Chest. 2009 May 29

Le Tourneau T, Lim V, Inamo J, Miller FA, Mahoney DW, Schaff HV, Enriquez-Sarano M

Background Thrombo-embolic events (TE) are frequent after mechanical mitral valve replacement (MVR) but their association to anticoagulation quality is unclear and was never studied in a population-based setting with complete anticoagulation record. Methods We compiled complete record of all residents of Olmsted County, MN, who underwent mechanical MVR between 1981 and 2004, for all TE, bleedings and international normalized ratios (INR) measured from prosthesis implantation. Results In the 112 residents (57 +/- 16 years, female 60%) who underwent mechanical MVR, 19,647 INR samples were obtained. While INR averaged 3.02 +/- 0.57, almost 40% of INR were below 2 or > 4.5. Thirty-four TE and 28 bleedings occurred during 8.2 +/- 6.1 year follow up. There was no trend of association of INR (average, SD-SD, growth variance rate or intensity specific incidence of events) with TE. Previous cardiac surgery (p = 0.014), and ball prosthesis (2.92[1.43-5.94], p = 0.003) independently determined TE. With MVR-ball, despite higher anticoagulation intensity (p = 0.002), 8-year freedom from TE was considerably lower (50 +/- 9 vs 81 +/- 5%, p < 0.0001). Compared to expected stroke rates in the population, stroke-risk was elevated with nonball MVR (2.6[1.3-5.2], p = 0.007) but considerable with MVR-ball (11.7[7.5-18.4], p < 0.0001). INR-variability (SD) was higher with higher INR-average (p < 0.0001). INR-variability (2.48[1.11-5.55], p = 0.027) and cancer history (p < 0.0001) independently determined bleeding rates. Conclusion This population-based comprehensive study of anticoagulation and TE post-MVR shows that in these closely anticoagulated patients, anticoagulation intensity is highly variable and not associated with TE incidence post-MVR. Higher anticoagulation intensity is linked to higher variability and thus to bleeding. The MVR-ball design is associated with higher TE rates notwithstanding higher anticoagulation intensity and should be retired worldwide.