Fauchier L, Clementy N, Pelade C, Collignon C, Nicolle E, and LipGYH. Patients With Ischemic Stroke and Incident Atrial Fibrillation: A Nationwide Cohort Study. Stroke. 2015
In this issue of Stroke, Fauchier and colleagues seek to identify predictors of incident atrial fibrillation (AF) after ischemic stroke. The prediction and therefore timely diagnosis of atrial fibrillation is of significant public health importance given that, as the authors point out, one in five of stroke can be attributed to AF.
The authors utilize a robust dataset that includes all hospitalizations in France. They identified 48,992 patients without known AF discharged after ischemic stroke during 2009 and calculated their CHADS2 and CHA2DS2-VASc scores. Patients with primary cardiac conditions served as a control, though only for a part of the analysis.
Over 15±5 months of follow-up, 4,828 patients were diagnosed with AF during a hospitalization. 7.88 patients per 100-person years developed incident AF after stroke, whereas the rate was 5.91% after a cardiac diagnosis. As a continuous variable, the CHADS2 and CHA2DS2-VASc scores were associated with incident AF with HR 1.70 (95% CI, 1.66-1.75) and 1.45 (1.42-1.48), respectively. The c statistic was a moderate 0.7. Unsurprisingly, of the CHADS2 and CHA2DS2-VASc variables, only age, hypertension, heart failure and vascular disease independently predicted AF.
The major limitations of this study are as follows: 1. They did not determine if CHADS2 and CHA2DS2-VASc scores predict AF in their control group; 2. To call AF diagnosed after a stroke “incident” is misleading – AF may have been present prior to the stroke as well; 3. AF is often asymptomatic – many patients with “incident” AF may never be hospitalized with AF; 4. Cryptogenic stroke patients in 2009 did not routinely undergo prolonged cardiac rhythm monitoring, the results of which would have been an ideal outcome measure.
The authors hope that their findings will help identify patients after a stroke who may benefit from prolonged monitoring for AF. The CHADS2 and CHA2DS2-VASc scores are inadequate for this purpose. If the goal is identification of patients for prolonged cardiac monitoring upon discharge after stroke, the use of CHADS2 and CHA2DS2-VASc scores presents an unnecessary handicap. Stroke patients routinely have additional data including echocardiogram (left atrial dilatation), MRI (e.g. embolic pattern of strokes), telemetry (frequent premature atrial complexes), labs (B-type natriuretic peptide) that may be helpful.
However, when it comes to stroke, secondary prevention is too late; primary prevention is the Holy Grail. It is for this purpose – for general population AF screening purposes – that the CHADS2 and CHA2DS2-VASc scores may be helpful. Unfortunately, the authors did not assess the test characteristics of these scores in their control group.