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Ann Thorac Surg 2004;77:688-692
© 2004 The Society of Thoracic Surgeons
, MDc
a Department of Biomedical Engineering, Lerner Research Institute, Cleveland, Ohio, USA
b Department of Thoracic and Cardiovascular Surgery, Kaufman Center for Heart Failure, Cleveland, Ohio, USA
c Department of Cardiology, The Cleveland Clinic Foundation, Cleveland, Ohio, USA
d Department of Surgery, Medical School, University of Minnesota, Minneapolis, Minnesota, USA
* Address reprint requests to Dr Fukamachi, Department of Biomedical Engineering, The Cleveland Clinic Foundation, 9500 Euclid Ave, Cleveland, OH 44195, USA.
e-mail: fukamach{at}bme.ri.ccf.org
Presented at the Thirty-ninth Annual Meeting of The Society of Thoracic Surgeons, San Diego, CA, Jan 31–Feb 2, 2003.
Abstract
PURPOSE: The purpose of this study was to evaluate the ability of the Myocor Coapsys device to restore leaflet apposition and valve competency off-pump in a canine model of functional mitral regurgitation (MR).
DESCRIPTION: The Coapsys device was surgically implanted in 10 dogs after MR induction by rapid ventricular pacing. The Coapsys consists of anterior and posterior epicardial pads connected by a subvalvular chord. The annular head of the posterior pad was positioned at the annular level to draw the posterior leaflet and annulus toward the anterior leaflet. Final device size was selected when MR was minimized or eliminated as assessed by color flow Doppler echocardiography.
EVALUATION: All implants were placed off-pump without atriotomy, and mean MR grade was reduced from 2.9 ± 0.7 to 0.6 ± 0.7 (p < 0.001) acutely. No hemodynamic compromise was noted.
CONCLUSIONS: The Coapsys device consistently and significantly reduced or eliminated functional MR acutely. Further study will be required to assess the chronic stability of the repair in this animal model.
| Dr. McCarthy discloses that he has a financial relationship with Myocor.
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Mitral regurgitation (MR) is commonly considered to be one of the initiators of heart failure, as well as an ongoing impetus of the progression of the disease. Annuloplasty is a widely used means for mitral valve (MV) repair. However, the surgical procedure requires the patient to be placed on cardiopulmonary bypass, and is not consistently effective in this patient population. The Coapsys device (Myocor Inc, Maple Grove, MN), which was designed to restore the septal-lateral annular geometry and counter the regional ventricular dilation, has the advantage of being placed without cardiopulmonary bypass and open-heart access, and can be adjusted under echo guidance. This study was undertaken to assess feasibility and monitor acute echocardiographic and hemodynamic changes.
Material and methods
The Coapsys concept
The Coapsys device was developed to treat patients with clinically significant MR and left ventricular (LV) dysfunction. The treatment is intended to be at least as effective as currently available treatments for MR, with the following added benefits: (1) ability to affect both the mitral annulus and the papillary muscle; (2) off-pump implantation; (3) simple implantation procedure; (4) intraoperatively assessable, tunable, and reversible implantation; and (5) potential for a more stable repair that does not impede annular dynamics. These benefits may translate into reduced operative morbidity/mortality for these procedures.
Coapsys design
The Coapsys device consists of two epicardial pads and an expanded polytetrafluoroethylene (ePTFE)-coated, braided polyethylene subvalvular chord. The two pads are located on the surface of the heart, with the load-bearing subvalvular chord passing through the ventricle (Fig 1).
The posterior pad has two heads, configured such that the annular head and papillary head create shape change at the mitral annulus level and papillary muscle level, respectively, when the anterior and posterior pads are drawn together. The device location is schematically shown in Figure 2.
The polyester-covered anterior pad is adjustable and utilizes a deployable pin mechanism to fix the opposing end after sizing the device.
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Functional MR with heart failure was induced by rapid ventricular pacing at 230 beats/min for an average of 32 ± 4 days in 10 adult mongrel dogs (body weight, 25.3 ± 1.1 kg) [1, 2]. On the day of study, the pacemaker was reduced to demand mode at 30 beats/min to resume normal sinus rhythm, and the animal was anesthetized with thiopental (5 to 15 mg/kg) and intubated. The anesthesia was maintained with isoflurane (0.5% to 2.5%). A catheter with two Millar pressure sensors (model SPC-562, Millar Instruments, Inc, Houston, TX) was placed to record aortic (AoP) and LV (LVP) pressures. Pulmonary artery pressure (PAP) and the central venous pressure (CVP) were monitored with a thermister tip balloon catheter. The chest was accessed through a median sternotomy. A 14-mm Transonic flow probe (model 14A165, Transonic Systems Inc, Ithaca, NY) was placed on the ascending aorta to measure cardiac output (CO). A Millar catheter (Millar Instruments, Inc) was inserted into the left atrium to monitor left atrial pressure (LAP).
Epicardial two-dimensional (2-D) echocardiograms were obtained to assess mitral and tricuspid regurgitation (grade 0 to 4) by color Doppler imaging. To estimate LV end-diastolic (EDV), end-systolic (ESV) volumes, and ejection fraction (EF = [EDV - ESV]/EDV x 100), epicardial real-time three-dimensional (3-D) echocardiograms (Volumetric Medical Imaging Inc, Durham, NC) were obtained in 8 dogs. Reconstructed 3-D echocardiograms were obtained in the remaining 2 dogs. The EDV and ESV were determined by rotated apical six-plane views with a multiplanar Simpson method [3].
Coapsys implant surgery
The appropriate sites for Coapsys device placement were identified through a combination of external landmarks and 2-D echocardiogram visualization of internal structures. The placement avoided papillary muscle interference, the mitral apparatus, and main coronary artery branches. The posterior position was approximately 2.5 cm from the atrio-ventricular groove and midway between the papillary muscles, with the annular head of the pad directly opposed to the valve annulus (Fig 2). The anterior position was at the base of the right ventricular outflow tract, approximately 2 cm on the right ventricular side of the left anterior descending artery. After site identification, the Coapsys device was placed using a specially designed delivery instrument.
The device size, hemodynamics, and echocardiographic measurements were recorded as the presizing data point. The Coapsys device was then sized by drawing the posterior leaflet and annulus toward the anterior leaflet using a specially designed sizing instrument. Final device size was selected when MR was minimized or eliminated as assessed by color Doppler images (postsizing). The measurements were repeated as the postsizing data point.
Statistical analysis
Data were expressed as mean ± standard deviation. A paired t test was used for each paired data (presizing and postsizing). In all analyses, a p value of less than 0.05 was considered statistically significant.
Results
All Coapsys device implantations were performed off-pump. The mean device size (epicardial to epicardial measurements) at presizing and postsizing was 7.0 ± 0.6 and 5.1 ± 0.3 cm, respectively. The mean percent linear reduction from presizing measurement was 26% ± 7%. Geometric change produced by the device in a representative dog is shown in Figure 3.
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The Coapsys device acutely reduced functional MR in the rapid ventricular pacing–induced functional MR model. Mitral regurgitation was consistently reduced in all animals after implantation. Hausmann and associates [4] reported that the goal of MV reconstruction should be a reduction of MR to no more than grade 1. In our study, the Coapsys device reduced MR to an acceptable level of 0.6 ± 0.7. It was observed that the location of the posterior pad relative to the mitral annulus was the most important point for achieving a perfect or nearly perfect result using this device. We always confirmed this position from a long-axis view of the 2-D echocardiogram so that the annular head compressed the mitral annulus effectively.
Functional MR results from dilatation of the mitral valve annulus or lateral papillary muscle displacement in dysfunctional left ventricles. Timek and associates [5] revealed that the reduction in mitral annular septal-lateral dimension abolished acute ischemic MR. Liel-Cohen and associates [6] reported that surgical LV remodeling is an effective method to reduce ischemic MR. Hung and associates [7] demonstrated that repositioning papillary muscles by an external device could reduce ischemic MR without compromising LV function. These studies imply that both annular reduction and papillary muscle repositioning are effective in reducing functional MR. For this reason, the Coapsys device was designed in such a way that the annular head imparts shape change to the mitral annulus, while the papillary head located between the papillary muscles, repositions the papillary muscles. This enabled the Coapsys device to reduce MV annular area and reposition the papillary muscles.
Annuloplasty is a widely used, effective means for MV repair [8]. Annuloplasty rings, however, abolish normal annular and posterior leaflet motion [9]. Leil-Cohen and associates [10] reported that annuloplasty for functional ischemic MR may allow lesions to persist, with abnormal tethering by displaced papillary muscles in dilated, hypokinetic LVs. In this regard, the Coapsys device may yield good performance when treating functional MR.
Indications for the device would focus primarily on patients with ischemic MR or dilated cardiomyopathy MR who have essentially normal leaflet structure and motion, with MR attributed mainly to annular dilatation or papillary muscle displacement with chordal tethering. The device is not intended to treat MR arising from degenerative diseases or congenital defects.
Study limitations
In this model of functional MR, valve dysfunction is produced through rapid ventricular pacing rather than ischemia. Whereas it is true that the underlying etiology is markedly different, it is also true that the resulting pathophysiology is similar.
This study was designed as a preliminary evaluation of the Coapsys system. Further evaluations in a chronically stable model of functional MR will be required to fully assess the potential of this type of device.
In conclusion, the Coapsys implantation procedure was simple, and it was placed off-pump successfully in all cases. The Coapsys device consistently and significantly reduced or eliminated functional MR acutely.
Disclosures and freedom of investigation
This study was financially supported by Myocor, Inc (Maple Grove, MN). Myocor, Inc provided the study material. The authors have performed a free and independent evaluation of this technology. The authors had full control of the design of the study, methods used, outcome parameters, analysis of data and production of the written report. Patrick M. McCarthy, MD, is a consultant to Myocor, Inc.
Footnotes
The Society of Thoracic Surgeons, the Southern Thoracic Surgical Association, and The Annals of Thoracic Surgery neither endorse nor discourage use of the new technology described in this article.
Discussion
DR VALVANUR A. SUBRAMANIAN (New York, NY): How do you monitor in the operating room, once you place this device. Do you measure the tethering distance of the mitral valve to the papillary muscle preoperatively or intraoperatively, and then try to make it better with the Coapsys device?
DR FUKAMACHI: We can measure the distance between the two pads with the sizing instrument, then we reduce the distance by a 5% increment and monitor the mitral regurgitation. By decreasing that dimension, mitral regurgitation is reduced, for example, from 4 plus down to 3, 2, and further, with a further dimension decrease reducing it to 1. But if you further decrease the dimension, and mitral regurgitation is still 1, and there is no more positive decrease, then we decide that level as the deployment level. So, we are monitoring the device dimension and mitral regurgitation. We choose a deployment level that minimizes or eliminates mitral regurgitation.
DR SUBRAMANIAN: In functional MR, either you can have an annular dilatation or change in the tethering distances between the papillary muscles. Are you doing anything to the mitral annulus with this?
DR FUKAMACHI: Yes. The posterior pad has two heads (annular head and papillary head), and the annular head is actually compressing the annulus. So it causes a shape change of the annulus, which improves the coaptation of mitral leaflets.
DR SULAIMAN B. HASAN (Charleston, WV): I enjoyed your paper very much, and this may indeed be a major advance in the treatment of mitral regurgitation.
I just have a question about the exact positioning about your anterior pad in relation to the anterior descending artery.
And the other thing that I was wondering about was whether you leave anything inside the ventricle, and exactly what is that? Is it a rigid device? Is it a string that holds the pads together?
DR FUKAMACHI: As to the first question, in relation to the LAD, usually the anterior pad position is about 2 cm lateral to the LAD. So we have no problem with the LAD.
In the ventricle, there is a subvalvular chord which connects two pads.
DR HASAN: Is that a string or is it a rigid structure?
DR FUKAMACHI: This is a string made of braided polyethylene coated by PTFE.
DR SARA J. SHUMWAY (Minneapolis, MN): Do you think this device will be equally effective no matter what the mitral valve pathology is?
DR FUKAMACHI: At this moment, we think that it works for a structurally normal mitral valve, that is, functional mitral regurgitation.
References
This article has been cited by other articles:
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  W. Y. Szeto, R. C. Gorman, J. H. Gorman III, and M. A. Acker Ischemic Mitral Regurgitation Card. Surg. Adult, January 1, 2008; 3(2008): 785 - 802. [Full Text]
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 M. J. Mack Percutaneous Mitral Valve Repair: A Fertile Field of Innovative Treatment Strategies Circulation, May 16, 2006; 113(19): 2269 - 2271. [Full Text] [PDF]
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 M. A. Borger, A. Alam, P. M. Murphy, T. Doenst, and T. E. David Chronic Ischemic Mitral Regurgitation: Repair, Replace or Rethink? Ann. Thorac. Surg., March 1, 2006; 81(3): 1153 - 1161. [Abstract] [Full Text] [PDF]
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Y. K. Mishra, S. Mittal, P. Jaguri, and N. Trehan Coapsys Mitral Annuloplasty for Chronic Functional Ischemic Mitral Regurgitation: 1-Year Results Ann. Thorac. Surg., January 1, 2006; 81(1): 42 - 46. [Abstract] [Full Text] [PDF]
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E. A. Grossi, P. C. Saunders, Y. J. Woo, D. M. Gangahar, J. C. Laschinger, D. C. Kress, M. P. Caskey, C. F. Schwartz, and J. Wudel Intraoperative Effects of the Coapsys Annuloplasty System in a Randomized Evaluation (RESTOR-MV) of Functional Ischemic Mitral Regurgitation Ann. Thorac. Surg., November 1, 2005; 80(5): 1706 - 1711. [Abstract] [Full Text] [PDF]
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