Anticoagulation in patients with atrial fibrillation: an audit.

1. Anticoagulation in patients with atrial fibrillation: an audit. Dr David Wright Dept of Haematology Pontefract General Infirmary

2. Atrial Fibrillation:incidence Prevalence begins to increase after age 40 and rises rapidly after age 65. 46 000 new cases per year More common in men than women AF accounts for 1.5% of stokes for 50-59 age group and 23.5% for 80-89 (Framingham study)

3. Atrial Fibrillation: risk of stroke Rate of ischaemic stroke in AF patients averages 5%/yr Risk increases with age, LV dysfunction, LA dilatation, hypertension, history of previous embolic event For patients with a prior cerebrovascular event the rate is 12%/yr

4. Arial Fibrillation: anticoagulation Numerous studies have demonstrated a significant stroke reduction with warfarin The average reduction is approx two thirds This equates to an absolute reduction of 3%/yr (NNT-32) For patients with a past history of CVA/TIA there is an absolute reduction of 8%/yr (NNT-13) Aspirin reduces the relative risk by 22%

5. Atrial Fibrillation: anticoagulation Six RCT with over 2900 patients Mean age 69yrs. 20% over 75yrs 20% previous CVA/TIA Average follow up 1.6 yrs Approximately 10% of patients stopped warfarin each year over the period of follow up

6. Anticoagulation: risk of bleeding Intracranial bleeding 0.5 - 1% pa Major extra-cranial bleeding 1 -2% pa Bleeding rate 1.7% pa <75yrs 4.2% pa >75yrs

7. Objectives of anticoagulation audit Document the demographic profile of the local patient population receiving warfarin for AF Compare this with study population from RCT Document the drop-out rate from warfarin therapy Calculate the rates of bleeding and breakthrough thromboembolic events Determine patient outcome over a 5 yr period

8. Audit: methods Dawn AC computer identified all patients starting warfarin for atrial fibrillation between Jan – June 1999 Case notes requested and anticoagulant records reviewed For those patients who died whilst taking warfarin information was obtained from the death certificate and/or post-mortem where available

9. Audit: methods The following information was extracted from case/anticoagulant records: Age,gender Co-morbidities inc previous history of CVA Details of any cardioversions Duration of anticoagulation and reason for stopping Clinical events: bleeding or thrombosis

10. Results: demographics 97 patients started warfarin for AF during the first 6 months of 1999 Case records were obtained for 95 patients Demographic details: 38 female, 57 male Mean age 71.4 yrs: range 26 – 89 yrs 32% of patients > 75yrs

11. Results: co-morbidities 23 pts (24%) had a PH of CVA/TIA 79 patients had one or more co-morbid conditions IHD 43% Hypertension 33% LV dysfunction 18% CCF 23% Diabetes 8% MVD/AVD 6%

12. Results Cardioversion was attempted in 26 pts (27%) and was successful in eight A further three patients spontaneously reverted to sinus rhythm Duration of anticoagulation ranged from 4 days to over 6yrs. Mean duration of warfarin clinic follow up 42.4 months. At the time of the audit 48 pts (51%) were still on warfarin

13. Comparison of local pt population with those in RCT

14. Results: stopping warfarin Warfarin was stopped in 47 pts. Reasons: death 24 reversion to sinus rhythm 11 bleeding 6 unknown 2 recurrent falls 1 liver dysfunction 1 aplastic anaemia 1 GI upset 1

15. Results: warfarin deaths Infection 7 Cardiac 5 Malignancy 3 COPD 2 Bowel ischaemia 2 CVD 2 Unrelated surgery 2 Unknown 1

16. Clinical events

17. Clinical events: incidence Major bleeding 2.8% pa Intracranial bleeding 0.35% pa All ischemic events 1.75% pa Cerebral ischemic events 1.4% pa

18. Bleeding episodes Eight pts suffered a major bleed: Mean age - 70.2 yrs ( range 54 – 84yrs) Mean duration of warfarin therapy – 29.5 months ( range 21 days – 67 months ) For pts <75yrs 2.6% pa >75yrs 3.4% pa

19. Ischaemic events Five pts suffered an ischemic event: Mean age 75yrs ( range 71 – 83 yrs ) Mean duration of warfarin therapy 30 months ( range 5 – 56 months ) For pts <75 yrs 0.88% pa >75 yrs 5% pa

20. Effect of prior history of CVA/TIA on outcome

21. Points of caution Retrospective rather than prospective study ? All clinical events captured Small number of clinical events precludes subgroup analysis

22. Conclusions The local population of patients starting warfarin therapy for AF is similar to those studied in RCTs, though the % over 75yrs is greater. Only around half of pts are still taking warfarin after 31/2 yrs The incidence of bleeding and ischemic events is comparable to that seen in RCTs The majority of adverse events occur whilst the INR is within the therapeutic range

23. Next steps Extend study to a full one year cohort. Accumulate more clinical events Examine INR control and correlation with clinical events ?future link between wafarin computer system and EPR