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Delayed Arterial Switch in D-transposition of the Great Arteries – Salvage Solution or Compromise?

Horatiu Suciu¹, Anca Sglimbea² ,Radu Deac¹
¹ 2nd Department of Cardiovascular Surgery for adults and Children
² 3rd Department of Cardiology-Children
Emergency Institute for Cardiovascular Diseases and Transplantation Tg. Mures, Romania

 

 

Correspondence

Horatiu Suciu
2nd Department of Cardiovascular Surgery for Adults and Children
Emergency Institute for Cardiovascular Diseases and Transplantation Tg. Mures, Romania
tel: 0040.265.216.368
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

 

Abstract

Arterial switch operation for d-transposition of the great arteries performed at 2-3 weeks of life is the surgical gold standard. As some patients fall out of this timing, an alternative method of late arterial switching after conditioning the left ventricle is still giving the patient the chance for an anatomical correction. We are presenting the case of a 3 month old infant with d-transposition of the great arteries. Operations preparing for and late arterial switch were performed in this patient. Technique and outcome of the two steps are presented and indications and peculiarities of the two step switch are discussed.

Key words: arterial switch, d-transposition of great arteries

  

Introduction

Anatomical correction for d-transposition of the great arteries (dTGA) by arterial switch has become the surgical gold standard in all pediatric cardiovascular centers. Reduced early mortality (less than 5% in unselected groups) and late complications and reinterventions (3,7%) have transformed a severe, invalidating disease in a curable one. The impressive results reported by the literature are obtained if the patient is operated in the first 2-3 weeks of life, when the left ventricle (LV), the sub pulmonary ventricle is still functioning at increased pressures and can easily support the systemic pressures after performing the switch operation.

There is a group of patients who can’t undergo operation in this period, considered safe: patients with postnatal complications (extra uterine life maladaptation, infections, premature-related) or the group, more often encountered in our particular situation that of patients not timely diagnosed. In these patients, the remaining option is that of physiological correction, meaning atrial switch, operation related to multiple early and late complications and almost completely abandoned in the recent years. In order to be able to perform a late arterial switch operation, the patient needs a retraining of the LV, to make it able to sustain systemic circulation, process called reconditioning The operation consists of the placement of a pulmonary arterial banding, with or without a systemic-to-pulmonary shunt for preserving a proper pulmonary output. Indications, technique and results of the reconditioning process are still under debate and reported in a reduced number of articles in the medical literature.

Case report

A three month old male infant was admitted to our department, emergently referred by the local pediatric cardiologist who had assessed the child because of failure to thrive and a systolic murmur. At admittance the infant, with weight 3.2 kg, was in poor general status, with generalized cyanosis, tachypnea with sub- and intercostals retractions, heart rate 140 BPM, blood pressure 76/38 mmHg, oxygen saturations of 63%. On X-ray, cardiomegaly with a cardiothoracic ratio of 0.61 and increased pulmonary blood flow could be documented. Cardiac ultrasound showed d-TGA with a minimal patent foramen ovale, a small patent ductus arteriosus and a small sub pulmonary ventricular septal defect. Because of a hypoxemic 3 month old infant, with insufficient mixing, signs of heart failure and a LV considered to be deconditioned, the decision was made to perform surgical atrial septectomy and banding of the pulmonary artery, in order to prepare the LV for a delayed arterial switch operation.

The operation was performed on extracorporal circulation, with central cannulation, arterial aortic and venous bicaval. On fibrillating heart, a minimal 2 cm atriotomy was made, the interatrial septum at the level of fossa ovalis was excised and a 1 cm atrial septal defect was created, enough to reach proper mixing. During reperfusion period, a band was put arround the truncus of the pulmonary artery, in order to train the LV for the corrective arterial switch operation. The antegrade gradient over the pulmonary banding was 80 mm Hg and the ratio of LV/RV pressure was 70%. Due to satisfying saturations of 75-80% on FiO2 30%, we didn’t perform an aorta-pulmonary shunt. Postoperative evolution was difficult, with a prolonged adaptation of the LV to the pulmonary banding.

The patient developed signs of congestive heart failure and inotropic support had to be maintained for 2 weeks, associated with vasodilator and diuretic therapy. The patient also had a prolonged pneumonia, with favourable evolution under combined antibiotic therapy. Six weeks after banding, arterial switch was performed, along with closure of the atrial and ventricular septal defects and also of the patent ductus arterious ( fig. 1, 2). The operation was done in extracorporeal circulation, with central cannulation, ischemic arrest, without circulatory arrest, in profound hypothermia of 22 degrees Celsius. Aortic cross clamping time was 130 minutes, duration of extracorporeal circulation was 273 minutes and total duration of the operation was 480 de minute. Priming with blood was used (cell saver washed packed blood cell), along with glucose, plasma and saline. The chest was kept open in order to avoid postoperative compression of the heart. Inotropic need was reduced. Post switch hemodynamical evolution was good, allowing for rapid reducing of inotropic support and closure of the chest at 36 hours postoperatively. Postoperative evolution encountered infectious complications, respectively sepsis and toxic hepatitis. The complications had a favorable evolution under therapy. The patient was released 3 weeks postoperatively, in stable hemodynamic conditions, without significant residual cardiac lesions.

d-transpozition 1

Figure 1. Coronary arteries prepared for reimplantation during arterial switch operation (authors archive)

 d-transpozition 2

Figure 2. Final aspect of the arterial switch operation(authors archive)

Discussion

In d-TGA, the capacity of the LV to sustain systemic circulation decreases progressively after 2 weeks of age, depending upon the patency of the ductus arteriousus, dimension of the atrial septal defect, level of pulmonary resistances and the degree of obstruction of the left ventricular outflow tract [1]. Assessment of the capacity of the LV to sustain systemic circulation depends on echocardiographyc, invasive and MRI assessments. Lacour-Gayet and colab. appreciated a LV as deconditioned if: age more than 3 weeks, banana shape of the LV on echocardiography, along with LV mass less than 35g/m2. Atrial switch should be performed when LV mass reaches 50 mg/m2. Helvind and assoc. defined the capacity of the LV to sustain systemic circulation upon two factors: ratio of LV/RV pressures of more than 0,75 and MRI measured LV mass of more than 80 g/m2. [2]

It seems to be a marked variability regarding the function of the LV among neonates and infants. In the literature, various protocols are described concerning the capacity of the LV to keep its function: opinions vary from performing arterial switch without any testing of LV function till the age of 2 month (Foran et al.) till the indication of reconditioning, based on ultrasound and angiographic criteria as early as the age of 2 weeks. As in Romania ECMO isn’t an option, proper assessment of the degree of conditioning of the LV makes the difference between survival and death [4]. As for our patient, age and clinical status dictated the therapeutical decision, considering that, at 3 month of age, the LV should be deconditioned.

Surgical correction was challenging, due to pericardial adhesions invariably developing after the first operation, and whose excision prolongs the duration of the procedure and the risk for bleeding. A positive aspect, from a technical point of view, is the fact that the stenosing band causes, at the level of the pulmonary truncus, an anastomosing orifice aproximatively equal to the aorta, facilitating anastomosis of the great vessels, between which there is usually a caliber mismatch in favor of the pulmonary artery. Rapid reconditioning is followed by a significant morbidity, as showed by the evolution of our patient. Sudden increase in the after load of the LV induces subendocardial ischemia, with consecutive severe ventricular dysfunction, till ventricular stunning. This is why a ventricular LV/RV pressure ratio of 65% is considered to reduce the rate of complications [5].

The quality of the ventricular mass obtained after reconditioning (due to hypertrophy and hyperplasia of the myocytes) and the long term function of this LV are still open questions. Studies from the 90th show that the function of the LV is reduced compared to the patients in whom primary arterial switch was performed. Longitudinal studies are necessary in order to confirm this theory. Essentially, a LV, even with a slightly reduced function is better, on long term, compared to a RV [6]. If considering Romania, a country with a significant lack of pediatric cardiologists, late diagnosis of congenital heart diseases remains a major problem. Under these circumstances, development of alternative therapeutic management for the patient in whom proper timing is missed, offering the chance for a anatomical correction, remains a salvaging option.

 

 

REFERENCES 

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