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J Am Coll Cardiol, 2004; 44:1143-1144, doi:10.1016/j.jacc.2004.06.009
© 2004 by the American College of Cardiology Foundation
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LETTER TO THE EDITOR

Anticoagulation management of patients with prosthetic valves

Eric G. Butchart, FRCS, FETCS, FESC

University Hospital of Wales, Cardiff CF14 4XW, Wales, United Kingdom

Christa Gohlke-Bärwolf, MD, FESC

Herz-Zentrum Bad Krozingen, , Bad Kronzingen, Germany

(Email: egbutchart{at}aol.com).

As authors of previous European guidelines on anticoagulation of patients after valve surgery and as members of a committee currently revising those guidelines, we are concerned to read the paper of Vink et al. (1) Their recommendation that all patients should be managed with an international normalized ratio (INR) of 3.0 to 4.5 reverses current trends to individualize antithrombotic management for each patient based on an assessment of their particular thromboembolic risk (2–4). Although having a "one size fits all" approach to anticoagulation management may have advantages for anticoagulation clinics, this approach will not benefit individual patients who may be exposed to the risks of unnecessarily high anticoagulation.

Their meta-analysis raises several concerns. First, meta-analysis is a technique for amalgamating data from randomized controlled trials (RCT) that have used the same methodology, not observational studies with different methodology. Second, reported thromboembolic rates are heavily influenced by definitions, data collection methods (prospective vs. retrospective), size and length of study, patient risk factors, concomitant surgery, and type of prosthesis (5,6). Other than the prosthetic type, these factors are not mentioned. Valve thrombosis rates are influenced by the number of patients who experienced anticoagulation interruption, to which most cases are related (7). Third, we question the use of target INRs rather than achieved INRs. Many events occur when the INR is outside the target range.

Fourth, retrospective conversion of prothrombin time ratios to INR has the potential to introduce huge errors. In American studies, it is highly unlikely that a single thromboplastin reagent would have been used for all patients in the study (8).

Finally, there is a lack of acknowledgment of the five published RCTs comparing different anticoagulation intensity (9–13). Although most of these RCTs have limited applicability because of their methodologies, all reached the conclusion that a higher intensity of anticoagulation did not reduce the incidence of thromboembolism. Four RCTs showed a higher incidence of bleeding with higher intensity anticoagulation. The only RCT not to show this effect used overlapping INR ranges and did not record events in the first three months (13).

Although Vink et al. (1) acknowledge that high-intensity anticoagulation results in a higher incidence of bleeding, they appear to minimize this danger. Use of a higher range of INR, 3.0 to 4.5, for all patients imposes an imperative for extremely tight INR control. High variability of INR, with >30% of INRs outside the range 2.0 to 4.0, is the strongest predictor of reduced survival after valve replacement (14). Furthermore, thromboembolic and bleeding events are not equivalent in terms of mortality risk. The one-year survival after ischemic stroke is about 80%, whereas the one-year survival after intracerebral hemorrhage is only about 20% (15).

The paper of Vink et al. (1) reinforces the view of the Dutch Thrombosis Service since the mid-1980s that all mechanical valve patients should have an INR of 3.0 to 4.5, (16) However, it is scientifically unsound in its methodology, ignores evidence for a contrary view, including RCTs and current guidelines (2,4,17), and takes a big step backward from the modern practice that is based on individual risk stratification and risk-adjusted intensity of anticoagulation. We believe that their recommendations should not be followed.


   References
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 References
 

  1. Vink R, Kraaijenhagen RA, Hutten BA, et al. The optimal intensity of vitamin K antagonists in patients with mechanical heart valves: a meta-analysis J Am Coll Cardiol 2003;42:2042-2048.[Abstract/Free Full Text]
  2. Gohlke-Bärwolf C, Acar J, Oakley C, et al. Guidelines for prevention of thromboembolic events in valvular heart diseaseStudy group of the working group on valvular heart disease of the European Society of Cardiology. Eur Heart J 1995;16:1320-1330.[Free Full Text]
  3. Butchart EG, Ionescu A, Payne N, et al. A new scoring system to determine thromboembolic risk after heart valve replacement Circulation 2003;108(Suppl II):68-74.
  4. ACC/AHA Task Force on Practice Guidelines ACC/AHA Guidelines for the management of patients with valvular heart disease J Am Coll Cardiol 1998;32:1486-1588.[Free Full Text]
  5. Edmunds LH. Thrombotic and bleeding complications of prosthetic heart valves Ann Thorac Surg 1987;44:430-445.[Abstract]
  6. Grunkemeier GL, Starr A, Rahimtoola SH. Prosthetic heart valve performance: long-term follow-up Curr Probl Cardiol 1992;17:331-406.
  7. Deviri E, Sareli P, Wisenbaugh T, Cronje SL. Obstruction of mechanical heart valve prostheses: clinical aspects and surgical management J Am Coll Cardiol 1991;17:646-650.[Abstract]
  8. Hirsh J, Levine M. Confusion over the therapeutic range for monitoring oral anticoagulation therapy in North America Thromb Haemost 1988;59:129-132.[Medline]
  9. Turpie AGG, Gunstensen J, Hirsh J, et al. Randomised comparison of two intensities of oral anticoagulation therapy after tissue heart valve replacement Lancet 1988;1:1242-1245.[Medline]
  10. Saour JN, Sieck JO, Mamo LAR, Gallus AS. Trial of different intensities of anticoagulation in patients with prosthetic heart valves N Engl J Med 1990;322:428-432.[Abstract]
  11. Altman R, Rouvier J, Gurfinkel E, et al. Comparison of two levels of anticoagulation therapy in patients with substitute heart valves J Thorac Cardiovasc Surg 1991;101:427-431.[Abstract]
  12. Acar J, Iung B, Biossell JP, et al. AREVA: multicenter randomized comparison of low-dose versus standard-dose anticoagulation in patients with mechanical prosthetic heart valves Circulation 1996;94:2107-2112.[Abstract/Free Full Text]
  13. Huth C, Friedl A, Rost A. Intensity of oral anticoagulation after implantation of St. Jude Medical aortic prosthesis: analysis of the GELIA database Eur Heart J Suppl 2001;3(Suppl Q):33-38.
  14. Butchart EG, Payne N, Li HH, et al. Better anticoagulation control improves survival after valve replacement J Thorac Cardiovasc Surg 2002;123:715-723.[Abstract/Free Full Text]
  15. Taylor TN, Davis PH, Torner JC, et al. Lifetime cost of stroke in the United States Stroke 1996;27:1459-1466.[Abstract/Free Full Text]
  16. Loeliger EA. Therapeutic target values in oral anticoagulationJustification of Dutch policy and a warning against the so-called moderate-intensity regimens. Ann Haematol 1992;64:60-65.[CrossRef][Medline]
  17. Stein PD, Alpert JS, Bussey HI, Dalen JE, Turpie AGG. Antithrombotic therapy in patients with mechanical and biological prosthetic heart valves Chest 2001;119(Suppl):220S-227S.[Free Full Text]




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