Motivation: Recently, I met a man with CHADS2 score of one. We shook hands, and he had atrial fibrillation. Slowing his heart down was relatively easy, but what about anti-coagulation, aspirin or warfarin? A CHADS2 score of one is a grey "intermediate risk" zone without clear indications for using warfarin or aspirin. About two years ago, a group from England and Netherland proposed a further refinement to the CHADS2 score (called CHA2DS2-VASc) to help decide on anti-coagulation in these intermediate risk cases.
Paper: Lip, G.Y.H., Nieuwlaat, R., Pisters, R., et. al. "Refining Clinical Risk Stratification for Predicting Stroke and Thromboembolism in Atrial Fibrillation Using a Novel Risk Factor-Based Approach: The Euro Heart Survey on Atrial Fibrillation." Chest (2010); 137: 263-272.
Methods: The authors proposed a revised point scoring system with the following components:
Congestive Heart Failure or LV dysfunction: 1
Hypertension: 1
Age 75 or over: 2
Age 65 or over: 1
Diabetes: 1
Stroke, TIA, or other embolic disease: 2
Vascular disease (MI, PAD, or known aortic plaque): 1
Female gender: 1
To validate the predictive value of this scoring system, the authors analyzed data from 1,084 patients without mitral stenosis or heart valve surgery who did not use warfarin. The authors tracked survival status and risk of thromboembolic disease. The patients were derived from Euro Heart Survey cohort, which tracked patients among 182 hospitals in 35 countries.
Results:
Cohort Characteristics: The patients in the tracked cohort were on average 66 years of age and 40.8% were women. The most common risk factor was hypertension (67.3%) followed by CAD (38.4%). Overall, 34.9% of the cohort had CHADS2 score of one, 20.4% with score of zero, and rest with higher scores. 74% took anti-platelet agents.
Thromboembolic Risk: The annual risk of thromboembolic events by risk factor is shown below (only the low risk rates are shown). Adjusted rate for aspirin use assumes a 22% risk reduction by aspirin use.
Score: 0 (103 patients, no risk factors) - Event rate: 0, annual rate adjusted for ASA use: 0
Score: 1 (162 patients) - Event rate: 0.6%, annual rate adjusted for ASA use: 0.7%
Score: 2 (184 patients) - Event rate: 1.6%, annual rate adjusted for ASA use: 1.9%
Score: 3 (203 patients) - Event rate: 3.9%, annual rate adjusted for ASA use: 4.7%
One of the novel risk factors that this scoring system adds is female gender. In univariate analysis, female gender is associated with event rate odds ratio of 2.53 (1.08-5.92).
Discussion: This paper provides help in further distinguishing patients really at low risk not requiring further treatment. I was pretty impressed with the zero annual event rate in patients with no risk factors. On the other hand, for patients with score of 2, treatment with warfarin is likely indicated since the risk of symptomatic embolic complication (1.9%) balances the risk of major bleeding (about the same risk). Especially in an older population, aspirin carries a major bleeding risk (estimated to be about the same in elderly population) but provides substantially decreased protection against embolic disease.
The study, while helpful, has some limitations. First, the analysis was done retrospectively in a cohort. It is unclear why these patients were not anti-coagulated. It is possible that factors which led to decision not to anti-coagulate also substantially modified the subsequent risk of embolic events (high risk behaviors such as IV drug use). Nonetheless, I think that this study adds to the identification of the truly low risk group.
Paper: Lip, G.Y.H., Nieuwlaat, R., Pisters, R., et. al. "Refining Clinical Risk Stratification for Predicting Stroke and Thromboembolism in Atrial Fibrillation Using a Novel Risk Factor-Based Approach: The Euro Heart Survey on Atrial Fibrillation." Chest (2010); 137: 263-272.
Methods: The authors proposed a revised point scoring system with the following components:
Congestive Heart Failure or LV dysfunction: 1
Hypertension: 1
Age 75 or over: 2
Age 65 or over: 1
Diabetes: 1
Stroke, TIA, or other embolic disease: 2
Vascular disease (MI, PAD, or known aortic plaque): 1
Female gender: 1
To validate the predictive value of this scoring system, the authors analyzed data from 1,084 patients without mitral stenosis or heart valve surgery who did not use warfarin. The authors tracked survival status and risk of thromboembolic disease. The patients were derived from Euro Heart Survey cohort, which tracked patients among 182 hospitals in 35 countries.
Results:
Cohort Characteristics: The patients in the tracked cohort were on average 66 years of age and 40.8% were women. The most common risk factor was hypertension (67.3%) followed by CAD (38.4%). Overall, 34.9% of the cohort had CHADS2 score of one, 20.4% with score of zero, and rest with higher scores. 74% took anti-platelet agents.
Thromboembolic Risk: The annual risk of thromboembolic events by risk factor is shown below (only the low risk rates are shown). Adjusted rate for aspirin use assumes a 22% risk reduction by aspirin use.
Score: 0 (103 patients, no risk factors) - Event rate: 0, annual rate adjusted for ASA use: 0
Score: 1 (162 patients) - Event rate: 0.6%, annual rate adjusted for ASA use: 0.7%
Score: 2 (184 patients) - Event rate: 1.6%, annual rate adjusted for ASA use: 1.9%
Score: 3 (203 patients) - Event rate: 3.9%, annual rate adjusted for ASA use: 4.7%
One of the novel risk factors that this scoring system adds is female gender. In univariate analysis, female gender is associated with event rate odds ratio of 2.53 (1.08-5.92).
Discussion: This paper provides help in further distinguishing patients really at low risk not requiring further treatment. I was pretty impressed with the zero annual event rate in patients with no risk factors. On the other hand, for patients with score of 2, treatment with warfarin is likely indicated since the risk of symptomatic embolic complication (1.9%) balances the risk of major bleeding (about the same risk). Especially in an older population, aspirin carries a major bleeding risk (estimated to be about the same in elderly population) but provides substantially decreased protection against embolic disease.
The study, while helpful, has some limitations. First, the analysis was done retrospectively in a cohort. It is unclear why these patients were not anti-coagulated. It is possible that factors which led to decision not to anti-coagulate also substantially modified the subsequent risk of embolic events (high risk behaviors such as IV drug use). Nonetheless, I think that this study adds to the identification of the truly low risk group.
Great Article! Thanks for posting! http://www.themitralvalve.org/mitralvalve/clinicalpresentationpathophysiology
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