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Ann Thorac Surg 2006;81:787
© 2006 The Society of Thoracic Surgeons
Advanced Cardiology Center, PO Box 6682, Marina Station, Mayaguez, PR 00681-6684
(Email: garciarinald{at}prtc.net).
I congratulate Dr Emery and colleagues [1] for their landmark study on the use of the St. Jude Medical cardiac valve prosthesis (St. Jude Medical Inc, St. Paul, MN) during a 25-year period. Long-term follow-up studies such as that published by Butchart [2], Grunkemeier and colleagues [3], and now Emery and colleagues [1] provide excellent longitudinal data on the long-term performance of specific cardiac prosthesis, help to clarify and differentiate patient-related and prosthesis-related events, and serve to advance the field and enhance patient care.
An observation from reviewing the study results presented is the apparent decrease in the number of patient deaths due to causes other than the valve prosthesis. With the number of patients having concomitant coronary bypass procedures (1,732 or 38%) and the high average age at the time of implant (AVR, 70 years; MVR, 67 years), I estimate that with such excellent follow-up results the number of deaths due to myocardial infarction would be significantly higher. The decreased mortality in the patient population undergoing cardiac valve replacement surgery increases the significance of other valve-related complications and increases the importance of more effective long-term treatments.
As stated by Emery and colleagues [1], "chronic anticoagulation remains the major cause of VREs in patients with mechanical prosthesis." This statement is thoroughly backed by the data presented. Major bleeding events, with significant mortality, occurred in 589 (19.7%) of the patients who underwent aortic valve replacement (AVR), with only 4% prior to discharge and 16% during the follow-up period. In addition, a significant number (421) of thrombotic or thromboembolic events occurred in the AVR patients, again with a majority of mortalities (58 of 61 patients) occurring after discharge.
Becker and colleagues [4] has established that thromboembolism after aortic valve replacement is due to "platelet activation and aggregation" and that "the contribution of coagulation factors to overall thrombotic potential is a secondary phenomenon." The large number of thromboembolic events in Emery and colleagues' [1] patients treated with warfarin is suggestive that addressing the role of platelets in patients with aortic prostheses may be of increased importance.
We are currently in the fifth year of a pilot study using clopidogrel-aspirin combination as the sole anticoagulant for patients with St. Jude Medical mechanical aortic prostheses. This protocol was previous tried by Schlitt and colleagues [5], but was discontinued when a patient with a history of a pulmonary embolus thrombosed his aortic valve. With more rigorous patient selection criteria, focus on a single type of prosthesis, and more information on proper dosage levels for clopidogrel and aspirin, we believe our study will more thoroughly evaluate the safety and efficacy of this drug combination.
We have now enrolled 84 patients followed-up for a total of 1,871 months, with 42 patients having greater than 24 months and 23 having more than 36 months post-AVR follow-up. Five patients (5.9%) bled, 4 of these patients required transfusion and 1 of these required a vagotomy and pyloroplasty for a bleeding duodenal ulcer 2 weeks after the aortic valve replacement. None of the patients has had a thromboembolic episode, peripheral or cerebral. Interestingly, 2 patients converted to warfarin by their primary physician have sustained hemispheric strokes.
We continue to be very enthusiastic with the use of anti-platelet agents for patients with St. Jude medical mechanical aortic prosthesis. Our initial data in our population of patients indicate a reduction in morbidity and mortality associated with warfarin anticoagulation.
Our study will close in April 2006 when the last of the first 50 patients completes 2-year follow-ups according to the protocol. We will continue to monitor all patients in the study and hopefully accumulate long-term data on them. We acknowledge that a prospective randomized study will be required to confirm our findings, and we hope that our continued study results support ongoing evaluation.
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