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Indications and timing for the bidirectional Glenn shunt versus the fenestrated Fontan circulation
Indications and timing for the bidirectional Glenn shunt versus the fenestrated Fontan circulation Richard A. Jonas, MD, Boston, Mass.
T
he traditional approach to the child with a single ventricle over the past 20 years has been a neonatal palliative operation followed by a Fontan procedure when pulmonary resistance is judged to be sufficiently low. Although the ideal age for the Fontan procedure was never clear, a completed ("nonfenestrated") Fontan-type circulation was generally believed to offer the best longterm quality of life to any child with a single ventricle. In 1988 my group' and others added the bidirectional Glenn shunt as an interim step in this pathway, especially for children who were considered to be at high risk for a onestep Fontan procedure, as was our experience with children with hypoplastic left heart syndrome. In 1989 an additional interim step was added in the form of the "fenestrated Fontan.'? Since that time I have been impressed by the excellent palliation achieved by these intermediate steps. In fact, the question as to when or even whether to proceed to the next step in the pathway is being asked of surgeons with increasing frequency by cardiologists and particularly by parents. Inherent inefficiency of the shunted/banded single ventricle
After a first-stage neonatal palliative procedure for single ventricle, whether it be a shunt, band, or more complex procedure such as a stage I Norwood procedure for hypoplastic left heart syndrome, the circulation is inherently inefficient because of recirculation of both pulmonary and systemic venous return. Pulmonary recirculation is particularly inefficient because pulmonary From the Department of Cardiac Surgery, The Children's Hospital, Boston, Mass. Received for publication Jan. 25, 1994. Accepted for publication March 16, 1994. Address for reprints: Richard A. Jonas, MD, Department of Cardiac Surgery, The Children's Hospital, 300 Longwood, Ave., Boston, MA02115. J 1HORAC CARDIOVASC SURG 1994;108:522-4 Copyright @ 1994 by Mosby-Year Book, Inc. 0022-5223/94 $3.00
522
+0
12/1/56250
venous blood is unable to collect more oxygen on a second pass through the lungs. On the other hand, recirculation of systemic venous return allows extraction of at least some of the residual oxygen in the systemic venous blood. Because of the decrease in pulmonary resistance with time, the proportion of the entire cardiac output passing to the lungs is likely to increase, that is, an increasing volume load for the single ventricle with no improvement in oxygen delivery to the body or even a decrease in oxygen delivery as systemic blood is stolen into the pulmonary circulation. Both the bidirectional Glenn shunt and Fontan shunt eliminate the inefficiency of pulmonary recirculation
The tendency has been to conceptualize the bidirectional Glenn shunt as physiologically equivalent to half a Fontan shunt. Some centers even use the term hemiFontan. Although this term may be appropriate if one thinks strictly in anatomic terms, it is not the case physiologically.Pulmonary recirculation is eliminated by both procedures. The only blood that passes to the lungs is systemic venous blood. Furthermore, any blood that has had a second pass through the systemic venous bed in the patient with a bidirectional Glenn circulation and is therefore more desaturated is able to take up a correspondingly greater amount of oxygen on its one pass through the lungs. However, this is not to say that the Fontan and bidirectional Glenn circulations are equivalent: in fact, fundamental differences exist that almost certainly will influence the late complications associated with these two forms of palliation. Differences between the nonfenestrated Fontan and bidirectional Glenn shunts
The arterial oxygen saturation in the patient with a completed Fontan operation is often about 95%, whereas it is usually closer to 85% with the bidirectional Glenn shunt. However, the price paid for the higher oxygen saturation with the Fontan operation is higher venous pressure in the right atrium, as well as in the hepatic, mesen-
The Journal of Thoracic and Cardiovascular Surgery Volume 108, Number 3
teric, and renal vascular beds. In addition, it was my clinical experience when I used to perform the completed Fontan operation that early postoperative cardiac output was often marginal, convalescence was slow, and pleural effusions lasting longer than 1 week occurred in 40% of patients.' In contrast, patients with a similar or greater risk profile undergoing a bidirectional Glenn shunt had a clinical appearance of greater cardiac output, hospitalization was commonly less than 1 week after the operation, and pleural effusions were rare. Late complications after bidirectional Glenn versus Fontan shunts The commonest problem after a bidirectional Glenn operation has been progressive cyanosis. Cyanosis may be due to the development of systemic venous collaterals that decompress the superior caval system into the inferior caval system: These collaterals can generally be dealt with successfully by coil embolization. A more troublesome problem may be the development of a pulmonary arteriovenous shunt. Although the very long-term experience with the classic Glenn shunt revealed a risk of formation of arteriovenous malformations that were amenable to coil embolization," my more recent short-term experience with the bidirectional Glenn shunt has been the formation of a diffuse arteriovenous shunt that is not readily amenable to coil embolization. Furthermore, analysis of our bidirectional Glenn experience" suggests that older age per se may be a risk factor for cyanosis, perhaps because of a lesser proportion of caval return from the superior vena cava relative to the inferior vena cava in the older child. Although scattered reports of pulmonary arteriovenous malformations after Fontan procedures have been published.' close analysis of these cases reveals that the arteriovenous malformations occurred in lungs that were not receiving hepatic venous blood. Presumably a hepatic factor exists that usually inhibits arteriovenous malformation. In support of this contention is the observation that pulmonary arteriovenous malformations tend to develop in patients with liver disease. Interestingly, liver transplantation has been associated with regression of arteriovenous malformations in at least two patients." Late problems with the Fontan circulation are due to the chronic elevation of intrabdominal venous pressure and right atrial pressure. Fontan and associates 7 described a rising late hazard function for death apparent 6 years after even a "perfect" Fontan operation. In their report describing 5 to 15 years' follow-up after the Fontan operation, Driscoll and colleagues'' from the Mayo Clinic described a 15% incidence of protein-losing enteropathy at 10 years, including some patients with cirrhosis. No useful management options were apparent
Jonas
523
for these difficult problems. In contrast, reports from Toronto and Yale4 describe a 10% incidence of pulmonary arteriovenous malformations at 10 years after classic Glenn shunts, and many of these were suitable for embolization. Supraventricular tachycardia after a Fontan procedure has been reported by a number of authors. Driscoll and coworkers" reported a 20% incidence between 5 and 15 years after the operation. Cromme-Dijkhuis and colleagues? found that 43% of patients had abnormalities on 24-hour ambulatory electrocardiograms at a median of 5 years after the operation. Other complications described after the Fontan procedure include stroke'' and right atrial thrombi.!? Exercise studies of patients late after the Fontan procedure have emphasized the limitation in cardiac output associated with exercise. l1 Oxygen delivery can be increased only by increasing oxygen extraction, with resulting profoundly low systemic venous saturation. I am not aware offormal exercise studies in which patients with a bidirectional Glenn shunt have been studied or compared with patients who have had the Fontan operation. Nevertheless, because the pulmonary and systemic vascular beds are not in series, it is likely that cardiac output can be increased more during exercise with the bidirectional Glenn circulation than with the Fontan circulation. Differences between the fenestrated and completed Fontan shunts Placement of a window in the baffle between the systemic and pulmonary venous atria as part of a Fontan procedure results in lower superior vena caval, inferior vena caval, and right atrial pressures.F Arterial oxygen saturation is lower, about 88% to 90%. By clinical assessment, cardiac output appears to be higher. Effusions lasting longer than 1 week occur in 10% of patients rather than 40%, and the duration of hospitalization is shorter. In theory, in these patients the cardiac output can be increased in response to exercise by shunting of blood right to left through the fenestration. Whether this shunting results in improved oxygen delivery is currently under study. The results of such studies will help to determine when or whether fenestrations should be closed. Strokes after single ventricle palliation One of the important risks of not completely separating the pulmonary and systemic venous returns is the risk that a systemic venous thrombus could embolize and cause a stroke or other systemic embolus. To date, this risk has not been clearly quantitated. Unfortunately, performance of a completed Fontan operation does not eliminate the risk of stroke' Perhaps thrombus forming on the
524
Jonas
pulmonary venous atrial side of the baffle or in the stump of the main pulmonary artery is the source of these emboli. This risk begs the question of the desirability of anticoagulation as a routine for all patients with single ventricle palliation. Conclusions
The various surgical options for single ventricle, including bidirectional Glenn, fenestrated Fontan, and completed Fontan circulations, are all palliative in nature with different advantages and disadvantages. The indications and timing for these options remain poorly defined. Careful, prospective, very long-term studies of late function and quality of life in patients with single ventricles of all forms are urgently needed. It is tempting to speculate that many patients may be best served by a longer period of palliation with the bidirectional Glenn shunt than is currently offered. Such a policy would shorten the total exposure of the intrabdominal organs and right atrium to elevated venous pressure with all its attendant late complications. Clearly, making such a change will be contingent on demonstration that this approach is not associated with an unacceptable risk of systemic embolism or permanent pulmonary damage caused by formation of diffuse arteriovenous malformations. In addition, the value of a permanently open fenestration after the Fontan procedure in allowing improved oxygen delivery during exercise also should be defined. REFERENCES I. Bridges ND, Jonas RA, Mayer JE, Flanagan MF, Keane JF, Castaneda AR. Bidirectional cavopulmonary anastomosis as interim palliation for high risk Fontan candidates. Circulation 1990;82(SuppI)IVI70-6. 2. Bridges ND, Lock JE, Castaneda AR. Baffle fenestration with subsequent transcatheter closure. Circulation 1990; 82:1681-9.
The Journal of Thoracic and Cardiovascular Surgery September 1994
3. Mayer JE, Bridges ND, Lock JE, Hanley FL, Jonas RA, Castaneda AR. Factors associated with marked reduction in mortality for Fontan operations in patients with single ventricle. J THORAC CARDIOVASC SURG 1992;103:444-52. 4. Kopf GS, Laks H, Stansel HC, Hellenbrand WE, Kleinman CS, Talner NS. Thirty-year follow-up of superior vena cava-pulmonary artery (Glenn) shunts. J THoRAc CARDlOVASC SURG 1990;100:662-71. 4a. Gross GJ, Jonas RA, Castaneda AR, Hanley FL, Mayer JE, Bridges ND. Maturational and hemodynamic factors predictive of increased cyanosis following bidirectional cavopulmonary anastomosis. Am J Cardiol [In press]. 5. Moore JW, Kirby WC, Madden W A, Gaither NS. Development of pulmonary arteriovenous malformations after modified Fontan operation. J THORAC CARDIOVASC SURG 1989;98: I 045-50. 6. Lacroix J, Blanchard H, de Ville de Goyet J, Weber A, Vliers A, Otte JB. Reversal of cirrhosis-related pulmonary shunting in two children by orthotopic liver transplantation. Transplantation 1992;53: 1135-8. 7. Fontan F, Kirklin JW, Fernandez G, et al. Outcome after a "perfect" Fontan operation. Circulation 1990;81:152036. 8. Driscoll DJ, Offord KP, Feldt RH, Schaff HV, Puga FJ, Danielson GK. Five- to fifteen-year follow-up after Fontan operation. Circulation 1992;85:469-96. 9. Cromme-Dijkhuis AH, Hess J, Hiihlen K, et al. Specific sequelae after Fontan operation at mid- and long-term follow-up. J THoRAc CARDIOVASC SURG 1993;106:1126-32. 10. Dobell ARC, Trusler GA, Smallhorn JF, Williams WG. Atrial thrombi after the Fontan operation. Ann Thorac Surg 1986;42:664-7. II. Gewillig MH, Lundstrom UR, Bull C, Wyse RKH, Deanfield JE. Exercise responses in patient with congenital heart disease after Fontan repair: patterns and determinants of performance. J Am Coli CardioI1990;15:1424-32. 12. Bridges ND, Mayer JE, Lock JE, et al. Effect of fenestration on outcome of the modified Fontan repair. Circulation 1992;86:1762-9.
T
he traditional approach to the child with a single ventricle over the past 20 years has been a neonatal palliative operation followed by a Fontan procedure when pulmonary resistance is judged to be sufficiently low. Although the ideal age for the Fontan procedure was never clear, a completed ("nonfenestrated") Fontan-type circulation was generally believed to offer the best longterm quality of life to any child with a single ventricle. In 1988 my group' and others added the bidirectional Glenn shunt as an interim step in this pathway, especially for children who were considered to be at high risk for a onestep Fontan procedure, as was our experience with children with hypoplastic left heart syndrome. In 1989 an additional interim step was added in the form of the "fenestrated Fontan.'? Since that time I have been impressed by the excellent palliation achieved by these intermediate steps. In fact, the question as to when or even whether to proceed to the next step in the pathway is being asked of surgeons with increasing frequency by cardiologists and particularly by parents. Inherent inefficiency of the shunted/banded single ventricle
After a first-stage neonatal palliative procedure for single ventricle, whether it be a shunt, band, or more complex procedure such as a stage I Norwood procedure for hypoplastic left heart syndrome, the circulation is inherently inefficient because of recirculation of both pulmonary and systemic venous return. Pulmonary recirculation is particularly inefficient because pulmonary From the Department of Cardiac Surgery, The Children's Hospital, Boston, Mass. Received for publication Jan. 25, 1994. Accepted for publication March 16, 1994. Address for reprints: Richard A. Jonas, MD, Department of Cardiac Surgery, The Children's Hospital, 300 Longwood, Ave., Boston, MA02115. J 1HORAC CARDIOVASC SURG 1994;108:522-4 Copyright @ 1994 by Mosby-Year Book, Inc. 0022-5223/94 $3.00
522
+0
12/1/56250
venous blood is unable to collect more oxygen on a second pass through the lungs. On the other hand, recirculation of systemic venous return allows extraction of at least some of the residual oxygen in the systemic venous blood. Because of the decrease in pulmonary resistance with time, the proportion of the entire cardiac output passing to the lungs is likely to increase, that is, an increasing volume load for the single ventricle with no improvement in oxygen delivery to the body or even a decrease in oxygen delivery as systemic blood is stolen into the pulmonary circulation. Both the bidirectional Glenn shunt and Fontan shunt eliminate the inefficiency of pulmonary recirculation
The tendency has been to conceptualize the bidirectional Glenn shunt as physiologically equivalent to half a Fontan shunt. Some centers even use the term hemiFontan. Although this term may be appropriate if one thinks strictly in anatomic terms, it is not the case physiologically.Pulmonary recirculation is eliminated by both procedures. The only blood that passes to the lungs is systemic venous blood. Furthermore, any blood that has had a second pass through the systemic venous bed in the patient with a bidirectional Glenn circulation and is therefore more desaturated is able to take up a correspondingly greater amount of oxygen on its one pass through the lungs. However, this is not to say that the Fontan and bidirectional Glenn circulations are equivalent: in fact, fundamental differences exist that almost certainly will influence the late complications associated with these two forms of palliation. Differences between the nonfenestrated Fontan and bidirectional Glenn shunts
The arterial oxygen saturation in the patient with a completed Fontan operation is often about 95%, whereas it is usually closer to 85% with the bidirectional Glenn shunt. However, the price paid for the higher oxygen saturation with the Fontan operation is higher venous pressure in the right atrium, as well as in the hepatic, mesen-
The Journal of Thoracic and Cardiovascular Surgery Volume 108, Number 3
teric, and renal vascular beds. In addition, it was my clinical experience when I used to perform the completed Fontan operation that early postoperative cardiac output was often marginal, convalescence was slow, and pleural effusions lasting longer than 1 week occurred in 40% of patients.' In contrast, patients with a similar or greater risk profile undergoing a bidirectional Glenn shunt had a clinical appearance of greater cardiac output, hospitalization was commonly less than 1 week after the operation, and pleural effusions were rare. Late complications after bidirectional Glenn versus Fontan shunts The commonest problem after a bidirectional Glenn operation has been progressive cyanosis. Cyanosis may be due to the development of systemic venous collaterals that decompress the superior caval system into the inferior caval system: These collaterals can generally be dealt with successfully by coil embolization. A more troublesome problem may be the development of a pulmonary arteriovenous shunt. Although the very long-term experience with the classic Glenn shunt revealed a risk of formation of arteriovenous malformations that were amenable to coil embolization," my more recent short-term experience with the bidirectional Glenn shunt has been the formation of a diffuse arteriovenous shunt that is not readily amenable to coil embolization. Furthermore, analysis of our bidirectional Glenn experience" suggests that older age per se may be a risk factor for cyanosis, perhaps because of a lesser proportion of caval return from the superior vena cava relative to the inferior vena cava in the older child. Although scattered reports of pulmonary arteriovenous malformations after Fontan procedures have been published.' close analysis of these cases reveals that the arteriovenous malformations occurred in lungs that were not receiving hepatic venous blood. Presumably a hepatic factor exists that usually inhibits arteriovenous malformation. In support of this contention is the observation that pulmonary arteriovenous malformations tend to develop in patients with liver disease. Interestingly, liver transplantation has been associated with regression of arteriovenous malformations in at least two patients." Late problems with the Fontan circulation are due to the chronic elevation of intrabdominal venous pressure and right atrial pressure. Fontan and associates 7 described a rising late hazard function for death apparent 6 years after even a "perfect" Fontan operation. In their report describing 5 to 15 years' follow-up after the Fontan operation, Driscoll and colleagues'' from the Mayo Clinic described a 15% incidence of protein-losing enteropathy at 10 years, including some patients with cirrhosis. No useful management options were apparent
Jonas
523
for these difficult problems. In contrast, reports from Toronto and Yale4 describe a 10% incidence of pulmonary arteriovenous malformations at 10 years after classic Glenn shunts, and many of these were suitable for embolization. Supraventricular tachycardia after a Fontan procedure has been reported by a number of authors. Driscoll and coworkers" reported a 20% incidence between 5 and 15 years after the operation. Cromme-Dijkhuis and colleagues? found that 43% of patients had abnormalities on 24-hour ambulatory electrocardiograms at a median of 5 years after the operation. Other complications described after the Fontan procedure include stroke'' and right atrial thrombi.!? Exercise studies of patients late after the Fontan procedure have emphasized the limitation in cardiac output associated with exercise. l1 Oxygen delivery can be increased only by increasing oxygen extraction, with resulting profoundly low systemic venous saturation. I am not aware offormal exercise studies in which patients with a bidirectional Glenn shunt have been studied or compared with patients who have had the Fontan operation. Nevertheless, because the pulmonary and systemic vascular beds are not in series, it is likely that cardiac output can be increased more during exercise with the bidirectional Glenn circulation than with the Fontan circulation. Differences between the fenestrated and completed Fontan shunts Placement of a window in the baffle between the systemic and pulmonary venous atria as part of a Fontan procedure results in lower superior vena caval, inferior vena caval, and right atrial pressures.F Arterial oxygen saturation is lower, about 88% to 90%. By clinical assessment, cardiac output appears to be higher. Effusions lasting longer than 1 week occur in 10% of patients rather than 40%, and the duration of hospitalization is shorter. In theory, in these patients the cardiac output can be increased in response to exercise by shunting of blood right to left through the fenestration. Whether this shunting results in improved oxygen delivery is currently under study. The results of such studies will help to determine when or whether fenestrations should be closed. Strokes after single ventricle palliation One of the important risks of not completely separating the pulmonary and systemic venous returns is the risk that a systemic venous thrombus could embolize and cause a stroke or other systemic embolus. To date, this risk has not been clearly quantitated. Unfortunately, performance of a completed Fontan operation does not eliminate the risk of stroke' Perhaps thrombus forming on the
524
Jonas
pulmonary venous atrial side of the baffle or in the stump of the main pulmonary artery is the source of these emboli. This risk begs the question of the desirability of anticoagulation as a routine for all patients with single ventricle palliation. Conclusions
The various surgical options for single ventricle, including bidirectional Glenn, fenestrated Fontan, and completed Fontan circulations, are all palliative in nature with different advantages and disadvantages. The indications and timing for these options remain poorly defined. Careful, prospective, very long-term studies of late function and quality of life in patients with single ventricles of all forms are urgently needed. It is tempting to speculate that many patients may be best served by a longer period of palliation with the bidirectional Glenn shunt than is currently offered. Such a policy would shorten the total exposure of the intrabdominal organs and right atrium to elevated venous pressure with all its attendant late complications. Clearly, making such a change will be contingent on demonstration that this approach is not associated with an unacceptable risk of systemic embolism or permanent pulmonary damage caused by formation of diffuse arteriovenous malformations. In addition, the value of a permanently open fenestration after the Fontan procedure in allowing improved oxygen delivery during exercise also should be defined. REFERENCES I. Bridges ND, Jonas RA, Mayer JE, Flanagan MF, Keane JF, Castaneda AR. Bidirectional cavopulmonary anastomosis as interim palliation for high risk Fontan candidates. Circulation 1990;82(SuppI)IVI70-6. 2. Bridges ND, Lock JE, Castaneda AR. Baffle fenestration with subsequent transcatheter closure. Circulation 1990; 82:1681-9.
The Journal of Thoracic and Cardiovascular Surgery September 1994
3. Mayer JE, Bridges ND, Lock JE, Hanley FL, Jonas RA, Castaneda AR. Factors associated with marked reduction in mortality for Fontan operations in patients with single ventricle. J THORAC CARDIOVASC SURG 1992;103:444-52. 4. Kopf GS, Laks H, Stansel HC, Hellenbrand WE, Kleinman CS, Talner NS. Thirty-year follow-up of superior vena cava-pulmonary artery (Glenn) shunts. J THoRAc CARDlOVASC SURG 1990;100:662-71. 4a. Gross GJ, Jonas RA, Castaneda AR, Hanley FL, Mayer JE, Bridges ND. Maturational and hemodynamic factors predictive of increased cyanosis following bidirectional cavopulmonary anastomosis. Am J Cardiol [In press]. 5. Moore JW, Kirby WC, Madden W A, Gaither NS. Development of pulmonary arteriovenous malformations after modified Fontan operation. J THORAC CARDIOVASC SURG 1989;98: I 045-50. 6. Lacroix J, Blanchard H, de Ville de Goyet J, Weber A, Vliers A, Otte JB. Reversal of cirrhosis-related pulmonary shunting in two children by orthotopic liver transplantation. Transplantation 1992;53: 1135-8. 7. Fontan F, Kirklin JW, Fernandez G, et al. Outcome after a "perfect" Fontan operation. Circulation 1990;81:152036. 8. Driscoll DJ, Offord KP, Feldt RH, Schaff HV, Puga FJ, Danielson GK. Five- to fifteen-year follow-up after Fontan operation. Circulation 1992;85:469-96. 9. Cromme-Dijkhuis AH, Hess J, Hiihlen K, et al. Specific sequelae after Fontan operation at mid- and long-term follow-up. J THoRAc CARDIOVASC SURG 1993;106:1126-32. 10. Dobell ARC, Trusler GA, Smallhorn JF, Williams WG. Atrial thrombi after the Fontan operation. Ann Thorac Surg 1986;42:664-7. II. Gewillig MH, Lundstrom UR, Bull C, Wyse RKH, Deanfield JE. Exercise responses in patient with congenital heart disease after Fontan repair: patterns and determinants of performance. J Am Coli CardioI1990;15:1424-32. 12. Bridges ND, Mayer JE, Lock JE, et al. Effect of fenestration on outcome of the modified Fontan repair. Circulation 1992;86:1762-9.