Pharmacodynamic Response to Warfarin After Conversion of Atrial Fibrillation or Flutter to Sinus Rhythm

Melissa C. Staats; Michael E. Ernst


Am J Health Syst Pharm. 2012;69(13):1158-1161. 

In This Article


A total of 46 patients (mean age, 64.5 years) had at least one evaluable set of INR values for pairwise comparison. Thirty-eight patients (83%) were men, and 31 (67%) underwent cardioversion as opposed to ablation. Their mean INR values in the four weeks before and four weeks after the restoration of normal sinus rhythm were 2.74 and 2.47, respectively (p = 0.039); the mean INR values in the expanded data collection periods (more than four weeks and up to three months) before and after the procedure were 2.63 and 2.48, respectively (p = 0.185).

As shown in Table 1, no significant difference was found in the mean weekly warfarin dose between the four-week periods before and after ablation or cardioversion. Likewise, no significant difference was found in the mean weekly dose between the four-week period before either procedure and the expanded period (more than four weeks, up to three months) after the procedure. However, a significant difference was found in the mean weekly warfarin dose between the expanded period before the procedures and the four-week period after the procedures and between the expanded periods before and after the procedures. Ten of 46 patients (22%) had a change in their mean weekly warfarin dose of ≥10% from the four-week period before the procedure to the end of the four-week postprocedure period. For the expanded periods, 5 of 27 patients (19%) had a change of the same magnitude in weekly warfarin dose.

No significant difference in mean systolic blood pressure was observed between the preprocedure and postprocedure periods (118.6 and 114.8 mm Hg, respectively; p = 0.081). However, mean diastolic blood pressure and heart rate in the postprocedure period (68.0 mm Hg and 67.4 beats/min) were significantly lower than in the preprocedure period (74.0 mm Hg and 88.3 beats/min; p < 0.001 for comparisons of both variables). Twelve patients (26%) had a medication change after an ablation or cardioversion procedure; the most common changes were dosage alterations for an agent intended to control the heart rate and the discontinuation of one medication. No clear association was observed between medication changes and warfarin dosage requirements.


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