# Thrombus formation after the Norwood procedure: Incidence, risk factors, and its impact on late outcomes

## TL;DR

Thrombus formation occurs in about 12% of patients after the Norwood procedure, mainly in the superior vena cava, and is linked to longer ICU stays and lower survival rates.

## Contribution

Identified restrictive atrial septal defect as a novel independent risk factor for thrombus formation after the Norwood procedure.

## Key findings

- Thrombus occurred in 11.7% of patients, most commonly in the superior vena cava.
- Patients with thrombus had lower 6-year survival (54%) compared to those without (70%).

## Abstract

Thrombus formation is a feared complication after congenital heart surgery. We aimed to clarify the clinical characteristics associated with thrombus formation after the Norwood procedure.

All neonates who underwent the Norwood procedure between 2001 and 2022 were reviewed. The incidence and location of thrombus were evaluated. Risk factors for thrombus formation and its impact on survival were analyzed.

Among 360 patients who were included, thrombus formation was detected in 42 patients (11.7 %) during the postoperative in-hospital period, with a median of 12 (range: 5–30) postoperative days. The most common site of thrombus was the superior vena cava in 9 (2.5 %) patients, followed by the right atrium in 8 (2.2 %). Patients who received a right ventricle to pulmonary artery conduit had a higher incidence of thrombus than those who received a modified Blalock-Taussig-Thomas shunt (16.4 vs. 7.7 %, p = 0.011). Patients with thrombus formation had a longer stay in the intensive care unit (ICU), than those without (median 21 vs. 13 days, p = 0.018). Survival after ICU discharge was lower in patients with thrombus than those without (57, 54, and 54 % vs 73, 71, and 70 % at 2, 4, and 6 years, respectively; p = 0.032). Restrictive atrial septal defect was identified as an independent risk for thrombus (odds ratio: 2.61; p = 0.005).

Thrombus formation was observed in 12 % of the patients during the hospital stay after the Norwood procedure and was associated with prolonged recovery and high mortality. A restrictive atrial septal defect was identified as a risk factor for thrombus formation.

•Thrombus formed in 11.7 % of patients after Norwood procedure, mainly in the superior vena cava.•Restrictive atrial septal defect emerged as an independent risk factor for thrombus formation.•Six-year survival was lower in patients with thrombus (54 %) compared to those without (70 %).

Thrombus formed in 11.7 % of patients after Norwood procedure, mainly in the superior vena cava.

Restrictive atrial septal defect emerged as an independent risk factor for thrombus formation.

Six-year survival was lower in patients with thrombus (54 %) compared to those without (70 %).