Sick sinus syndrome elevates stroke risk in patients with atrial fibrillation with low CHA2DS2-VASC score

Atrial fibrillation (AF) and isolated sick sinus syndrome (SSS, without AF) are both associated with increased stroke risk. Although AF and SSS often co-exist as tachy-bradyarrhythmia, the impact of SSS on stroke risk among patients with AF remains unclear.

The aim of this study was to evaluate whether SSS is independently associated with incident ischemic stroke in patients with AF.

We analyzed a hospital-based cohort of 24,960 patients with AF from 2010 to 2021. SSS was defined strictly as symptomatic sinus node dysfunction requiring pacemaker implantation. The primary end point was ischemic stroke hospitalization. Cox models adjusted for CHA₂DS₂-VASc (congestive heart failure, hypertension, age ≥75 years, diabetes mellitus, stroke or transient ischemic attack, vascular disease, age 65 to 74 years, sex category) score were used to assess associations.

Of the 24,960 patients with AF, 1624 had SSS and a pacemaker, whereas 23,336 did not. Patients with SSS were older, more often female, and had higher CHADS₂ and CHA₂DS₂-VASc scores. Over a mean follow-up of 4.07 ± 3.55 years, stroke incidence was 4.02% per patient-year in the SSS group vs 3.03% in the non-SSS group (P < .001). After adjustment, SSS was associated with a 23% higher stroke risk (hazard ratio [HR] 1.23, 95% confidence interval [CI] 1.10-1.37, P < .001). This association was strongest in patients with CHA₂DS₂-VASc scores ≤2 (HR 2.13, 95% CI 1.76-2.58, P < .001), but not significant in those with scores >2 (HR 1.02, 95% CI 0.89-1.17, P = .722).

SSS independently predicts higher stroke risk in patients with AF, particularly among those with lower baseline CHA₂DS₂-VASc scores. This finding may help refine stroke prevention strategies.