Bidirectional cavapulmonary anastomosis as a stage of haemodynamic correction of left heart hypoplasia syndrome

Objective. To retrospectively analyse the perioperative characteristics of patients with left heart hypoplasia syndrome, to assess immediate and long-term results after bi-directional cavapulmonary anastomosis. Materials and methods. During the period from 2010 to 2023, the Amosov National Institute of Cardiovascular Surgery performed a bidirectional cavapulmonary anastomosis in 8 patients with left heart hypoplasia syndrome: 7 boys and 1 girl. The median age of patients at the time of the intervention was 8 months. The main research methods were transthoracic echocardiography and cardiac catheterisation. Results. No patient died in the early postoperative period. In 2 patients, before the bidirectional cavapulmonary anastomosis, there was high pressure in the pulmonary artery system due to the presence of hemodynamically significant collateral vessels that were endovascularly closed before the intervention. All patients underwent the second stage of haemodynamic correction in the form of a bidirectional cavapulmonary anastomosis. The average duration of the operation was 480 minutes, and the artificial circulation was 117 minutes. The median transpulmonary gradient at the intraoperative stage was 6 mm Hg, in the postoperative period - 7 mm Hg. The pressure in the superior vena cava system and blood saturation after the second stage of hemodynamic correction were 15 mm Hg and 84%, respectively. Sympathomimetic support lasted 48 hours, and the total length of stay in the intensive care unit was 168 hours. The third stage of haemodynamic correction was performed in 4 patients. Conclusions. Bidirectional cavapulmonary anastomosis in patients with left heart hypoplasia syndrome provides better pulmonary circulation, which contributes to increased blood saturation, eliminates volume overload of the right ventricle, reducing venous return to it, and delays the development of heart failure. It is important to perform each stage of haemodynamic correction in a timely manner, which affects early and long-term results, the severity of preoperative and postoperative haemodynamics, interstage survival rates and postoperative complications.

Left ventricular hypoplasia syndrome (LVH) is one of the most complex congenital heart disease (CHD) and great vessels, characterised by a combination of pathologies such as mitral valve (MV), left ventricle (LV), aortic valve (AV) hypoplasia or atresia, and varying degrees of ascending aortic hypoplasia.Children with this pathology are born with a frequency of 0.016-0.036% of all children with CHD [1].According to the literature, SGVHD was detected in 7.7% of 2381 newborns with heart disease (0.163 per 1000 live births).In newborns with heart disease, this anomaly is one of the most common causes of death (15-25%) [2].
In 1958, the term "left heart hypoplasia syndrome" was first mentioned by J. A. Noonan and A. S. Nadas [3], and the first results of surgical correction of LVH were reported by W. I. Norwood and co-authors in 1981 [4].
About 200 children with this pathology are born in Ukraine every year.The results of recent studies have made it possible to distinguish the ARF into a distinct clinical and anatomical unit.The Amosov National Institute of Cardiovascular Surgery of the National Academy of Medical Scienc-es of Ukraine successfully performed the first stage of haemodynamic correction, or Norwood-I surgery, in a child with ARF in 2010.
The prognosis in these patients directly depends on the anatomy and physiology of the SVLVS.Anatomically, there are 5 types of SVLVS [5] (Table 1).
In terms of haemodynamics and physiology, SGVHD (see Figure ) is a dactus-dependent heart defect with a functionally single ventricle (SV).
Without specialised cardiac surgery, the condition of newborns with this defect deteriorates sharply due to a decrease in pulmonary vascular resistance and closure of the patent ductus arteriosus (PDA), which causes 100% of children to die within the first weeks of life.In the presence of a moderate degree of LV hypoplasia with valve stenosis, life expectancy can increase to several weeks and months.
Currently, there is a three-stage method of haemodynamic correction of CHF proposed by W. Norwood [4]: Norwood I -creation of a free and permanent outlet to the systemic circulation by forming a neo-aorta, applying The Ukrainian Journal of Clinical Surgery a systemic-pulmonary anastomosis and atrioseptectomy; Norwood II -formation of a bidirectional cavapulmonary anastomosis (DCPA) to provide a stable and controlled source of pulmonary circulation; Norwood III -formation of a total cavapulmonary anastomosis with the creation of a wide connection at the atrial level.
The aim of the study was to retrospectively analyse the perioperative characteristics of patients with SGLVS, to assess the immediate and long-term results after DKA.

Materials and methods
In the period from 2010 to 2023, the Amosov National Institute of Cardiovascular Surgery of the National Academy of Medical Sciences of Ukraine performed DCPA as the second stage of haemodynamic correction in 8 patients with ARF -7 (87.5%) boys and 1 (12.5%)girl.No genetic or chromosomal pathology was detected in these children.
Upon admission, all patients underwent anthropometric measurements (Table 2), general clinical and biochemical blood tests, bacteriological tests, and instrumental studies: electrocardiography (ECG), chest radiography, echocardiography (Echocardiography), and cardiac catheterisation.The latter two methods, which were used to assess the state of haemodynamics (Table 3), played the greatest role in preoperative preparation and evaluation of immediate and long-term results.

The Ukrainian Journal of Clinical Surgery
According to the ECG, predominant hypertrophy and signs of overload of the LV, especially in the early postoperative period, in the form of low QRS complexes and deviation of the electrical axis to the right, were observed, signs of chronic coronary artery disease were also assessed, and cardiac arrhythmias (arrhythmia) were differentiated.
Radiological examinations were performed in direct projection, they allowed to assess the overall size of the heart and individual cardiac arches, the condition of the lung tissue and pulmonary circulation.
Particular attention was paid to the functional parameters of the ventricle and valves during echocardiography: EF, EF, RV or ESV, EF, HOC, size and function of atrioventricular valves.To determine further surgical tactics, we consider cardiac catheterisation to be the "gold standard", during which hemodynamic features were studied with the assessment of RV function, tricuspid valve and the presence of a uni-or bi-directional shunt through the atrial septal defect, as well as blood oxygen saturation, the size of the IVC and pressure in it, pulmonary veins, right and left atria and aorta, and the size of the LA branches.
Method of surgical correction.In all patients, the second stage of hemodynamic correction in the form of DCPA for-mation was performed with cardiopulmonary bypass (CPB) on parallel perfusion under normothermia.The surgical access in all patients was a midline sternotomy, and cardiolysis was performed with the isolation of the IAD and right LA to the partial branches.After connecting the CABG, the modified Bleloc-Taussig anastomosis or the Sano anastomosis was first sutured and cut off.The next step was to cut off the IAD from the right atrium and suture it with a double-row suture.After that, the IAD was sutured into the right LA end laterally, forming the DCAP.

Results
No patient died in the early postoperative period.In 2 patients, before DCPA, there was high pressure in the LA system due to the presence of hemodynamically significant collateral vessels that were endovascularly closed before the intervention.

Note
Note.

The Ukrainian Journal of Clinical Surgery
After disconnection of the SC, the transpulmonary gradient was assessed, which ideally should be less than 10 mm Hg if the pressure in the IVC system is within acceptable limits (Table 4).
In the analysis of postoperative parameters (Table 5), special attention was paid to the median venous pressure in the IVC system, the median transpulmonary gradient, the median systemic oxygen saturation and the duration of artificial lung ventilation (ALV).It should be noted that the uncomplicated course of the early postoperative period was observed in 6 (75%) patients.The remaining 2 (25%) patients had cardiac weakness, which was successfully treated with sympathomimetic drugs (see Table 5).
The third stage of haemodynamic correction in the form of a total cavapulmonary anastomosis was performed in 4 patients.
In the long-term postoperative period, 1 patient underwent radiopaque dilatation of the main bronchus and stenting of the left LA.

Discussion
SGVHD is one of the most challenging CHDs for paediatric cardiologists and cardiac surgeons, with 100% of patients dying without surgery.According to the Society of Thoracic Surgeons' CHD surgical correction database, in 2019, mortality rates after the first stage of the Norwood palliative procedure were 15%, after Hemi-Fontan/Glenn surgery -1.8%, and after Fontan surgery -1.0% [6].
Heart transplantation is considered a radical correction of CHD, but due to the shortage of donor hearts for newborns, 20% of children on the waiting list die before they receive a new heart, so the alternative is the three-stage Norwood palliative procedure [7], the ultimate goal of which is to separate the systemic and pulmonary circulation.In its turn, the LV will become the systemic ventricle and pump oxygenated blood to the body, while all deoxygenated venous blood from the body will passively enter the pulmonary circulation.The optimal timing of the first stage of the Norwood procedure is 2-7 days of life, the second -at the age of 4-6 months, and the third -at about 2 years of age [8].Preoperative preparation, surgical intervention and the postoperative period require a specialised multidisciplinary approach to patients with this pathology [9].The timeliness of each stage of haemodynamic correction has a positive effect on early and long-term results, preoperative and postoperative haemodynamics, interstage survival rates, and postoperative complications.Due to DCPA, systemic saturation is increased, venous return to the RV is reduced, and its overload is eliminated, which significantly delays the development of heart failure [9].Cardiologists should pay special attention to the interstage periods in terms of monitoring the child's condition.

Conclusions
1. DCPA in patients with ARF provides better pulmonary circulation, which helps to increase blood saturation, eliminates volume overload of the LV, reducing venous return to it, and delays the development of heart failure.
2. It is important to perform each stage of the Norwood procedure in a timely manner, as this affects early and longterm results, the severity of preoperative and postoperative haemodynamics, interstage survival rates and postoperative complications.
3. Given the shortage of donor children's hearts, the timely three-stage surgical treatment proposed by Norwood gives good results and the possibility of postponing transplantation.
Funding.There were no external sources of funding or support.No honoraria or other compensation was paid.
Author contributions.All authors contributed equally to this work.
Conflict of interest.The authors who participated in this study have declared that they have no conflicts of interest regarding this manuscript.
Consent for publication.All authors have read and approved the final version of the manuscript.All authors have agreed to the publication of this manuscript.
Ethical aspects.All procedures performed in the study with the involvement of patients complied with ethical standards for clinical practice and the Declaration of Helsinki, 1964, as amended.