2.1.1 HLHS is a combination of congenital abnormalities of the left side of the heart. Without surgical intervention it is fatal in the first weeks of life.
2.1.2 The standard treatment for HLHS is a staged reconstruction requiring up to three complex open heart operations over three or more years (stages 1 to 3). Some children who survive staged reconstruction will reach adulthood in good health. However, some may need other cardiac procedures or a heart transplant at a later stage.
2.2.1 The hybrid procedure is performed under general anaesthesia or conscious sedation as soon as possible after birth. The aim is to improve the systemic circulation, while restricting the blood flow to the lungs (to prevent the development of pulmonary hypertension). This delays the need for high-risk open heart surgery reconstruction until the patient is older. It involves:
banding of the right and left branches of the pulmonary artery either by open surgery, via a median sternotomy, or by a percutaneous endovascular technique
endovascular insertion of a stent into the ductus arteriosus, via a percutaneous approach
atrial balloon septostomy by a percutaneous endovascular technique.
2.2.2 The individual components of the hybrid procedure may be carried out synchronously or may be staged depending on individual patient need.
2.3.1 In three case series including HLHS patients treated by the hybrid procedure, 90% (52/58), 52% (15/29) and 57% (8/14) of patients survived to undergo stage 2 reconstruction (two and three patients in the first two studies were waiting for the stage 2 procedure at publication). Survival after the stage 2 operation was 88% (46/52) and 75% (6/8) in the first and third series, respectively.
2.3.2 In a case series of 40 patients, 88% (15/17) of patients treated by the hybrid procedure survived the procedure, of whom 27% (4/15) subsequently died before further surgical treatment, and 67% (10/15) were treated with a heart transplant.
2.3.3 A study of 22 patients compared 5 high-risk HLHS patients treated by the hybrid procedure with 17 standard- and high-risk patients treated with stage 1 reconstruction. All five patients treated by the hybrid procedure and 65% (11/17) of patients treated by stage 1 reconstruction survived their respective operations. Two of the five hybrid procedure survivors and 9% (1/11) of stage 1 reconstruction survivors died before undergoing a stage 2 operation. For more details, refer to the 'Sources of evidence' section.
2.3.4 The Specialist Advisers stated that the efficacy of the hybrid procedure is uncertain because only small numbers of patients have been reported. One stated that the long-term efficacy, specifically survival following the hybrid procedure compared with the standard open heart procedure without the hybrid procedure, is not clear in the literature.
2.4.1 The case series of 58 patients reported 30-day mortality of 3% (2/58) after the hybrid procedure. The case series of 29 patients reported five hospital deaths (17%).
2.4.2 In the case series of 40 patients, 35% (6/17) had complications relating to an intraluminal banding device used to band the pulmonary artery. In two patients the banding device was larger than required, resulting in excessive restriction of blood flow, two further patients developed acute pulmonary artery occlusion at the site of the device and in a further two patients the device was either placed or embolised further into the pulmonary circulation. For more details, refer to the 'Sources of evidence' section.
2.4.3 The Specialist Advisers stated potential, theoretical events to include death, brain damage, bleeding, infection, heart failure, damage to pulmonary arteries, stent migration, stent stenosis, stent thrombosis, migration of the pulmonary artery bands and perforation of the ductus arteriosus. One Specialist Adviser suggested that the procedure may shift mortality from the neonatal period to the infant period.