Mechanical Heart Valves

 

The position of a mechanical valve influences the thrombosis risk with several studies showing that aortic valve replacements have a significantly lower risk of thrombosis than valves in the mitral position.  A German study in 2005 of  2,735 patients with aortic valve, mitral valve or combined valve replacements reported 51 thromboembolic events with an incidence of  0.53% per patient-year for aortic valves versus 1.64% per patient year for mitral valves1.

 

 

An earlier study from Cannegeiter et al showed a similar result with an  incidence of 0.5 per 100 patient-years among patients with an aortic valve, 0.9 per 100 patient-years among patients with a mitral valve, and 1.2 per 100 patient-years among those with both an aortic and a mitral valve2.

Therefore all mechanical mitral valve replacements are regarded as high risk.

An uncomplicated Aortic valve however has a low thrombotic risk. The influence of other risk factors, other than a prior stroke, remains uncertain  but it is reasonable to assume that the presence of atrial fibrillation, diabetes , heart failure or hypertension will have some influence on thrombotic risk.

  1. Thromboembolic and Bleeding Complications Following St. Jude Medical Valve Replacement*: Results of the German Experience With Low-Intensity Anticoagulation Study. D Hering, et al. Chest 2005: 127;53From the Department of Cardiology (Drs. Hering, Piper, and Horstkotte), Heart Center North-Rhine Westphalia, Bad Oeynhausen; Institute for Medical Outcome Research (Drs. Bergemann and Hillenbach), Loerrach; Department of Cardiothoracic and Vascular Surgery (Dr. Dahm), University Hospital Mainz, Mainz; and Department of Cardiothoracic Surgery (Dr. Huth), Otto-von-Guericke-University, Magdeburg, Germany..Correspondence to: Dieter Horstkotte, MD, Department of Cardiology, Heart Center North-Rhine Westphalia, Ruhr University, Bad Oeynhausen, Georgstrasse 11, 32545 Bad Oeynhausen, Germany; e-mail: akohlstaedt@hdz-nrw.de

  2. Optimal Oral Anticoagulant Therapy in Patients with Mechanical Heart Valves.  S.C. Cannegieter, et al.  N Engl J Med 1995; 333:11