A BETETR SCORE FOR AF STROKE RISK

Further data confirming that the CHA₂DS₂-VASc score is preferable to the CHADS₂ score in identifying patients with atrial fibrillation (AF) at very low risk for stroke who do not need anticoagulation have come from a large German registry study.

In the AFNET (German Competence Network on Atrial Fibrillation) registry, which included 8847 patients with nonvalvular AF, more than one third of the strokes or other thromboembolic events that occurred in the mean follow-up period of 5 years were in patients assigned a CHADS₂ score of 0 or 1, indicating that oral anticoagulation is not definitively recommended.

In contrast, using the CHA₂DS₂-VASc score, which adds age 65 to 74 years, vascular disease, and female sex as stroke risk factors to the CHADS₂ score, led to the reclassification of more than half of the patients with CHADS₂ scores 0 or 1 to a CHA₂DS₂-VASc score of 2 and higher, in whom oral anticoagulation is the recommended treatment.

Only 8 strokes and other thromboembolic events were observed in patients classified as CHA₂DS₂-VASc 0 at baseline (excluding strokes occurring in association with cardioversion or ablation).

"A CHADS₂ score of 0 or 1 does not appear to be suitable to identify patients with AF at low risk for stroke while CHA₂DS₂-VASc picks up these patients," said Professor Michael Nabauer, MD, University Hospital Grosshadern, Munich, Germany, at a press conference held during the European Society of Cardiology (ESC) Congress last week.

"The risk of stroke in patients with a CHA₂DS₂-VASc score of 0 over a mean follow-up of 5.1 years was very low. Our data support the current recommendation that oral anticoagulation is not beneficial in patients with 'lone AF' or a CHA₂DS₂-VASc score of 0."

The analysis was based on the prospective AFNET registry, which included 9575 patients with AF, 8847 of whom had nonvalvular AF. Follow-up was for a mean of 5.1 years, and stroke events were adjudicated by a critical event committee.

On enrollment, almost half of patients with nonvalvular AF were assigned a CHADS₂ score of 0 (16.2%) or 1 (31.5%), indicating that oral anticoagulation was not definitively recommended. But 145 of the 405 (38%) strokes and other thromboembolic events (transient ischemic attack, systemic embolism) during follow-up occurred in these patients classified as "low-risk."

Table 1. Events in Patients by CHADS₂ Scores

Endpoint	CHADS2 Score ≤ 2	CHADS2 Score = 1	CHADS2 Score = 0
Patients (n)	4631	2786	1430
Events (stroke/transient ischemic attack/systemic embolism) (n)	258	100	45

Application of the CHA₂DS₂-VASc score reclassified 54% of patients with CHADS₂ scores 0 or 1 to a CHA₂DS₂-VASc score of 2 and higher, in whom oral anticoagulation is the recommended treatment. In addition, only about half the patients previously classified as having a CHADS₂ score of 0 were assigned a CHA₂DS₂-VASc score of 0, indicating a very low stroke risk.

Table 2. Events in Patients With CHADS₂ Score 0 and 1 Reclassified by CHA₂DS₂-VASc Score

Endpoint	CHA2DS2-VASc ≤ 2	CHA2DS2-VASc Score = 1	CHA2DS2-VASc Score = 0
Patients (n)	2270	1133	795
Events (stroke/transient ischemic attack/systemic embolism) (n)	90	36	19

Of the 19 events, in the patients with CHA₂DS₂-VASc of 0, 4 were periprocedural events, and 7 occurred after progression of CHA₂DS₂-VASc score, leaving 8 residual events in this group.

Professor Guenter Breithardt, who was also involved in the study, explained to Medscape Medical News that the CHA₂DS₂-VASc score was already recommended in preference to the CHADS₂ score in the guidelines. "But we need more confirmatory data and this is what this study provides."

"This was a large registry with all levels of care included, not just one subgroup, so it is a realistic picture of the German population," he said. "Also there was a critical event committee to adjudicate all strokes, which is unique for a registry study. And we had over 95% follow-up which is again unusual for a registry study. So this is sound substantiation of what we are now coming to accept."

Professor Breithardt pointed out that a large number of strokes occur in low-risk patients. "Percentage-wise they are low risk but the numbers are substantial. This is similar to ejection fraction and MI [myocardial infarction]: while ejection fraction less than 35 is high risk, patients with ejection fractions greater than 35 account for the majority of sudden deaths. So looking at the low risk population is very valuable.

"Previously low-risk AF patients have not been treated properly. Many of them need anticoagulant therapy but have not been given it," he added. "The CHA₂DS₂-VASc score picks these patients up."

Also commenting for Medscape Medical News, Professor Robert Hatala, PhD, National Cardiovascular Institute, Bratislava, Slovakia, agreed that CHA₂DS₂-VASc score is less sensitive to misjudgment because it has more components. "It definitely gives a more precise prediction of risk."

More Education Needed

But he stressed that much more education of doctors is needed on these scores. He noted that at a recent symposium he attended, mostly with cardiologists and internists in the audience, attendees were asked if they knew what the CHADS₂ score was and if they used it. "One third said they yes to both, one third said they knew what it was but didn't use it, and one third didn't even know what it was."

"Now that we have the new oral anticoagulant drugs that are easy to administer, we need to make sure their use is maximized to prevent stroke, and the most cost-effective way to do this is to make stroke risk scores such as CHA₂DS₂VASc become everyday routine by the primary care physician. We need to drum home this message."

Chair of the ESC press conference at which this study was discussed, Professor Harry Crijns, Maastricht University Medical Center, the Netherlands, added: "The most important point to take from this work is that during follow-up patients may develop new risk factors: they grow older or develop clinically significant hypertension or other vascular disease. Monitoring such clinical changes during follow-up and installing anticoagulation and other vascular prophylactic therapies as needed may save lives," he said.

"Another message here is that the very-low-risk CHA₂DS₂-VASc 0 AF patient may suffer cardiovascular events during subsequent interventional treatment indicating that low risk does not preclude adverse events of interventions such as ablation or cardioversion."

European Society of Cardiology (ESC) Congress 2013. Abstract 4381. Presented September 3, 2013.