Front Panel Painting “LIFE” By William T Chua MD

B. Risk Modification: Its Safety and Limitations
In 2007, a meta-analysis of antithrombotic therapy for SPAF was conducted. Its objective was
to characterize the efficacy and safety of anticoagulants and antiplatelet agents for SPAF. All
published randomized trials of antithrombotic therapy for SPAF with a mean follow-up of 3
months were included and 29 trials were identified involving a total of 28,044 participants and
mean follow-up of 1.5 years. Treatment comparisons included: warfarin vs. placebo (6 trials;
N=2900), aspirin vs. placebo (7 trials; N=3990) and warfarin vs. aspirin (8 trials; N=3647). 9
Table 4 shows the six key randomized controlled studies in the prevention of stroke in AF. They
pointed out that warfarin reduced the risk of stroke by 64% compared to placebo, that it was
better than aspirin in reducing thromboembolism and stroke by 38% and that aspirin (ASA) had
only limited efficacy of 19% reduction of stroke compared to placebo. 9 Of these studies, all
were for primary prevention with only EAFT that showed secondary prevention with warfarin.
To achieve the beneficial effect of anticoagulation, the international normalized ratio (INR)
should be from 2 to 3 and at a higher intensity of anticoagulation of 2.5 to 3.5 for those with
mechanical prosthetic valve. 10
Table 4: Reductions in thromboembolic risk with warfarin compared with placebo 11
Study
Primary
Outcome
Annual Rate
Warfarin
Placebo
RRR
(%)
P-value
TIA and AF
Primary Prevention
AFASAK
SPAF
BAATAF
CAFA
SPINAF
Secondary
Prevention
EAFT
S, NSE, TIA, ICB
S, NSE
S
S, NSE, ICB, FB
S
2.7
2.3
0.4
3.4
0.9
6.2
7.1
3.0
4.6
4.3
56
67
86
26
79