| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | SEARCH |
|
MMCTS
(July 23, 2007). doi:10.1510/mmcts.2006.002345 Copyright © 2007 European Association for Cardio-thoracic Surgery Procedure Neonatal aortic arch surgeryPediatric Cardiac Surgery Unit, S. Orsola-Malpighi Hospital, University of Bologna Medical School, Via Massarenti 9, 40138 Bologna, Italy * Corresponding author: * Pediatric Cardiac Surgery Unit Director, Tel.: +39-051-6363156; fax: +39-051-6363157.gargiulo{at}aosp.bo.it
Surgical repair of the aortic arch is entailed in the neonatal period of patients with: hypoplastic left heart syndrome, interrupted aortic arch, hypoplastic aortic arch and complex aortic coarctation. Aortic arch surgery requires a period of circulatory arrest and deep hypothermia. Cerebral selective perfusion has recently been introduced as an alternative to circulatory arrest with the aim of reducing mortality and neurological complications. Moreover, the arch reconstruction phase can be safely performed under moderate hypothermia and with cerebral and myocardial perfusion (on beating heart), thus, completely avoiding cerebral ischemia and completely avoiding or drastically reducing myocardial ischemia.
Key Words: Antegrade selective cerebral perfusion • Aortic arch hypoplasia • Circulatory arrest • Interrupted aortic arch
Aortic coarctation without associated intracardiac lesions, with or without posterior arch hypoplasia, is safely and effectively repaired via left posterolateral thoracotomy. On the contrary, median sternotomy and cardiopulmonary bypass are necessary for aortic arch reconstruction in the following conditions: hypoplastic left heart syndrome (which is not the object of the present section), interrupted aortic arch (IAA), complete aortic arch hypoplasia (AAH), complex aortic arch hypoplasia (very short proximal arch associated with hypoplastic and long distal arch and isthmus: ‘bovine truncus’ pattern of the arch branches) or coarctation with posterior arch hypoplasia associated with other cardiac lesions [1,2,3,4]. Proximal arch, distal arch, and isthmus are considered hypoplastic when sized <60, 50, and 40% of the ascending aorta, respectively, according to Moulaert [5], or the anterior arch is smaller than 1 mm/per kg of body weight plus 1, according to Karl [6]. Although deep hypothermic circulatory arrest has been extensively used in neonates for aortic arch surgery [7, 8], the incidence of seizures and choreoathetosis and the high impact on the neuro-developmental outcome of such a technique [9, 10], has prompted surgeons to explore safer cerebral protection strategies. Intermittent cerebral perfusion combined with deep hypothermia, proposed by Kimura and colleagues [11] in 1994, was the first successful attempt to provide a longer uneventful ischemic period for the brain. Since then many different techniques and strategies have been developed and proposed in order to achieve a satisfactory continuous cerebral perfusion during the entire procedure [4, 12,13,14,15,16,17,18].
Aortic arch hypoplasia: end-to-end extended anastomosis (Schematic 1A–F) A central venous line is positioned either in the right jugular or right subclavian vein; it is advisable to avoid left central venous access because the presence of the catheter into the innominate vein would reduce its mobilization during the procedure.
The arterial catheter is positioned into the right radial or brachial artery or, in case of right aberrant subclavian artery, into the right temporal artery, to obtain a pressure monitoring during the antegrade cerebral perfusion as well. Electrodes for continuous monitoring of the tissue oxygen saturation (Invos System: Somanetics Corp., Troy, MI – MMCTSLink 151) of the brain and kidneys are positioned (Video 1).
Aortic arch branches and ductus arteriosus are dissected free and surrounded. Arterial cannulation is attained to the distal ascending aorta or to the innominate artery. The arterial cannula utilized is a 14G peripheral venous catheter (Insyte: Infusion Therapy System Inc., Sandy, UT) partially covered with a suction tube and with a second 14G Insight cannula inserted into the proximal ascending aorta (Video 2). Both cannulae are connected with a ‘Y’ connector to the pump arterial line. Right atrial cannulation through the atrial appendage or bicaval cannulation, entering the right atrium with two 12F curved cannulae (Baxter International Inc., San Diego, CA) is achieved and cardiopulmonary bypass is commenced. The ductus arteriosus is doubly ligated with two 3/0 silk ties and divided (Video 3). The pump is started at a base flow of 150 ml/kg/min and adjusted to maintain systemic pressure not above 40 mmHg and mixed venous blood oxygen saturation, continuously monitored, of approximately 60–65%. The patient's body internal temperature is lowered to 27 °C. Extensive mobilization of the aortic arch and branches and descending thoracic aorta is routinely performed in order to complete a tension-free anastomosis and to avoid left bronchus or tracheal compression. Then vascular clamps are applied at the descending aorta, left common carotid and subclavian arteries, proximal ascending aorta, and at the base of the innominate artery (Video 4).
Flow is then reduced at 20 ml kg-1xmin-1 baseline, to maintain selective cerebral and myocardial perfusion and adjusted to maintain a radial artery pressure of 30–40 mmHg and a venous O2 saturation above 60–70%. The heart is perfused and keeps beating through the procedure with no ischemic changes on the ECG. Aortic isthmus is transected and the ductal tissue is completely excised. Then a longitudinal incision is made in the posterior wall of the descending aorta (Video 5).
A generous incision is made in the aortic arch concavity up to the origin of the brachiocephalic arterial trunk/distal ascending aorta (Video 6). A stay suture is placed to the anterior rim of the arch incision to expose the posterior rim in order to facilitate the anastomosis.
An end-to-end extended anastomosis is then completed with a 7/0 absorbable monofilament running suture (PDS (polydioxanone): Ethicon Inc., Somerville, NJ – MMCTSLink 152)_(Videos 7,8,9).
Fibrin glue (Tissucol, Baxter Inc., San Diego, CA – MMCTSLink 64) is utilized to minimize bleeding after removal of the clamps (Video 10).
Aortic arch hypoplasia: end-to-side extended anastomosis (Schematic 2A–B) In the case of a very long and exceptionally narrow posterior arch (Video 11) an end-to-side extended anastomosis can be performed instead, between the descending and ascending aorta. The posterior arch is suture closed at its end beyond the orifice of the left subclavian artery (Videos 12,13,14,15).
Interrupted aortic arch: end-to-side extended anastomosis (Schematic 3A–D) In the case of interrupted aortic arch (Videos 16 and, 17), two 14G peripheral venous catheters (Insyte: Infusion Therapy System Inc., Sandy, UT) are inserted for arterial cannulation: one at the base of the innominate artery and the other at the main pulmonary artery or ductus arteriosus, to achieve distal body perfusion and cooling, with the pulmonary arteries temporarily occluded to avoid pulmonary steal of the pump systemic flow (Videos 18 and 19).
When a rectal temperature of 26–27 °C is reached, the ductus arteriosus can be doubly ligated and divided and the main pulmonary arterial cannula removed and inserted into the ascending aorta for the myocardial selective perfusion after positioning of the clamps (Videos 20,21,22).
An end-to-side extended anastomosis is performed between the descending and the ascending aorta, (Videos 23,24,25,26,27).
For the intracardiac phase, the distal clamps are released and the full flow is reinstituted; then cold cardioplegia is run antegradely through the ascending aorta cannula into the aortic root, a standard cardioplegic cardiac arrest is obtained and the procedure is completed.
Between December 1997 and January 2007, 55 consecutive neonates weighing from 1 kg to 4.5 kg, underwent arch reconstruction with antegrade selective cerebral perfusion (ASCP) for interrupted aortic arch (IAA) 18 (type A, n=11 and type B, n=7) or coarctation of the aorta with arch hypoplasia (CoA/Arch Hypo) 37. During the arch reconstruction, 25 patients received continuous coronary perfusion through the second arterial cannula. Eleven patients had unbalanced ventricles (double inlet left ventricle 6, tricuspid atresia 4 and complete atrio-ventricular septal defect 1). The 11 patients with unbalanced ventricles underwent Damus-Kay-Stansel (anastomosis between the pulmonary artery and the ascending aorta) and arch repair 9; pulmonary artery banding and arch repair 2. Among the 44 patients with balanced ventricles, 35 received single stage repair whilst 9 underwent arch repair and pulmonary artery banding. The arch was repaired with extended end-to-end or end-to-side direct anastomosis in 47 and 8 patients, respectively. In two patients additional procedure was required for residual gradient within the posterior aortic arch: left subclavian flap turn-up aortoplasty and posterior arch enlargement connecting the bases of the left common carotid and left subclavian arteries, respectively. Left ventricular outflow tract obstruction was considered significant in three patients and was addressed at the time of the arch repair; three other patients underwent left ventricular outflow tract obstruction relief later during the follow-up.
Postoperative course All other patients were free from neurological symptoms and at follow-up have been growing and developing normally. Six patients died in the early postoperative period (11%), two had a single ventricle palliation, two had an additional procedure for left ventricular outflow tract obstruction and the remaining two patients had arch reconstruction and banding. ASCP duration did not affect early mortality. None of the patients has experienced re-coarctation or aneurysm formation or has been receiving medication for persistent systemic hypertension.
Neonatal aortic arch surgery for interruption or coarctation with arch hypoplasia, has bared dissimilar and controversial results either in terms of morbidity and mortality and in terms of freedom from recurrent obstruction; moreover, it has been accomplished with various surgical techniques and cerebral and myocardial protection strategies (Table 1).
Deep hypothermic cardiac arrest (DHCA) has been extensively used for repair of congenital cardiac malformations with aortic arch involvement. However, the relatively high incidence of neurological complications and the limited safe period of time have encouraged surgeons to avoid circulatory arrest and to develop safer techniques to protect the brain during arch reconstructive surgery. We have used antegrade selective cerebral perfusion for arch reconstruction since 1997, thus, reducing the hypothermic circulatory arrest time in the early time-span of our experience, and allowing us to completely avoid it since 1999. Selective cerebral perfusion can be accomplished by advancing the arterial cannula from the distal ascending aorta into the innominate artery or positioning the cannula inside the innominate ostia under direct vision upon opening the arch. In these cases a brief period of circulatory arrest may be necessary to safely achieve this and to complete the reconstruction. This problem can be obviated by directly innominate artery or very distal ascending aorta cannulation using an appropriately sized soft-tipped cannula. Indeed, ASCP duration was not a risk factor, thus demonstrating that ASCP compared to DHCA can provide a longer safe period for the patient. Hypothermia has been proven to decrease cellular metabolism, lowering oxygen consumption and consequently reducing the adverse impact of ischemia [19]. Conversely, deep hypothermia is suspected to be responsible for tissue damage on the brain and lung [20], capillary leak syndrome, generalized inflammatory reaction and coagulopathy. Moreover, deep hypothermia should be combined with a higher degree of hemodilution to counteract increased fluid viscosity and cell membrane rigidity, which consequently reduces the blood's oxygen carrying capacity. Recent studies have shown the superiority of brain protection for higher hematocrit levels [21]. We believe that when ASCP is carried out, there is no longer a need for deep hypothermia, thus, a moderate grade of hypothermia with a mild degree of hemodilution might be effective in protecting other organs from ischemic damage and optimizing cerebral oxygen supply. The appropriate perfusion rate for the brain in the neonate during selective cerebral perfusion remains controversial. During selective cerebral perfusion an ideal flow rate of 50 ml kg-1 min-1 has been advocated on the base of theoretical calculations [13], but many different protocols have been proposed to date [14]. This uncertainty regarding optimum cerebral flow and the management of the ASCP has prompted surgeons to utilize control systems to evaluate the effectiveness of cerebral perfusion such as transcranial Doppler ultrasonography or near-infrared spectroscopy. In our experience, mixed venous O2 saturation and radial/temporal arterial pressure have proved to be simple and reliable methods to adjust flow rate during either CPB or ASCP. Higher venous saturations, especially in association with moderate hypothermia, may infer that flow is ineffective or possibly excessive and thus potentially dangerous. In the case of interrupted or hypoplastic aortic arch and coarctation, an intra-cardiac systemic obstruction can complicate intra- or post-operative management of such patients, thus, it should be routinely ruled out and when hemodynamically significant it should be surgically addressed [22]. In our experience, it was necessary to relieve the left ventricular outflow tract obstruction at the time of the arch repair in three patients (in the biventricular repair group); nevertheless, in three other patients the obstruction was either undervalued or increased during the follow-up thus necessitating a late operation. Left ventricular outflow tract obstruction is an important factor affecting survival and reintervention rates after arch obstruction repair. No consensus exists yet with regard to definition and diagnosis of left ventricular outflow tract obstruction and the need for surgical treatment of it. The Congenital Heart Surgeons Society institutions carried a multicentric study on 472 neonates with IAA and low birth weight, type B interruption and associated complex malformations were identified as risk factors for mortality and for initial left ventricular outflow tract obstruction procedures; whether the optimal method of repair was direct anastomosis with non-PTFE patch augmentation in terms of better long-term survival and freedom from reintervention [23]. In our experience, end-to-end extended anastomosis allowed for a complete resolution of the arch obstruction without the use of prosthetic moreover, it may be effective in reducing re-coarctation rate and long-term complications incidence. Furthermore, antegrade selective cerebral perfusion has been a safe and effective procedure throughout and it may improve outcome of neonatal aortic arch surgery, minimizing neurological complications without the need for deep hypothermia.
|
|||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
| HOME | HELP | FEEDBACK | SUBSCRIPTIONS | SEARCH |
Top
Summary
Introduction
