Imaging in Transcatheter Mitral Valve Replacement: State-of-Art Review

Mitral regurgitation is the second-most frequent valvular heart disease in Europe and it is associated with high morbidity and mortality. Recognition of MR should encourage the assessment of its etiology, severity, and mechanism in order to determine the best therapeutic approach. Mitral valve surgery constitutes the first-line therapy; however, transcatheter procedures have emerged as an alternative option to treat inoperable and high-risk surgical patients. In patients with suitable anatomy, the transcatheter edge-to-edge mitral leaflet repair is the most frequently applied procedure. In non-reparable patients, transcatheter mitral valve replacement (TMVR) has appeared as a promising intervention. Thus, currently TMVR represents a new treatment option for inoperable or high-risk patients with degenerated or failed bioprosthetic valves (valve-in-valve); failed repairs, (valve-in-ring); inoperable or high-risk patients with native mitral valve anatomy, or those with severe annular calcifications, or valve-in-mitral annular calcification. The patient selection requires multimodality imaging pre-procedural planning to select the best approach and device, study the anatomical landing zone and assess the risk of left ventricular outflow tract obstruction. In the present review, we aimed to highlight the main considerations for TMVR planning from an imaging perspective; before, during, and after TMVR.

778 Acute clinical valve thrombosis after transcatheter mitral valve-in-valve replacement

Aims Transcatheter heart valve (THV) thrombosis is a frequent and potentially life-threatening complication of transcatheter mitral valve replacement (TMVR), occurring in approximately 12% of patients (mainly within the first 3 months after the procedure). The majority of THV thromboses is non-obstructive and subclinical, and remains undetected until a routine echocardiogram is performed. Methods A 65 years old male was suffering from post-ischaemic dilated cardiomyopathy and severe left ventricle systolic dysfunction (LVEF 28%), secondary to a previous STEMI in 2010 treated with primary PCI on proximal LAD; after the STEMI he developed a left ventricle aneurysm and a subsequent severe secondary mitral regurgitation. In late 2020 he underwent a surgical valve replacement with a biologic valve (Perimount Magna Mitral Ease n. 27), alongside a left ventricle reshaping (Dor procedure). After a few months, the patient developed worsening dyspnoea and severe exercise intolerance; a transesophageal echocardiogram (TEE) showed an extensive valve degeneration with diffuse leaflet thickening determining severe valve stenosis and regurgitation. The patient was then admitted to the Cardiology department. A coronary angiography was performed, showing good result of previous PCI and excluding other critical stenoses. The patient then underwent a transcatheter valve-in-valve replacement with a Sapien S3 n. 29 in mitral position. The patient was already in chronic therapy with acetilsalicilic acid (ASA), and after the procedure anticoagulant therapy with Warfarin was started. In the post-procedural period the patient developed an acute worsening of the LVEF with severe hypotension, likely due to after-load mismatch; hence, supportive inotropic therapy with Adrenalin and Enoximone was required. A TEE performed 7 days after the procedure showed absence of diastolic excursion of posterior and lateral cusps and leaflet thickening with a 4 mm thrombotic apposition on the ventricular side, determining severe valve stenosis with markedly increased transvalvular gradients (peak gradient 20 mmHg, mean gradient 11 mmHg). A CT scan of the heart confirmed the valve thrombosis on the inferior and lateral leaflets. Results Unfractioned heparin (UFH) was then added to ASA and Warfarin (INR target of 3.0). After 11 days of aggressive antithrombotic therapy a new TEE was performed, showing marked reduction in transvalvular gradients (peak gradient 10 mmHg, mean gradient 5 mmHg) due to partial dissolution of the thrombotic formation. Warfarin was then stopped, and after switching from UFH to Enoxaparin the patient was discharged asymptomatic and in good general conditions, with indication of follow-up with TEE at 1 month. Conclusions Valve-in-valve TMVR is a relatively new and still infrequent procedure, therefore few evidences about its complications are currently available. Thrombosis on these valves is not rare (12%), but usually develops on the atrial side of the leaflets; interestingly, in this patient the thrombosis was on the ventricular side, likely due to an acute reduction in flow velocity caused by the after-load mismatch and the subsequent cardiogenic shock.

763 Feasibility and reliability of a comprehensive three-dimensional transesophageal echocardiography screening process for transcatheter mitral valve replacement

Aims The planning of transcatheter mitral valve replacement (TMVR) requires cardiac imaging assessment to establish patient eligibility according to mitral valve anatomy, device characteristics and risk of left ventricular outflow tract (LVOT) obstruction. In this setting, computed tomography (CT) is considered the reference method. Although recent studies demonstrated that three-dimensional transesophageal echocardiographic (3D-TEE) assessment of mitral anatomy presents a good agreement compared to CT, its potential role in the TMVR planning has never been fully evaluated. To test feasibility and reliability of a comprehensive 3D-TEE screening in candidates for TMVR. Methods We performed a single-centre retrospective observational study including 59 consecutive patients referred to our centre for TMVR due to high surgical risk, who performed a pre procedural CT and 3D-TEE screening. The measurements of mitral annulus (MA), native LVOT and predicted Neo-LVOT, assessed with CT and 3D-TEE were collected in order to evaluate their concordance in the assessment of TMVR eligibility. The final suitability decision was given by the valve manufacturer based on CT measurements and then compared with the screening results obtained with 3D-TEE evaluation. 3D-TEE measurements were obtained with a post processing analysis using a novel automated software platform (3mensio Structural Heart 10.1 - 3mSH, Pie Medical Imaging, Bilthoven, Netherlands). Results Excellent correlation was found between 3D-TEE and CT measurements for MA area (r =0.85), antero-posterior diameters (r= 0.81), native LVOT (r=0.82) and Neo-LVOT areas (r=0.95) (all P-values <0.0001). Among 59 patients screened, 17 did not undergo the intervention because were found ineligible due to small predicted neo-LVOT, too small or too large MA area. Among the 42 patients with a successful screening, 32 underwent TMVR and all of them showed a correct implantation and no LVOT obstruction at post procedural echocardiographic evaluation. An almost perfect agreement among CT and 3D-TEE was found in assessing the eligibility for TMVR implantation (Cohen kappa 0.82, P<0.001). Interobserver and intraobserver agreements were found excellent for the parameters appraised with ICCs >0.80. Conclusions 3D-TEE appraisements of MA dimensions, native LVOT and Neo-LVOT are feasible in patients candidate for TMVR, showing good correlations with CT measurements and high accuracy to predict TMVR screening success.

26 Procedural planning and tip-to-base lampoon to succeed in a complex valve-in-valve TMVR procedure

Aims Left ventricle outflow tract (LVOT) obstruction is a feared complication of transcatheter mitral valve replacement (TMVR) procedures. Multimodal imaging evaluation is the key to identify at-risk patient and select the best management. Methods and results An 83-year-old woman with a history of mitral valve replacement with a 27-mm Carpentier-Edwards bioprosthesis (Edwards Lifesciences, Irvine, CA) for rheumatic heart disease was admitted to our department complaining worsening effort dyspnoea. Clinical evaluation revealed a grade 3/6 holosystolic murmur. She underwent combined transthoracic and transesophageal echocardiography (TEE) which demonstrated mitral bioprosthesis degeneration leading to severe stenosis (mean gradient = 13 mmHg, PHT-derived area = 0.9 cm2) and moderate regurgitation, with preserved biventricular function, and severe pulmonary hypertension (pulmonary artery systolic pression = 65 mmHg). The patient presented a high estimated risk for redo-surgery (Society of Thoracic Surgeons score estimated mortality: 6%) due to her complex medical history, including advanced chronic kidney disease and permanent atrial fibrillation; therefore, she underwent evaluation for valve-in-valve TMVR. Cardiac computed tomography (CT) revealed bioprosthetic anterior leaflet in tight contact with the septum in systole; predicted neo-LVOT using virtual 26-mm Sapien S3 (Edwards Lifesciences, Irvine, CA) valve was 150 mm2, conferring a high risk of fixed LVOTO. A 26-mm Sapien S3 valve was selected based on CT derived surgical valve ID of 24 mm. After Heart Team discussion, we performed a modified LAMPOON technique to achieve tip-to-base laceration of the bioprosthetic leaflet beside the LVOT, in order to prevent LVOT obstruction. Briefly, after transseptal puncture through right femoral vein access (16 Fr), we crossed the mitral prosthesis using a balloon wedge end-hole catheter, through which we advanced a 300 cm 0.014-inch wire into the ascending aorta, where it was snared from left arterial femoral access (8 Fr) and covered by a micro-catheter. The wire was previously kinked mid-shaft to form a ‘flying-V’ that was focally denuded and positioned at the target bioprosthetic leaflet’s tip using TEE and fluoroscopy. The guidewire was pulled toward the valve ring and electrified at 70 W with continuous 5% dextrose flush until adequate tip-to-base leaflet laceration. Thereafter, we successfully implant a 26-mm Sapien S3 valve. Maximal LVOT gradient post implant was 5 mmHg. The patient was discharged on post-operative day two and she recovered well, reporting functional and symptomatic improvement at 6-month follow-up. Conclusions our case highlights the importance of multimodality imaging and careful procedural planning to succeed even in complex valve-in-valve TMVR procedures. Transcatheter electrosurgery is an emerging tool for percutaneous structural heart interventions.