<p><strong>BACKGROUND: </strong>Pulmonary venous obstruction after repair of total anomalous pulmonary venous connection (TAPVC) results in substantial morbidity and mortality. Risk factors for postoperative obstruction remain ambiguous. Additionally, the existing literature has no standard definition for preoperative obstruction making patient counseling difficult.</p>

<p><strong>METHODS: </strong>All patients undergoing repair of TAPVC at our institution from 1/1/06 to 10/23/17 were identified. The primary outcome was the development of postoperative obstruction, analyzed as a time-to-event outcome. Clinical information was extracted to assess risk factors. Degrees of preoperative obstruction were defined based on echocardiographic, catheterization, and clinical findings. Univariable and multivariable Cox proportional hazard regression methods were used to identify factors associated with the primary outcome.</p>

<p><strong>RESULTS: </strong>During the study interval, 119 patients underwent repair of TAPVC (40% single-ventricle), and 25 patients (21%) developed postoperative obstruction. Risk factors associated with obstruction were heterotaxy syndrome, single-ventricle heart disease, additional surgeries at the time of vein repair, mixed-type TAPVC, and preoperative obstruction. Having even mild preoperative obstruction (≥1.2 m/s by Doppler echocardiography) was predictive of postoperative obstruction. A multivariable model showed mixed-type TAPVC and the presence of preoperative obstruction were associated with over 2-fold greater hazards of obstruction.</p>

<p><strong>CONCLUSIONS: </strong>TAPVC in the setting of heterotaxy and single-ventricle remains challenging with high rates of postoperative obstruction. Mixed-type TAPVC is an independent risk factor for postoperative obstruction, particularly in patients with isolated TAPVC. Even mild preoperative obstruction is a risk factor for postoperative obstruction. These results may help risk-stratify TAPVC patients.</p>

<p>Total anomalous pulmonary venous connection (TAPVC) is a rare form of congenital heart disease in which the pulmonary veins drain by various pathways to the right atrium instead of the left atrium. Postoperative obstruction of the pulmonary veins is a known complication. Identifying risk factors for morbidity and mortality is important for counseling and monitoring. We describe a pattern of postoperative obstruction in a specific arrangement of mixed TAPVC. Five patients with a type of mixed TAPVC, namely, three pulmonary veins connecting to the coronary sinus and the left upper pulmonary vein (LUPV) connecting to the innominate vein, were identified over an 11-year period at our institution. Two additional patients with this TAPVC arrangement were cared for at our institution after having surgery at other institutions. Of these, one patient received only comfort care at birth due to other clinical issues. The six other patients underwent surgical unroofing of the coronary sinus. The anomalous LUPV was not addressed during the initial surgery in any of these cases. Following repair, one patient died from non-cardiac reasons. The remaining five patients all developed obstruction of the repaired pulmonary veins with decompression through the unrepaired LUPV, requiring surgical revision. Three patients underwent a second reoperation as well. Three of the six repaired patients also developed refractory atrial arrhythmias. This cohort suggests that this mixed TAPVC pattern predisposes patients to obstruction after surgical repair. Further investigation may aid pediatric cardiologists in risk-stratifying and counseling these patients. Alternative surgical approaches may need to be considered.</p>