AMSTERDAM – Use of the CHA2DS2-VASc score markedly improves classification of atrial fibrillation patients who are truly at low risk of stroke, compared with the commonly used CHADS2 score, a German national study found.
"We do not feel that a CHADS2 risk score of 0 or 1 is suitable to identify low-risk patients. The CHA2DS2-VASc score provides a more refined risk stratification in low-risk patients. In the real life, prospective German AFNET [German Competence Network on Atrial Fibrillation] registry, a CHA2DS2-VASc score of 0 identifies a subgroup of patients with very low stroke risk unlikely to benefit from oral anticoagulation therapy," Dr. Michael Näbauer said at the annual congress of the European Society of Cardiology.
Among 795 patients in the AFNET registry who had a CHA2DS2-VASc score of 0, only 8 correctly categorized patients had a nonprocedurally related stroke, transient ischemic attack (TIA), or thromboembolism during 5 years of prospective follow-up, reported Dr. Näbauer, head of the echocardiographic unit at Ludwig Maximilians University Hospital, Munich.
A transcontinental split exists at present regarding the best clinical decision tool for assessing stroke risk in patients with atrial fibrillation (AF), and thus identifying those in whom oral anticoagulation is or is not warranted. Current American guidelines recommend using the CHADS2 score, while more recent ESC guidelines released last year advocate superseding CHADS2 with the newer CHA2DS2-VASc scoring system (Eur. Heart J. 2012;33:2719-47).
Dr. Michael Näbauer
Dr. Näbauer’s report from the German AFNET registry highlighted the advantages of using CHA2DS2-VASc. Among 8,847 patients with nonvalvular AF participating in the registry run by physicians having a special interest in atrial fibrillation, 16.2% were assigned a CHADS2 score of 0 and 31.5% had a score of 1, meaning their stroke risk going forward was too low to justify the routine use of prophylactic oral anticoagulation therapy, with its attendant bleeding risk.
Here’s the deal killer for the CHADS2 scoring system, he said: Of the 403 stroke, TIA, and thromboembolic events that occurred in the nearly 9,000 AF patients during 5 years of prospective follow-up, 36% occurred in patients with a CHADS2 score of 0 or 1.
"This finding suggests that CHADS2 classes 0 and 1 contain subgroups of patients with significant stroke risk that may be identified by refined stroke risk classification," the cardiologist noted.
Application of the CHA2DS2-VASc score to the AFNET population resulted in reclassification of 126 of the 145 CHADS2 class 0 or 1 patients who had a stroke, TIA, or thromboembolism to a higher-risk CHA2DS2-VASc category where oral anticoagulation is appropriate.
Of the 45 stroke events that occurred among 1,430 patients who were CHADS2 class 0, 12 events occurred in patients who were CHA2DS2-VASc class 2 and 14 in CHA2DS2-VASc class 1 – groups in which oral anticoagulation is recommended.
Moreover, 4 of the 19 stroke events occurring in the 795 patients who were CHA2DS2-VASc class 0 happened in association with AF ablation or cardioversion procedures, when oral anticoagulation is temporarily discontinued. Another seven stroke events occurred in patients whose true CHA2DS2-VASc score had increased from 0 during follow-up, mainly because of advancing age. So ultimately only 8 of 795 patients correctly classified as CHA2DS2-VASc 0 had a stroke event unrelated to a cardiac procedure during 5 years of follow-up.
Dr. Robert Hatala
Session cochair Dr. Robert Hatala said that the AFNET experience highlights an important clinical lesson: Stroke risk in AF patients is not static. It changes over time, and periodic reassessment is essential.
"All of the risk scores are imperfect. It’s really very important to relook at your patients and not give them a fixed stamp forever. The risk scores change over time as patients get older, perhaps receive a diagnosis of hypertension, or develop congestive heart failure, maybe with preserved systolic function. So restratify," urged Dr. Hatala, head of cardiology and director of the arrhythmia and pacing center at Slovak Medical University, Bratislava, Slovakia.
Dr. Näbauer and Dr. Hatala reported having no relevant financial conflicts.