eComment: Anticoagulation for mechanical heart valves: a current assessment.

Table 1 Reported cases of well functioning mechanical valve without anticoagulation Reference Mean age n Type of Position Mean follow-up Treatment with Peak (years) valve (n) of valve period without anticoagulation gradient anticoagulation (months) across (years) valve thrombotic prophylaxis are from non-randomized case series without controls w2x. Uncomplicated functioning without anticoagulation of various mechanical valves including Bjork–Shiley (B-S), Star–Edwards (S-E) and Lille-hei–Kaster (L-K) in aortic or mitral positions have been reported (Table 1) w3–8x. It is observed that mechanical valves at aortic position are durable without anticoagula-tion irrespective of type of valve used as Bjork–Shiley, Starr–Edwards or St Jude Medical as in our case w2–7x. Interestingly, Andersen and Alstrup followed 43 patients (mean age 52 years) who discontinued anticoagulation after 12 months of isolated mechanical aortic valve replacement and were followed for a mean period of 7.2 years without anticoagulation w3x. They noted after 10 years, 41% incidence of thromoboembolic events and 17% mortality. Bjork et al. postulated that all thromboembolic complications in mechanical heart valves start from a thrombus lining that covers the suture ring w9, 10x. The thrombus organizes to a fibrous white sheet over the suture ring, which then can protrude out over the polished surface of the valve ring flange. Pieces of the thrombus can be knocked off by the disc and cause emboli. To diminish thrombo-embolic complications, one must either prevent this thrombus from protruding into the groove between the suture ring and the valve flange or allow the thrombus to be organized as a thin covering with endothelium-like cells as a continuation from the suture ring over the valve flange. This type of covering was obtained during a short period of anticoagulation by applying a microporous surface to the Björk–Shiley Monostrut mitral valve. They observed two goats with microporous surfaced B-S mitral valve without anticoagulation for five years. These animals had a total of six pregnancies with delivery of 14 newborns without any thrombotic complications w9, 10x. The same group in 1999 demonstrated the favorable outcome in 12 patients with Bjork–Shiley Monstrut mechanical mitral valve with a microporous surface without anticoagulation for 11– 13 years w4x. It is unusual that a functioning St Jude Medical aortic valve is present without anticoagulation for over twenty-three years. The potential factors underlying in the normal valvular mechanics in our patient remains unclear. Guidelines are sorely needed in patients with mechanical valves who subsequently develop a contraindication and …