Early outcome of transannular patch repair of tetralogy of Fallot with or without pericardial monocusp in pulmonary position

INTRODUCTION

Tetralogy of Fallot (TOF) and associated variants represents about 10% of all forms of congenital heart disease, and TOF is considered the abundant form among cyanotic congenital heart diseases ¹.

Cooperation between cardiologists and pediatric cardiac surgeons is needed for early diagnosis and proper management in order to improve the outcome and decrease morbidity and mortality ². It comprises a wide clinical and anatomical spectrum with different approaches for surgical management. In Patients with smaller right ventricular outflow tract (RVOT) and pulmonary valve annulus a transannular patch is usually needed which can be fashioned simply by autologous pericardium ³.

Although this repair has the advantage of durability but it acutely renders the status of the right ventricle from being pressure-loaded into volume-loaded ⁴.

This result in variable degree of pulmonary insufficiency (PI) that causes temporary and/or delayed RV dysfunction and this chronic RV volume overload can lead to late biventricular dysfunction and tricuspid insufficiency necessitating the need for pulmonary valve insertion ^5,6.

In order to eliminate volume overload, in the short term, some groups have advocated monocusp valve insertion ⁷. A number of materials including pericardial, synthetic membrane, and homograft monocusp valves have been used in an attempt to mitigate the free PI associated with simple transannular patching ^8,9.

This study aims to evaluate the early outcome of pericardial monocusp placement in pulmonary position during repair of tetralogy of Fallot when transannular patch (TAP) is indicated.

Our Primary end point was to determine the effectiveness and safety of Insertion of a pericardial monocusp placement in the pulmonary position during tetralogy of Fallot repair if transannular patch is indicated.

The Secondary end points are; the intensive care unit stay, the hospital stay, grade of pulmonary valve regurgitation and grade of tricuspid valve regurgitation.

PATIENTS AND METHODS

Type of the study: This is a prospective, comparative, non-randomized, non-blinded, multicenter cohort study.

Place of settings: Al-Azhar University Hospital and National Heart Institute.

Patient population: Sixty patients underwent surgical correction of tetralogy of fallot by means of transannular patch repair with the following criteria:

Inclusion criteria: Age between six months and twelve years, both sexes and McGoon ratio equal or more than 1.6/1.

Exclusion criteria:  Redo cases, Abnormal coronary anatomy and associated major congenital cardiac defects like atrioventricular canal, and absent pulmonary valve.

Ethical consideration: The local Ethical Committee approved the study. Consent was taken from the patients’ families prior to enrollment in the study.

Methods: This study was conducted in the period from June 2016 to December 2018. Patients were divided into two groups. Group I: thirty patients didn’t receive pericardial monocusp in the pulmonary position. Group II: thirty patients received it in the pulmonary position.

All patients were offered full history taking, clinical examination, routine preoperative laboratory investigations, electrocardiography, and trans-thoracic echocardiography. Multislice CT and angiography were done in selected cases.

All patients were approached via median sternotomy under general anesthesia with endotracheal intubation. Dissection of the thymus gland with removal of one or both lobes for better exposure if needed. Then generous pericardiectomy taking care not to injure the phrenic nerves.

The harvested pericardium was treated with 0.6 % gluteraldehayde solution for ten minutes to be used for right ventricular outflow tract (RVOT) reconstruction and monocusp fashioning. This was followed by anatomy inspection, heparin administration, routine PDA or ligamentum ligation then conduction of cardiopulmonary bypass (CPB) via aorto-bicaval cannulation with systemic cooling to 28°C. After the aorta was cross-clamped, cold crystalloid cardioplegia was administered and repeated every 30 minutes, in conjunction with topical ice saline slush. Trans-atrial approach was used for initial assessment and VSD closure using Gor-tex patch with continuous sutures. When a transannular patch was decided, the RVOT was then approached through the tricuspid valve then via a limited infundibulotomy either without insertion of pericardial monocusp in the pulmonary position in group I or with monocusp placement using the previously taken pericardium in group II.

The technique of pericardial monocusp insertion: We can insert a monocusp valve in any sized patient when the monocusp leaflet is tailored (hand-made) to fit the RVOT that is enlarged by a transannular outflow patch. We fashion the previously gluteraldehyde-treated pericardium as hemi-oval shape. The dimensions of the pericardial monocusp leaflet are measured by a ruler or fashioned over a proper size Hegar dilator or any other feasible method like using silk. The length of the monocusp is determined by measuring the length of the incision from the right ventricle to the pulmonary annulus. The width is measured by holding the horizontal edges of the incision open by stay stitches. The monocusp is sewn with 6-0 polypropylene suture over the proximal half of the RVOT incision. Then trans-annular patch is sewn across the entire RVOT onto the main PA with a second suture line using 6-0 polypropylene stitch. In order to ensure monocusp coaptation to the conal septum and/or residual pulmonary valve tissue, the width and length of the monocusp are kept mildly redundant.

Then closure of any identified PFO or atrial septal defect if present, weaning of CPB, obtaining medical and surgical hemostasis, closure of sternum, and transfer of the patient to the intensive care unit (ICU) mechanically ventilated.

Operative reported data were; Cardio-pulmonary bypass time, aortic cross-clamp time, right ventricular pressure post-repair, central venous pressure post-repair and inotropic support used.

Postoperative data included; mechanical ventilation time, ICU stay, pre-discharge & after six months follow up echocardiography, hospital stay and mortality.

Statistical analysis:

Data were analyzed using Statistical Program for Social Science (SPSS) version 20.0. Quantitative data were expressed as mean ± standard deviation (SD). Qualitative data were expressed as frequency and percentage. Independent-samples t-test of significance was used when comparing between two means. Chi-square (X2) test of significance was used in order to compare proportions between two qualitative parameters. Probability P-value

RESULTS

The mean age of our patients in group I was 15.633±8.904 and in group II was 14.333±4.163 months. The mean body weight in group I was 9±1.702 kg, while in group II it was 9.883±2.12 without statistical significance between both groups.

Echocardiography was routinely performed preoperatively to all patients that showed; similar mean pulmonary annulus diameters in both groups around 0.790±0.202 cm. The mean McGoon ratio was also similar in both groups without significant difference. Also, there was no statistical difference regarding pressure gradient across RVOT in both groups.

Intra-operatively; the mean cross clamp time showed statistical significance between two groups with P

Table 1:Aortic Cross clamp time.

The cross clamp time didn’t affect the mean cardiopulmonary bypass time which was 77.467±15.956 in group I and 84.167 ± 9.931 minutes in group II with no statistical significance (P=0.056).

The pressure values in right ventricle and the central venous pressure (CVP) post repair were not statistically significant between the two groups.

Postoperatively;the mechanical ventilation time showed no statistical significance despite being shorter in group II. The mean ICU stay time in group I was statistically higher than in group II with P=0.021. The mean hospital stay showed statistical significance between two groups, P

Fig. 1: Hospital utilization.

In pre-discharge echocardiography;the mean grade of pulmonary regurgitation was significantly higher in group I than group II with P

Table 2:  Pre-discharge ECHO:

Regarding pressure gradient across RVOT there was no statistical significance between the two groups (P=0.421). In group I; it ranged between 9-27 mmHg with mean±SD 14.793 ± 4.135. While in group II; its ranged between 9-45 with mean±SD 16.103 ± 7.650. That favors the monocusp in the early postoperative period. Table (2)

Seven patients (11.66%) were lost in follow up during the study; five in group I representing and two patients in group II. The median follow up time in group I was 170.22 and in group II it was 196.21 days.

In follow up echocardiography; the mean grade of pulmonary regurgitation in group I was statistically higher than in group II with P

Table 3:  Follow up ECHO