Management of atrial fibrillation based on guidelines – part II
Initial approach to atrial fibrillation
The immediate priority in a patient presenting with atrial fibrillation is the control of ventricular rate to reasonable range. Then the need for anticoagulation has to be assessed depending on the duration and risk factors. Whether to opt for a rhythm control strategy is the next consideration. Finally the treatment of underlying heart disease is very important in overall management of the patient with atrial fibrillation.
Upstream therapies in atrial fibrillation
‘Upstream’ therapy for prevention of atrial remodelling has been evaluated in a few prospective and retrospective studies, but the concept is still controversial. Angiotensin-converting enzyme inhibitors, angiotensin receptor blockers, statins, fish oils, glucocorticoids and moderate physical activity have all been considered in this upstream therapy and found to useful to a variable extent in both primary and secondary prevention of atrial fibrillation.
Oral anticoagulation in atrial fibrillation
Since thromboembolism and resultant strokes are an important risk of atrial fibrillation, oral anticoagulation is an important consideration. CHADS2 score was developed to assess the risk of thromboembolism in non rheumatic atrial fibrillation and has been discussed earlier. CHADS2 is short for congestive heart failure, hypertension, age, diabetes mellitus and stroke (doubled). Each component except stroke are allotted one point each while stroke or TIA is allotted two points. Total possible score is 6. The risk of stroke increases steadily from 1.9% to 18.2% as the score reaches 6, though there were only few patients with the highest score in the index study. Oral anticoagulation is indicated if the score is two or more. CHA2DS2-VASc risk factor based point scoring system for atrial fibrillation is meant for assessing the risk of thromboembolism in nonvalvular atrial fibrillation in a better way than CHADS2. CHA2DS2-VASc considers previous stroke/TIA/systemic embolism and age 75 years and above as major risk factors with 2 points each. Other clinically relevant non-major risk factors allotted 1 point each are congestive heart failure/left ventricular dysfunction, hypertension, diabetes mellitus, vascular disease (prior myocardial infarction, peripheral arterial disease or aortic plaque), age between 65-74 years and female sex. Total score possible is 9 in the CHA2DS2-VASc scoring system. Just as in the CHADS2 score, the age adjusted stroke risk rises from 0% with a score of zero to 15.2% with a CHA2DS2-VASc score of 9. The lower number of individuals in the highest scores were also noted in the index study for this scoring system as well. If the CHADS2 score is two or more, the patient needs long term oral anticoagulation. If the score is lesser, age is considered. If age is 75 years or more, the patient still needs anticoagulation. If the age is less than 75 years, presence of two or more other risk factors from the CHA2DS2-VASc score is considered as an indication for anticoagulation. If patient has only one other risk factor, oral anticoagulation or aspirin (preferably the former) is given. If there are no risk factors, no anti thrombotic therapy or aspirin (preferably the former) is recommended.
Assessment of bleeding risk while planning oral anticoagulation
Potential bleeding risk has always been a worry especially when anticoagulating elderly with atrial fibrillation. In fact this often leads to deferring of anticoagulation, most often in the elderly who also have a higher benefit in terms of prevention of stroke. The HAS BLED [Hypertension, Abnormal renal/liver function, Stroke, Bleeding history or predisposition, Labile international normalized ratio, Elderly (>65 years), Drugs (antiplatelet agents or non-steroidal anti inflammatory drugs)/alcohol concomitantly] bleeding risk score has been introduced to counter this problem. Maximum number of points possible on the HAS BLED score is 9.
HAS BLED scoring is based on the EuroHeart Survey involving about four thousand subjects with atrial fibrillation . In this study, number of bleeds per 100 patient years ranged from 1.13 to 12.5 when scores increased from 0 to 5. There were only two patients with a score of 6 and no patient had scores above 6.
While deciding on long term oral anticoagulation the risk of bleeding should be less than the risk due to stroke for a beneficial effect of anticoagulation to be obtained.
- Pisters R, Lane DA, Nieuwlaat R, de Vos CB, Crijns HJ, Lip GY.. A novel user friendly score (HAS-BLED) to assess one-year risk of major bleeding in atrial fibrillation patients: The Euro Heart Survey. Chest 2010; 138:1093-100