Posterior Thoracic Echocardiography for Assessment of Native and Prosthetic Aortic Valves in the Presence of Pleural Effusion

CASE SERIES Posterior Thoracic Echocardiography for Assessment of Native and Prosthetic Aortic Valves in the Presence of Pleural Effusion Ming-Sum Lee, MD, PhD, Tasneem Z. Naqvi, MD, FRCP(UK), MMM Videos online at www.jultrasoundmed.org Many patients with aortic stenosis have difficult imaging windows due to advanced age, kyphosis, prior chest surgeries, radiation-induced skin changes, or hyperinflated lungs from pulmonary disease. Here we describe 4 cases to illustrate that in a subset of patients with pleural effusion, a posterior imaging approach can be used to obtain diagnostic images for native and prosthetic aortic valves. In these cases, nondiagnostic transthoracic echocardiographic images were obtained from conventional imaging windows, leading to inaccurate or incomplete assessment of the aortic valve. In all cases, images obtained from a posterior thoracic approach provided important additional diagnostic information. Key Words—aortic stenosis; echocardiography; pleural effusion; prosthetic aortic valve; vascular ultrasound Received July 11, 2013, from the Division of Cardiology, Department of Medicine, University of Southern California, Los Angeles, California USA (M.-S.L., T.Z.N.); and Mayo Clinic, Scottsdale, Arizona USA (T.Z.N.). Revision requested August 13, 2013. Revised manuscript accepted for publication August 16, 2013. Address correspondence to: Tasneem Z. Naqvi, MD, FRCP(UK), MMM, Mayo Clinic, 13400 E Shea Blvd, Scottsdale, AZ 95259 USA. E-mail: naqvi.tasneem@mayo.edu Abbreviations TEE, transesophageal echocardiography; TTE, transthoracic echocardiography doi:10.7863/ultra.33.4.721 T ransthoracic echocardiography (TTE) is the primary imaging modality used for patient selection before transcutaneous aortic valve replacement or surgical aortic valve replacement.1 After aortic valve replacement, TTE is also the main imaging modality used to assess prosthetic valve function serially during the follow-up period. Patients with severe aortic stenosis are often elderly and may have age-related kyphosis, prior chest surgeries, and other comorbidities, including chronic pulmonary disease, that make them poor surgical candidates. These comorbidities often make obtaining good TTE images difficult. In a considerable number of aortic valve replacement cases, diagnostic information cannot be obtained with regular transthoracic imaging. Many patients being considered for aortic valve replacement have congestive heart failure and bilateral pleural effusions. Here we describe 4 cases in which TTE performed using traditional windows was nondiagnostic, whereas clinically relevant information was obtained by performing TTE from a left posterior thoracic window. ©2014 by the American Institute of Ultrasound in Medicine | J Ultrasound Med 2014; 33:721–727 | 0278-4297 | www.aium.org Lee and Naqvi—Posterior Thoracic Echocardiography in the Presence of Pleural Effusion Case Descriptions Case 1 A 75-year-old male patient with a history of chronic obstructive pulmonary disease presented with respiratory failure and was admitted to the intensive care unit. Transthoracic echocardiography was performed to determine whether there was a cardiac etiology for his respiratory failure. It showed a calcified aortic valve. Continuous wave Doppler imaging across the aortic valve from an apical 5-chamber view revealed a peak velocity of 3.2 m/s, suggesting moderate aortic stenosis (Figure 1A). There was parallel alignment of the Doppler beam with the aortic valve, but the Doppler signal was weak, and the Doppler envelopes appeared incomplete. Additional Doppler gradients were obtained from a left posterior thoracic view, taking advantage of the good acoustic characteristics of left-sided pleural effusion. Using the same gain settings, the Doppler signal was stronger, and Doppler envelopes were clearer, showing that the peak velocity across the valve was 4.1 m/s, consistent with severe aortic stenosis (Figure 1B). Case 2 A 75-year-old male patient with aortic stenosis was referred for consideration of transcutaneous aortic valve replacement. He had a history of a spinal arteriovenous fistula that was treated with cobalt radiation. It unfortunately led to T4 compression and paraplegia. Because of severe bilateral peripheral arterial disease and nonhealing wounds, he underwent a bilateral above-the-knee amputation. His history was also notable for multivessel coronary disease and ischemic cardiomyopathy. He had chronic congestive heart failure symptoms refractory to medical therapy and large chronic bilateral pleural effusion. Transthoracic echocardiography was performed to evaluate the degree of aortic stenosis. Baseline images were technically challenging because the patient was unable to lie flat, and chronic chest wall edema and prior radiation made his entire anterior chest wall skin thickened and leatherlike. An apical 5-chamber view from the standard anterior approach showed poor endocardial definition and a calcified aortic valve that was poorly visualized (Figure 2A). Continuous wave Doppler imaging to evaluate gradients across the aortic valve showed a weak Doppler signal with incomplete jet envelopes (Figure 2C). Images from a posterior thoracic approach were obtained with the patient sitting upright in his wheelchair. Visualization of the left ventricle was improved, showing depressed left ventricular function (Figure 2B). Parallel alignment of the Doppler beam with the aortic valve was 722 possible from this window (Figure 2D). Doppler signals were improved, allowing assessment of aortic valve gradients and showing peak and mean aortic valve gradients of 57 and 34 mm Hg, respectively, and an estimated aortic valve area of 0.8 cm2, consistent with low-flow, low-gradient aortic stenosis (Figure 2D). Dobutamine infusion was performed with the patient sitting upright and by using the posterior thoracic imaging approach. With dobutamine at 20-μg/kg/min, an increase in peak and mean aortic valve gradients to 74 and 43 mm Hg was achieved, corresponding to an estimated aortic valve area of 0.7 cm2 (Figure 2E). The patient was deemed a reasonable candidate for transcutaneous aortic valve replacement and was scheduled to undergo the procedure. Figure 1. A, Continuous wave Doppler imaging across the aortic valve from an apical 5-chamber view showed a peak velocity across the aortic valve that was 3.2 m/s. B, The same patient was imaged from a left posterior thoracic window, where the ultrasound beam traveled through a left-sided pleural effusion before reaching the heart. The Doppler signal obtained from this window was more dense and showed a higher peak velocity across the aortic valve, at 4.1 m/s. A B J Ultrasound Med 2014; 33:721–727 Lee and Naqvi—Posterior Thoracic Echocardiography in the Presence of Pleural Effusion A Figure 2. A, Transthoracic echocardiography was performed to evaluate the aortic valve. An apical 5-chamber view was obtained from the standard approach. Endocardial definition was poor. A calcified aortic valve was poorly visualized (see Video 1). B, Transthoracic echocardiography using a posterior window showed left posterior pleural effusion (PE) and the adjacent left ventricle (LV). Left ventricular systolic function was moderately reduced, with the ejection fraction calculated as 37% (see Video 2). The aortic valve (arrowhead) position allowed parallel alignment with the Doppler beam for obtaining transaortic gradients. C, Continuous wave Doppler imaging across the aortic valve obtained from the standard apical 5-chamber view showed weak Doppler signals and incomplete jet envelopes. D, The same patient was imaged from a posterior approach. Continuous wave Doppler imaging through the aortic valve now showed an improved Doppler signal, with peak and mean transaortic gradients of 57 and 34 mm Hg, respectively. E, Dobutamine echocardiography was performed with posterior imaging. With dobutamine at 20 μg/kg/min, the peak and mean transaortic gradients increased to 74 and 43 mm Hg, consistent with severe aortic stenosis. Ventricular ectopy was present at baseline, and ventricular bigeminy was present during dobutamine infusion. B D C E J Ultrasound Med 2014; 33:721–727 723 Lee and Naqvi—Posterior Thoracic Echocardiography in the Presence of Pleural Effusion Case 3 In this case, TTE was performed to evaluate prosthetic valve function in a patient who had undergone transcutaneous aortic valve replacement with a CoreValve (Medtronic, Inc, Edgewater, MD). Images were initially obtained from standard views. On the parasternal long-axis view and the apical 5-chamber view, the CoreValve could be seen in the aortic position. No perivalvular leaks were detected from these views (Figure 3, A and B). Because of the poor image quality, additional images were obtained from a left posterior approach in this patient with pleural effusion. The CoreValve, including details of the nitinol stent, could be clearly visualized from this view (Figure 3C). Color flow Doppler imaging using the posterior thoracic window revealed two jets of a trace paravalvular leak (Figure 3D). This leak was completely missed in images obtained from the traditional approach (Figure 3, A and B). Case 4 A 16-year-old male patient with Marfan syndrome underwent aortic valve replacement and aortic root placement (the Bentall procedure) for aortic regurgitation and an ascending aortic aneurysm. The patient also had a history of bioprosthetic mitral valve replacement. Transthoracic echocardiography was performed to assess prosthetic valve function. On an apical 5-chamber view, the color flow Doppler signal in the aortic root was prematurely cut off because of shadowing from the aortic root graft (Figure 4A). Continuous wave Doppler imaging showed reasonable signals of aortic regurgitation, but the Doppler envelope of forward flow for evaluating gradients across the prosthetic valve was incomplete (Figure 4C). Despite multiple attempts to reangle the ultrasound probe, complete Doppler profiles could not be obtained because of a shadowing artifact from the aortic root graft. Taking advantage of the patient’s pleural effusion, a posterior approach was attempted. This approach allowed improved image quality and showed a well-seated aortic valve bioprosthesis (Figure 4, B and D) with an intravalvular leak (Figure 4E). It also allowed parallel alignment of the ultrasound beam with the aortic valve such that complete Doppler envelopes could be obtained to assess prosthetic valve function (Figure 4D). The color flow Doppler signal into the ascending aorta could now be seen (Figure 4F). 724 Discussion Obtaining good TTE images can be technically challenging in a number of patients. This problem is particularly relevant to patients being evaluated for transcutaneous aortic valve replacement, since these patients are often older and have poor acoustic windows. Transesophageal echocardiography (TEE) can be used for better assessment of the aortic valve. However, TEE generally requires sedation and is associated with potential complications. In patients with poor oxygenation, such as those with pulmonary edema from heart failure or those with severe lung disease, intubation is often required with TEE. Another challenge with TEE is the difficulty in aligning the ultrasound beam to obtain the highest transaortic Doppler gradients, and afterload reduction from sedation could affect the hemodynamics, leading to gradients that are not truly representative. Since TEE is an invasive procedure, it is not possible to perform it repeatedly for follow-up after valve replacement. The favorable acoustic quality of pleural effusion enables good ultrasound beam penetration. Here we show that in patients with pleural effusion, a left posterior TTE approach allows improved visualization of the aortic valve prosthesis, allowing detection of intravalvular or perivalvular leaks that could not be detected with the standard approach. The posterior approach also allows parallel alignment of the Doppler beam with the aortic valve and improved Doppler signals so that accurate measurements of aortic valve gradients can be made. The main limitation of this approach is that patients need to have left pleural effusion. Also, this imaging window does not provide adequate assessment of the aortic annulus for aortic valve sizing. For aortic annulus sizing, computed tomography and TEE are still the preferred modalities. The posterior TTE imaging approach is useful before aortic valve replacement for determining the degree of aortic stenosis. It is also particularly useful for follow-up of prosthetic valve function after valve replacement. In conclusion, in patients with pleural effusion in whom conventional TTE is technically difficult and fails to provide adequate assessment of a native or prosthetic aortic valve, it is reasonable to attempt a posterior imaging approach, as it may provide additional diagnostic information, as illustrated in the cases presented. J Ultrasound Med 2014; 33:721–727 Lee and Naqvi—Posterior Thoracic Echocardiography in the Presence of Pleural Effusion Figure 3. A, An apical 5-chamber view showed the CoreValve in the aortic position (arrow) (see Video 3). B, Color flow interrogation of the CoreValve from this view revealed no evidence of a perivalvular leak (see Video 4). C, The same patient was imaged from a posterior thoracic approach. The CoreValve (arrow), including details of the nitinol stent, could be delineated (see Video 5). D, Color flow interrogation of the CoreValve now showed two jets of a trace perivalvular leak (arrows) (see video 6). The perivalvular leak was seen in images obtained from the standard windows. Ao indicates aorta; LA, left atrium; LV, left ventricle; and PE, pleural effusion. C A D B J Ultrasound Med 2014; 33:721–727 725 Lee and Naqvi—Posterior Thoracic Echocardiography in the Presence of Pleural Effusion A Figure 4. A, Color flow Doppler imaging of a patient who underwent aortic root replacement and aortic valve replacement. Color flow was cut off abruptly because of a shadowing artifact from the aortic root graft. B, Imaging from a posterior thoracic approach showed an uninterrupted color Doppler flow signal into the ascending aorta. C, A continuous wave Doppler profile from a standard apical 5-chamber view showed adequate signals of aortic regurgitation, but the Doppler envelope of forward flow was incomplete. D, A continuous wave Doppler profile obtained from a posterior window now showed complete Doppler envelopes. E, (opposite page) Imaging from a posterior thoracic window showed a normally functioning bioprosthetic aortic valve, as well as a normally functioning bioprosthetic mitral valve. F, Color flow Doppler imaging showed an intravalvular leak and no perivalvular leak. Ao indicates ascending aorta; AV, bioprosthetic aortic prosthesis; LA, left atrium; LV, left ventricle; MV, bioprosthetic mitral prosthesis; and PE, pleural effusion. C B D 726 J Ultrasound Med 2014; 33:721–727 Lee and Naqvi—Posterior Thoracic Echocardiography in the Presence of Pleural Effusion E F References 1. Zamorano JL, Badano LP, Bruce C, et al. EAE/ASE recommendations for the use of echocardiography in new transcatheter interventions for valvular heart disease. J Am Soc Echocardiogr 2011; 24:937–965. J Ultrasound Med 2014; 33:721–727 727