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, 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.
The CHADS/CHADS2 algorithm is as follows:
Risk of Stroke
According to the findings of the JAMA study, the risk of stroke as a percentage per year is:
|| Risk of Stroke Per 100 Patient Years
|| 95% CIs from JAMA Study
Recommendations for Anticoagulation
The following treatment strategies were recommended by the authors of theJAMA and Circulation articles:
|| Anticoagulation Therapy
|| 325 mg/day most likely to offer benefit, although lower doses may be similarly efficacious
|| Aspirin or Warfarin
|| Raise INR to 2.0-3.0, depending on factors such as patient preference
|| 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.
- ^ 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.