The CHADS₂ score is a clinical prediction rule for estimating the risk of stroke in patients with non-rheumatic atrial fibrillation (AF), a common and serious heart rhythm disturbance. This score is simple and has been validated by many studies in different groups of AF patients. 

The CHADS₂ acronym stands for Congestive heart failure, Hypertension, Age ≥75 years, Diabetes mellitus, and prior Stroke or transient ischemic attack (TIA). Each factor scores one point, except for prior stroke or TIA, which scores two points. The total score ranges from 0 to 6, with higher scores indicating a greater risk of stroke.

The clinical utility of the CHADS₂ score is to help clinicians decide whether or not to anticoagulate a patient with AF. Patients with a score of 0 are at low risk and do not require anticoagulation. Patients with a score of 1 can be considered for anticoagulation, and those with a score of 2 or more should definitely be anticoagulated, unless contraindicated.

The CHADS₂ score should not be used in patients with rheumatic AF, valvular heart disease, or those who have a contraindication to antico

CHADS₂ score for stroke risk in atrial fibrillation

# Description:
The CHADS₂ score is a clinical prediction rule for estimating the risk of stroke in patients with non-rheumatic atrial fibrillation (AF), a common and serious heart rhythm disturbance. This score is simple and has been validated by many studies in different groups of AF patients. 

The CHADS₂ acronym stands for Congestive heart failure, Hypertension, Age ≥75 years, Diabetes mellitus, and prior Stroke or transient ischemic attack (TIA). Each factor scores one point, except for prior stroke or TIA, which scores two points. The total score ranges from 0 to 6, with higher scores indicating a greater risk of stroke.

The clinical utility of the CHADS₂ score is to help clinicians decide whether or not to anticoagulate a patient with AF. Patients with a score of 0 are at low risk and do not require anticoagulation. Patients with a score of 1 can be considered for anticoagulation, and those with a score of 2 or more should definitely be anticoagulated, unless contraindicated.

The CHADS₂ score should not be used in patients with rheumatic AF, valvular heart disease, or those who have a contraindication to antico
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# Inputs:
A. Age >= 75 years (+1)
B. Hypertension (+1)
C. Diabetes mellitus (+1)
D. Congestive heart failure (+1)
F. History of stroke or transient ischemic attack (+2)
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# Scoring:
- If score == 0, then Annual risk of stroke is 1.9%
- If score == 1, then Annual risk of stroke is 2.8%
- If score == 2, then Annual risk of stroke is 4.0%
- If score == 3, then Annual risk of stroke is 5.9%
- If score == 4, then Annual risk of stroke is 8.5%
- If score == 5, then Annual risk of stroke is 12.5%
- If score == 6, then Annual risk of stroke is 18.2%)