CHADS Score or CHADS2 Score is an clinical prediction rule for estimating the risk of stroke in patients with atrial fibrillation (AFIB), a common and usually benign heart arrythmia. It is used to determine the degree of anticoagulation therapy required,[1] since AFIB can cause the stasis of blood in the heart chambers, leading to the formation of a mural thrombus that can dislodge into the blood flow, reaching the brain and causing a stroke. A high CHADS score corresponds to a greater risk, and vice-versa. The CHADS/CHADS2 algorithm was validated by a cohort study published in JAMA in 2001 using 1,733 Atrial fibrillation patients tracked through Medicare claims.[2]
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Algorithm
The CHADS/CHADS2 algorithm is as follows:[3]
| C: | Congestive heart failure | = 1 point |
| H: | Hypertension (or treated hypertension) | = 1 point |
| A: | Age >75 years | = 1 point |
| D: | Diabetes | = 1 point |
| S: | Prior Transient ischemic attack or Stroke | = 2 points |
Risk of Stroke
According to the findings of the JAMA study, the risk of stroke as a percentage per year is:
| Score | Risk of Stroke Per 100 Patient Years | 95% CIs from JAMA Study |
|---|---|---|
| 0 | 1.9% | |
| 1 | 2.8% | |
| 2 | 4.0% | |
| 3 | 5.9% | |
| 4 | 8.5% | |
| 5 | 12.5% | |
| 6 | 18.2% |
Recommendations for Anticoagulation
The following treatment strategies were recommended by the authors of theJAMA and Circulation articles:
| Score | Risk | Anticoagulation Therapy | Considerations |
|---|---|---|---|
| 0 | Low | Aspirin | 325 mg/day most likely to offer benefit, although lower doses may be similarly efficacious |
| 1-2 | Moderate | Aspirin or Warfarin | Raise INR to 2.0-3.0, depending on factors such as patient preference |
| 3+ | High | Warfarin | Raise INR to 2.0-3.0, unless contraindicated (e.g., history of falls, clinically significant GI bleeding, inability to obtain regular INR screening) |
Criticism of CHADS
The main criticism of the CHADS/CHADS2 scoring system is that someone with atrial fibrillation and a previous history of stroke, but no other risk factors (i.e. CHADS2 Score = 2), is only classified as moderate risk, whereas that person is in fact at high risk of another stroke.
References
- ^ Gage BF, van Walraven C, Pearce L, et al. (2004). "Selecting patients with atrial fibrillation for anticoagulation: stroke risk stratification in patients taking aspirin". Circulation 110 (16): 2287–92. doi:10.1161/01.CIR.0000145172.55640.93. PMID 15477396.
- ^ Gage BF, Waterman AD, Shannon W, Boechler M, Rich MW, Radford MJ (2001). "Validation of clinical classification schemes for predicting stroke: results from the National Registry of Atrial Fibrillation". JAMA 285 (22): 2864-70. PMID 11401607.
- ^ Risk of Stroke with AF. VA Palo Alto Medical Center and at Stanford University: the Sportsmedicine Program and the Cardiomyopathy Clinic. Retrieved on 2007-09-14.
