Asou et al., in 1996,¹ described a technique of selective cerebral perfusion applicable to initial palliative surgery (Fig. 1). Cardiopulmonary bypass is established as usual by pulmonary arterial and atrial cannulation. During the phase of cooling, a 4 mm polytetrafluoroethylene graft is anastomosed to the brachiocephalic artery, and this is connected to the arterial cannula by a Y-connector. After systemic cooling has been accomplished, the arterial cannula to the pulmonary trunk is clamped and removed, and the brachiocephalic artery is occluded proximal to the site of insertion of the shunt. Perfusion via the brachiocephalic artery is maintained at 50 mm/kg/min, and arterial pressure is monitored in the left temporal artery. After reconstruction of the aortic arch, flow is increased back to a level of 150 mm/kg/min so as to perfuse the whole body. The neoaorta is recannulated, and the cannula in the polytetrafluoroethylene graft is occluded and removed. The graft is then used to complete the construction of the systemic-to-pulmonary arterial shunt. Asou and colleagues¹ used this technique initially in 8 neonates with hypoplastic left heart syndrome, with 5 survivors. Pigula et al.² used similar methods of selective cerebral perfusion. They utilized near infrared spectroscopy to estimate cerebral blood volume and saturations of oxygen (Fig. 2). With their technique, the duration of circulatory arrest was limited to a few minutes, during which time the atrial septectomy was performed. They found that cerebral flow at a level of 20 mm/kg/min, with clamping of the descending thoracic aorta, resulted in estimates of the index of cerebral blood volume and oxygen saturation that were comparable to those observed during whole body perfusion on conventional cardiopulmonary bypass. A variety of fundamentally similar techniques of cannulation have been utilized by other investigators to perform the augmentation of the aortic arch in hypoplastic left heart syndrome without circulatory arrest. To date, there are no studies of outcome reflecting the neurologic state of patients supported with these innovative palliative techniques.

Figure 1. Asou et al. from Japan in 1996 described selective cerebral perfusion via a polytetrafluoroethylene (PTFE) graft anastomosed to the brachiocephalic artery during the period of circulatory arrest. A Y-connector was placed in the arterial line for this purpose. From: Asou T, Kado H, Imoto Y, et al. Selective cerebral perfusion technique during aortic arch repair in neonates. Ann Thorac Surg 1996; 61: 1546–1548.

Figure 2. Relative cerebral blood volume index (CrBVI) and oxygen saturation (CrSO2) as a function of regional low-flow perfusion rate (RLFP). Reacquisition of baseline values occurs consistently, and is mirrored by return to baseline in oxygen saturation. From: Pigula FA, Nemoto EM, Griffith BP, et al. Regional low-flow perfusion provides cerebral circulatory support during neonatal aortic arch reconstruction. J Thorac Cardiovasc Surg 2000; 119: 333.

Kishimoto et al.³ reported performing the first stage of palliation on a beating heart. They used two arterial inflow cannulas. A 2.1 mm metal cannula was introduced into the brachiocephalic artery, and a separate larger cannula was placed in the descending thoracic aorta. Venous cannulation was through both superior and inferior caval veins. On bypass, a cross clamp was placed on the proximal aortic arch. Coronary and cerebral perfusion were maintained via the cannula in the brachiocephalic artery. The left carotid and subclavian arteries were temporarily occluded. The pulmonary trunk was divided, and connected to the aortic arch using a pericardial graft without enlargement of the ascending aorta. A 6 mm xeno-pericardial conduit with a bicuspid valve was interposed between a right ventriculotomy and the pulmonary arteries to provide flow of blood to the lungs. They used the technique in 7 patients between 1992 and 1999, with no operative deaths, albeit that one patient died 2 months postoperatively with stenosis of the conduit stenosis and hypoxia, and two more patients died of heart failure 4 months and 29 months after the initial operation. Only one patient in the series survived to undergo a second stage procedure 5 months after the initial operation.

Imoto et al., in 1999,⁴ also reported efforts to achieve initial palliation without circulatory arrest. They utilized the polytetrafluoroethylene graft anastomosed to the brachiocephalic artery as the site of the arterial inflow, again with bicaval venous drainage. Elevation of the heart from the pericardial space allowed access to the descending thoracic aorta in the posterior mediastinum for placement of a second arterial inflow cannula (Fig. 3). Bypass flow was 180 mm/kg/min at 30.4°C. After clamping the distal arch, the left subclavian artery, and the descending thoracic aorta, the arterial duct was ligated, and an anastomosis was performed between the thoracic aorta and the arch. The undersurface of the aortic arch was incised, and the incision extended onto the ascending aorta. Under cardioplegic arrest, the neoaorta was constructed by making a direct anastomosis of the proximal pulmonary trunk to the ascending aorta and aortic arch. The polytetrafluoroethylene graft was subsequently disconnected from the arterial inflow cannula, trimmed, and anastomosed to the right pulmonary artery. Their case report indicated that their patient was well 5 months after this initial palliative procedure.

Figure 3. Perfusion of the lower body by cannulation of the descending thoracic aorta (Des Ao) in the pericardial sac combined with cerebral perfusion. Abbreviation: E-PTFE: Expanded polytetrafluoroethylene. From: Imoto Y, Kado H, Yasui H, et al. Norwood procedure without circulatory arrest. J Thoracic Cardiovasc Surg 1999; 68: 559–561.

While some investigators have focused on modifying the techniques of extracorporeal circulatory support for the first stage of palliation, others have modified the operative procedure itself in a number of ways. One theme central to several of these innovations has been the elimination of any foreign material when amalgamating the aorta with the pulmonary arteries, and when reconstructing the aortic arch. Interestingly, the dependence upon autologous arterial tissue was a feature of the first stage of palliation as initially described by Norwood two decades ago. He and his associates found later that the use of a homograft patch to augment the neoaorta and arch was associated with reduction in the incidence of late obstruction. The elimination of any foreign material, nonetheless, has been revisited by several investigators who refer to their operations as “Modified Norwood Procedures.” Fraser and Mee, in 1995,⁵ reported the use of such a procedure in 13 neonates (Fig. 4). In their operation, the pulmonary trunk was transected obliquely, beginning just proximal to the right pulmonary orifice. The proximal descending thoracic aorta and arteries arising from the aortic arch were extensively mobilized. The thoracic aorta was anastomosed to the undersurface of the aortic arch. The proximal pulmonary trunk was incorporated into the anastomosis between the arch and the descending thoracic aorta. The mean circulatory arrest time in this group of patients was 32 min. Catheterization of 7 patients 2 months to 4 months postoperatively showed no evidence of recurrent aortic coarctation. There was, however, evidence of coronary ischemia in 2 patients who required revision, and coronary ischemia was suspected in one patient who died. In these patients, there was probably some limitation of flow into the long ascending aorta, which was not incised and enlarged as in Norwood's first stage of palliation. In the 2 patients who were successfully revised, the ascending aorta was divided and translocated to the brachiocephalic artery, with resolution of the coronary ischemia. Proponents of this technique have emphasized the advantage of the shortened circulatory arrest time. The role of this technique in terms of long-term effects on aortic growth and coronary perfusion requires further evaluation.

Figure 4. Modified Norwood procedure using only autologous tissue. A 3.0 to 4.0 mm water repellant fabric shunt provides flow of blood to the lungs. From: Fraser CD Jr, Mee RBB. Modified Norwood procedure for hypoplastic left heart syndrome. Ann Thorac Surg 1995; 60: 546S–549S.

Ishino et al.⁶ reported a large experience with a technique similar to that described above (Fig. 5). Performing operations in 120 cases, they achieved early survival in 68%. In most instances, all ductal tissue was excised, and the descending aorta was anastomosed to the aortic arch and proximal pulmonary trunk as described by Fraser and Mee.⁵ In 22 patients, continuity of the aortic arch was maintained, and the proximal pulmonary trunk was anastomosed directly to the opening in the arch. The incidence of obstruction in the neo-aortic arch was 23%. At the time of their report, 71 patients had undergone a second stage procedure, and 3 patients had undergone completion of the Fontan circulation. Circulatory arrest times for the first stage varied from 57 to 105 min. There was significant mortality between the first and second stages of palliation, which raised concern with respect to the adequacy of coronary perfusion in patients whose tiny ascending aorta had not been augmented.

Figure 5. Modified Norwood procedure with autologous tissue. PTFE: polytetrafluoroethylene; RPA: right pulmonary artery; MPA: main pulmonary artery; D. Ao: descending aorta; LPA: left pulmonary artery. From: Ishino K, Stumper O, Brawn WJ, et al. The modified Norwood procedure for hypoplastic left heart syndrome: early to intermediate results of 120 patients with particular reference to aortic arch repair. J Thorac Cardiovasc Surg 1999; 117: 920–930.

Another technical modification, similar in concept to an operation performed decades earlier by Doty, was described by Pridjian et al. in 1995.⁷ Anastomosis of the pulmonary trunk to the underside of the transverse aortic arch was performed, with placement of a fenestrated patch within the pulmonary trunk to divide the systemic and pulmonary flows. The procedure was performed in two patients, both of whom survived initially.

The technical modification to Norwood's initial palliative procedure which has attracted the most recent attention, and been greeted with the greatest degree of enthusiasm, is the procedure utilizing a conduit from the right ventricular outflow tract to carry the blood to the lungs in place of the systemic arterial-to-pulmonary shunt. Interestingly enough, this methodology was used three times by Norwood himself very early in his surgical experience in Boston (Fig. 6), and was described in the paper published in 1981 on the evolution of palliative surgery for hypoplastic left heart syndrome.⁸ Curiously, this idea remained dormant for nearly two decades. It was greeted with much enthusiasm when described by Sano and associates during the Third World Congress of Pediatric Cardiology and Cardiac Surgery in Toronto. The interposition of a 5 or 6 mm polytetrafluorethylene graft between a ventriculotomy high on the anterior wall of the right ventricle and the confluence of the pulmonary arteries appears to provide adequate levels of flow to the lungs, while avoiding the significant diastolic run-off and potential for coronary ischemia that is often problematic in first stage palliation incorporating a systemic-to-pulmonary arterial shunt. This modification is believed to simplify postoperative management, as fluctuations in pulmonary blood flow are better tolerated. Perhaps the largest experience to date using this method is the experience of Norwood himself, along with his associate Pizarro at the Nemours Cardiac Center in Delaware (Fig. 7). In their initial report of this modification,⁹ they described operations in 15 patients, with 1 early death. Diastolic blood pressure was noted to be consistently higher in the early postoperative period among these patients than in a comparable group who had undergone the conventional procedure using a systemic-to-pulmonary arterial shunt (Fig. 8). As this modification of the Norwood procedure seems to be gaining increasing popularity, it remains to be determined what the effect of the right ventriculotomy will be on long-term function of the systemic right ventricle when supporting the Fontan circulation.

Figure 6. One of Norwood's earliest methods of first stage palliation for hypoplastic left heart syndrome, using a Dacron conduit with a heterograft valve placed between the right ventricle and the pulmonary arteries. From: Norwood WI, Lang P, Castañeda AR, Campbell DW. Experience with operations for hypoplastic left heart syndrome. J Thorac Cardiovasc Surg 1981; 82(4): 511–519.

Figure 7. First stage palliation using a polytetrafluoroethylene conduit placed from the right ventricle to the pulmonary arteries as the source of pulmonary blood flow. From: Pizarro C, and Norwood WI. Right ventricle to pulmonary artery conduit has a favorable impact on post-operative physiology after Stage I Norwood: preliminary results. Eur J Cardiothorac Surg 2003; 23(6): 991–995.

Figure 8. Using the conduit from the right ventricle to the pulmonary arteries conduit, consistently higher diastolic blood pressures were observed post-operatively at 1, 8, and 24 h. From: Pizarro C, and Norwood WI. Right ventricle to pulmonary artery conduit has a favorable impact on post-operative physiology after Stage I Norwood: preliminary results. Eur J Cardiothorac Surg 2003; 23(6): 991–995.

At a rapid rate, technical advances are being made with respect to preoperative, intraoperative, and postoperative management of the abnormal physiologic state associated with hypoplastic left heart syndrome, and with respect to the surgical exercises themselves. Modifications to operative techniques are still evolving, with the goal of reducing the potential harmful effects of cardiopulmonary bypass and hypothermic circulatory arrest. Further progress in these areas is expected to contribute to the optimization not only of survival, but also functional and neurologic outcomes.