Adult Congenital Heart Reviews
Ono M, Burri M, Mayr B, Anderl L, Strbad M, Cleuziou J, Hager A, Hörer J, Lange R.
Ann Thorac Surg. 2020 Aug 20:S0003-4975(20)31323-0. doi: 10.1016/j.athoracsur.2020.06.030. Online ahead of print.
Take Home Points:
- The outcome of Glenn shunt is generally good with the majority of the patients proceeding to Fontan completion.
- Hypoplastic left heart syndrome, unbalanced atrioventricular septal defect, high pulmonary artery pressure and a reduced ventricular function at the time of superior cavopulmonary shunt were identified as risk factors for failure to successfully complete the Fontan procedure.
- Atrio-ventricular valve regurgitation, despite associated with unbalanced atrioventricular septal defect and a reduced ventricular function, is not associated with failure to successful Fontan completion.
Commentary from Dr. MC Leong (Kuala Lumpur, Malaysia), section editor of ACHD Journal Watch: While the outcomes of total cavopulmonary connections are widely reported, there is a paucity of outcome data on the second stage single ventricular palliation. Such palliation includes fashioning of a superior cavopulmonary connection (bidirectional Glenn shunt) or in some centers, a hemi-Fontan procedure. This study aimed at analyzing the outcomes of all single ventricles which have undergone the second stage palliation and identifying the factors that are associated with death or failure to progress to a Fontan completion.
This is a single center, retrospective review of a database of 525 patients with single ventricles who underwent bidirectional Glenn shunt at the German Heart Center in Munich between January 1998 and December 2018. Baseline characteristics of the patient population were as tabulated in Table 1. The median time of Glenn shunt was 4.7 month (IQR, 3.0-7.4) while the median weight was 5.6 kg (IQR, 4.7-7.0). The perioperative data was summarized in Table 2. Of note is the patients with unbalanced atrioventricular septal defect were at greatest risk of early death (10.0%), whereas early death occurred in hypoplastic left heart syndrome patients was only 3.6% of all patients. Interestingly, in the early postoperative period, 55 patients required cardiac catheterization because of severe cyanosis and subsequent surgical/catheter interventions. The etiology for cyanosis were Glenn pathway stenosis (n=31), veno-venous collaterals (n=11), cavopulmonary pathway thrombus (n=4), and undetermined (n=9). In all 9 patients whose etiology was undetermined, placement of a systemic to the branch pulmonary shunt and performing a pulmonary septation to create unilateral Glenn shunt to the contralateral pulmonary artery was performed, out of which, five patients died postoperatively.
Of the 514 early survivors, 15 patients were lost to follow-up after hospital discharge (Figure 1). The median follow-up period was 3.4 years (IQR, 1.5-8.7) for the remaining 499 patients. A competitive risk analysis was performed onto patients who had Fontan completion, death, and ‘being alive without Fontan’. Patients who failed to achieve successful Fontan completion was defined as those who died before Fontan completion; patients who were considered unsuitable for Fontan completion; and patients who died early after Fontan completion (death within 30 days), because they failed to establish successful Fontan circulation. The cumulative incidence of Fontan completion (83.9% at 3 years and 87.1% at 5 years), the cumulative incidence of death (10.4% at 3 years and 10.7% at 5 years), and survival without Fontan completion (5.7% at 3 years and 2.2% at 5 years) are shown in Figure 2. Freedom from mortality before the Fontan procedure, unsuitability for the Fontan procedure, and early mortality after the Fontan procedure at 1, 2, and 3 years were 91.9%, 87.3%, and 86.1%, respectively.
Multivariate analysis showed that hypoplastic left heart syndrome, unbalanced atrio-ventricular septal defect (AVSD), high pulmonary artery pressure and a reduced ventricular function at Glenn shunt were associated with failure to achieve an eventual successful Fontan completion. Although significant atrioventricular valve regurgitation requiring intervention was not identified as an independent risk in multivariate model, the incidence of atrioventricular valve intervention was significantly higher in patients with unbalanced AVSD (26.7% vs. 10.3%, p=0.006) and in patients with reduced ventricular function (26.1% vs. 9.8%, p=0.001).
Apart from the conclusions that the study came to, this study also raised two important issues. (1) The timing of Glenn shunt needs to be balanced between overloading the ventricle with a systemic to pulmonary artery shunt and the need to grow the pulmonary artery to a caliber suitable for the eventual Fontan completion. In this study, the Glenn shunts were performed relatively early at the median age of 4.7 month (IQR, 3.0-7.4). Meanwhile, pulmonary artery reconstruction was required in 189 (36%) patients during Glenn shunt. As many as 129 (25%) patients required bilateral branch pulmonary arteries repair. It is possible that many of them required pulmonary artery intervention to enlarge the pulmonary arteries, which may alter the dimension of the pulmonary artery outside of the lungs but not the pulmonary arterial tree within the lungs. The calibers of the pulmonary arteries are not only anatomical but also physiologically linked to the long-term outcome of the eventual Fontan procedure; (2) If a patient presents with unexplained cyanosis post Glenn shunt, the prognosis is poor. In this study, 9 patients had no recognizable anatomic defect, and hypoxemia was perceived to be secondary to inadequate pulmonary blood flow. Implanting an additional systemic to pulmonary shunt and pulmonary artery septation which supposedly meant to improve oxygenation, unfortunately, yielded in 5 deaths. These patients may perhaps benefit from other treatment options.