'Low-Risk' Valvular AF in Some May be Risky Enough for Oral Anticoagulation

September 11, 2020

Some patients with "valvular" atrial fibrillation (AF) and stroke-risk scores low enough for oral anticoagulation (OAC) not to be indicated may actually face enough thromboembolic risk to justify the lifelong therapy, a new report suggests.

The conclusion was based on analysis of nationwide Danish registries. Researchers found that the risk at 1 year extended into the range anticoagulation is considered worth prescribing among patients with AF and type 2 valvular heart disease (VHD) who weren't on OAC and were otherwise considered low risk for stroke.

Thromboembolic risk was especially elevated in those younger than 65, found the study published August 28 in JACC: Clinical Electrophysiology, with lead author Line Melgaard, MSc, PhD, from Aalborg University, Denmark, who also presented it during the virtual European Society of Cardiology (ESC) Congress 2020.

In patients with type 2 VHD who have a bioprosthetic heart valve or valvular disease other than moderate-to-severe mitral stenosis of rheumatic origin, OAC tends to be guided by CHA2DS2-VASc scores, although without specific clinical trial support, the report notes. Guidelines already specify OAC for patients with rheumatic moderate-to-severe mitral valve disease.

In patients with AF and type 2 VHD who don't have a "strong recommendation" for OAC and may lack any such recommendation, "the risk of thromboembolism may exceed the level above which oral anticoagulation is considered beneficial," Melgaard told theheart.org | Medscape Cardiology.

The risk required for a net clinical benefit from OAC, she and her colleagues note in their report, is commonly cited as at least 1.0 event per 100 person-years, which works out to a 1-year risk of at least 1.0%.

But in the analysis, that risk reached 1.4% for patients with AF and type 2 VHD with no comorbidities, and 1.5% for such patients younger than 65 with either 0 or 1 comorbidity.    

The findings, Melgaard said in an interview, suggest that patients with AF and type 2 VHD younger 65 years with no stroke risk factors, for whom OAC is currently not recommended, "may not be a truly low-risk subgroup" and may benefit from anticoagulation therapy.

But there is a caveat in this observational study: confidence intervals for the observed increases in thromboembolic risk for patients with type 2 VHD included 1.0, the proposed threshold for net OAC benefit, which the authors attribute possibly to diminishing sample sizes after stratification by age and comorbidities.

"Additional studies need to confirm our findings before changes to guidelines can be suggested," Melgaard said. "Nevertheless, our study clearly raises the hypothesis that AF patients with type 2 VHD and 0 or 1 established stroke risk factors could benefit from oral anticoagulant treatment."  

The analysis encompassed 55,613 adults with AF included in Danish nationwide registries from 2000 to 2018, including 1907 patients with type 2 VHD, and who had not received OAC within the prior 180 days.

Grouped by VHD status and number of comorbidities, 41,120 and 12,586 patients did not have type 2 VHD but had 0 or 1 comorbidities, respectively. And, 1253 and 654 patients had type 2 VHD with 0 or 1 comorbidities, respectively.

The included comorbidities consisted of heart failure, hypertension, diabetes, or vascular disease; that is, components of the CHA2DS2-VASc score excluding age, sex, and history of thromboembolism.

Table. Adjusted Risk (AR) for Stroke or Systemic Embolism at 1 Year by VHD Type Status, Stratified by Age Group

Overall Without Type 2 VHD, AR (%) (95% CI) With Type 2 VHD, AR (%) (95% CI)
0 Comorbidities 0.8 (0.4-0.6) 1.4 (0.5-2.3)
1 Comorbidity 1.2 (1.0-1.4) 1.1 (0.4-2.2)
< 65 y    
0 Comorbidities 0.5 (0.4-0.6) 1.5 (0.7-2.8)
1 Comorbidity 0.9 (0.7-1.2) 1.5 (0.6-3.4)
65-74 y    
0 Comorbidities 1.5 (1.3-1.8) 1.2 (0.5-2.6)
1 Comorbidity 1.8 (1.4-2.3) a

Comorbidity defined as components of the CHA2DS2-VASc score other than age, sex, and history of thromboembolism: congestive heart failure, hypertension, diabetes mellitus, or vascular disease

a too few events for analysis; CI = confidence interval; y = years

 

Melgaard said only a minority of the patients with type 2 VHD had bioprosthetic valves — 18% and 22% of those with 0 and 1 comorbidity, respectively — which could be either surgically implanted or transcatheter valves. The groups were too small for their risks to be analyzed separately.

The study was supported by the "Bristol-Myers Squibb/Pfizer European Thrombosis Investigator Initiated Research Program 2018." Melgaard discloses receiving grant support from Bristol-Myers Squibb/Pfizer. Disclosures for the other authors are in the report.

European Society of Cardiology (ESC) Congress 2020; presented August 27, 2020.

J Am Coll Cardiol EP; 2020. Published August 28, 2020. Abstract

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