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Variations on the theme of Fontan: Consideration of the bidirectional cavopulmonary connection or the fenestrated Fontan
EVALUATION
AND
MANAGEMENT
trated Fontan, what is less clear (and this is being charitable) are those specific indications for a bidirectional cavopulmonary connection as staging toward the Fontan vs. the application of a fenestrated Fontan. Historically, patients with cyanotic congenital heart disease were first palliated utilizing a true physiologic shunt in the form of a systemic to puhnonary artery connection. This still remains an important type of palliation, particularly early in infancy (probably less than 4 to 6 months of age) when other procedures are not readily applicable. Concern over distortion of pulmonary arteries and the development of obstructive pulmonary vascular disease were early problems now usually overcome by careful selection of shunt size to limit flow as well as by modifications in surgical technique. More recently, concern has been raised with respect to the long-term influence of the imposed volume load on ventricular performance as well as on atrioventricular valve regurgitation (2). The principle realized by Dr. William Glenn in creating a more efficient means of achieving pulmonary blood flow by utilizing a systemic venous to pulmonary arterial anastomosis has been the basis of modifications that have culminated in recent application of a "partial" Fontan principle. Accordingly, the two most commonly employed surgical interventions have been the bidirectional superior vena cavopuhnonary anastomosis (BCPA) and the fenestrated "total" cavopulmonary anastomosis. Although some centers advocate a fenestrated approach for all patients regardless of risk, both procedures are currently advocated for the high risk patient destined to be palliated with a completed total cavopulmonary connection (3,4).
C O N G E N I T A L H E A R T DISEASE
BRIEF REVIEW
Variations on the Theme of Fontan: Consideration of the Bidirectional Cavopulmonary Connection or the Fenestrated Fontan David G. Nykanen, MD and Robert M. Freedom, MD, Division d Cardiology, Department of Paediatrics, Hospital for Sick Children and the Department of Pediatrics, Universi~ of Toronto Faculty of Medicine, Toronto, Ontario, Canada
~
ecause the untreated natural history of patients with the usual forms of univentricular heart is so poor, some form of intervention would seem justified (1). Excellent early, midterm and late results with either the classical Fontan operation or the total cavopulmonary connection in carefully chosen patients are now readily achievable in a large number of centers. Nonetheless, the classical Fontan operation, total cavopulmonary bypass or a W of the many variations on the theme of Fontan must be considered truly palliative because survival in any number of long-term studies demonstrates an increasing late harard function. The management of those patients considered less than ideal candidates by virtue of age, increased puhnonary vascular resistance, severe pulmonary artery hypoplasia or distortion, atrioventricular valve regurgitation, ventricular hypertrophy or dirainished ventricular function (systolic or diastolic) represents a medical and surgical challenge. Any intervention in these patients must be characterized by low operative mortality rates and sustained palliation with an emphasis on quality of life as well as a reduction in continuing mortality rates. In addition, the ideal procedure should not interfere with future consideration for cardiac transplantation or progression to total cavopulmonary connection should the patient become a more suitable candidate. Thus the palliative management of patients with complex congenital heart disease considered at high risk for either a classical Fontan operation or a total cavopulmonary connection remains both controversial and challenging. Included in the more recent surgical algorithms to reduce the mortality rate of the Fontan operation are the bidirectional cavopulmonary connection or the fenestrated Fontan. These maneuvers are not universally endorsed, however, and the Mayo Clinic, with its very large surgical numbers, does not fenestrate. For those institutions, however, who actively consider and perform the bidirectional cavopulmonary connection or the fenes-
Bidirectional Cavopulmonary Connection The bidirectional (superior vena) cavopulmonary anastomosis increases effective pulmonary blood flow while decreasing total pulmonary blood flow relative to a systemic arterial shunt. Most patients undergoing a bidirectional cavopulmonary anastomosis achieve an oxygen saturation of approximately 85% with a low operative mortality rate and reasonable long-term results (4,5). Patients with significant pulmonary artery distortion, an unequivocal risk factor at Fontan's operation, can undergo pulmonary artery reconstruction concurrently with a bidirectional cavopulmonary connection. Similarly, those patients with double-inlet ventricle, etc., treated with banding of the main pulmonary artery as palliation in infancy, do not fare well at Fontan especially if subaortic stenosis has occurred or has been unmasked. Such patients can be treated with a bidirectional cavopulmonary anastomosis as well as with a connection between the ascending aorta and main pulmonary trunk (thus providing treatment for the ventricular outflow tract obstruction). Thus, it is contemporary practice in many
ACC CURRENT JOURNAL REVIEW May/lune 1993 © 1995 by the Amencan College of (iardiolog~.~
49
1062-1458/95/$9.50 SSDI 1062-1458(95)00055 O
EVALUATION
AND
MANAGEMENT
w,ith permanently fenestrated interventions is at present unknown. A significant contribution to the late hazard function associated with either the classical Fontan operation or with the total cavopulmonary operation is progressive ventricular dysfunction. Differences in systemic ventricular morphology and the work associated with long-term maintenance of flow to two resistances in parallel may be responsible for this deterioration in myocardial performance. In addition, some contribution to this myocardial dysfunction may result from increased coronary sinus pressure with a negative impact on myocardial blood flow unless the coronary sinus is decompressed to the pulmonary venous atrium at the time of intracardiac surgery. The initial application of the fenestration was to compensate for unfavorable ventricular systolic function and compliance reflecting remodeling of ventricular form and function that occurs so dramatically and rapidly after conversion to a Fontan circulation. This seems to have allowed younger patients and those with other risk factors ultimately to achieve total palliation (8). Whether improved survival and decreased morbidity is the result of fenestration remains to be proved by a randomized case-controlled multicentered investigation. There is little evidence that a truly inoperable patient can become operable by virtue of fenestration. The ability to simply convert a partial to a total cavopulmonary connection with the fenestrated approach represents the distinct advantage over staging by BCPA. If one accepts that a fenestrated approach should be reserved for high and not low risk patients, then reversibility of risk factors is mandatory in applying this approach. For example, if significant atrioventricular valve regurgitation mitigated against Fontan because of the volume load on the systemic ventricle, a fenestrated strategy seems appropriate if the regurgitation were expected to improve with reduction of ventricular end-diastolic volume. If, however, the problem was that of sustained severe hypertrophy with ventricular dysfunction, one would predict ventricular remodeling to worsen the ventricular performance, and such an approach for longterm palliation would not be appropriate because of prohibitive risk relative to other forms of palliation (9,10). It is unclear at present whether the BCPA results in less clinically significant early diastolic dysfunction with ventricular decompression; however, one would expect the central inferior venous pressures to be less when only the ventricular compliance and not the added effect of a pulmonary vascular bed in series is present. Hence, in this setting, a BCPA appears preferable. The integration of pulmonary artery anatomic variations and calculated pulmonary vascular resistance represent ongoing difficulties in the management of high risk patients. Recently, attention has been directed to objective quantification of the size of the pulmonal 7 arteries as an incremental
centers, including ours, to convert a systemic-to-pulmonary arterial shunt to a BCPA at 4 to 6 months, also addressing at that intervention any pulmonary arterial stenosis. With time, however, it appears that patients previously treated with a bidirectional cavopulmonary anastomosis may become progressively more cyanotic. This deterioration may reflect relatively less systemic venous return from the head and neck, a consequence of normal maturation. Other mechanisms responsible for this deterioration include development of systemic venous collaterals draining either to the inferior vena cava, thus decreasing the effective pulmonary blood flow, or to the pulmonary venous system, resulting in an obligatory right to left shunt. In the setting of the classic Glenn anastomosis, the late development of pulmonary arteriovenous malformations in the ipsilateral lung is a grevious complication (6). The etiology of pulmona U arteriovenous malformations in this setting is unclear. However, anatomic considerations and the observation that these lesions also occur in the setting of chronic liver disease suggest the possibility of a protective hepatic venous influence. Prevention or regression of these fistulae may result in improved long-term results. Whereas both venous collateral and arteriovenous malformation development may be amenable to surgical or transcatheter intervention, the occurrence of these complications may thwart further palliation with cardiac transplantation. Fenestrated Fontan The concept of leaving a residual right-to-left atrial communication as an interim measure to manage patients early in the postoperative period was initially applied to patients believed to be at higher risk for a Fontan procedure. Improved hospital survival rates and less associated complications are attributed to the ability of the fenestration to maintain ventricular preload and cardiac output while maintaining acceptable postoperative central venous pressures. The improved hemodynamics are notably achieved at the expense of systemic arterial saturation; however, tissue oxygen delivery is improved by virtue of the increased cardiac output. Within a relatively short period of time (usually several months or less) the aim of this approach is to close the fenestration either by tightening a previously placed snare or by transcatheter device occlusion, thus effecting the complete separation of the systemic venous from the pulmonary venous circulations. If further evaluation on test occlusion of the fenestration suggests that closure is not possible, the patient is left with persistent desaturation at a value equivalent to patients with a bidirectional cavopulmonary connection (7). Identification of preoperative determinants of an inability to eventually achieve complete separation of the systemic venous from the pulmonary venous circulations would be useful because the late follow-up of patients
ACC CURRENT JOURNAL REVIEW May/June 1995
50
EVALUATION
AND
risk factor for Fontan (9). Indeed, if proximal discrete lesions are amenable to surgical or transcatheter improvement, the application of either technique can be viewed as an interim palliation in the agenda concluding in complete separation of the circulations. However, early conversion to a total connection is more attractive with simple closure of a fenestration. Similarly, the young patient's pulmonary arteries are expected to grow. This may be the reason for improved success of the BCPA in young infants as an interim measure where a total anastomosis is not feasible and a decreased volume load on the ventricle is desired. There is evidence that there is a lower limit to the size of the pulmonary arteries that can accommodate the flow expected in a Fontan type of operation that is independent of the pulmonary vascular resistance and may reflect vascular compliance (11). The extent to which a partial Fontan may be applicable to patients with small pulmona W arteries relative to the BCPA is unknown. The presence of severe pulmonary vascular disease or multiple severe peripheral pulmonary artery stenoses are contraindications to either a BCPA or partial Fontan. Both conditions result in significant elevations in central pulmonary artery pressure that, at indexes greater than 2 to 4 Wood units, would likely preclude either form of palliation. In these patients a systemic shunt with or without a venous anastomosis is the only surgical option for the progressively cyanotic patient short of heart-lung transplantation. In addition, measurement of pulmonary vascular resistance can be difficult, particularly in patients with complex anatomy including those with multiple sources of puhnonary blood flow and persistent systemic to pulmonary artery collaterals. In these patients a pulmonary artery pressure of >20 mm Hg in the absence of increased pulmonary, flow or significant atrioventricular valve regurgitation likely indicates unfavorable postoperative hemodynamic state thus dictating similar management. The influence of age on the outcome of either a fenestrated Fontan or BCPA is the subject of ongoing considerations. Despite a downward trend most surgical centers do not advocate a Fontan or total cavopulmonary anastomosis for patients aged <1 year. In the patient aged < 4 years the fenestrated strategy may be responsible for recent improved reported surgical outcomes. More recently, the BCPA has also been applied to the very young infant. An acceptable systemic saturation is achieved in these patients presumably on the basis of increased blood flow to the head due to differences in body proportion of the young infant relative to the child. The greater proportion of systemic venous return entering the pulmonary artery from the superior vena cava results in an increased effective pulmonary blood flow. Indeed, current studies suggest that early application of the BCPA can be achieved with low mortality and morbidity rates, perhaps resulting in a better Fontan candidate because
MANAGEMENT
of early reduction in volume load to the ventricle (12). With these issues in mind a BCPA could be contemplated for patients aged > 4 months while reserving the fenestrated operation for patients over 1 year of age. In summary, the choice of palliation for the patient believed at high risk for either a classical Fontan or total cavopulmonary anastomosis relies on the identification of incremental risk factors and their believed reversibility. In the patient believed to be a permanently poor candidate there seems no advantage to a fenestrated Fontan over a bidirectional superior cavopulmona U anastomosis with respect to level of saturation achieved. Indeed, the fenestrated approach could prove to have a higher operative risk with an unfavorable long-term result. If a patient becomes a better Fontan candidate over time, the procedure could then reasonably be fenestrated in an effort to improve the immediate postoperative hemodynamics. Alternatively, the patient with risk factors immediately amenable to surgical intervention are better served by the partial Fontan approach. As little follow-up is available for patients whose hemodynamics will not tolerate fenestration occlusion, close follow up of this unique subset of patients is imperative to determine the long-term consequences of these incomplete procedures.
REFERENCES 1. Moodie DS, Rltter DG, Tajik AJ, O:Fallon W M Long-term follow-up in the unoperated univentricular heart. Am J Cardiol 198ar;53:1124-8. 2. KirklinJK, Blackstone EH, KirklinJW, Pacifico AD, Bargeron LMJr. The Fontan operation: ventricular hypertrophy, age, and date of operation as risk factors. J Thorac Cardiovasc Surgery 1986;92:1049-64. 3. Bridges ND, LockJE, Castaneda AR. BaNe fenestration with subsequent transcatheter closure, modification of the Fontan operation for patients at increased risk. Circulation 1990;82:1681-9. 4. Bridges ND, Jonas RA, Mayer JE, Flanagan MF, Keane JF, Castaneda AR. Bidirectional cavopulmonary anastomosis as interim palliation for high-risk Fontan candidates. Early results. Circulation 1990;82(suppl IV):IV-170IV-176 5. di Carlo D, Williams WG, Freedom RM, Trusler GA, Rowe RD. The role of cava-pulmona~, (Glenn) anastomosis in the palliative treatment of congenital heart disease J Thorac Cardiovasc Surg 1982:38:437-42. 6. Kopf G5, Laks H, Stansel HC, Hellenbrand WE, Kleinman CS, Talner NS. Thirty-year follow-up of superior vena cava-pulmona W arte U (Glenn) shunts. J Thorac Cardiovasc Surg 1990;100:662-71. 7 Srivastava D, Preminger TJ, Spevak PJ, LockJE. Development of puhnonary arteriovenous malformations following cavopulmonary anastomoses. Circulation 1993;88(part 2):I-149. 8 Kopf GS, Kleinman CS, Hijazi ZM, Fahey JT, Dewar ML, Hellenbrand W E Fenestrated Fontan operation with delayed transcatheter closure of atrial septal defect. Improved results in high-risk patients. J Thorac Cardiovase Surg I992;103:1039-48 9. Fontan F, Fernandez G, Costa F, et ah The size of the pulmonary- arteries and the results of the Pontan operation. J Thorac Cardiovasc Surg 1989;98: 711-24 10. Seliem M, Muster AJ, Paul MH, Benson DW. Relation between preop-
ACC CURRENI JOURNALREVIEWMay/June 1995
51
EVALUATION
AND
erative left ventricular muscle mass and outcome of the Fontan procedure in patients with tricuspid atresia. J Am Coll Cardiol 1989;14:750 5.
MANAGEMENT
pulmonaD' shunt in young infants. Postoperative course and early results. Circulation 1993;88(part 2): 149-58.
11. Senkazi H, Isoda T, Ishizawa A, Hishi T. Reconsideration of criteria for the Fontan operation. Influence of puhnonary artery size on postoperative hemodynmiacs o[ the Fontan operation Circulation 1994;89:266-71
Ad&~:ss correspondence and reprint requests to R.M Freedom, MD, Division o] Cardiology, Room 1503, Hospital jbr 5ick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8.
12. Chang AC, Hanley FL, Wernovsky G, et al. Early bidirectional caw>
Post4ontan patient:. Tracy and her 4-H fair-winning rabbit--Bugsy. (Courtesy of Donald A. Girod, MD, Chief, Pediatric Cardiology, Indiana University School of Medicine.)
ACC CURRENTJOURNALREVIEW May/]unc 1995
52
AND
MANAGEMENT
trated Fontan, what is less clear (and this is being charitable) are those specific indications for a bidirectional cavopulmonary connection as staging toward the Fontan vs. the application of a fenestrated Fontan. Historically, patients with cyanotic congenital heart disease were first palliated utilizing a true physiologic shunt in the form of a systemic to puhnonary artery connection. This still remains an important type of palliation, particularly early in infancy (probably less than 4 to 6 months of age) when other procedures are not readily applicable. Concern over distortion of pulmonary arteries and the development of obstructive pulmonary vascular disease were early problems now usually overcome by careful selection of shunt size to limit flow as well as by modifications in surgical technique. More recently, concern has been raised with respect to the long-term influence of the imposed volume load on ventricular performance as well as on atrioventricular valve regurgitation (2). The principle realized by Dr. William Glenn in creating a more efficient means of achieving pulmonary blood flow by utilizing a systemic venous to pulmonary arterial anastomosis has been the basis of modifications that have culminated in recent application of a "partial" Fontan principle. Accordingly, the two most commonly employed surgical interventions have been the bidirectional superior vena cavopuhnonary anastomosis (BCPA) and the fenestrated "total" cavopulmonary anastomosis. Although some centers advocate a fenestrated approach for all patients regardless of risk, both procedures are currently advocated for the high risk patient destined to be palliated with a completed total cavopulmonary connection (3,4).
C O N G E N I T A L H E A R T DISEASE
BRIEF REVIEW
Variations on the Theme of Fontan: Consideration of the Bidirectional Cavopulmonary Connection or the Fenestrated Fontan David G. Nykanen, MD and Robert M. Freedom, MD, Division d Cardiology, Department of Paediatrics, Hospital for Sick Children and the Department of Pediatrics, Universi~ of Toronto Faculty of Medicine, Toronto, Ontario, Canada
~
ecause the untreated natural history of patients with the usual forms of univentricular heart is so poor, some form of intervention would seem justified (1). Excellent early, midterm and late results with either the classical Fontan operation or the total cavopulmonary connection in carefully chosen patients are now readily achievable in a large number of centers. Nonetheless, the classical Fontan operation, total cavopulmonary bypass or a W of the many variations on the theme of Fontan must be considered truly palliative because survival in any number of long-term studies demonstrates an increasing late harard function. The management of those patients considered less than ideal candidates by virtue of age, increased puhnonary vascular resistance, severe pulmonary artery hypoplasia or distortion, atrioventricular valve regurgitation, ventricular hypertrophy or dirainished ventricular function (systolic or diastolic) represents a medical and surgical challenge. Any intervention in these patients must be characterized by low operative mortality rates and sustained palliation with an emphasis on quality of life as well as a reduction in continuing mortality rates. In addition, the ideal procedure should not interfere with future consideration for cardiac transplantation or progression to total cavopulmonary connection should the patient become a more suitable candidate. Thus the palliative management of patients with complex congenital heart disease considered at high risk for either a classical Fontan operation or a total cavopulmonary connection remains both controversial and challenging. Included in the more recent surgical algorithms to reduce the mortality rate of the Fontan operation are the bidirectional cavopulmonary connection or the fenestrated Fontan. These maneuvers are not universally endorsed, however, and the Mayo Clinic, with its very large surgical numbers, does not fenestrate. For those institutions, however, who actively consider and perform the bidirectional cavopulmonary connection or the fenes-
Bidirectional Cavopulmonary Connection The bidirectional (superior vena) cavopulmonary anastomosis increases effective pulmonary blood flow while decreasing total pulmonary blood flow relative to a systemic arterial shunt. Most patients undergoing a bidirectional cavopulmonary anastomosis achieve an oxygen saturation of approximately 85% with a low operative mortality rate and reasonable long-term results (4,5). Patients with significant pulmonary artery distortion, an unequivocal risk factor at Fontan's operation, can undergo pulmonary artery reconstruction concurrently with a bidirectional cavopulmonary connection. Similarly, those patients with double-inlet ventricle, etc., treated with banding of the main pulmonary artery as palliation in infancy, do not fare well at Fontan especially if subaortic stenosis has occurred or has been unmasked. Such patients can be treated with a bidirectional cavopulmonary anastomosis as well as with a connection between the ascending aorta and main pulmonary trunk (thus providing treatment for the ventricular outflow tract obstruction). Thus, it is contemporary practice in many
ACC CURRENT JOURNAL REVIEW May/lune 1993 © 1995 by the Amencan College of (iardiolog~.~
49
1062-1458/95/$9.50 SSDI 1062-1458(95)00055 O
EVALUATION
AND
MANAGEMENT
w,ith permanently fenestrated interventions is at present unknown. A significant contribution to the late hazard function associated with either the classical Fontan operation or with the total cavopulmonary operation is progressive ventricular dysfunction. Differences in systemic ventricular morphology and the work associated with long-term maintenance of flow to two resistances in parallel may be responsible for this deterioration in myocardial performance. In addition, some contribution to this myocardial dysfunction may result from increased coronary sinus pressure with a negative impact on myocardial blood flow unless the coronary sinus is decompressed to the pulmonary venous atrium at the time of intracardiac surgery. The initial application of the fenestration was to compensate for unfavorable ventricular systolic function and compliance reflecting remodeling of ventricular form and function that occurs so dramatically and rapidly after conversion to a Fontan circulation. This seems to have allowed younger patients and those with other risk factors ultimately to achieve total palliation (8). Whether improved survival and decreased morbidity is the result of fenestration remains to be proved by a randomized case-controlled multicentered investigation. There is little evidence that a truly inoperable patient can become operable by virtue of fenestration. The ability to simply convert a partial to a total cavopulmonary connection with the fenestrated approach represents the distinct advantage over staging by BCPA. If one accepts that a fenestrated approach should be reserved for high and not low risk patients, then reversibility of risk factors is mandatory in applying this approach. For example, if significant atrioventricular valve regurgitation mitigated against Fontan because of the volume load on the systemic ventricle, a fenestrated strategy seems appropriate if the regurgitation were expected to improve with reduction of ventricular end-diastolic volume. If, however, the problem was that of sustained severe hypertrophy with ventricular dysfunction, one would predict ventricular remodeling to worsen the ventricular performance, and such an approach for longterm palliation would not be appropriate because of prohibitive risk relative to other forms of palliation (9,10). It is unclear at present whether the BCPA results in less clinically significant early diastolic dysfunction with ventricular decompression; however, one would expect the central inferior venous pressures to be less when only the ventricular compliance and not the added effect of a pulmonary vascular bed in series is present. Hence, in this setting, a BCPA appears preferable. The integration of pulmonary artery anatomic variations and calculated pulmonary vascular resistance represent ongoing difficulties in the management of high risk patients. Recently, attention has been directed to objective quantification of the size of the pulmonal 7 arteries as an incremental
centers, including ours, to convert a systemic-to-pulmonary arterial shunt to a BCPA at 4 to 6 months, also addressing at that intervention any pulmonary arterial stenosis. With time, however, it appears that patients previously treated with a bidirectional cavopulmonary anastomosis may become progressively more cyanotic. This deterioration may reflect relatively less systemic venous return from the head and neck, a consequence of normal maturation. Other mechanisms responsible for this deterioration include development of systemic venous collaterals draining either to the inferior vena cava, thus decreasing the effective pulmonary blood flow, or to the pulmonary venous system, resulting in an obligatory right to left shunt. In the setting of the classic Glenn anastomosis, the late development of pulmonary arteriovenous malformations in the ipsilateral lung is a grevious complication (6). The etiology of pulmona U arteriovenous malformations in this setting is unclear. However, anatomic considerations and the observation that these lesions also occur in the setting of chronic liver disease suggest the possibility of a protective hepatic venous influence. Prevention or regression of these fistulae may result in improved long-term results. Whereas both venous collateral and arteriovenous malformation development may be amenable to surgical or transcatheter intervention, the occurrence of these complications may thwart further palliation with cardiac transplantation. Fenestrated Fontan The concept of leaving a residual right-to-left atrial communication as an interim measure to manage patients early in the postoperative period was initially applied to patients believed to be at higher risk for a Fontan procedure. Improved hospital survival rates and less associated complications are attributed to the ability of the fenestration to maintain ventricular preload and cardiac output while maintaining acceptable postoperative central venous pressures. The improved hemodynamics are notably achieved at the expense of systemic arterial saturation; however, tissue oxygen delivery is improved by virtue of the increased cardiac output. Within a relatively short period of time (usually several months or less) the aim of this approach is to close the fenestration either by tightening a previously placed snare or by transcatheter device occlusion, thus effecting the complete separation of the systemic venous from the pulmonary venous circulations. If further evaluation on test occlusion of the fenestration suggests that closure is not possible, the patient is left with persistent desaturation at a value equivalent to patients with a bidirectional cavopulmonary connection (7). Identification of preoperative determinants of an inability to eventually achieve complete separation of the systemic venous from the pulmonary venous circulations would be useful because the late follow-up of patients
ACC CURRENT JOURNAL REVIEW May/June 1995
50
EVALUATION
AND
risk factor for Fontan (9). Indeed, if proximal discrete lesions are amenable to surgical or transcatheter improvement, the application of either technique can be viewed as an interim palliation in the agenda concluding in complete separation of the circulations. However, early conversion to a total connection is more attractive with simple closure of a fenestration. Similarly, the young patient's pulmonary arteries are expected to grow. This may be the reason for improved success of the BCPA in young infants as an interim measure where a total anastomosis is not feasible and a decreased volume load on the ventricle is desired. There is evidence that there is a lower limit to the size of the pulmonary arteries that can accommodate the flow expected in a Fontan type of operation that is independent of the pulmonary vascular resistance and may reflect vascular compliance (11). The extent to which a partial Fontan may be applicable to patients with small pulmona W arteries relative to the BCPA is unknown. The presence of severe pulmonary vascular disease or multiple severe peripheral pulmonary artery stenoses are contraindications to either a BCPA or partial Fontan. Both conditions result in significant elevations in central pulmonary artery pressure that, at indexes greater than 2 to 4 Wood units, would likely preclude either form of palliation. In these patients a systemic shunt with or without a venous anastomosis is the only surgical option for the progressively cyanotic patient short of heart-lung transplantation. In addition, measurement of pulmonary vascular resistance can be difficult, particularly in patients with complex anatomy including those with multiple sources of puhnonary blood flow and persistent systemic to pulmonary artery collaterals. In these patients a pulmonary artery pressure of >20 mm Hg in the absence of increased pulmonary, flow or significant atrioventricular valve regurgitation likely indicates unfavorable postoperative hemodynamic state thus dictating similar management. The influence of age on the outcome of either a fenestrated Fontan or BCPA is the subject of ongoing considerations. Despite a downward trend most surgical centers do not advocate a Fontan or total cavopulmonary anastomosis for patients aged <1 year. In the patient aged < 4 years the fenestrated strategy may be responsible for recent improved reported surgical outcomes. More recently, the BCPA has also been applied to the very young infant. An acceptable systemic saturation is achieved in these patients presumably on the basis of increased blood flow to the head due to differences in body proportion of the young infant relative to the child. The greater proportion of systemic venous return entering the pulmonary artery from the superior vena cava results in an increased effective pulmonary blood flow. Indeed, current studies suggest that early application of the BCPA can be achieved with low mortality and morbidity rates, perhaps resulting in a better Fontan candidate because
MANAGEMENT
of early reduction in volume load to the ventricle (12). With these issues in mind a BCPA could be contemplated for patients aged > 4 months while reserving the fenestrated operation for patients over 1 year of age. In summary, the choice of palliation for the patient believed at high risk for either a classical Fontan or total cavopulmonary anastomosis relies on the identification of incremental risk factors and their believed reversibility. In the patient believed to be a permanently poor candidate there seems no advantage to a fenestrated Fontan over a bidirectional superior cavopulmona U anastomosis with respect to level of saturation achieved. Indeed, the fenestrated approach could prove to have a higher operative risk with an unfavorable long-term result. If a patient becomes a better Fontan candidate over time, the procedure could then reasonably be fenestrated in an effort to improve the immediate postoperative hemodynamics. Alternatively, the patient with risk factors immediately amenable to surgical intervention are better served by the partial Fontan approach. As little follow-up is available for patients whose hemodynamics will not tolerate fenestration occlusion, close follow up of this unique subset of patients is imperative to determine the long-term consequences of these incomplete procedures.
REFERENCES 1. Moodie DS, Rltter DG, Tajik AJ, O:Fallon W M Long-term follow-up in the unoperated univentricular heart. Am J Cardiol 198ar;53:1124-8. 2. KirklinJK, Blackstone EH, KirklinJW, Pacifico AD, Bargeron LMJr. The Fontan operation: ventricular hypertrophy, age, and date of operation as risk factors. J Thorac Cardiovasc Surgery 1986;92:1049-64. 3. Bridges ND, LockJE, Castaneda AR. BaNe fenestration with subsequent transcatheter closure, modification of the Fontan operation for patients at increased risk. Circulation 1990;82:1681-9. 4. Bridges ND, Jonas RA, Mayer JE, Flanagan MF, Keane JF, Castaneda AR. Bidirectional cavopulmonary anastomosis as interim palliation for high-risk Fontan candidates. Early results. Circulation 1990;82(suppl IV):IV-170IV-176 5. di Carlo D, Williams WG, Freedom RM, Trusler GA, Rowe RD. The role of cava-pulmona~, (Glenn) anastomosis in the palliative treatment of congenital heart disease J Thorac Cardiovasc Surg 1982:38:437-42. 6. Kopf G5, Laks H, Stansel HC, Hellenbrand WE, Kleinman CS, Talner NS. Thirty-year follow-up of superior vena cava-pulmona W arte U (Glenn) shunts. J Thorac Cardiovasc Surg 1990;100:662-71. 7 Srivastava D, Preminger TJ, Spevak PJ, LockJE. Development of puhnonary arteriovenous malformations following cavopulmonary anastomoses. Circulation 1993;88(part 2):I-149. 8 Kopf GS, Kleinman CS, Hijazi ZM, Fahey JT, Dewar ML, Hellenbrand W E Fenestrated Fontan operation with delayed transcatheter closure of atrial septal defect. Improved results in high-risk patients. J Thorac Cardiovase Surg I992;103:1039-48 9. Fontan F, Fernandez G, Costa F, et ah The size of the pulmonary- arteries and the results of the Pontan operation. J Thorac Cardiovasc Surg 1989;98: 711-24 10. Seliem M, Muster AJ, Paul MH, Benson DW. Relation between preop-
ACC CURRENI JOURNALREVIEWMay/June 1995
51
EVALUATION
AND
erative left ventricular muscle mass and outcome of the Fontan procedure in patients with tricuspid atresia. J Am Coll Cardiol 1989;14:750 5.
MANAGEMENT
pulmonaD' shunt in young infants. Postoperative course and early results. Circulation 1993;88(part 2): 149-58.
11. Senkazi H, Isoda T, Ishizawa A, Hishi T. Reconsideration of criteria for the Fontan operation. Influence of puhnonary artery size on postoperative hemodynmiacs o[ the Fontan operation Circulation 1994;89:266-71
Ad&~:ss correspondence and reprint requests to R.M Freedom, MD, Division o] Cardiology, Room 1503, Hospital jbr 5ick Children, 555 University Avenue, Toronto, Ontario, Canada M5G 1X8.
12. Chang AC, Hanley FL, Wernovsky G, et al. Early bidirectional caw>
Post4ontan patient:. Tracy and her 4-H fair-winning rabbit--Bugsy. (Courtesy of Donald A. Girod, MD, Chief, Pediatric Cardiology, Indiana University School of Medicine.)
ACC CURRENTJOURNALREVIEW May/]unc 1995
52