Lead‐to‐Vein Ratio and Long‐Term Vascular Safety After Transvenous Pacing in Children Weighing ≤15 Kg

BACKGROUND: Transvenous pacing in low-weight children is technically feasible, but its clinical use depends on long-term venous patency, system performance, and ventricular function. We aimed to describe imaging-defined venous abnormalities and clinically overt vascular events after first transvenous pacemaker implantation and to explore whether the lead-to-vein ratio provides anatomical information beyond body weight. METHODS: This prospective observational cohort included 35 children weighing ≤15 kg undergoing first transvenous pacemaker implantation between 2010 and 2020. The primary vascular endpoint was imaging-defined venous thrombosis, occlusion, or stenosis ≥50%; clinical impact was recorded separately. Device-related safety, minimum venous diameter, lead-to-vein ratio, ventricular function, synchrony, and paced QRS duration were analyzed using non-parametric, exact, and exploratory univariable tests. RESULTS: Median follow-up was 6.7 [4.5-8.2] years. Eleven patients weighed <10 kg and 3 weighed <5 kg. The imaging-defined vascular endpoint occurred in 6/35 patients; 5 were asymptomatic surveillance findings and 1 was clinically symptomatic. The lead-to-vein ratio was higher in patients with the endpoint than in those without events (0.59 [0.55-0.63] vs. 0.47 [0.43-0.51]; p = 0.003). A ratio >0.55 was associated with more frequent imaging-defined endpoints (4/8 vs. 2/27; odds ratio 12.5; 95% confidence interval 1.7-92.3). Left ventricular ejection fraction remained preserved. CONCLUSION: During the first transvenous system lifespan, imaging-defined venous abnormalities were relatively frequent but mostly asymptomatic, whereas clinically overt vascular complications were uncommon. The lead-to-vein ratio may support anatomical pre-implant risk stratification, although multicenter validation and follow-up beyond generator replacement are required.