Atrial Embolization after a Transcatheter Mitral Valve Replacement

Abstract

MITRAL REGURGITATION (MR) IS the most prevalent form of valve disease, affecting about 10% of people over the age of 75 years and is associated with increased mortality.1Coffey S Cairns BJ Iung B. The modern epidemiology of heart valve disease.Heart. 2016; 102: 75-85Crossref PubMed Scopus (133) Google Scholar,2Overtchouk P Piazza N Granada J et al.Advances in transcatheter mitral and tricuspid therapies.BMC Cardiovasc Disord. 2020; 20: 1Crossref PubMed Scopus (25) Google Scholar Management is dependent on the cause, pathophysiology, and predicted treatment efficacy. Although the historic gold standard for disease refractory to medical therapy is valve repair or replacement, over the last decade several transcatheter strategies have emerged, providing less invasive alternative options to elderly and frail patients at high risk for cardiac surgery. Transcatheter mitral valve replacement (TMVR) using a valve-in-native valve approach has become a well-established alternative option for patients with severe primary and secondary MR considered at high or prohibitive surgical risk.3Goode D Dhaliwal R Mohammadi H. Transcatheter mitral valve replacement: State of the art.Cardiovasc Eng Technol. 2020; 11: 229-253Crossref PubMed Scopus (17) Google Scholar Mitral leaflets cannot be assessed by fluoroscopy, so procedural success relies on echocardiographic guidance by transesophageal echocardiogram (TEE).4Wunderlich NC Siegel RJ. Peri-interventional echo assessment for the MitraClip procedure.Eur Heart J Cardiovasc Imaging. 2013; 14: 935-949Crossref PubMed Scopus (86) Google Scholar Echocardiographers must be able to provide a comprehensive assessment immediately prior to, during, and after implantation in order to define not only success, but also problematic anatomy and inadequate deployment. A 78-year-old woman with history of non-rheumatic mitral stenosis and regurgitation, hypertension, pulmonary hypertension, pulmonary embolism, aortic stenosis status post-transcatheter aortic valve replacement with a 23 mm Edwards Sapien valve (Edwards Lifesciences, Irvine, CA), and coronary artery disease presented for elective TMVR. Past surgical history included prophylactic alcohol septal ablation 2 weeks preoperatively to treat septal hypertrophy (2.29 cm), and subsequent permanent pacemaker implantation for complete heart block. On a planning Multidetector Computed Tomography (MDCT) scan, the patient had 270° of circumferential calcium in the mitral annulus (Fig 1). The lateral mitral annulus calcium thickness was measured as 10 mm and medial annular thickness was measured as 11.1 mm, with a calculated mitral annular calcification (MAC) score of 8. Given her comorbidities and severity of her mitral annular calcification, TMVR was chosen rather than open surgical intervention. A transapical approach for TMVR was planned because the patient had anomalous venous return with the absence of a direct inferior vena cava to right atrium blood flow, with blood return via the hemiazygous vein. A 26 mm Sapien 3 Ultra valve was chosen due to her calculated annular area of 4.55 cm2 by planning CT (Fig 1 and Table 1).Table 1Displays Edwards Sapien Valve Size and Corresponding Native Valve Annulus Area.Edwards Sapien Valve size20 mm23mm26 mm29 mmNative Valve Annulus Area (CT scan)273-345 mm2338-430 mm2430-546 mm2540-683 mm2Abbreviations: CT, computed tomography. Open table in a new tab Abbreviations: CT, computed tomography. Pre-implantation 2-dimensional and 3-dimensional TEE examinations were performed (Video 1, Figure 1A) and a 26 mm Edwards Sapien 3 Ultra valve was deployed with 15% oversizing (Video 2). Post-implantation TEE images were obtained (Videos 2-4, Figure 2A and B). The patient was extubated and transferred to the intensive care unit in stable condition. Upon arrival in the intensive care unit, the patient experienced immediate hemodynamic distress, with worsening respiratory failure, flash pulmonary edema, and acute heart failure. The patient was reintubated, and emergent bedside TEE (Figure 2C & 2D, Video 5) revealed an embolized mitral valve into the left atrium, severe mitral regurgitation, and intermittent obstruction of left atrial outflow. After the valve embolization was identified, the patient was emergently returned to the operating room and the mitral valve was replaced with a 29 mm St. Jude Epic valve via a traditional midline sternotomy, bicaval cannulation, and cardiopulmonary bypass (Video 6). The patient had an uncomplicated intraoperative and postoperative course, with follow up TEE showing no paravalvular regurgitation, and a mean gradient of 5 mmHg across the replaced mitral valve. The patient was discharged one week after her surgery. Given the clinical context provided, and Videos 1- 4, did this patient demonstrate risk factors for mitral valve embolization? Atrial embolization is a feared, but well described complication of TMVR, with a reported incidence of 0.8% to 6.25% during implantation, and confers a nearly 3-fold increase in 1-year mortality.5Guerrero M Wang DD Pursnani A et al.a cardiac computed tomography-based score to categorize mitral annular calcification severity and predict valve embolization.JACC Cardiovasc Imaging. 2020; 13: 1945-1957Crossref PubMed Scopus (48) Google Scholar, 6Guerrero M Dvir D Himbert D et al.Transcatheter mitral valve replacement in native mitral valve disease with severe mitral annular calcification: Results from the first multicenter global registry.JACC Cardiovasc Interv. 2016; 9: 1361-1371Crossref PubMed Scopus (208) Google Scholar, 7Gregory SH Sodhi N Zoller JK et al.Anesthetic considerations for the transcatheter management of mitral valve disease.J Cardiothorac Vasc Anesth. 2019; 33: 796-807Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar, 8Guerrero M Urena M Himbert D et al.1-Year outcomes of transcatheter mitral valve replacement in patients with severe mitral annular calcification.J Am Coll Cardiol. 2018; 71: 1841-1853Crossref PubMed Scopus (201) Google Scholar Given that valve embolization is a catastrophic event, with significant associated morbidity, it is essential that cardiac anesthesiologists maintain a high index of suspicion perioperatively and carefully consider preoperative risk factors, CT findings, and intraoperative TEE findings. Previously described risk factors for embolization include: undersized implanted valve, left ventricular outflow tract(LVOT) obstruction, MAC score ≤ 7, mitral regurgitation as the primary pathology, and relatively shallow or atrial deployment.5Guerrero M Wang DD Pursnani A et al.a cardiac computed tomography-based score to categorize mitral annular calcification severity and predict valve embolization.JACC Cardiovasc Imaging. 2020; 13: 1945-1957Crossref PubMed Scopus (48) Google Scholar, 6Guerrero M Dvir D Himbert D et al.Transcatheter mitral valve replacement in native mitral valve disease with severe mitral annular calcification: Results from the first multicenter global registry.JACC Cardiovasc Interv. 2016; 9: 1361-1371Crossref PubMed Scopus (208) Google Scholar, 7Gregory SH Sodhi N Zoller JK et al.Anesthetic considerations for the transcatheter management of mitral valve disease.J Cardiothorac Vasc Anesth. 2019; 33: 796-807Abstract Full Text Full Text PDF PubMed Scopus (13) Google Scholar, 8Guerrero M Urena M Himbert D et al.1-Year outcomes of transcatheter mitral valve replacement in patients with severe mitral annular calcification.J Am Coll Cardiol. 2018; 71: 1841-1853Crossref PubMed Scopus (201) Google Scholar Factors associated with lower risk of embolization include annular calcium thickness of ≥5 mm, calcium distribution of >270° of annular circumference, anterolateral trigone calcification, and anterior mitral leaflet calcification. These factors contribute to TMVR device anchoring, thereby lowering the risk of embolization or migration into the LA.5Guerrero M Wang DD Pursnani A et al.a cardiac computed tomography-based score to categorize mitral annular calcification severity and predict valve embolization.JACC Cardiovasc Imaging. 2020; 13: 1945-1957Crossref PubMed Scopus (48) Google Scholar CT-based MAC score was developed by Guerrero et al. and is calculated using (1) average calcium thickness (mm), (2) degrees of annulus circumference involved, (3) calcification at one or both fibrous trigones, and (4) calcification of one or both leaflets.8Guerrero M Urena M Himbert D et al.1-Year outcomes of transcatheter mitral valve replacement in patients with severe mitral annular calcification.J Am Coll Cardiol. 2018; 71: 1841-1853Crossref PubMed Scopus (201) Google Scholar Based on the previously described risk factors, a greater calcium burden should confer a higher success rate for anchoring a replacement valve. The patient in question had near-total circumferential calcium deposition, but despite this, embolization still occurred. Of particular importance, in the same study where Guerrero et al. identified a 6.9% risk of embolization, the authors also determined postoperatively that all cases had received relatively undersized replacement valves.5Guerrero M Wang DD Pursnani A et al.a cardiac computed tomography-based score to categorize mitral annular calcification severity and predict valve embolization.JACC Cardiovasc Imaging. 2020; 13: 1945-1957Crossref PubMed Scopus (48) Google Scholar,9Guerrero M Wang DD O'Neill W Percutaneous rescue of an embolized valve after transcatheter mitral valve replacement.JACC Cardiovasc Interv. 2017; 10: 627-629Crossref PubMed Scopus (9) Google Scholar In TMVR for failing surgical bioprosthesis or ring, the sizing of a prosthetic valve primarily relies on the manufacturer reported true internal diameter of the surgical device,10Urena M Himbert D Brochet E et al.Transseptal transcatheter mitral valve replacement using balloon-expandable transcatheter heart valves: A step-by-step approach.JACC Cardiovasc Interv. 2017; 10: 1905-1919Crossref PubMed Scopus (47) Google Scholar whereas in the native mitral annulus, the sizing relies on a MDCT annulus measurement. This measurement is often complicated by the mitral annulus’ nonplanar saddle shape. In native mitral annuli, factors such as leaflet calcification, noncircumferential calcification, and extension of annular calcification plays a role in determining the degree of implanted valve oversizing (usually 10%-25%), with a general rule that a greater degree of oversizing is required for a less calcified annulus.10Urena M Himbert D Brochet E et al.Transseptal transcatheter mitral valve replacement using balloon-expandable transcatheter heart valves: A step-by-step approach.JACC Cardiovasc Interv. 2017; 10: 1905-1919Crossref PubMed Scopus (47) Google Scholar In the authors’ patient, the replacement valve was chosen based on the consensus of 2 structural heart experts after consideration of CT annulus sizing. During the procedure, moderate eccentric paravalvular regurgitation was noted (Video 3), and the interventricular septum appeared to be intermittently in contact with the prosthetic mitral valve during end-systole, with associated mild rocking motion of the implanted MV along its interface with the anterior mitral valve leaflet (Video 4). Though there was no hemodynamic evidence of LVOT obstruction, Video 4 demonstrates a likely mechanical etiology for valve embolization and is consistent with previously described LVOT obstruction as a risk factor. Despite this patients’ prior septal ablation, the interventricular septum was seen in contact with the inferior portion of the implanted valve during systole, pushing the valve upward toward the left atrium. Based on published risk factors, preoperatively this patient should have carried an intermediate risk for valve embolization. Her high native valve calcium burden, (MAC score 8) would be generally protective, though the annulus had only 270° of calcification and her anterior mitral valve leaflet did not demonstrate heavy calcification. Furthermore, given the MDCT annular measurement, the chosen valve should have been appropriately sized. Embolization may have been primarily related to imprecise deployment of the valve, or due to cardiac motion during deployment resulting in inadequate fixation of the valve in the mitral annulus.5Guerrero M Wang DD Pursnani A et al.a cardiac computed tomography-based score to categorize mitral annular calcification severity and predict valve embolization.JACC Cardiovasc Imaging. 2020; 13: 1945-1957Crossref PubMed Scopus (48) Google Scholar Another possible explanation for the timing of this embolization may center around periextubation changes in intrathoracic pressures and ventricular loading conditions. In the setting of an imperfect valve deployment, increased left ventricular pressure and acute changes in preload associated with extubation and coughing may have precipitated a progressive unwitnessed increase in paravalvular regurgitation, possibly to the point of complete detachment of the implanted valve from the annulus. Given the finding of intermittent septal contact, an acute decrease in left ventricular preload could have acutely increased the degree of valve-septal contact and led to detachment. In the procedure suite, the subtle rocking motion of the implanted valve coupled with significant paravalvular MR was likely a harbinger for subsequent valve embolization (Videos 3 and 4). It is possible that further balloon dilation or oversizing would have prevented this event, but due to the area of poor contact being the interface with the less calcified section of anterior mitral leaflet, it is not certain that this would have led to significantly improved fixation. Additionally, balloon dilation and excess oversizing carries significant risks, including potential impact on the existing transcatheter aortic valve replacement, entrapment and blockage of the prosthesis, and rupture of the mitral annulus.11Pirelli L Hong E Steffen R et al.Mitral valve-in-valve and valve-in-ring: Tips, tricks, and outcomes.Ann Cardiothorac Surg. 2021; 10: 96-112Crossref PubMed Google Scholar To decrease the risk of embolization, some operators advocate deploying the valve in conical shape and flare in the LV.12Urena M Himbert D Brochet E et al.Transseptal transcatheter mitral valve replacement using balloon-expandable transcatheter heart valves: a step-by-step approach.JACC Cardiovasc Interv. 2017; 10: 1905-1919Crossref PubMed Scopus (50) Google Scholar Though a few cases of catheter-based interventions to treat valve embolization have been published, unfortunately, this situation most often requires emergent surgical intervention.5Guerrero M Wang DD Pursnani A et al.a cardiac computed tomography-based score to categorize mitral annular calcification severity and predict valve embolization.JACC Cardiovasc Imaging. 2020; 13: 1945-1957Crossref PubMed Scopus (48) Google Scholar,9Guerrero M Wang DD O'Neill W Percutaneous rescue of an embolized valve after transcatheter mitral valve replacement.JACC Cardiovasc Interv. 2017; 10: 627-629Crossref PubMed Scopus (9) Google Scholar Considering the risks of embolization using TMVR, further refinement of patient selection and pre-procedural evaluation is required. In this case, TEE provided a valuable, rapid method of detection of embolization of the replacement mitral valve, as well as demonstrated intraoperative findings which were likely predictive of future embolization. MR has a high prevalence in older patient populations. For patients with significant comorbidities and associated high surgical risk, TMVR is an emerging treatment option. Given the complexity of mitral valve anatomy and its pathology, thoughtful patient selection is essential to minimize complications. It is, therefore, crucial to understand the role of multimodal imaging tools, particularly TEE, for procedural guidance and post-procedural minimization of complications. It is essential that interventional echocardiographers be able to identify patients at particular risk of valve embolization by identifying concerning intraoperative TEE findings.