Event Rate for Patients with Atrial Fibrillation with and without Low Molecular Weight Heparin Bridging.

The benefit of ’bridging’ atrial fibrillation patients with low molecular weight heparin until their INRs are at therapeutic levels with coumadin is unclear. Using a replicative hospital database available for IRB approved protocols and quality control analyses, we compared a cohort of patients over 65 years of age discharged with a diagnosis of atrial fibrillation (index date) who had been bridged (n=201) with a cohort of patients over 65 years of age who were not bridged on discharge but who achieved a therapeutic INR within 30 days of coumadin initiation (nonbridged and early INR, NB-E, n=1376). Log rank Mantel Haenszel two group comparisons were used to test for differences in time to event rate for admission for CVA, admission for hemorrhage, and number of laboratory INRs in therapeutic range (NLTR). The incidence of CVA admissions in the bridged group at 15, 30, 60, 90, 180 and 365 days was 0%, 0%, 0%, 0%, 0.5% and 1.2% whereas for the NB-E it was 0.1%, 0.3%, 0.8%, 1.3%, 1.8% and 2.8%. This difference did not reach statistical significance (p=0.19). No difference was noted in the time to admission for hemorrhage (3.5% at day 15, remaining unchanged at 30, 60 and 90 days for the bridged patients vs. 1.0%, 1.9%, 3.1% and 4.2% for NB-E patients, p=0.67). When NLTR were expressed as dichotomous variables (INR<1.9=bad, 2–3.5=good, 3.6–20=bad) and assessed for one year from index date, there was no significant difference (good = 55.3% NLTR for bridged vs. 52.3% for NB-E). When either of these groups were compared to patients with AF who did not achieve therapeutic INRs until after 30 days (but less than one year, NB-L, n=2061), there was a difference in the incidence of admissions for CVA that was significant (0.2%, 0.7%, 1.1%, 1.2%, 2.5% and 4.8% at day 15, 30, 60, 90, 180, 365, p=0.025 vs. bridged, and p=0.048 vs. NB-E), NLTR (45.2%), but not in the incidence of admission for hemorrhage at 90 days (0.7%, 1.4%, 2.6% and 3.9% at 15, 30, 60 and 90 days). Because no risk factors prompting the decision to bridge patients were examined, the non-significant decreased incidence of CVA admissions in bridged patients may be important, since it may be that patients who were bridged were at higher risk for stroke than those who were not bridged (early or late). Future randomized trials with risk group stratification will be necessary to elucidate this but these data demonstrate there is no significant additional hemorrhagic risk for patients with atrial fibrillation who are bridged with low molecular weight heparin and suggest a potential benefit to early effective anticoagulation.