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Ann Thorac Surg 2003;76:1774
© 2003 The Society of Thoracic Surgeons
a MedicalCV, Inc, 9725 South Robert Trail, Inver Grove Heights, MN 55077, USA
e-mail: medaffairs{at}medcvinc.com
To the Editor:
An article by Edwards and colleagues [1] reported an unfavorable experience with the Omniscience mechanical valve, the previous cardiac valve model of MedicalCV, Inc. MedicalCV, Inc, is concerned about unjustifiably alarming patients worldwide with the Omniscience valve (about 50,000 implants) and considers itself obliged to comment on complications reported in this article. However, it is handicapped by a lack of pertinent information from the authors, despite repeated requests and regulatory requirements.
The reported high rates of thromboembolism and hemorrhage contrast with several other studies, some of which the authors cited. Edwards and co-workers described inadequate anticoagulation in at least 50% of patients with valve thrombosis and 30% of those with thromboembolism and overanticoagulation in 38% of patients with hemorrhage, findings indicating poor patient compliance, inadequate therapy management, or both. These are precursors of poor results, regardless of valve model. It would have been useful, therefore, to compare the reported complication rates with the same center’s contemporary experience with other mechanical valves; a search of the literature revealed no such publications.
Seventeen patients were in the non-guideline complication category "limited disc excursion," although the auther did not provide disc opening measurements and methodology. Cardiac valves are passive devices; a disc opens to the degree demanded by cardiac stroke volume. Three explanted valves were returned to MedicalCV for evaluation (>11 years ago). All patients had chronic atrial fibrillation, one had a paravalvular leak, and two had undergone prior valve replacement. Therefore, limited disc excursion could be the effect of atrial fibrillation or a poor ventricle—rather than the cause. Exacerbating these poor ventricular conditions was the high number of patients who had had a previous valve operation (24.5%). Limited disc excursion could also be caused by myocardial interference with mitral disc motion as a result of ventricular size regression. In this regard, the authors did not indicate their preference regarding valve sizing, posterior leaflet preservation, or valve orientation. Company records show the mean mitral valve size selected by Edwards and associates was 29.6 mm, and this reveals a tendency toward oversizing.
At the inception of Doppler echocardiography, the phenomenon of gradient "overestimation" was not commonly recognized. MedicalCV is aware of a case at this institution where cardiologists urged reoperation because of high gradients at echocardiography. At reoperation, the Omniscience aortic valve exhibited a low pressure gradient by manometric measurement, and the surgeon elected not to replace the prosthesis.
Contrary to statements in the article, two explants evaluated by the Georgia Institute of Technology demonstrated no structural or functional abnormalities. Subsequent examination at MedicalCV’s laboratories confirmed these findings. Qualitative examination of the wear track indicated occasional partial opening in vivo, probably caused by the patients’ atrial fibrillation.
Space limitations prevent detailing the divergent references and the numerous statistical deficiencies in this article. For instance, the number of patients is smaller than reported to MedicalCV with implantation cards, there were either 20 or 22 patients having multiple-valve replacement (Table 1), and even the implantation period does not match what is shown in the company’s verifiable records.
It is unfortunate that the authors did not share their dissatisfaction with MedicalCV, Inc. The authors and their patients could have benefited from information available to the company from other physicians with Omniscience valve experience.
Footnotes
1 Dr Mikhail discloses that he has a financial relationship with MedicalCV, Inc. 
References
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