The quality of warfarin therapy and CHA2DS2-VASc score associate with the incidence of myocardial infarction and cardiovascular outcome in patients with atrial fibrillation: data from the nationwide FinWAF Registry

Aims The impact of the quality of warfarin therapy on cardiovascular outcomes excluding stroke is largely unknown. The aims of this study were to evaluate the association between the warfarin control and the incidence and outcome of myocardial infarction (MI) and to validate the predictive value of the CHA2DS2-VASc score for MI in atrial fibrillation (AF) patients taking warfarin. Methods and results The nationwide FinWAF Registry consists of 54 568 AF patients (mean age 73.31 +/- 10.7 years, 52% men) taking warfarin. The quality of warfarin therapy was assessed continuously by calculating the time in therapeutic range within a 60-day window using the Rosendaal method (TTR60). Adjusted Cox proportional hazards models were prepared for the incidence of MI and cardiovascular mortality in six different TTR60 categories. During the 3.2 +/- 1.6 years of follow-up, the annual incidence of MI (95% confidence interval) was 3.3% (3.0-3.5%), 2.9% (2.6-3.3%), 2.4% (2.1-2.7%), 1.9% (1.7-2.2%), 1.7% (1.5-2.0%), and 1.2% (1.1-1.3%) among patients with TTR60 <40%, 40-50%, 50-60%, 60-70%, 70-80%, and >80%, respectively. Well-managed warfarin therapy (TTR60 >80%) was associated also with a lower cardiovascular mortality, whereas a high CHA(2)DS(2)-VASc score correlated with poor outcome. Conclusion Cardiovascular outcome was superior among AF patients with good warfarin control and in those with a low CHA(2)DS(2)-VASc score. The inverse association between the TTR60 and incidence of MI and cardiovascular mortality indicate that in AF patients the quality of warfarin therapy is critical not only for prevention of stroke but also with regard to cardiovascular outcome.