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Index Predicts Stroke in Elderly Patients With Atrial Fibrillation

A new stroke-risk index with the mnemonic CHADS2 could help predict stroke in elderly patients with atrial fibrillation (AF).

CHADS2 combines five factors from two existing classification schemes researched by the Atrial Fibrillation Investigators (AFU) group and the Stroke Prevention and Atrial Fibrillation (SPAF) team. It could also help doctors select patients for antithrombotic therapy, its North American developers suggest.
Dr. Brian F. Gage, assistant professor of medicine at Washington University in St. Louis, Missouri, comments: "The two predictor models were helpful, but discrepancies between them sometimes led to confusion.

"We needed a simple, uniform system to help select warfarin for patients at moderate or high risk of stroke, while avoiding this potentially dangerous blood thinner in low-risk patients."

Dr. Gage and other investigators from Washington University; Innovative Emergency Management in Baton Rouge, Louisiana; and Yale-New Haven Hospital in New Haven, Connecticut report: "Because the net benefit of antithrombotic therapy correlates with the underlying risk of stroke, CHADS2 may be helpful in several clinical settings."

They outline three possibilities.

"In identifying low-risk patients, a CHADS2 score of zero identifies an AF population who should be offered the option of aspirin therapy.

"In addition, CHADS2 could aid in decision-making for patients with AF who are undergoing surgical or dental procedure because perioperative management depends on their risk of hemorrhage from the procedure compared with the underlying thrombotic risk.

"Also in patients for whom taking warfarin would be burdensome, CHADS2 could facilitate risk stratification and selection of antithrombotic therapy based on patient-specific risk of stroke."

CHADS2 was formed by assigning one point for each of four risk factors: congestive heart failure, hypertension, age 75 years and older and diabetes mellitus. Two points were assigned for a patient having had a stroke or transient ischemic attack.

Researchers drew data from peer-review organizations in seven states in developing CHADS2. This was assembled in the National Registry of AF. Participants included 1,733 Medicare recipients aged from 65 to 95 years. All had non-rheumatic AF and had not been prescribed warfarin when released from hospital.

Investigators covered 2,121 patient-years of follow-up. They found that 94 patients were re-admitted to hospital for ischemic stroke.

Using the AFI and SPAF formulae predicted stroke better than chance, the researchers note, but not as accurately as the CHADS2 index.

"Stroke rate per 100 patient-years without antithrombotic therapy increased by a factor of 1.5 for each one point increase in the CHADS2 score," they explain.
JAMA, 2001; 285: 2864-2870.

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