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Original Articles |
From the Department of Cardiology (S.S., P.K., R.E.), West German Heart Center, Essen, Germany; the Department of Medicine (L.B.), Montreal Heart Institute, Montréal, Canada; the Department of Cardiology (L.P., V.L., P.L.), University Hospital of Liège, Liège, Belgium; the Department of Cardiology (R.H., P.S.), R-WTH University Hospital Aachen, Aachen, Germany; the Cardiovascular Center OLV Ziekenhuis (J.B., M.V.), Aalst, Belgium; Medical College of Wisconsin (D.M.), Milwaukee, Wis; and Department of Cardiovascular Medicine (S.E., T.S.), Cleveland Clinic, Cleveland, Ohio.
Correspondence to Stefan Sack, MD, Klinikum Schwabing, Städtisches Klinikum München GmbH, Kölner Platz 1, D-80804 München, Germany. E-mail stefan.sack{at}klinikum-muenchen.de
Received June 26, 2008; accepted April 20, 2009.
| Abstract |
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Methods and Results— Symptomatic (New York Heart Association class 2 or 3) patients with primarily functional mitral regurgitation (MR) were included. A diagnostic PTMA procedure was performed in the coronary sinus venous continuity. MR was assessed and the PTMA device adjusted to optimize efficacy. If MR reduction (
1 grade) was observed, placement of a PTMA implant was attempted. Implanted patients were evaluated with echocardiographic, quality of life, and exercise capacity metrics. Nineteen patients received a diagnostic PTMA study. Diagnostic PTMA was effective in 13 patients (MR grade 3.2±0.6 reduced to 2.0±1.0), and PTMA implants were placed in 9 patients. Four devices were removed uneventfully (7, 84, 197, and 216 days), 3 for annuloplasty surgery due to observed PTMA device migration and/or diminished efficacy. No procedure or device-related major adverse events with permanent sequela were observed in any of the diagnostic or implant patients. Sustained reductions of mitral annulus septal-lateral dimension from 3D echo reconstruction dimensions were observed (4.0±1.2 mm at 3 months).
Conclusions— Percutaneous implantation of the PTMA device is feasible and safe. Acute results demonstrate a possibly meaningful reduction of MR in responding patients. Sustained favorable geometric modification of the mitral annulus has been observed, though reduction of MR has been limited. The PTMA method warrants continued evaluation and development.
Key Words: annuloplasty coronary sinus heart failure mitral valve regurgitation
| Introduction |
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Current therapeutic interventions to limit the impact of MR include both medical and surgical therapies.13,14 Surgical valve repair is performed via placement of an annuloplasty ring and/or mitral leaflet-subvalvular apparatus repair or mitral valve replacement.15,16 Current guidelines encourage surgical therapy for patients with symptoms, atrial fibrillation/arrhythmias, pulmonary hypertension, or changes in left ventricular function.17,18 Many patients who might otherwise benefit from treatment are excluded because they are unsuitable for such highly invasive open chest surgery due to the associated surgical morbidity and mortality.19,20 Similarly, many patients with mild MR at the time of surgical revascularization progress to significant MR after coronary artery bypass grafting.21
Various investigators have proposed less invasive repair techniques to interrupt the natural history of MR in ischemic heart disease and heart failure.22–24 Current efforts include approaches to directly clip25 the mitral leaflets or modify the mitral annulus via the coronary sinus26,27 and various other novel techniques.28 Preliminary data in both animal models and initial, temporary human studies have demonstrated the potential of the PTMA device (Viacor Inc, Wilmington, Mass) and the method to reduce the mitral annular septal-lateral dimension and limit MR.29,30 This report describes initial results and procedure revisions in an intention-to-implant feasibility study.
| Methods |
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PTMA Device Description
The Viacor PTMA system uses 2 primary structural elements: a multilumen PTFE (Teflon) PTMA catheter and Nitinol (nickel-titanium alloy) PTMA treatment rods. The PTMA catheter is provided in both diagnostic and implant versions. The PTMA system has been described previously.31 The PTMA implant device incorporates an integral proximal titanium access hub to facilitate the delivery and fix the position of the PTMA rods within the implant system. The implant differs from the diagnostic device in that the treatment section of the implant is fitted with an integral, nonabsorbable external polyester surgical suture winding to enhance the stability of the PTMA implant system. The diagnostic and implant PTMA rods are equivalent; each is formed from a single Nitinol wire that is profiled to provide precise, incremental application of stiffness to the posterior mitral annulus and thus reduce the septal-lateral dimension of the valve, improve leaflet coaptation, and reduce MR.
Procedure
Interventional device placement was performed in the cardiac catheterization laboratory after induction of general anesthesia. Transesophageal echocardiography (TEE) was used to measure quantitative procedural baseline MR and the septal-lateral annular dimension. For the most recent 15 patients enrolled in the study, a contrast enhanced, multidetector computed tomography (MDCT) scan was obtained before the procedure, and the dataset selectively rendered (M2S, West Lebanon, NH) and reviewed from the perspective of standard fluoroscopic viewing angles, both before the catheterization procedure and then continuously throughout the case in matched viewing angles. Arterial access was obtained for coronary angiography by standard techniques. Percutaneous venous access was obtained via the right or left subclavian vein. Access to the coronary sinus was established using standard 8F coronary sinus (CSG) sheaths (St Jude Apeel or Biotronik ScoutPro). After occlusive venography to demonstrate course and patency of the venous anatomy in multiple fluoroscopic views, a guide wire was advanced into the descending anterior interventricular vein. If the descending anterior interventricular vein could not be accessed, the case was terminated.
The Viacor 7F, 3-lumen PTMA diagnostic multilumen catheter was advanced over a 0.025-in or, in later cases, 0.035-in guide wire through the CSG sheath and into the coronary sinus under fluoroscopic guidance. The PTMA catheter was advanced until the distal radio-opaque marker was observed to have advanced 2 to 3 cm past the great cardiac vein into the anterior interventricular vein. PTMA diagnostic rods were progressively inserted into the PTMA diagnostic catheter to increase and adjust the treatment effect on the mitral annulus as observed by TEE with hemodynamic manipulation as needed to standardize arterial blood pressure during anesthesia. Up to 3 PTMA treatment rods were placed simultaneously within the PTMA catheter. Rods of various stiffness and design were used to apply stiffnesses of 100 to 600 g/cm selectively to the P2 segment of the mitral valve Angiographic, ECG and echocardiographic parameters were continuously monitored and recorded. Ultimate device size and position was determined by maximal reduction in the mitral annular dimensions with accompanying reduction in MR. If no treatment effect was observed via TEE with diagnostic PTMA, the devices were withdrawn and the patient was recovered. If treatment benefit was noted, and angiography verified no impingement on coronary circulation or PTMA device instability, the diagnostic catheter was exchanged for the implant PTMA catheter and rods. To conclude the implant procedure, the titanium PTMA implant hub was closed, sutured to subclavian fascia, the skin closed, and the patient was recovered.
Postprocedural Evaluation
Patients continued the standard medical care for heart failure without protocol directed changes. Echocardiography, clinical examination, and laboratory assessments were performed at 24 hours post-implantation and at
14, 30, 180, and 360 days. Three-dimensional geometric tracing of the mitral valve annulus at end diastole from echocardiographic volume datasets was performed using Tomtec 4D Cardio-View (Tomtec Imaging Systems, GmbH, Germany) software to assess changes in mitral annular geometry. Quality of life and exercise tolerance were performed at 30 and 180 days. Echocardiography was evaluated both by the enrolling centers and by the echocardiography core laboratory (Cleveland Clinic, Cleveland, Ohio). Quantitative echocardiography of TEE procedural images was also performed by the enrolling centers during and after procedures.
| Results |
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| Discussion |
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Procedural and Implant Considerations
As has been previously reported, coronary venous anatomy and the adjacent mitral apparatus are highly variable.32,33 The primary end point for this feasibility study is safety; procedure decisions were thus taken with considerable caution. As the device is removable at any point, in the event of clinical uncertainty, procedures were discontinued and no implant devices placed.
Variability in the anatomy of the coronary venous system, including tortuosity and narrow diameters, and also the structural interrelation with the mitral apparatus, was appreciated to impact both deliverability and stability of the PTMA device. Retrograde venography is limited in its utility in reliably guiding anterior vein subselection. Multidetector computed tomography utilization in screening to demonstrate continuity of the coronary venous system and coregistration with fluoroscopic images improved technical success and proved a valuable asset to the procedure.34,35 Successive device iterations improved PTMA device deliverability, particularly the most recent change to 0.035-in guide wire compatibility on the diagnostic and implant devices.
The implants that have achieved stable results chronically as shown in Figure 6 were placed somewhat distal of the CSO, thus sacrificing maximum geometric efficacy for chronic stability. Current device improvements are directed toward adjusting the stabilizing properties of the PTMA system to facilitate increased geometric efficacy with a stable device.
Arterial impingement with coronary sinus mitral repair devices has been a significant concern raised by multiple authors.23–27,32 We have only experienced the one described event treated with circumflex stenting. No evidence of arterial impingement was observed in any of the subsequent cases in this cohort. This result may be due to the design of PTMA device, which is exerting generally diffuse and outboard pressure in the vicinity of typical circumflex coronary crossover. Given the close relationship and highly variable nature of the venous and arterial courses and the close proximity and significant elastic stiffness of the PTMA device, possible arterial interaction will continue to be carefully evaluated both during screening diagnostic and interventional procedures.
PTMA requires successful long-term engagement of the coronary venous continuity relying on the structural integrity of the PTMA nitinol rods and anatomic stability of the PTMA device for long-term effect. Initial results from other mitral annular remodeling devices have highlighted the concerns regarding the durability challenges for structural implants placed in the coronary venous continuity,26 as have the results for surgical annuloplasty36,37 and biventricular pacing.38,39 The first PTMA implant was accompanied by Nitinol fracture within the first 72 hours requiring explant. Fatigue and design properties of the Nitinol were modified as were the durability test criteria and implant procedures. Subsequent long-term implants have not evidenced any structural failures.
Evidence for Effect
In this initial series, particularly in cases where the patient characteristics and device placement were favorable, significant acute geometric reductions of mitral annular septal-lateral dimension and associated MR have been observed. Surgical experience suggests that a septal-lateral annular reduction of at least 8 mm is typically required for a successful repair in a straightforward case.28,40 Multiple cases in this series have acutely demonstrated corrections of this magnitude (Figure 3). However, the aggregate sustained reduction of the septal-lateral dimension of the mitral annulus (Figure 6) has been less than the typical surgical correction. Not surprisingly, the associated late reductions of MR have been similarly modest. Further examination of the clinical efficacy of this anatomic effect as correlated to MR, chamber volumes, and clinical outcomes requires further study because the clinical efficacy of a partial correction may have limited benefit in a broad range of patients. Thus, speculation as to the clinical impact of the PTMA device in its early form is premature.
Study Limitations
The number of patients enrolled so far has been small and the iterative nature of the investigation limits the generalizability of the results. The protocol and device continues to undergo fundamental improvements. Long-term efficacy and safety remain unknown, including implications for subsequent procedures such as cardiac pacing and retrograde cardioplegia, although successful mitral annular surgery after PTMA implant demonstrates PTMA does not appear to limit surgical options for patients.
| Conclusions |
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| Acknowledgments |
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This study was funded by Viacor Inc.
Disclosures
Drs Sack, Bilodeau, Pierard, Lancellotti, Legrand, Hoffmann, Bartunek, Shiota, and Ellis received research support directly related to the conduct of this study from Viacor Inc. Dr Marks is an employee of Viacor Inc. The authors had full access to the data and take responsibility for its integrity. All authors have read and agree to the manuscript as written.
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