AF screening tied to reduction in stroke risk in patients with high NT-proBNP

Screening for atrial fibrillation (AF) is associated with a reduction in the risk of stroke in individuals with a high NT-proBNP* level, according to a post hoc analysis of the LOOP study.

“Implantable loop recorder (ILR) screening for AF was associated with a 40-percent reduction in stroke risk in persons with NT-proBNP >15 pmol/L, but not in those with NT-proBNP ≤15 pmol/L,” said Dr Søren Zöga Diederichsen from Rigshospitalet – Copenhagen University Hospital, Copenhagen, Denmark, at EHRA 2023.

Those with high NT-proBNP level had a significantly reduced risk of stroke or systemic embolism (SE) with ILR screening (hazard ratio [HR], 0.60, 95 percent confidence interval [CI], 0.40–0.90; p=0.013). For those with low proBNP levels, there was no trend towards a benefit from ILR screening and subsequent anticoagulation (HR, 1.11, 95 percent CI, 0.76–1.62; p=0.58).

“There was a significant interaction between the randomized arms for this outcome,” said Diederichsen. The p-value for interaction was 0.029.

“The signal was totally the same when cardiovascular (CV) death was included,” he continued. A significant reduction in stroke, SE, and CV death risk was seen among those with high (HR, 0.70, 95 percent CI, 0.53–0.94; p=0.018) but not low (HR, 1.11, 95 percent CI, 0.79–1.55; p=0.55) NT-proBNP levels. P-value for interaction was 0.045.

NT-proBNP tied to AF diagnosis

LOOP is an AF screening trial that included AF-naïve individuals who had at least one risk factor for stroke (hypertension, diabetes, heart failure, or previous stroke). A total of 6,004 participants were randomized 1:3 to either continuous AF screening using an ILR or usual care. Those in the ILR arm were initiated on anticoagulant therapy upon AF detection (episodes ≥6 minutes).

The investigators conducted a substudy on LOOP participants who had baseline NT-proBNP measurement (n=5,819; mean age 75 years, 54 percent male). Of these, 49 percent had high NT-proBNP levels.

Those with high NT-proBNP were much more likely to be diagnosed with AF, be it in the ILR (HR, 1.84, 95 percent CI, 1.51–2.25; p<0.0001) or the usual-care arm (HR, 2.79, 95 percent CI, 2.30–3.40; p<0.0001).

In the ILR arm, individuals with high NT-proBNP levels also had longer AF episodes, lasting at least a full day (HR, 2.45, 95 percent CI, 1.46–4.10; p=0.00065).

The overall incidence of stroke/SE was 5.3 percent (n=310), yielding an event rate of 1.04. For the composite of stroke, SE, and CV death, the corresponding rate was 8.1 percent (n=470), generating an event rate of 1.57. Stroke was the most prevalent event for both outcomes.

Individuals with high NT-proBNP level did not have a higher risk of stroke/SE per se (HR, 1.23, 95 percent CI, 0.97–1.55; p=0.087), but did have a higher risk when CV death was incorporated into the composite endpoint (HR, 1.62, 95 percent CI, 1.33–1.97; p<0.0001).

“[These findings suggest that] NT-proBNP was associated with AF diagnosis, AF ≥24 hours, stroke, and CV death,” said Diederichsen.

NT-proBNP a useful biomarker

“AF is an important and potentially modifiable risk factor for stroke … In this population with an increased risk of stroke, [our findings suggest that NT-proBNP could be] a useful biomarker to select individuals for AF screening to prevent stroke,” noted Diederichsen and colleagues.

“High NT-proBNP levels may identify individuals with a more clinically relevant AF burden. As these findings are exploratory, further studies are warranted,” they concluded.