III. Hypoplastic Left Heart Syndrome
Hypoplastic Left Heart Syndrome William I. Norwood, Jr, MD, PhD Department of Surgery, University of Pennsylvania School of Medicine, and Division of Cardiothoracic Surgery, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
The evolution of the present approach to the newborn with hypoplastic left heart is outlined. Preoperatively, maintenance of ductal patency with prostaglandin El and balancing of systemic and pulmonary blood flow are essential. Operative details of the first-stage palliation and the definitive second-stage procedure are described. The more recent adoption of an intermediate-stage hemiFontan procedure is also described. Since January 1989, 151 patients have been treated using this three-stage
H
ypoplastic left heart syndrome is the most common form of congenital cardiac malformation where there is only one fully developed ventricle. It represents fully 9% of those heart defects of infants with critical heart disease [l].Untreated, it is universally fatal and accounts for 25% of deaths in the first few weeks of life. Although lethal if left untreated, this malformation is eminently treatable with conventional reconstructive surgical techniques or, as advocated by some, heart replacement, with results comparable with other forms of complex congenital cardiac disease [2-51. This report outlines one means of approaching hypoplastic left heart syndrome and its contemporary results. The central anatomical feature of hypoplastic left heart syndrome is severe aortic valve hypoplasia or, more often, aortic valve atresia. As a consequence of limited outflow, the left ventricle develops abnormally and is hypoplastic or virtually absent. There is associated mitral valve hypoplasia or atresia. Twenty-five percent of children have either double-outlet right ventricle with aortic valve atresia and left ventricular hypoplasia or complete common atrioventricular canal malaligned over the right ventricle and associated left ventricular hypoplasia and aortic valve atresia with or without double-outlet right ventricle. The most obvious physiological consequence of this anatomical constellation is that systemic blood flow is provided virtually in its entirety from the right ventricle through a patent ductus arteriosus. The fetus is generally well and unaffected by the anatomical abnormality, but two of the natural changes from the fetal to the newborn physiology are life threatening. As the ductus arteriosus Presented in part at the Current Controversies and Techniques in Congenital Heart Surgery Meeting, Baltimore, MD, Sep 8-9, 1989. Address reprint requests to Dr Norwood, Division of Cardiothoracic Surgery, The Children’s Hospital of Philadelphia, 34th St and Civic Blvd, Philadelphia, PA 19104.
0 1991 by The Society of Thoracic Surgeons
approach, with 109 early survivors. Seventy-eight have undergone the hemi-Fontan operation with nine deaths (5 of whom came to this stage early nonelectively because of shunt failure or ventricular dysfunction). Twentyseven of the 78 patients undergoing hemi-Fontan operation have subsequently undergone definitive Fontan procedures with no deaths. (Ann Thorac Surg 1991;52:688-95)
closes, systemic perfusion is impaired. In addition, a natural decrease in pulmonary vascular resistance shortly after birth results in a volume shift from the systemic to the pulmonary circulation, also impairing systemic perfusion. Satisfactory systemic perfusion and oxygenation can be maintained in the newborn by assuring patency of the ductus arteriosus and adequate intravascular volume and by avoiding large differences between systemic and pulmonary vascular resistance. As will be discussed, the last two principles are critically important in the management after palliative operation for hypoplastic left heart syndrome as well.
Preoperative Management In virtually all neonates with hypoplastic left heart syndrome, continuous infusion of prostaglandin El satisfactorily maintains patency of the ductus arteriosus. Only rarely, when there is virtual absence of an interatrial communication, does hypoxemia as a consequence of a low pulmonary to systemic blood flow ratio occur. Rather, the baby is most often threatened not by metabolically important hypoxemia but by decreased systemic perfusion as a consequence of low pulmonary vascular resistance or increased systemic vascular resistance. In this circumstance, hypoventilation to increase carbon dioxide tension and pulmonary vascular resistance, and occasionally continuous infusion of sodium nitroprusside to decrease abnormally elevated systemic vascular resistance, can approximate the satisfactory physiological state of the fetus with hypoplastic left heart syndrome. The use of catecholamines is almost never necessary or appropriate. As with single ventricle complex, babies with hypoplastic left heart syndrome are ultimately treatable by some modification of the Fontan procedure. However, at birth the lungs are immature and the vascular resistance is naturally high, precluding a Fontan procedure in the neonatal period. 0003-4975/91/$3.50
Ann Thorac Surg 1991;52:688-95
Fig 1. Exposure and cannulation for first-stage palliation. (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
Yet, these infants are dependent on patency of the ductus arteriosus. Although the ductus arteriosus can be opened and maintained with continuous infusion of prostaglandins, prolonged association of the pulmonary circulation with the systemic circulation will result in either intractable congestive heart failure or, ultimately, development of pulmonary vascular obstructive disease. Therefore, it was clear even from the beginning of our surgical development that staged management is necessary. The initial palliation is embodied by three basic principles. First, the aorta must be associated directly with the right ventricle in a fashion guaranteeing unobstructed flow from right ventricle to the systemic circulation, with growth potential obviating further aortic operation. Second, pulmonary blood flow must be regulated for proper growth and development and maturation of the pulmonary vasculature to avoid the development of pulmonary vascular obstructive disease and to minimize the volume load on the right ventricle. Finally, a large interatrial communication is necessary to avoid pulmonary venous hypertension and its consequences. The surgical details of initial palliation have evolved over the last decade. It is a personal prejudice that the intricacies that have been inserted have an important impact on the physiological stability of these patients, subsequent suitability for a Fontan procedure, and survival with a good long-term functional result after the Fontan procedure.
CONGENITAL HEART NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
689
osus is to be avoided; it is unnecessary and requires excessive manipulation of the cardiovascular structures. A minimal amount of distortion, manipulation, and trauma to the delicate neonatal cardiovascular structures is essential to preserve anatomy and function. A single venous cannula is placed through the right atrial appendage, and cardiopulmonary bypass is instituted. The right and left pulmonary artery branches are rapidly occluded to ensure systemic perfusion through the ductus arteriosus. The baby is cooled on bypass while esophageal, nasopharyngeal, and rectal temperatures are monitored. The rectal temperature reaches 20°C after approximately 15 minutes of cardiopulmonary bypass. During this time, the branch vessels of the aortic arch are exposed and looped with suture tourniquets in preparation for circulatory arrest. Dissection is carried around the aortic arch onto the thoracic aorta in the posterior mediastinum. At this point, the branch vessels of the aortic arch are occluded, the circulation is discontinued, and the blood is drained into the venous reservoir. After removal of the arterial and venous cannulas, the atrial septum is excised to allow unimpeded pulmonary venous return to the right atrium (Fig 2). The main pulmonary artery, which has been separated from the diminutive ascending aorta during the cooling phase of cardiopulmonary bypass, is transected adjacent to the takeoff of the right pulmonary artery, and the distal stump of the main pulmonary artery is closed with a patch (Fig 3). Patch closure is recommended to ensure continuity between the right and left pulmonary artery branches. The ductus arteriosus is then exposed, ligated, and transected at its entrance to the thoracic aorta. An incision
Operative Procedure Through a conventional midline sternotomy incision, the thymus gland is excised, exposing the diminutive aortic arch and its branch vessels (Fig 1).Cannulation for arterial infusion is conveniently achieved in the proximal main pulmonary artery just above the sinuses of Valsalva. The tip of a 10F aortic cannula is introduced 3 to 4 mm into the artery. Threading the cannula through the ductus arteri-
Fig 2 . First-stage palliation: the atrial septum is excised and the main pulmonary artery is transected. (Reprinted from Edmunds LH lr, Norwood W l , Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
690
CONGENITAL HEART NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
in the aorta is carried distally 1 to 2 cm into the thoracic aorta (Fig 4) and also proximally into the aortic arch and ascending aorta to the level of the rim of the transected proximal main pulmonary artery. Because the isthmus of the aorta and the aortic arch actually function as a branch of the main pulmonary artery-ductus-thoracic aorta continuum, the junction of the isthmus and thoracic aorta is gusseted with a patch to avoid subsequent development of distal aortic arch obstruction (Fig 5). A piece of pulmonary homograft is used for this patch because it is thin, pliable, and hemostatic. At this point, we favor the construction of a short central shunt of 4-mm tube graft between the inferior aspect of the augmented aortic arch and the confluence of the branch pulmonary arteries (Fig 6). The rationale for a central shunt is to obtain more even distribution of flow and thus uniform growth of the right and left pulmonary arteries. The remaining pulmonary homograft gusset is then carried to 5 mm above the end of the most proximal incision in the ascending aorta (Fig 7). The proximal transected main pulmonary artery is then anastomosed to the ascending aorta and homograft gusset, thus creating outflow from the right ventricle to the augmented aorta through the pulmonary valve (Figs 8, 9). Cardiopulmonary bypass is reinstituted and the patient is rewarmed to 37°C. The tourniquets on the branch vessels of the aortic arch are removed, but those on the branch pulmonary arteries remain until the time of weaning from cardiopulmonary bypass. After weaning, the cannulas are removed and a pressure monitoring line is placed through the right atrial appendage cannulation site.
Ann Thorac Surg 1991;52:688-95
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Fig 4. First-stage palliation: incision in aorta. (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea & Febiger, 1989, by permission.)
Postoperative Management Using the lowest possible mean airway pressure, ventilation is adjusted to maintain the carbon dioxide tension between 20 and 30 mm Hg to minimize pulmonary vascular resistance. Generally, the oxygen tension ranges from 40 to 45 mm Hg. However, an arterial oxygen tension of 50 mm Hg or greater suggests a large pulmonary to systemic flow ratio, which may result in inadequate systemic perfusion. When this occurs, the ventilator may be used to adjust the pulmonary to systemic flow ratio by rapidly decreasing the inspired oxygen fraction to 30 mm Hg and allowing carbon dioxide tension to increase to 40 mm Hg, with a concomitant increase in pulmonary vascular resistance. Pharmacologic support is rarely necessary in the postoperative period. After the previously described palliative operation, the right ventricle is subjected to both volume and pressure load greater than normal for a right ventricle. With a view to long-term preservation of ventricular function, early assessment for suitability for the Fontan procedure is undertaken when the infant is 12 to 18 months of age. At this age, the pulmonary resistance generally has decreased to less than 2.5 Wood units and the ventricular end-diastolic pressure has remained normal (less than 7 to 8 mm Hg). The following operation may be planned.
Second-Stage Fontan Procedure Fig 3. First-stage palliation: closure of main pulmonary artery stump. (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission .)
Again, the heart is exposed through a midline sternotomy, and cannulation for cardiopulmonary bypass is achieved by placement of an arterial cannula in the ascending aorta and a single venous cannula through the right atrial appendage (Fig 10). The systemic to pulmo-
Ann Thorac Surg 1991;52:68&95
CONGENITAL HEART NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
691
nary artery shunt is exposed and occluded as cardiopulmonary bypass is begun, and the patient’s core temperature is reduced to 20°C. During this cooling phase on cardiopulmonary bypass, the right and left pulmonary artery branches are exposed
from pericardial reflection to pericardial reflection. This exposure prepares for widely augmenting the pulmonary arteries to avoid proximal pulmonary arterial obstruction from unrecognized irregularities in size (Figs 11, 12). During a period of circulatory arrest, the pulmonary arteries are opened and an incision in the right atrium is made from the sulcus terminalus superiorly to the right lateral insertion of the eustachian valve inferiorly. The interatrial communication is inspected and enlarged if possible. A final incision is then made in the superior right atrium adjacent to the right pulmonary artery and carried into the posterior aspect of the right superior vena cava immediately adjacent to the most rightward aspect of the incision in the right pulmonary artery (Fig 13). A suture line is begun between the inferior lip of the incised right pulmonary artery and the posterior lip of the right superior vena caval-right atrial incision (Fig 14). This will provide the floor for the anastomosis of the systemic venous return to the pulmonary arterial tree. A piece of tube graft 10 mm in diameter, of sufficient length to extend from the inferior vena caval-right atrial junction to the right superior vena caval-right atrial junction, is cut in half lengthwise (Fig 15). This is for use as a baffle to channel inferior vena caval flow along the right lateral aspect of the right atrium to the anastomosis between the right atrium and the pulmonary arterial tree superiorly. The baffle is sutured around the orifice of the inferior vena cava along the right lateral floor and free wall of the right atrium and around the patulous orifice in the superior dome of the right atrium (Figs 16, 17). This particular baffling technique was introduced to minimize problems associated with tricuspid prolapse or regurgitation, or with obstruction of pulmonary venous return to
Fig 6 . First-stage palliation: construction of central shunt. (PTFE = polytetrafluoroethylene.) (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Maluern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 7 . First-stage palliation: completion of homograft gusset. (Reprinted from Edmunds LH J r , Norwood W l , Low DW. Atlas of cardiothoracic surgery. Maluern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 5. First-stage palliation: gusseting of isthmus-thoracic aorta junction. (Reprinted from Edmunds LH J r , Norwood WI, Low DW. Atlas of cardiothoracic surgery. Maluern, PA: Lea 6 Febiger, 1989, by permission.)
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CONGENITAL HEART NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
the right ventricle, which was experienced early in this series with an alternative baffling technique. The construction of the systemic venous pulmonary arterial system is completed by gusseting the pulmonary arterial incision with an elongated triangular patch, beginning on the left pulmonary artery. As the right pulmonary artery and adjacent right superior vena cava are approached, the base of the triangular patch is sutured onto the anterior lip of the right superior vena caval-right atrial incision, providing a roof for the anastomosis (Figs 18, 19). The patient is placed back on cardiopulmonary bypass after closure of the initial right atriotomy and rewarmed to 37°C.
\
Hemi-Fontan Procedure In the last 2 years, it has become apparent that mortality and morbidity may be reduced by separating the Fontan operation into two procedures: initial anastomosis of the superior vena cava to the pulmonary arteries, followed in 6 months by channeling of the inferior vena cava to the pulmonary arteries. The rationale is that diminution in end-diastolic volume develops rapidly in some patients after removal of the volume demands associated with a systemic to pulmonary artery shunt. Moreover, preoperative physiological information does not predict those patients in whom rapid contraction of end-diastolic volume will develop. The anatomical and physiological consequences of this process are an apparent increase in wall thickness, because muscle mass does not change as rapidly, and the diastolic function of the ventricle is impaired resulting in an increased end-diastolic pressure, increased central venous pressure, and decreased cardiac output. To minimize the physiological significance of such a rapid geometrical change, dividing the Fontan procedure into two parts is postulated to allow a decrease in end-diastolic volume and a commensurate decrease in muscle mass while only half of the systemic venous return is obligated to flow passively through the pulmonary vascular bed. When the end-diastolic volume and wall thickness ratio Fig 9. First-stage palliation: completion of right uentricleaugmented aorta outflow. (Reprinted from Edmunds LH Jr, Norzuood W l , Low D W . Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 8 . First-stage palliation: creation of outflow from right ventricle to augmented aorta. (Reprinted from Edmunds LH Ir, Norwood WI, Low D W . Atlas of cardiothoracic surgery. Malvern, PA: Lea b Febiger, 1989, by permission.)
have normalized, completion of the Fontan procedure may be undertaken.
Results The results of reconstructive operation for hypoplastic left heart syndrome continue to improve, for both initial palliation and later reconstructive operation, as we gain ever-increasing knowledge of the anatomy and physiology of this complex group of patients and of the surgical procedures required for them. In the 2-year period beginning January 1989, 151 newborns entered our institution for palliative operation. There were 42 (28%) early and 5
Ann Thorac Surg 1991;52:688-95
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CONGENITAL HEAN' NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
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Fig 10. Exposure and cannulation for second-stage Fontan. (Reprinted from Edmunds LH lr' Norwood wl' Low Dw' Of cardiothoracic surgery. Malvern, PA: Lea &? Febiger, 1989, by permission.)
Fig 12. Second-stage Fontan: completion of pulmonary artery augmentation, (Reprintedfrom LH Norwood wl, Low Dw, Atlas of cardiothoracic surgery. Malvern, PA: Lea B Febiger, 1989, by permission.)
(5%) late deaths among these patients. Seventy-eight of the 104 survivors have already undergone a hemi-Fontan operation (anastomosis of the superior vena cava to the branch pulmonary arteries). Among the 9 patients who
died (12%), 5 came to hemi-Fontan operation earlier than 5 months of age because of ventricular dysfunction or shunt failure, which may have unfavorably affected the postoperative physiology. Of the 27 patients in this group
Fig 11. Second-stage Fontan: use of homograft for pulmonary artery augmentation. (Reprinted from Edmunds LH Jr, Norwood Wl, Low D W . Atlas of cardiothoracic surgery. Malvern, PA: Lea G. Febiger, 1989, by permission.)
Fig 23. Second-stage Fontan: right atrial incision. (Reprinted from Edmunds LH Jr, Norwood W l , Low D W . Atlas of cardiothoracic surgery. Malvern, PA: Lea B Febiger, 1989, by permission.)
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CONGENITAL HEART NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
Ann Thorac Surg 1991;52:68%95
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Fig 14. Second-stage Fontan: suture line between right pulmonary artery and right atrium. (Reprinted from Edmunds LH Ir, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 16. Second-stage Fontan: construction of baffle. (Reprinted f r m Edmunds LH ]r, Nomood Wl, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea & Febiger, 1989, by permission.)
who have undergone completion of the Fontan operation, there has been no mortality. At present, our management scheme is palliation of the newborn, hemi-Fontan procedure at 6 months of age, and completion of the Fontan procedure at 12 months of age. The approach outlined
here for reconstructive therapy of this malformation will continue to evolve. The challenge for the future is to characterize better this group of lesions so that the preoperative, operative, and postoperative management may be further improved.
Fig 15. Second-stage Fontan: 10-mm polytetrafluoroethylene (PTFE) tube graft used as baffle. (Reprinted from Edmunds LH Jr, Norwood W l , Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 17. Second-stage Fontan: final suture line. (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
CONGENITAL HEART NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
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inbphimu-ahry Fig 18. Second-stage Fontan: completed repair. (Reprinted from Edmunds LH jr, Norwood W I , Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
References 1. Fyler DC. Report of the New England Regional Infant Cardiac
Program. Pediatrics 1980;65(Suppl):463.
2. Pigott JD, Murphy JD, Barber B, Norwood WI. Palliative reconstructive surgery for hypoplastic left heart syndrome. Ann Thorac Surg 1988;45:122-8.
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Fig 19. Second-stage Fontan: alternative tube graft. (Reprinted from Edmunds LH Ir, Norwood W l , Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
3. Norwood WI, Lang P, Hansen D. Physiologic repair of aortic atresia-hypoplastic left heart syndrome. N Engl J Med 1983; 308:23. 4. Bailey LL, Nelson-Cannarella SL, Doroshow RW. Cardiac allotransplantation in newborns as therapy for hypoplastic left heart syndrome. N Engl J Med 1986;315:949. 5 . Barber G, Murphy JD, Pigott JD, Norwood WI. The evolving pattern of survival following palliative surgery for hypoplastic left heart syndrome. J Am Coll Cardiol 1988;2:139A.
EDITOR’S NOTE This article traces the important evolution of multiple changes in technique and management of the newborn with hypoplastic left heart syndrome. Norwood recently updated his results with 386 patients: 163 had completed a Fontan operation with 29 deaths (18%),with another 39 patients awaiting hemi-Fontan and 60 awaiting Fontan. He highlights the development from his “original” first stage, which incorporated an atrial septa1 baffle with 10 deaths (37%), to the use of an intraatrial Gore-Tex tunnel going from the inferior vena cava to the pulmonary artery in 80 patients with 15 deaths (19%). As noted in the final discussion in his article, these early deaths were attributed tp the sudden conversion to a Fontan physiology with its rapid decrease in end-diastolic volume resulting in an abrupt change in ventricular geometry, with increased wall thickness and decreased diastolic compliance, leading to decreased pulmonary blood flow. The more recent “routine” employment of a hemiFontan has resulted in a further spectacular decrease in the overall mortality. In this procedure, the superior vena cava is divided and both ends are anastomosed end-toside to the right pulmonary artery-the superior end to the upper surface, and the cardiac end to the inferior
surface of the right pulmonary artery. The intraatrial superior vena caval orifice is occluded with a patch. This is excised at a subsequent procedure when the patient is converted to a Fontan with an intraatrial Gore-Tex tunnel. This hemi-Fontan creates a bidirectional Glenn type of physiology but minimizes the dissection at the subsequent procedure. Using this three-stage approach, Norwood has performed the hemi-Fontan in 106 patients with 6 deaths (6%); 56 patients have undergone the completed Fontan with only 4 deaths (7%) and only 1 death in the last 30 patients (his overall experience is 193 hemi-Fontan operations with 22 deaths [11%],with 3 patients undergoing transplantation rather than Fontan). Norwood’s recommendation is to perform the first stage in the newborn period, perform the hemi-Fontan at 6 to 8 months of age, and complete the modified Fontan operation at 12 to 18 months.
Anthony L. Moulton, M D Brown UniversitylMiriam Hospital 164 S u m m i t A v e Providence, XI 02906
Hypoplastic Left Heart Syndrome William I. Norwood, Jr, MD, PhD Department of Surgery, University of Pennsylvania School of Medicine, and Division of Cardiothoracic Surgery, The Children’s Hospital of Philadelphia, Philadelphia, Pennsylvania
The evolution of the present approach to the newborn with hypoplastic left heart is outlined. Preoperatively, maintenance of ductal patency with prostaglandin El and balancing of systemic and pulmonary blood flow are essential. Operative details of the first-stage palliation and the definitive second-stage procedure are described. The more recent adoption of an intermediate-stage hemiFontan procedure is also described. Since January 1989, 151 patients have been treated using this three-stage
H
ypoplastic left heart syndrome is the most common form of congenital cardiac malformation where there is only one fully developed ventricle. It represents fully 9% of those heart defects of infants with critical heart disease [l].Untreated, it is universally fatal and accounts for 25% of deaths in the first few weeks of life. Although lethal if left untreated, this malformation is eminently treatable with conventional reconstructive surgical techniques or, as advocated by some, heart replacement, with results comparable with other forms of complex congenital cardiac disease [2-51. This report outlines one means of approaching hypoplastic left heart syndrome and its contemporary results. The central anatomical feature of hypoplastic left heart syndrome is severe aortic valve hypoplasia or, more often, aortic valve atresia. As a consequence of limited outflow, the left ventricle develops abnormally and is hypoplastic or virtually absent. There is associated mitral valve hypoplasia or atresia. Twenty-five percent of children have either double-outlet right ventricle with aortic valve atresia and left ventricular hypoplasia or complete common atrioventricular canal malaligned over the right ventricle and associated left ventricular hypoplasia and aortic valve atresia with or without double-outlet right ventricle. The most obvious physiological consequence of this anatomical constellation is that systemic blood flow is provided virtually in its entirety from the right ventricle through a patent ductus arteriosus. The fetus is generally well and unaffected by the anatomical abnormality, but two of the natural changes from the fetal to the newborn physiology are life threatening. As the ductus arteriosus Presented in part at the Current Controversies and Techniques in Congenital Heart Surgery Meeting, Baltimore, MD, Sep 8-9, 1989. Address reprint requests to Dr Norwood, Division of Cardiothoracic Surgery, The Children’s Hospital of Philadelphia, 34th St and Civic Blvd, Philadelphia, PA 19104.
0 1991 by The Society of Thoracic Surgeons
approach, with 109 early survivors. Seventy-eight have undergone the hemi-Fontan operation with nine deaths (5 of whom came to this stage early nonelectively because of shunt failure or ventricular dysfunction). Twentyseven of the 78 patients undergoing hemi-Fontan operation have subsequently undergone definitive Fontan procedures with no deaths. (Ann Thorac Surg 1991;52:688-95)
closes, systemic perfusion is impaired. In addition, a natural decrease in pulmonary vascular resistance shortly after birth results in a volume shift from the systemic to the pulmonary circulation, also impairing systemic perfusion. Satisfactory systemic perfusion and oxygenation can be maintained in the newborn by assuring patency of the ductus arteriosus and adequate intravascular volume and by avoiding large differences between systemic and pulmonary vascular resistance. As will be discussed, the last two principles are critically important in the management after palliative operation for hypoplastic left heart syndrome as well.
Preoperative Management In virtually all neonates with hypoplastic left heart syndrome, continuous infusion of prostaglandin El satisfactorily maintains patency of the ductus arteriosus. Only rarely, when there is virtual absence of an interatrial communication, does hypoxemia as a consequence of a low pulmonary to systemic blood flow ratio occur. Rather, the baby is most often threatened not by metabolically important hypoxemia but by decreased systemic perfusion as a consequence of low pulmonary vascular resistance or increased systemic vascular resistance. In this circumstance, hypoventilation to increase carbon dioxide tension and pulmonary vascular resistance, and occasionally continuous infusion of sodium nitroprusside to decrease abnormally elevated systemic vascular resistance, can approximate the satisfactory physiological state of the fetus with hypoplastic left heart syndrome. The use of catecholamines is almost never necessary or appropriate. As with single ventricle complex, babies with hypoplastic left heart syndrome are ultimately treatable by some modification of the Fontan procedure. However, at birth the lungs are immature and the vascular resistance is naturally high, precluding a Fontan procedure in the neonatal period. 0003-4975/91/$3.50
Ann Thorac Surg 1991;52:688-95
Fig 1. Exposure and cannulation for first-stage palliation. (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
Yet, these infants are dependent on patency of the ductus arteriosus. Although the ductus arteriosus can be opened and maintained with continuous infusion of prostaglandins, prolonged association of the pulmonary circulation with the systemic circulation will result in either intractable congestive heart failure or, ultimately, development of pulmonary vascular obstructive disease. Therefore, it was clear even from the beginning of our surgical development that staged management is necessary. The initial palliation is embodied by three basic principles. First, the aorta must be associated directly with the right ventricle in a fashion guaranteeing unobstructed flow from right ventricle to the systemic circulation, with growth potential obviating further aortic operation. Second, pulmonary blood flow must be regulated for proper growth and development and maturation of the pulmonary vasculature to avoid the development of pulmonary vascular obstructive disease and to minimize the volume load on the right ventricle. Finally, a large interatrial communication is necessary to avoid pulmonary venous hypertension and its consequences. The surgical details of initial palliation have evolved over the last decade. It is a personal prejudice that the intricacies that have been inserted have an important impact on the physiological stability of these patients, subsequent suitability for a Fontan procedure, and survival with a good long-term functional result after the Fontan procedure.
CONGENITAL HEART NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
689
osus is to be avoided; it is unnecessary and requires excessive manipulation of the cardiovascular structures. A minimal amount of distortion, manipulation, and trauma to the delicate neonatal cardiovascular structures is essential to preserve anatomy and function. A single venous cannula is placed through the right atrial appendage, and cardiopulmonary bypass is instituted. The right and left pulmonary artery branches are rapidly occluded to ensure systemic perfusion through the ductus arteriosus. The baby is cooled on bypass while esophageal, nasopharyngeal, and rectal temperatures are monitored. The rectal temperature reaches 20°C after approximately 15 minutes of cardiopulmonary bypass. During this time, the branch vessels of the aortic arch are exposed and looped with suture tourniquets in preparation for circulatory arrest. Dissection is carried around the aortic arch onto the thoracic aorta in the posterior mediastinum. At this point, the branch vessels of the aortic arch are occluded, the circulation is discontinued, and the blood is drained into the venous reservoir. After removal of the arterial and venous cannulas, the atrial septum is excised to allow unimpeded pulmonary venous return to the right atrium (Fig 2). The main pulmonary artery, which has been separated from the diminutive ascending aorta during the cooling phase of cardiopulmonary bypass, is transected adjacent to the takeoff of the right pulmonary artery, and the distal stump of the main pulmonary artery is closed with a patch (Fig 3). Patch closure is recommended to ensure continuity between the right and left pulmonary artery branches. The ductus arteriosus is then exposed, ligated, and transected at its entrance to the thoracic aorta. An incision
Operative Procedure Through a conventional midline sternotomy incision, the thymus gland is excised, exposing the diminutive aortic arch and its branch vessels (Fig 1).Cannulation for arterial infusion is conveniently achieved in the proximal main pulmonary artery just above the sinuses of Valsalva. The tip of a 10F aortic cannula is introduced 3 to 4 mm into the artery. Threading the cannula through the ductus arteri-
Fig 2 . First-stage palliation: the atrial septum is excised and the main pulmonary artery is transected. (Reprinted from Edmunds LH lr, Norwood W l , Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
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CONGENITAL HEART NORWOOD HYPOPLASTIC LEFT HEART SYNDROME
in the aorta is carried distally 1 to 2 cm into the thoracic aorta (Fig 4) and also proximally into the aortic arch and ascending aorta to the level of the rim of the transected proximal main pulmonary artery. Because the isthmus of the aorta and the aortic arch actually function as a branch of the main pulmonary artery-ductus-thoracic aorta continuum, the junction of the isthmus and thoracic aorta is gusseted with a patch to avoid subsequent development of distal aortic arch obstruction (Fig 5). A piece of pulmonary homograft is used for this patch because it is thin, pliable, and hemostatic. At this point, we favor the construction of a short central shunt of 4-mm tube graft between the inferior aspect of the augmented aortic arch and the confluence of the branch pulmonary arteries (Fig 6). The rationale for a central shunt is to obtain more even distribution of flow and thus uniform growth of the right and left pulmonary arteries. The remaining pulmonary homograft gusset is then carried to 5 mm above the end of the most proximal incision in the ascending aorta (Fig 7). The proximal transected main pulmonary artery is then anastomosed to the ascending aorta and homograft gusset, thus creating outflow from the right ventricle to the augmented aorta through the pulmonary valve (Figs 8, 9). Cardiopulmonary bypass is reinstituted and the patient is rewarmed to 37°C. The tourniquets on the branch vessels of the aortic arch are removed, but those on the branch pulmonary arteries remain until the time of weaning from cardiopulmonary bypass. After weaning, the cannulas are removed and a pressure monitoring line is placed through the right atrial appendage cannulation site.
Ann Thorac Surg 1991;52:688-95
I
4
hcisian umed to lm/ ~pi9#iwI
\\adstpure
pdkv~ty&ey
Fig 4. First-stage palliation: incision in aorta. (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea & Febiger, 1989, by permission.)
Postoperative Management Using the lowest possible mean airway pressure, ventilation is adjusted to maintain the carbon dioxide tension between 20 and 30 mm Hg to minimize pulmonary vascular resistance. Generally, the oxygen tension ranges from 40 to 45 mm Hg. However, an arterial oxygen tension of 50 mm Hg or greater suggests a large pulmonary to systemic flow ratio, which may result in inadequate systemic perfusion. When this occurs, the ventilator may be used to adjust the pulmonary to systemic flow ratio by rapidly decreasing the inspired oxygen fraction to 30 mm Hg and allowing carbon dioxide tension to increase to 40 mm Hg, with a concomitant increase in pulmonary vascular resistance. Pharmacologic support is rarely necessary in the postoperative period. After the previously described palliative operation, the right ventricle is subjected to both volume and pressure load greater than normal for a right ventricle. With a view to long-term preservation of ventricular function, early assessment for suitability for the Fontan procedure is undertaken when the infant is 12 to 18 months of age. At this age, the pulmonary resistance generally has decreased to less than 2.5 Wood units and the ventricular end-diastolic pressure has remained normal (less than 7 to 8 mm Hg). The following operation may be planned.
Second-Stage Fontan Procedure Fig 3. First-stage palliation: closure of main pulmonary artery stump. (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission .)
Again, the heart is exposed through a midline sternotomy, and cannulation for cardiopulmonary bypass is achieved by placement of an arterial cannula in the ascending aorta and a single venous cannula through the right atrial appendage (Fig 10). The systemic to pulmo-
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nary artery shunt is exposed and occluded as cardiopulmonary bypass is begun, and the patient’s core temperature is reduced to 20°C. During this cooling phase on cardiopulmonary bypass, the right and left pulmonary artery branches are exposed
from pericardial reflection to pericardial reflection. This exposure prepares for widely augmenting the pulmonary arteries to avoid proximal pulmonary arterial obstruction from unrecognized irregularities in size (Figs 11, 12). During a period of circulatory arrest, the pulmonary arteries are opened and an incision in the right atrium is made from the sulcus terminalus superiorly to the right lateral insertion of the eustachian valve inferiorly. The interatrial communication is inspected and enlarged if possible. A final incision is then made in the superior right atrium adjacent to the right pulmonary artery and carried into the posterior aspect of the right superior vena cava immediately adjacent to the most rightward aspect of the incision in the right pulmonary artery (Fig 13). A suture line is begun between the inferior lip of the incised right pulmonary artery and the posterior lip of the right superior vena caval-right atrial incision (Fig 14). This will provide the floor for the anastomosis of the systemic venous return to the pulmonary arterial tree. A piece of tube graft 10 mm in diameter, of sufficient length to extend from the inferior vena caval-right atrial junction to the right superior vena caval-right atrial junction, is cut in half lengthwise (Fig 15). This is for use as a baffle to channel inferior vena caval flow along the right lateral aspect of the right atrium to the anastomosis between the right atrium and the pulmonary arterial tree superiorly. The baffle is sutured around the orifice of the inferior vena cava along the right lateral floor and free wall of the right atrium and around the patulous orifice in the superior dome of the right atrium (Figs 16, 17). This particular baffling technique was introduced to minimize problems associated with tricuspid prolapse or regurgitation, or with obstruction of pulmonary venous return to
Fig 6 . First-stage palliation: construction of central shunt. (PTFE = polytetrafluoroethylene.) (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Maluern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 7 . First-stage palliation: completion of homograft gusset. (Reprinted from Edmunds LH J r , Norwood W l , Low DW. Atlas of cardiothoracic surgery. Maluern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 5. First-stage palliation: gusseting of isthmus-thoracic aorta junction. (Reprinted from Edmunds LH J r , Norwood WI, Low DW. Atlas of cardiothoracic surgery. Maluern, PA: Lea 6 Febiger, 1989, by permission.)
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the right ventricle, which was experienced early in this series with an alternative baffling technique. The construction of the systemic venous pulmonary arterial system is completed by gusseting the pulmonary arterial incision with an elongated triangular patch, beginning on the left pulmonary artery. As the right pulmonary artery and adjacent right superior vena cava are approached, the base of the triangular patch is sutured onto the anterior lip of the right superior vena caval-right atrial incision, providing a roof for the anastomosis (Figs 18, 19). The patient is placed back on cardiopulmonary bypass after closure of the initial right atriotomy and rewarmed to 37°C.
\
Hemi-Fontan Procedure In the last 2 years, it has become apparent that mortality and morbidity may be reduced by separating the Fontan operation into two procedures: initial anastomosis of the superior vena cava to the pulmonary arteries, followed in 6 months by channeling of the inferior vena cava to the pulmonary arteries. The rationale is that diminution in end-diastolic volume develops rapidly in some patients after removal of the volume demands associated with a systemic to pulmonary artery shunt. Moreover, preoperative physiological information does not predict those patients in whom rapid contraction of end-diastolic volume will develop. The anatomical and physiological consequences of this process are an apparent increase in wall thickness, because muscle mass does not change as rapidly, and the diastolic function of the ventricle is impaired resulting in an increased end-diastolic pressure, increased central venous pressure, and decreased cardiac output. To minimize the physiological significance of such a rapid geometrical change, dividing the Fontan procedure into two parts is postulated to allow a decrease in end-diastolic volume and a commensurate decrease in muscle mass while only half of the systemic venous return is obligated to flow passively through the pulmonary vascular bed. When the end-diastolic volume and wall thickness ratio Fig 9. First-stage palliation: completion of right uentricleaugmented aorta outflow. (Reprinted from Edmunds LH Jr, Norzuood W l , Low D W . Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 8 . First-stage palliation: creation of outflow from right ventricle to augmented aorta. (Reprinted from Edmunds LH Ir, Norwood WI, Low D W . Atlas of cardiothoracic surgery. Malvern, PA: Lea b Febiger, 1989, by permission.)
have normalized, completion of the Fontan procedure may be undertaken.
Results The results of reconstructive operation for hypoplastic left heart syndrome continue to improve, for both initial palliation and later reconstructive operation, as we gain ever-increasing knowledge of the anatomy and physiology of this complex group of patients and of the surgical procedures required for them. In the 2-year period beginning January 1989, 151 newborns entered our institution for palliative operation. There were 42 (28%) early and 5
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Fig 10. Exposure and cannulation for second-stage Fontan. (Reprinted from Edmunds LH lr' Norwood wl' Low Dw' Of cardiothoracic surgery. Malvern, PA: Lea &? Febiger, 1989, by permission.)
Fig 12. Second-stage Fontan: completion of pulmonary artery augmentation, (Reprintedfrom LH Norwood wl, Low Dw, Atlas of cardiothoracic surgery. Malvern, PA: Lea B Febiger, 1989, by permission.)
(5%) late deaths among these patients. Seventy-eight of the 104 survivors have already undergone a hemi-Fontan operation (anastomosis of the superior vena cava to the branch pulmonary arteries). Among the 9 patients who
died (12%), 5 came to hemi-Fontan operation earlier than 5 months of age because of ventricular dysfunction or shunt failure, which may have unfavorably affected the postoperative physiology. Of the 27 patients in this group
Fig 11. Second-stage Fontan: use of homograft for pulmonary artery augmentation. (Reprinted from Edmunds LH Jr, Norwood Wl, Low D W . Atlas of cardiothoracic surgery. Malvern, PA: Lea G. Febiger, 1989, by permission.)
Fig 23. Second-stage Fontan: right atrial incision. (Reprinted from Edmunds LH Jr, Norwood W l , Low D W . Atlas of cardiothoracic surgery. Malvern, PA: Lea B Febiger, 1989, by permission.)
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Fig 14. Second-stage Fontan: suture line between right pulmonary artery and right atrium. (Reprinted from Edmunds LH Ir, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 16. Second-stage Fontan: construction of baffle. (Reprinted f r m Edmunds LH ]r, Nomood Wl, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea & Febiger, 1989, by permission.)
who have undergone completion of the Fontan operation, there has been no mortality. At present, our management scheme is palliation of the newborn, hemi-Fontan procedure at 6 months of age, and completion of the Fontan procedure at 12 months of age. The approach outlined
here for reconstructive therapy of this malformation will continue to evolve. The challenge for the future is to characterize better this group of lesions so that the preoperative, operative, and postoperative management may be further improved.
Fig 15. Second-stage Fontan: 10-mm polytetrafluoroethylene (PTFE) tube graft used as baffle. (Reprinted from Edmunds LH Jr, Norwood W l , Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
Fig 17. Second-stage Fontan: final suture line. (Reprinted from Edmunds LH Jr, Norwood WI, Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
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inbphimu-ahry Fig 18. Second-stage Fontan: completed repair. (Reprinted from Edmunds LH jr, Norwood W I , Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
References 1. Fyler DC. Report of the New England Regional Infant Cardiac
Program. Pediatrics 1980;65(Suppl):463.
2. Pigott JD, Murphy JD, Barber B, Norwood WI. Palliative reconstructive surgery for hypoplastic left heart syndrome. Ann Thorac Surg 1988;45:122-8.
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Fig 19. Second-stage Fontan: alternative tube graft. (Reprinted from Edmunds LH Ir, Norwood W l , Low DW. Atlas of cardiothoracic surgery. Malvern, PA: Lea 6 Febiger, 1989, by permission.)
3. Norwood WI, Lang P, Hansen D. Physiologic repair of aortic atresia-hypoplastic left heart syndrome. N Engl J Med 1983; 308:23. 4. Bailey LL, Nelson-Cannarella SL, Doroshow RW. Cardiac allotransplantation in newborns as therapy for hypoplastic left heart syndrome. N Engl J Med 1986;315:949. 5 . Barber G, Murphy JD, Pigott JD, Norwood WI. The evolving pattern of survival following palliative surgery for hypoplastic left heart syndrome. J Am Coll Cardiol 1988;2:139A.
EDITOR’S NOTE This article traces the important evolution of multiple changes in technique and management of the newborn with hypoplastic left heart syndrome. Norwood recently updated his results with 386 patients: 163 had completed a Fontan operation with 29 deaths (18%),with another 39 patients awaiting hemi-Fontan and 60 awaiting Fontan. He highlights the development from his “original” first stage, which incorporated an atrial septa1 baffle with 10 deaths (37%), to the use of an intraatrial Gore-Tex tunnel going from the inferior vena cava to the pulmonary artery in 80 patients with 15 deaths (19%). As noted in the final discussion in his article, these early deaths were attributed tp the sudden conversion to a Fontan physiology with its rapid decrease in end-diastolic volume resulting in an abrupt change in ventricular geometry, with increased wall thickness and decreased diastolic compliance, leading to decreased pulmonary blood flow. The more recent “routine” employment of a hemiFontan has resulted in a further spectacular decrease in the overall mortality. In this procedure, the superior vena cava is divided and both ends are anastomosed end-toside to the right pulmonary artery-the superior end to the upper surface, and the cardiac end to the inferior
surface of the right pulmonary artery. The intraatrial superior vena caval orifice is occluded with a patch. This is excised at a subsequent procedure when the patient is converted to a Fontan with an intraatrial Gore-Tex tunnel. This hemi-Fontan creates a bidirectional Glenn type of physiology but minimizes the dissection at the subsequent procedure. Using this three-stage approach, Norwood has performed the hemi-Fontan in 106 patients with 6 deaths (6%); 56 patients have undergone the completed Fontan with only 4 deaths (7%) and only 1 death in the last 30 patients (his overall experience is 193 hemi-Fontan operations with 22 deaths [11%],with 3 patients undergoing transplantation rather than Fontan). Norwood’s recommendation is to perform the first stage in the newborn period, perform the hemi-Fontan at 6 to 8 months of age, and complete the modified Fontan operation at 12 to 18 months.
Anthony L. Moulton, M D Brown UniversitylMiriam Hospital 164 S u m m i t A v e Providence, XI 02906
