The Bilateral Bidirectional Glenn Operation as a Risk Factor Prior to Fontan Completion in Complex Congenital Heart Disease Patients

Background:

The Glenn procedure is performed as a second-stage palliative procedure toward the completion of Fontan circulation in patients with a functionally univentricular heart. Safe Fontan completion requires normal ventricular function, competent atrioventricular valves, normal pulmonary arteries anatomy, and low pulmonary vascular resistances (PVRs). Clinical observations revealed that patients who previously underwent bilateral Glenn (b-Glenn) had a stormier postoperative course in respect to patients after unilateral Glenn (u-Glenn) postoperatively after Fontan completion. This retrospective study was designed to compare and analyze the outcomes of patients following Fontan completion with previous u-Glenn versus b-Glenn.

Patients and Methods:

A total of 98 patients were divided into two groups. Group 1 included 80 patients with unilateral superior vena cava (SVC), and group 2 included 18 patients with bilateral SVC. Univariate and multivariate analyses were performed with regard to mortality and failure.

Results:

Prior to Fontan, G1 and G2 had similar demographic and physiological findings including: age, weight, cardiac malformation type, and hemodynamic measurements. Specifically, the mean PVRs were 1.66 + 1.29 in G1 and 1.49 + 0.82 in G2 (p-value non-significant). Regarding outcomes: stormy postoperative course, Fontan failure, and early mortality were all significantly higher in G2. G1 mortality rate was 3.7%, versus 22% in G2. Late Fontan failure rates were 6% for G1 (defined: pulmonary hypertension, heart failure, protein losing enteropathy (PLE), and persistent low systemic venous saturation), and 22% for G2.

Conclusions:

Our results have demonstrated that patients after b-Glenn have a tendency for worse outcomes upon Fontan completion. The b-Glenn is associated with pulmonary artery bifurcation stenosis and presents multiple sources of pulmonary blood flow where conventional PVR calculation might be imprecise and misleading since it considers the lungs as a single unit. Therefore, b-Glenn engenders correction of the conventional PVR calculation to consider each lung separately. Furthermore, the surgical approach for patients with persistent left SVC and univentricular heart should be modified.