Ann Thorac Surg 2004;77:1849-1850
© 2004 The Society of Thoracic Surgeons
How to do it
Creation of a diaphragm patch to facilitate placement of the AbioCor implantable replacement heart
Robert D. Dowling, MDa*,
Aziz S. Ghaly, MDa,
Laman A. Gray, Jr, MDa
a Department of Surgery, Division of Thoracic and Cardiovascular Surgery, University of Louisville School of Medicine, Louisville, Kentucky, USA
Accepted for publication July 21, 2003.
* Address reprint requests to Dr Dowling, 201 Abraham Flexner Way, Ste 1200, Louisville, KY 40202, USA
e-mail: rdowling{at}ucsamd.com
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Abstract
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One of the concerns when placing a total artificial heart is whether the device will fit in the thoracic cavity without impinging on vital structures. We report the creation of a patch in a recipient of the AbioCor Implantable Replacement Heart that allowed for an appropriate fit of the device without adversely affecting pulmonary and hemodynamic functions.
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Introduction
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The AbioCor Implantable Replacement Heart (IRH; ABIOMED, Danvers, MA) has been introduced into a clinical trial for patients with end-stage heart disease who are not candidates for other therapies [1]. Problems with fit of the Jarvik heart and the CardioWest heart (CardioWest Technologies, Inc., Tucson, AZ) suggested the need for improved methods to determine fit before operative therapy. A software program was developed (AbioFit; ABIOMED) to assist in determining, with a high degree of accuracy, whether the thoracic unit will fit in an orthotopic position without compromising the vital mediastinal structures. This program shows the anatomic relationship between the device and surrounding structures, particularly the left pulmonary veins, the inferior vena cava, and the left lower lobe bronchus [2]. We recently implanted the AbioCor IRH into a 65-year-old man who had adequate preoperative AbioFit results. However, at the time of operation, concerns about the device impingement on the left pulmonary vein stimulated us to create a diaphragmatic patch to allow for caudad displacement of the thoracic unit.
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Technique
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A 65-year-old man with previous aortic valve replacement and end-stage valvular cardiomyopathy underwent placement of an AbioCor IRH. The technique of placement of the AbioCor IRH was performed as previously described [2]. The initial placement of the thoracic unit in the pericardial space was performed, and the patient was successfully weaned from cardiopulmonary bypass. He demonstrated normal hemodynamics with flows greater than 6 L/min and normal left and right atrial filling pressures. Initially, approximation of the sternum demonstrated no alteration of hemodynamics, but the left pulmonary vein blood flow velocities gradually increased from 60 to 100 mL/s. Attempts to reposition the device at a more caudal location by placing sutures through the eyelets attached to the device resulted in worsening of the hemodynamics with closure of the sternum. We therefore decided to create a space for the device in the central tendon of the diaphragm. First, 2 marking stitches were placed on each side of the part of the diaphragm in contact with the thoracic unit. Then an incision was made in the diaphragm that connected the 2 marking stitches (Fig 1).
A 2 millimeter Gore-Tex patch (W. L. Gore & Associates, Newark, DE) was then tailored to the size of the area of the diaphragm in contact with the device and sewn to the edges of the divided diaphragm with a running 2-0 Prolene (Ethicon, Somerville, NJ) suture (Fig 2).
The patch was left quite wide being approximately 8 centimeters in width at its widest point. Finally, the device was allowed to rest on the patch, acquiring a more caudad position, and relieving pressure on the left pulmonary veins. This allowed for successful sternal closure with maintenance of normal hemodynamics. Chest radiograph demonstrated that an appreciable portion of the device sits below the level of the diaphragm.
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Comment
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The AbioCor IRH has been recently introduced into clinical trials for patients with end-stage heart failure. Before initiation of clinical trials, multiple anatomic fit studies were performed [3–5]. Recently, a computer software program was developed that allows for virtual surgery implantation of the AbioCor IRH thoracic unit. All potential candidates undergo a computerized tomography scan of the chest. The virtual surgery program (AbioFit) is then performed. The native ventricles are "removed," and the thoracic unit is implanted as would be performed at operation. This virtual model is designed to determine whether the AbioCor IRH can be positioned in the chest without impinging on vital structures such as the left pulmonary veins and left lower lobe bronchus. Along with a number of anatomic dimensions, the AbioFit is used by the surgical team to help determine whether the AbioCor IRH will have a high degree of certainty of fitting into the chest before they proceed with operative therapy. Additionally, this computer program has the potential for assessing the fit or design of other implantable devices.
Although in this recipient the AbioFit predicted an appropriate fit, there was a modest increase in the pulmonary vein velocities. Our previously used methods of tacking the device caudad by using eyelets on the thoracic unit resulted in decreased outputs on sternal closure.
Previous anatomic fit studies of total artificial hearts demonstrated that one of the most critical dimensions is the distance from the pulmonary bifurcation to the level of the diaphragm. Our clinical impression with previous implants also supported this observation. We therefore believed that placement of a diaphragmatic patch would likely improve the fit by allowing a caudal displacement of the device, which would alleviate any compression on the left hilum. Placement of the patch was easily accomplished with a piece of Gore-Tex patch that facilitated sternal closure without altering hemodynamics or blood flows in the pulmonary veins. There was no evidence of hemodynamic or pulmonary compromise after the operation. This simple technique may be a useful adjunct in patients with borderline fit of the AbioCor IRH or future generation artificial heart devices.
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References
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- Dowling R.D., Etoch S.W., Stevens K.A., Johnson A.C., Gray L.A. Status of the AbioCor implantable replacement heart. Ann Thorac Surg 2001;71(3 Suppl):S147-149.[Abstract/Free Full Text]
- Dowling R.D., Etoch S.W., Stevens K., et al. Initial experience with the totally implantable AbioCor replacement heart at the University of Louisville. ASAIO J 2000;46:579-581.[Medline]
- Parnis S.M., Yu L.S., Ochs B.D., et al. Chronic in vivo evaluation of an electrohydraulic total artificial heart. ASAIO J 1994;40:M489-493.[Medline]
- Jacobs G., Agishi T., Ecker R., Meaney T., Kiraly R.J., Nosé Y. Human thoracic anatomy relevant to implantable artificial heart. Artif Organs 1978;2:64-84.[Medline]
- Fujimoto K., Smith W.A., Jacobs G., et al. Anatomical considerations in the design of a long-term implantable human left ventricle assist system. Artif Organs 1985;9:361-374.[Medline]
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