Change in AFib risk score predicts stroke better than single measurement

Analyzing the change in stroke risk factors for atrial fibrillation (AFib) patients was far more powerful in predicting stroke than assessing baseline risk factors alone, researchers reported in the Journal of the American College of Cardiology.

The findings highlight how the risk profile in AFib changes over time, the authors said, especially as patients become older and accumulate additional comorbidities. During follow-up, nearly 60 percent of 31,039 Taiwanese participants experienced at least one new-onset comorbidity contained in the CHA2DS2-VASc score, a validated risk prediction tool for AFib patients.

In the CHA2DS2-VASc score, one point is assigned for congestive heart failure, diabetes, vascular disease, hypertension, age 65 to 74 and female sex. Two points are assigned for age of at least 75 years and a previous history of stroke or transient ischemic attack.

Patients were only included in the study if they had AFib, did not receive antiplatelet agents or oral anticoagulants (OACs) and did not have comorbidities of the CHA2DS2-VASc score at baseline other than age and sex.

“AFib is a disease of older adults and is usually associated with multiple comorbidities,” wrote lead author Tze-Fan Chao, MD, with Taipei Veterans General Hospital, and colleagues. “Therefore, even if a patient does not have important systemic diseases when AFib is diagnosed, it is highly probable that incident comorbidities could develop thereafter, which could substantially increase the risk of ischemic stroke. However, the dynamic change of the CHA2DS2-VASc score and its impact on the stroke risk of patients with AFib have never been previously investigated, despite our recognition that the risk does not remain static.”

Using baseline and follow-up assessments, the researchers documented the change in CHA2DS2-VASc score in each patient, called Delta CHA2DS2-VASc. The mean baseline score was 1.29 and increased to 2.31 during follow-up, giving the cohort an average Delta CHA2DS2-VASc score of 1.02.

During nearly 172,000 person-years of follow-up, 4,103 patients in the study experienced ischemic stroke. Among those patients:

  • 89.4 percent had a Delta CHA2DS2-VASc score of at least 1, compared with 54.6 percent of patients who didn’t experience stroke.
  • 64.4 percent of patients accumulated at least one new-onset comorbidity during follow-up. Hypertension accounted for half of those cases, followed by congestive heart failure (35.4 percent) and diabetes (14.4 percent).
  • For patients who experienced stroke with new-onset comorbidities, 49.9 percent developed one new comorbidity, 36.5 percent developed two, 12.1 percent developed three and 1.4 percent developed four.

“Importantly, the risk of ischemic stroke was even higher within several months after the score changed, and therefore, clinicians should keep alert for the development of new comorbidities among patients with AFib,” Chao et al. wrote. “OACs should be offered without delay for the previously (baseline-defined) low-risk patients (i.e., CHA2DS2-VASc score 0 for men and 1 for women), unless contraindicated. For patients who have already received OACs, compliance of medications and risk factor management should be further emphasized and confirmed.”

The researchers demonstrated the predictive ability—measured by Area Under the Curve (AUC)—of Delta CHA2DS2-VASc was far superior to baseline assessment and marginally better than follow-up assessment alone. The AUC for Delta CHA2DS2-VASc was 0.742 compared to 0.578 for baseline assessment and 0.729 for follow-up CHA2DS2-VASc scores.

However, the authors said the aim of the study wasn’t to propose Delta CHA2DS2-VASc as a replacement for risk assessment.

“Our main purpose was to emphasize that the stroke risk of patients with AFib may continuously increase, and careful regular evaluation and/or detection of incident comorbidities with reassessment of the CHA2DS2-VASc score and stroke prevention strategy during each patient visit are important,” they wrote. “Because stroke risk typically increases with time, incident comorbidities should be evaluated periodically and stroke prevention therapy adjusted accordingly.”

In an accompanying editorial, Brian F. Gage, MD, MSc, agreed with this recommendation, noting current AFib guidelines state, “Individual risk varies over time, so the need for anticoagulation must be re-evaluated periodically in all patients with AFib.”

In addition, Gage said the exclusion of various baseline risk factors limited the predictive ability of the initial CHA2DS2-VASc score in this cohort, possibly overemphasizing the superiority of the Delta measurement. Several questions must be addressed before Delta CHA2DS2-VASc plays a role in clinical decision-making, Gage added.

“Would use of a Delta CHA2DS2-VASc score increase the appropriate use of anticoagulant therapy? Or would it obfuscate prescription of stroke prophylaxis?” he wrote. “More importantly, how would use of a Delta CHA2DS2-VASc score affect clinical outcomes? Because answers to these questions are unknown, potential use of the proposed Delta CHA2DS2-VASc score awaits further research.”