in cardiac arrest patients found to have cardiac standstill on the bedside emergency department echocardiogram. Acad Emerg Med 2001;8:616-21. REFERENCES References can be found www.expertconsult.com. on Expert Consult @ 49 CHAPTER 5 REFERENCES 1. Labovitz AJ, Noble VE, Bierig M, et al. Focused cardiac ultrasound in the emergent setting: a consensus statement of the American Society of Echocardiography and the American College of Emergency Physicians. J Am Soc Echocardiogr 2010;23:1225-30. 2. Perera P, Mailhot D, Riley D, et al. The RUSH exam: Rapid Ultrasound in SHock in the evaluation of the critically ill. Emerg Med Clin North Am 2010;28:29-56. 3. Moore C, Rose GA, Tayal VS, et al. Determination of left ventricular function by emergency physician echocardiography of hypotensive patients. Acad Emerg Med 2002;9:186-93. 4. Jones AE, Tayal VS, Sullivan DM, et al. Randomized controlled trial of immediate vs. delayed goal-directed ultrasound to identify the etiology of nontraumatic hypotension in emergency department patients. Crit Care Med 2004;32:1703-8. 5. Mandavia D, Hoffner R, Mahaney K, et al. Bedside echocardiography by emergency physicians. Ann Emerg Med 2001;38:377-82. 6. Plummer D, Brunnette D, Asinger R, et al. Emergency department echocardiography improves outcome in penetrating cardiac injury. Ann Emerg Med 1992;21:709-12. EMERGENCY CARDIAC ULTRASOUND 7. Blaivas M, Fox J. Outcome in cardiac arrest patients found to have cardiac standstill on the bedside emergency department echocardiogram. Acad Emerg Med 2001;8:616-21. 8. Tsung JW, Blaivas M. Feasibility of correlating the pulse check with focused point-of-care echocardiography during pediatric cardiac arrest: a case series. Resuscitation 2008;77:264-9. 9. Breitkreutz R, Walcher F, Seeger F. Focused echocardiographic evaluation in resuscitation management: concept of an advanced life support–conformed algorithm. Crit Care Med 2007;35:S150-61. 10. Ladato J, Ward R, Lang R. Echocardiographic predictors of pulmonary embolism in patients referred for helical CT. Echocardiography 2008;25:584-90. 11. McConnell MV, Solomon SD, Rayan ME, et al. Regional right ventricular dysfunction detected by echocardiography in acute pulmonary embolism. Am J Cardiol 1996;78:469-73. 12. Rudski LG, Lai WW, Afilalo J, et al. Guidelines for the echocardiographic assessment of the right heart in adults: a report from the American Society of Echocardiography. J Am Soc Echocardiogr 2010;23:685-713. 13. Jones AE, Tayal VS, Sullivan DM, et al. Randomized controlled trial of immediate vs. delayed goal-directed ultrasound to identify the etiology of nontraumatic hypotension in emergency department patients. Crit Care Med 2004;32:1703-8. 49.e1