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Towards the optimal Fontan operation: a single-institution experience
PEDIATRIC SURGERY
Towards the optimal Fontan operation: a singleinstitution experience
concentrated on the expansion of the original atriopulmonary connection model and its upgrade into the hydraulically more efficient total cavopulmonary connection model.4 Finally, the third era (1990 to the present day) has involved optimisation of the total cavopulmonary connection and a search for its best spatial arrangement. Over the last 25-year period, our group has actively participated in the quest for the ideal technical assemblage and clinical utilisation of the Fontan circulation with a number of both clinical and computational fluid dynamic studies. The following is a brief review of the contributions developed at Bambino Gesu` Children’s Hospital in Rome, Italy, which started around the middle of the second ‘Fontan era’.
Roberto M Di Donato Antonio Amodeo Mauro Grigioni
Abstract Many groups, including ours, have played a more or less significant role in the development and evolution of the Fontan operation that has taken place over the past four decades. This is a brief review of the contributions developed by our institution. Contributions to clinical and technical areas include: development of the ventricular exclusion concept; promoting the staged approach to the Fontan operation by bidirectional cavopulmonary anastomosis with or without a modified DamuseKayeeStansel anastomosis; endorsement of the total extracardiac cavopulmonary connection; a rational approach to the management of systemic venous aberrances in singleventricle patients; and criteria for transition to heart transplantation. Contributions to computational fluid dynamics include: investigation of the best spatial arrangement for the total extracardiac cavopulmonary anastomosis and identification of the so-called ‘beneficial vortex’; studies on the effect of unbalanced pulmonary resistances on the hydrodynamic performance of the total extracardiac cavopulmonary connection; and a rationale for the management of systemic venous anomalies in single-ventricle patients.
Clinical and technical contributions Ventricular exclusion Shortly after the introduction of the Fontan operation for tricuspid atresia, it became increasingly evident that the use of the atriopulmonary connection could be extended to the surgical treatment of a variety of otherwise anatomically uncorrectable univentricular5,6 and occasionally biventricular7 lesions (the modified Fontan operation). This was made possible by the addition of the so-called ventricular exclusion procedure, i.e. the combined obliteration of the atrial communication and of the right-sided atrioventricular valve. Originally, we anchored the occluding patch directly to the leaflets of the right atrioventricular valve with interrupted mattress sutures placed 1 mm away from the valve annulus. However, late dehiscence of the patch occurred in 3 of 5 patients treated by this technique. Therefore, it was decided to suture the ventricular exclusion patch onto the structurally more resilient atrial wall, about 5 mm away from the annulus of the right atrioventricular valve. This manoeuvre allowed the atrioventricular node to be avoided and exiled the coronary sinus onto the ventricular side of the patch but above the right atrioventricular valve, without haemodynamic consequences.8
Keywords bidirectional cavopulmonary anastomosis; Fontan operation; total cavopulmonary connection
Since its introduction for the treatment of tricuspid atresia in 1968, the Fontan operation has evolved into the universal surgical solution for the entire spectrum of functionally univentricular conditions, as well as for some very complex biventricular conditions.1 The historical development of the Fontan operation can be divided into three eras (Figure 1). The first era, between 1950 and 1975, focused on theorisation of the ‘dispensable right ventricle’ concept2 and culminated in clinical application of the Glenn shunt (1958)3 and the atriopulmonary anastomosis (Fontan operation; 1968e1971).1 The second era (1975e1990)
Staging towards a Fontan operation The results of initial surgical series of modified Fontan operations carried an unexpected rate of attrition at repair despite adherence to the classical ‘10 commandments’ of Fontan and Baudet.5,9 It was then realised that the circulatory pattern of all univentricular hearts, whether in their natural history or after a neonatal palliation, is one of recirculating parallel pulmonary and systemic flows. The ensuing chronic volume overload may induce progressive ventricular dilatation with increasing biomechanical wall stress and potentially irreversible changes in myocytic structure. The sudden application of a Fontan operation, which abruptly removes the excessive load, may determine an unfavourable geometric adjustment of the systemic ventricle that ultimately results in relative ventricular hypertrophy and secondary diastolic dysfunction.10 Somewhat empirically, borrowing from previous works of Haller et al.,11 Azzolina et al.,12 Hopkins et al.13 and Kawashima et al.,14 in 1985 we promoted the use of bidirectional cavopulmonary anastomosis (BCPA) as a staged or definitive palliation in candidates who were less than ideal for a Fontan operation. Only one death occurred among the first 18 high-risk
Roberto M Di Donato MD is Director of Cardiac Surgery Service of the Medical-Surgical Department of Paediatric Cardiology, Bambino Gesu` Children’s Hospital, Rome, Italy. Antonio Amodeo MD is Senior Associate of Cardiac Surgery Service of the Medical-Surgical Department of Paediatric Cardiology, Bambino Gesu` Children’s Hospital, Rome, Italy. Mauro Grigioni Eng is Director of the Laboratory of Biomedical Engineering, Superior Institute for Health, Rome, Italy.
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Era 2
Era 1 Fontan operation 1971
Total cavopulmonary connection 1988
Bidirectional Glenn 1966
.
1960
Historical breakthroughs
The dispensable RV 1975
Glenn shunt 1958
1950
Era 3
.
.
1970
BGH contributions
.
.
1985
1980
.
1990
‘Ventricular exclusion’ TECPC
‘An expanded horizon’
Bidir. Glenn ± Kaye anastomosis
1995
2000
‘Beneficial vortex’ Pulm. AV fistulas after Kawashima
2005
.
Confluent SVCs
HepaticHeart to-azygos transplant vein anastomosis
Figure 1 A schematic history of contributions to the surgical treatment of single-ventricle patients. AV, atrioventricular; BGH, Bambino Gesu` Children’s Hospital; RV, right ventricle; SVC, superior vena cava; TECPC, total extracardiac cavopulmonary connection.
patients, including four with interruption and azygos continuation of the inferior vena cava.15 We postulated that the BCPA ‘could avoid the sudden reduction of ventricular compliance that can be one of the reasons for failure of the Fontan principle in patients with a previous ventricular work load. The concept that the BCPA modulates the process of ventricular remodelling by partial volume unloading in single-ventricle patients has gained worldwide acceptance,16 and this procedure is now universally considered to be an obligatory intermediate step preparatory to a Fontan operation.17 In the case of concomitant systemic outflow obstruction and consequent pressure overload, the degree of relative ventricular hypertrophy is even more prominent, further exacerbating the unfavourable geometric adaptation of the systemic ventricle to volume unloading at the time of Fontan repair. In 1986, we began to combine the BCPA with a DamuseKayeeStansel anastomosis to bypass the subaortic obstruction, obtaining simultaneous volume and pressure unloading.18 The incorporation of the pulmonary artery root into the aortic reconstruction seemed preferable to either subaortic resection or the placement of a valved conduit between the ventricle and the ascending aorta due to the reduced risk of damaging the coronary arteries, the conducting tissue and the ventricular myocardium. A preliminary follow-up study on the first 23 patients showed no subaortic gradient at rest and a low enddiastolic ventricular pressure (a mean of 8 mmHg). Nine patients reached the Fontan stage with no hospital mortality, a major achievement considering the average worldwide early mortality of up to 40% for similar patients at that time.19
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Concerning the potential use of BCPA as a definitive palliation, we were soon dissuaded because of the frequent occurrence of pulmonary arteriovenous malformations and systemic-topulmonary collaterals beginning about 2 years after the procedure.20,21 This complication is possibly related to the lack of exposure of the pulmonary circulation to a putative hepatic or splanchnic vasoactive peptide carried only in the hepatic venous return, which is typically excluded in this cardiovascular arrangement.22 Therefore, we no longer endorse the use of BCPA as a definitive surgical solution for high-risk candidates for a Fontan operation, nor do we encourage the addition of an alternative source of pulmonary blood flow, since this necessarily imposes a largely unpredictable volume load that potentially neutralises the process of ventricular remodelling sought by staging the Fontan operation.23 The extracardiac total cavopulmonary connection In 1988, Mark de Leval introduced the revolutionary concept of a total cavopulmonary connection, i.e. a combination of a BCPA with a tubular intra-atrial baffle connecting the inferior vena cava to the pulmonary arteries (the lateral tunnel technique).4 The rationale for this approach is that directing the systemic venous flows as concentric laminar wedges along cylindrical conduits assures a considerably more efficient kinetic energy preservation than do the stagnating, spinning swirls in the atrial reservoir of the old-fashioned atriopulmonary anastomosis. This hydraulic behaviour intuitively translates into increased functional performance and longevity of the total cavopulmonary
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approach, and many failing atriopulmonary anastomoses are nowadays converted into this rather than the patient being diverted to heart transplantation. Furthermore, as it keeps away from the atrioventricular node and leaves the atrial chamber at low pressure, this technique both reduces the risk of early or late arrhythmias and minimises the risk of atrial thrombosis.4 Shortly after de Leval’s seminal contribution, Marcelletti et al., from our own institution, proposed extracardiac modification of the total cavopulmonary connection, with interposition of a prosthetic conduit between the inferior vena cava and the pulmonary artery.24 After initial scepticism, mostly due to the use of a cylindrical prosthesis without growth potential and to a potential risk for thrombosis, this surgical solution, also called the extracardiac Fontan procedure, has gained unanimous approval and is now the primary choice of Fontan operation worldwide. Virtually equivalent to the lateral tunnel technique in many aspects, the extracardiac Fontan approach has two main advantages: it is technically simpler and more reproducible, irrespective of the underlying anatomical complexity, and, more importantly, it is performed without aortic cross-clamping and may in fact even be performed without cardiopulmonary bypass.25 Furthermore, it avoids having prosthetic material inside the atrium. After 15 years of follow-up,26e28 the overall survival, functional status and cardiopulmonary performance of survivors of the extracardiac Fontan procedure compared favourably with other series of patients undergoing the lateral tunnel approach. Overall survival was, in fact, 85% and 92%, including and excluding operative deaths respectively. Seventy-seven per cent of survivors (127 of 165) were in New York Heart Association (NYHA) functional class I. The incidence of late major problems was also lower than that reported late after other Fontan-type operations (24%). Nineteen patients had arrhythmias (11%), 12 of which were bradyarrhythmias and 7 tachyarrhythmias. Five patients (3%), in the initial part of the series, but none in the prevalent and more recent group with a polytetrafluoroethylene conduit, had obstruction of the extracardiac conduit. Six patients (3.5%) had acquired stenosis of the left pulmonary artery. Five patients experienced ventricular failure (3%), leading to heart transplantation in three. Proteinlosing enteropathy was found in two patients (1%). The incidence of late reintervention was 12.7% (21 of 165 patients, including 15 epicardial pacemaker implantations). Four patients died (2.3%), two after heart transplantation.28
1. The ‘unifocal’ bilateral BCPA is a Y-shaped side-by-side anastomosis of the two caval stumps under the aortic arch to form a single superior vena cava that is subsequently anastomosed end-to-side to the top of the pulmonary artery confluence.29 Six infants received this surgical solution, with one hospital death possibly related to an underestimated collateral pulmonary venous problem. 2. The hepato-azygous venous connection, first reported by Baskett et al.,31 is the direct anastomosis of an atrial cuff collecting all hepatic veins to the adjacent segment of the azygos/hemiazygos vein.30 Five patients underwent this procedure, one during the Kawashima anastomosis. All patients survived the operation. At a mean follow-up of 15.6 7.40 months (4e24 months) after unifocal bilateral BCPA and of 38.7 13.2 months (25.1e 60.0 months) after direct hepato-azygos venous connection, respectively, all patients are in NYHA class I.40 High-risk Fontan patients and transition to heart transplantation Orthotopic heart transplantation remains the ultimate resort for failing single-ventricle physiology, but in our experience it has entailed a substantial early mortality rate (68.0 9.3%). Between 1988 and 2002, 25 single-ventricle patients (mean age 9.3 7.1 years) underwent heart transplantation. Transition to heart transplantation occurred from a shunt stage in 10, from a BCPA stage in 9, and after Fontan failure in 6. Heart transplantation following BCPA showed 100% long-term survival, as opposed to 66.7 15.7% survival for patients after a systemic-topulmonary shunt, and 33.3 19.2% for those following failing a Fontan procedure ( p ¼ 0.032). Regression logistic modelling indicated a failing Fontan circulation as a predictor of higher mortality after orthotopic heart transplantation ( p ¼ 0.041). Therefore, we believe that replacement therapy should be considered in the decision-making process as an alternative to Fontan completion in high-risk candidates.32,33
Computational fluid dynamic studies Since de Leval’s original contribution, the science of computational fluid dynamics has become a valued auxiliary tool in the pursuit of the best design and hydraulic performance for cavopulmonary connections to compensate for the lack of a pulmonary ventricular pump.34,35 As recently pointed out by Bove et al., the ideal cavopulmonary connection should have minimal energy loss, potential for growth and equivalent vena caval and hepatic vein distribution to both lungs.36
Management of systemic venous anomalies Aberrant systemic venous connections may endanger the outcome of conventional cavopulmonary anastomoses. We have focused our attention on two conditions in particular: bilateral superior vena cava and interruption/azygos continuation of the inferior vena cava. A bilateral bidirectional Glenn anastomosis may, in fact, trigger both thrombosis and unfavourable growth of the central pulmonary arteries,29 whereas the so-called Kawashima operation, employed for single-ventricle and azygos continuation of the inferior vena cava, may produce both pulmonary arteriovenous malformations, in the case of isolated cavopulmonary anastomosis, and hepatic-vein-to-pulmonary artery channel thrombosis at eventual Fontan completion.30 Recently, we adopted two innovative surgical approaches addressing these systemic venous ‘anomalies’ in single-ventricle patients:
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‘Beneficial vortex’ and best spatial arrangement The best spatial arrangement of a total cavopulmonary connection remains controversial. Based on our clinical experience with total extracardiac Fontan procedures, we performed quantitative and qualitative flow analysis on two in vitro models simulating the most frequent arrangements applied to our patients. Two main groups were identified among 110 patients undergoing total extracardiac cavopulmonary connection: type 1, those with leftsided inferior vena cava anastomosis, and type 2, those with facing superior and inferior vena cava anastomoses. Flow measurements, a power dissipation study and a finite-element numerical simulation were carried out.
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Conclusion
A total extracardiac cavopulmonary connection with left-sided diversion of the inferior vena caval conduit anastomosis was characterised by a central vortex and a weakly dissipative recirculating zone regulating the caval flow partitioning and modulating the flow distribution into the pulmonary arteries. This ‘beneficial vortex’ provides a more favourable energy-saving pattern than is seen with the total extracardiac cavopulmonary connection with directly opposed cavopulmonary anastomoses.37,38
In the four decades of its history, the Fontan operation has undergone an impressive number of technical, clinical and philosophical advancements and has become established as the only and very reasonable conventional surgical option for patients with highly complex congenital heart anomalies, particularly those with a univentricular heart. Many groups, including ours, have more or less significantly contributed to progress in this field, based on a mix of clinical experience, surgical ingenuity and parallel laboratory work. The issue in the future will be to see how much we can further improve the longterm functional outcome of these patients, relying on a pumpless cavopulmonary circulation.
Effect of unbalanced pulmonary resistances on hydrodynamic performance In the presence of unbalanced pulmonary resistances, a slight flow acceleration with recirculation may be observed due to the increased flow rate in one of the two pulmonary arteries. Therefore, in the asymmetrical total extracardiac cavopulmonary connection, the collision and interaction of caval flows results in kinetic energy losses and viscous dissipation that decreases fluid dynamic efficiency. The results of our numerical investigations showed that a higher resistance in the left pulmonary artery caused the greater loss of hydraulic power for the total cavopulmonary connection under study, while a minimum loss was seen after balancing the pulmonary resistances and, consequently, the flow repartition towards the lungs. Based on this observation, we endorse the use of the transvenous stenting technique in the cases with branch pulmonary artery stenosis, particularly of the left pulmonary artery.39
Conflict of interest None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper. A
REFERENCES 1 Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971; 26: 240e8. 2 Sade RM, Castaneda AR. The dispensable right ventricle. Surgery 1975; 77: 624e31. 3 Glenn WW. Circulatory bypass of the right side of the heart. IV. Shunt between superior vena cava and distal right pulmonary artery; report of clinical application. N Engl J Med 1958; 259: 117e20. 4 de Leval MR, Kilner P, Gewillig M, Bull C. Total cavopulmonary connection: a logical alternative to atriopulmonary connection for complex Fontan operations. Experimental studies and early clinical experience. J Thorac Cardiovasc Surg 1988; 96: 682e95. 5 Marcelletti C, Mazzera E, Olthof H, et al. Fontan’s operation: an expanded horizon. J Thorac Cardiovasc Surg 1980; 80: 764e9. 6 Corno A, Becker AE, Bulterijs AH, et al. Univentricular heart: can we alter the natural history? Ann Thorac Surg 1982; 34: 716e27. ¨ren DR, Schuilenburg RM, Becker AE. Fontan’s 7 Marcelletti C, Du operation for Ebstein’s anomaly. J Thorac Cardiovasc Surg 1980; 79: 63e6. 8 Di Donato RM, Becker AE, Nijveld A, et al. Ventricular exclusion during Fontan operation: an evolving technique. Ann Thorac Surg 1985; 39: 283e5. 9 Gale AW, Danielson GK, McGoon DC, Mair DD. Modified Fontan operation for univentricular heart and complicated congenital lesions. J Thorac Cardiovasc Surg 1979; 78: 831e8. 10 Di Donato RM. The Fontan operation 30 years later. Cardiol Young 2004; 14(Suppl 3): 66e70. 11 Haller JA, Adkins JC, Rauenhorst J. Total bypass of the superior vena cava into both lungs. Surg Forum 1964; 15: 264e5. 12 Azzolina G, Eufrate S, Pensa P. Tricuspid atresia: experience in surgical management with a modified cavopulmonary anastomosis. Thorax 1972; 27: 111e5. 13 Hopkins RA, Armstrong BE, Serwer GA, Peterson RJ, Oldham Jr HN. Physiological rationale for a bidirectional cavo-pulmonary shunt. J Thorac Cardiovasc Surg 1985; 90: 391e8. 14 Kawashima Y, Kitamura S, Matsuda H, et al. Total cavopulmonary shunt operation in complex cardiac anomalies. A new operation. J Thorac Cardiovasc Surg 1984; 87: 74e81.
Rationale for the management of systemic venous anomalies in single-ventricle patients The reported application of two innovative surgical techniques for the enhanced management of systemic venous anomalies in single-ventricle patients was supported by computational fluid dynamic studies, currently in publication. From these studies, we derived two basic principles: 1. The venous unifocalisation principle, achieved by side-byside anastomosis between transected bilateral superior venae cavae, or by end-to-side anastomosis between the hepatic veins and the nearby segment of azygos vein, essentially reproduces the normal anatomical pattern of the systemic venous system in which all tributaries converge, at a more or less acute angle, into vessels of progressively larger calibre. Furthermore, it presumably takes advantage of the ensuing flow enhancement effect in the downstream vessels, typically characterised by increased flow output, streamlined flow pattern and possibly increased flow velocity rate. 2. The cavopulmonary polarisation principle pursues the best spatial arrangement of opposite caval channels connecting to the pulmonary arteries, by avoiding fluid collision and minimising power dissipation. The rationale for a unifocal bilateral BCPA is that a single and centrally located cavopulmonary connection provides an unopposed and symmetrical bilateral distribution of pulmonary blood flow, allowing growth of the central pulmonary arteries and preventing thrombus formation. In the case of a direct hepato-azygous connection, the ‘unifocalisation’ of the hepatic venous return and the ‘unipolarisation’ of the whole systemic venous return (i.e. the single cavopulmonary anastomosis) prevent the problem of flow unbalance and collision that is typically seen in the old-fashioned hepatic vein-to-pulmonary artery conduit.
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15 Mazzera E, Corno A, Picardo S, et al. Bidirectional cavopulmonary shunts: clinical applications as staged or definitive palliation. Ann Thorac Surg 1989; 47: 415e20. 16 Rychik J, Jacobs ML, Norwood Jr WI. Acute changes in left ventricular geometry after volume reduction operation. Ann Thorac Surg 1995; 60: 1267e73. discussion 1274. 17 Albanese SB, Carotti A, Di Donato RM, et al. Bidirectional cavopulmonary anastomosis in patients under two years of age. J Thorac Cardiovasc Surg 1992; 104: 904e9. 18 Di Donato R, Di Carlo DC, Giannico S, Marcelletti C. Palliation of complex cardiac anomalies with subaortic obstruction: new operative approach. J Am Coll Cardiol 1989; 13: 406e12. 19 Di Donato RM, Amodeo A, di Carlo DD, et al. Staged Fontan operation for complex cardiac anomalies with subaortic obstruction. J Thorac Cardiovasc Surg 1993; 105: 398e404. discussion 404e5. 20 Amodeo A, Di Donato R, Carotti A, Marino B, Marcelletti C. Pulmonary arteriovenous fistulas and polysplenia syndrome. J Thorac Cardiovasc Surg 1994; 107: 1378e9. 21 McElhinney DB, Reddy VM, Tworetzky W, Petrossian E, Hanley FL, Moore P. Incidence and implications of systemic to pulmonary collaterals after bidirectional cavopulmonary anastomosis. Ann Thorac Surg 2000; 69: 1222e8. 22 Ikai A, Riemer RK, Ma X, Reinhartz O, Hanley FL, Reddy VM. Pulmonary expression of the hepatocyte growth factor receptor c-Met shifts from medial to intimal layer after cavopulmonary anastomosis. J Thorac Cardiovasc Surg 2004; 127: 1442e9. 23 Di Donato RM. Invited commentary. Ann Thorac Surg 2005; 79: 36e7 [on: Berdat PA, Belli E, Lacour-Gayet F, Planche C, Serraf A. Additional pulmonary blood flow has no adverse effect on outcome after bidirectional cavopulmonary anastomosis. Ann Thorac Surg 2005; 79: 29e36.]. 24 Marcelletti C, Corno A, Giannico S, Marino B. Inferior vena cavapulmonary artery extracardiac conduit. A new form of right heart bypass. J Thorac Cardiovasc Surg 1990; 100: 228e32. 25 Shiraishi S, Uemura H, Kagisaki K, Koh M, Yagihara T, Kitamura S. The off-pump Fontan procedure by simply cross-clamping the inferior caval vein. Ann Thorac Surg 2005; 79: 2083e7. discussion 2087e8. 26 Giannico S, Corno A, Marino B, et al. Total extracardiac right heart bypass. Circulation 1992; 86(5 Suppl): II110e7. 27 Amodeo A, Galletti L, Marianeschi S, et al. Extracardiac Fontan operation for complex cardiac anomalies: seven years’ experience. J Thorac Cardiovasc Surg 1997; 114: 1020e30 [discussion 1030e1]. 28 Giannico S, Hammad F, Amodeo A, et al. Clinical outcome of 193 extracardiac Fontan patients: the first 15 years. J Am Coll Cardiol 2006; 47: 2065e73.
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29 Amodeo A, Di Donato RM. The unifocal bilateral bidirectional cavopulmonary anastomosis. Ann Thorac Surg 2007; 84: 2134e5. 30 Amodeo A, Di Carlo D, Grigioni M, De Santis M, Di Donato RM. Early primary Kawashima operation combined with direct hepatic vein-toazygos vein connection: a new logical approach. J Thorac Cardiovasc Surg 2005; 129: 949e50. 31 Baskett RJ, Ross DB, Warren AE, Sharratt GP, Murphy DA. Hepatic vein to the azygous vein anastomosis for pulmonary arteriovenous fistulae. Ann Thorac Surg 1999; 68: 232e3. 32 Michielon G, Parisi F, Di Carlo D, et al. Orthotopic heart transplantation for failing single ventricle physiology. Eur J Cardiothorac Surg 2003; 24: 502e10 [discussion 510]. 33 Michielon G, Parisi F, Squitieri C, et al. Orthotopic heart transplantation for congenital heart disease: an alternative for high-risk Fontan candidates? Circulation 2003; 108(Suppl 1): II140e9. 34 de Leval MR, Dubini G, Migliavacca F, et al. Use of computational fluid dynamics in the design of surgical procedures: application to the study of competitive flows in cavo-pulmonary connections. J Thorac Cardiovasc Surg 1996; 111: 502e13. 35 Sharma S, Goudy S, Walker P, et al. In vitro flow experiments for determination of optimal geometry of total cavopulmonary connection for surgical repair of children with functional single ventricle. J Am Coll Cardiol 1996; 27: 1264e9. 36 Bove EL, de Leval MR, Migliavacca F, Balossino R, Dubini G. Toward optimal hemodynamics: computer modeling of the fontan circuit. Pediatr Cardiol 2007; 28: 477e81. 37 Amodeo A, Grigioni M, Oppido G, et al. The beneficial vortex and best spatial arrangement in total extracardiac cavopulmonary connection. J Thorac Cardiovasc Surg 2002; 124: 471e8. 38 Amodeo A, Grigioni M, D’Avenio G, Daniele C, Di Donato RM. The patterns of flow in the total extracardiac cavopulmonary connection. Cardiol Young 2004; 14(Suppl 3): 53e6. 39 Grigioni M, Amodeo A, Daniele C, D’Avenio G, Formigari R, Di Donato RM. Particle image velocimetry analysis of the flow field in the total cavopulmonary connection. Artif Organs 2000; 24: 946e52. 40 Amodeo A, Grigioni M, Filippelli S, et al. Improved management of systemic venous anomalies in single ventricle: new rationale. J Thorac Cardiovasc Surg, in press.
Acknowledgment We are indebted to Dr Carlo Marcelletti, who started and contributed greatly to our achievements in the quest for the ‘ideal’ Fontan operation.
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Towards the optimal Fontan operation: a singleinstitution experience
concentrated on the expansion of the original atriopulmonary connection model and its upgrade into the hydraulically more efficient total cavopulmonary connection model.4 Finally, the third era (1990 to the present day) has involved optimisation of the total cavopulmonary connection and a search for its best spatial arrangement. Over the last 25-year period, our group has actively participated in the quest for the ideal technical assemblage and clinical utilisation of the Fontan circulation with a number of both clinical and computational fluid dynamic studies. The following is a brief review of the contributions developed at Bambino Gesu` Children’s Hospital in Rome, Italy, which started around the middle of the second ‘Fontan era’.
Roberto M Di Donato Antonio Amodeo Mauro Grigioni
Abstract Many groups, including ours, have played a more or less significant role in the development and evolution of the Fontan operation that has taken place over the past four decades. This is a brief review of the contributions developed by our institution. Contributions to clinical and technical areas include: development of the ventricular exclusion concept; promoting the staged approach to the Fontan operation by bidirectional cavopulmonary anastomosis with or without a modified DamuseKayeeStansel anastomosis; endorsement of the total extracardiac cavopulmonary connection; a rational approach to the management of systemic venous aberrances in singleventricle patients; and criteria for transition to heart transplantation. Contributions to computational fluid dynamics include: investigation of the best spatial arrangement for the total extracardiac cavopulmonary anastomosis and identification of the so-called ‘beneficial vortex’; studies on the effect of unbalanced pulmonary resistances on the hydrodynamic performance of the total extracardiac cavopulmonary connection; and a rationale for the management of systemic venous anomalies in single-ventricle patients.
Clinical and technical contributions Ventricular exclusion Shortly after the introduction of the Fontan operation for tricuspid atresia, it became increasingly evident that the use of the atriopulmonary connection could be extended to the surgical treatment of a variety of otherwise anatomically uncorrectable univentricular5,6 and occasionally biventricular7 lesions (the modified Fontan operation). This was made possible by the addition of the so-called ventricular exclusion procedure, i.e. the combined obliteration of the atrial communication and of the right-sided atrioventricular valve. Originally, we anchored the occluding patch directly to the leaflets of the right atrioventricular valve with interrupted mattress sutures placed 1 mm away from the valve annulus. However, late dehiscence of the patch occurred in 3 of 5 patients treated by this technique. Therefore, it was decided to suture the ventricular exclusion patch onto the structurally more resilient atrial wall, about 5 mm away from the annulus of the right atrioventricular valve. This manoeuvre allowed the atrioventricular node to be avoided and exiled the coronary sinus onto the ventricular side of the patch but above the right atrioventricular valve, without haemodynamic consequences.8
Keywords bidirectional cavopulmonary anastomosis; Fontan operation; total cavopulmonary connection
Since its introduction for the treatment of tricuspid atresia in 1968, the Fontan operation has evolved into the universal surgical solution for the entire spectrum of functionally univentricular conditions, as well as for some very complex biventricular conditions.1 The historical development of the Fontan operation can be divided into three eras (Figure 1). The first era, between 1950 and 1975, focused on theorisation of the ‘dispensable right ventricle’ concept2 and culminated in clinical application of the Glenn shunt (1958)3 and the atriopulmonary anastomosis (Fontan operation; 1968e1971).1 The second era (1975e1990)
Staging towards a Fontan operation The results of initial surgical series of modified Fontan operations carried an unexpected rate of attrition at repair despite adherence to the classical ‘10 commandments’ of Fontan and Baudet.5,9 It was then realised that the circulatory pattern of all univentricular hearts, whether in their natural history or after a neonatal palliation, is one of recirculating parallel pulmonary and systemic flows. The ensuing chronic volume overload may induce progressive ventricular dilatation with increasing biomechanical wall stress and potentially irreversible changes in myocytic structure. The sudden application of a Fontan operation, which abruptly removes the excessive load, may determine an unfavourable geometric adjustment of the systemic ventricle that ultimately results in relative ventricular hypertrophy and secondary diastolic dysfunction.10 Somewhat empirically, borrowing from previous works of Haller et al.,11 Azzolina et al.,12 Hopkins et al.13 and Kawashima et al.,14 in 1985 we promoted the use of bidirectional cavopulmonary anastomosis (BCPA) as a staged or definitive palliation in candidates who were less than ideal for a Fontan operation. Only one death occurred among the first 18 high-risk
Roberto M Di Donato MD is Director of Cardiac Surgery Service of the Medical-Surgical Department of Paediatric Cardiology, Bambino Gesu` Children’s Hospital, Rome, Italy. Antonio Amodeo MD is Senior Associate of Cardiac Surgery Service of the Medical-Surgical Department of Paediatric Cardiology, Bambino Gesu` Children’s Hospital, Rome, Italy. Mauro Grigioni Eng is Director of the Laboratory of Biomedical Engineering, Superior Institute for Health, Rome, Italy.
PAEDIATRICS AND CHILD HEALTH 19:S1
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PEDIATRIC SURGERY
Era 2
Era 1 Fontan operation 1971
Total cavopulmonary connection 1988
Bidirectional Glenn 1966
.
1960
Historical breakthroughs
The dispensable RV 1975
Glenn shunt 1958
1950
Era 3
.
.
1970
BGH contributions
.
.
1985
1980
.
1990
‘Ventricular exclusion’ TECPC
‘An expanded horizon’
Bidir. Glenn ± Kaye anastomosis
1995
2000
‘Beneficial vortex’ Pulm. AV fistulas after Kawashima
2005
.
Confluent SVCs
HepaticHeart to-azygos transplant vein anastomosis
Figure 1 A schematic history of contributions to the surgical treatment of single-ventricle patients. AV, atrioventricular; BGH, Bambino Gesu` Children’s Hospital; RV, right ventricle; SVC, superior vena cava; TECPC, total extracardiac cavopulmonary connection.
patients, including four with interruption and azygos continuation of the inferior vena cava.15 We postulated that the BCPA ‘could avoid the sudden reduction of ventricular compliance that can be one of the reasons for failure of the Fontan principle in patients with a previous ventricular work load. The concept that the BCPA modulates the process of ventricular remodelling by partial volume unloading in single-ventricle patients has gained worldwide acceptance,16 and this procedure is now universally considered to be an obligatory intermediate step preparatory to a Fontan operation.17 In the case of concomitant systemic outflow obstruction and consequent pressure overload, the degree of relative ventricular hypertrophy is even more prominent, further exacerbating the unfavourable geometric adaptation of the systemic ventricle to volume unloading at the time of Fontan repair. In 1986, we began to combine the BCPA with a DamuseKayeeStansel anastomosis to bypass the subaortic obstruction, obtaining simultaneous volume and pressure unloading.18 The incorporation of the pulmonary artery root into the aortic reconstruction seemed preferable to either subaortic resection or the placement of a valved conduit between the ventricle and the ascending aorta due to the reduced risk of damaging the coronary arteries, the conducting tissue and the ventricular myocardium. A preliminary follow-up study on the first 23 patients showed no subaortic gradient at rest and a low enddiastolic ventricular pressure (a mean of 8 mmHg). Nine patients reached the Fontan stage with no hospital mortality, a major achievement considering the average worldwide early mortality of up to 40% for similar patients at that time.19
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Concerning the potential use of BCPA as a definitive palliation, we were soon dissuaded because of the frequent occurrence of pulmonary arteriovenous malformations and systemic-topulmonary collaterals beginning about 2 years after the procedure.20,21 This complication is possibly related to the lack of exposure of the pulmonary circulation to a putative hepatic or splanchnic vasoactive peptide carried only in the hepatic venous return, which is typically excluded in this cardiovascular arrangement.22 Therefore, we no longer endorse the use of BCPA as a definitive surgical solution for high-risk candidates for a Fontan operation, nor do we encourage the addition of an alternative source of pulmonary blood flow, since this necessarily imposes a largely unpredictable volume load that potentially neutralises the process of ventricular remodelling sought by staging the Fontan operation.23 The extracardiac total cavopulmonary connection In 1988, Mark de Leval introduced the revolutionary concept of a total cavopulmonary connection, i.e. a combination of a BCPA with a tubular intra-atrial baffle connecting the inferior vena cava to the pulmonary arteries (the lateral tunnel technique).4 The rationale for this approach is that directing the systemic venous flows as concentric laminar wedges along cylindrical conduits assures a considerably more efficient kinetic energy preservation than do the stagnating, spinning swirls in the atrial reservoir of the old-fashioned atriopulmonary anastomosis. This hydraulic behaviour intuitively translates into increased functional performance and longevity of the total cavopulmonary
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approach, and many failing atriopulmonary anastomoses are nowadays converted into this rather than the patient being diverted to heart transplantation. Furthermore, as it keeps away from the atrioventricular node and leaves the atrial chamber at low pressure, this technique both reduces the risk of early or late arrhythmias and minimises the risk of atrial thrombosis.4 Shortly after de Leval’s seminal contribution, Marcelletti et al., from our own institution, proposed extracardiac modification of the total cavopulmonary connection, with interposition of a prosthetic conduit between the inferior vena cava and the pulmonary artery.24 After initial scepticism, mostly due to the use of a cylindrical prosthesis without growth potential and to a potential risk for thrombosis, this surgical solution, also called the extracardiac Fontan procedure, has gained unanimous approval and is now the primary choice of Fontan operation worldwide. Virtually equivalent to the lateral tunnel technique in many aspects, the extracardiac Fontan approach has two main advantages: it is technically simpler and more reproducible, irrespective of the underlying anatomical complexity, and, more importantly, it is performed without aortic cross-clamping and may in fact even be performed without cardiopulmonary bypass.25 Furthermore, it avoids having prosthetic material inside the atrium. After 15 years of follow-up,26e28 the overall survival, functional status and cardiopulmonary performance of survivors of the extracardiac Fontan procedure compared favourably with other series of patients undergoing the lateral tunnel approach. Overall survival was, in fact, 85% and 92%, including and excluding operative deaths respectively. Seventy-seven per cent of survivors (127 of 165) were in New York Heart Association (NYHA) functional class I. The incidence of late major problems was also lower than that reported late after other Fontan-type operations (24%). Nineteen patients had arrhythmias (11%), 12 of which were bradyarrhythmias and 7 tachyarrhythmias. Five patients (3%), in the initial part of the series, but none in the prevalent and more recent group with a polytetrafluoroethylene conduit, had obstruction of the extracardiac conduit. Six patients (3.5%) had acquired stenosis of the left pulmonary artery. Five patients experienced ventricular failure (3%), leading to heart transplantation in three. Proteinlosing enteropathy was found in two patients (1%). The incidence of late reintervention was 12.7% (21 of 165 patients, including 15 epicardial pacemaker implantations). Four patients died (2.3%), two after heart transplantation.28
1. The ‘unifocal’ bilateral BCPA is a Y-shaped side-by-side anastomosis of the two caval stumps under the aortic arch to form a single superior vena cava that is subsequently anastomosed end-to-side to the top of the pulmonary artery confluence.29 Six infants received this surgical solution, with one hospital death possibly related to an underestimated collateral pulmonary venous problem. 2. The hepato-azygous venous connection, first reported by Baskett et al.,31 is the direct anastomosis of an atrial cuff collecting all hepatic veins to the adjacent segment of the azygos/hemiazygos vein.30 Five patients underwent this procedure, one during the Kawashima anastomosis. All patients survived the operation. At a mean follow-up of 15.6 7.40 months (4e24 months) after unifocal bilateral BCPA and of 38.7 13.2 months (25.1e 60.0 months) after direct hepato-azygos venous connection, respectively, all patients are in NYHA class I.40 High-risk Fontan patients and transition to heart transplantation Orthotopic heart transplantation remains the ultimate resort for failing single-ventricle physiology, but in our experience it has entailed a substantial early mortality rate (68.0 9.3%). Between 1988 and 2002, 25 single-ventricle patients (mean age 9.3 7.1 years) underwent heart transplantation. Transition to heart transplantation occurred from a shunt stage in 10, from a BCPA stage in 9, and after Fontan failure in 6. Heart transplantation following BCPA showed 100% long-term survival, as opposed to 66.7 15.7% survival for patients after a systemic-topulmonary shunt, and 33.3 19.2% for those following failing a Fontan procedure ( p ¼ 0.032). Regression logistic modelling indicated a failing Fontan circulation as a predictor of higher mortality after orthotopic heart transplantation ( p ¼ 0.041). Therefore, we believe that replacement therapy should be considered in the decision-making process as an alternative to Fontan completion in high-risk candidates.32,33
Computational fluid dynamic studies Since de Leval’s original contribution, the science of computational fluid dynamics has become a valued auxiliary tool in the pursuit of the best design and hydraulic performance for cavopulmonary connections to compensate for the lack of a pulmonary ventricular pump.34,35 As recently pointed out by Bove et al., the ideal cavopulmonary connection should have minimal energy loss, potential for growth and equivalent vena caval and hepatic vein distribution to both lungs.36
Management of systemic venous anomalies Aberrant systemic venous connections may endanger the outcome of conventional cavopulmonary anastomoses. We have focused our attention on two conditions in particular: bilateral superior vena cava and interruption/azygos continuation of the inferior vena cava. A bilateral bidirectional Glenn anastomosis may, in fact, trigger both thrombosis and unfavourable growth of the central pulmonary arteries,29 whereas the so-called Kawashima operation, employed for single-ventricle and azygos continuation of the inferior vena cava, may produce both pulmonary arteriovenous malformations, in the case of isolated cavopulmonary anastomosis, and hepatic-vein-to-pulmonary artery channel thrombosis at eventual Fontan completion.30 Recently, we adopted two innovative surgical approaches addressing these systemic venous ‘anomalies’ in single-ventricle patients:
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‘Beneficial vortex’ and best spatial arrangement The best spatial arrangement of a total cavopulmonary connection remains controversial. Based on our clinical experience with total extracardiac Fontan procedures, we performed quantitative and qualitative flow analysis on two in vitro models simulating the most frequent arrangements applied to our patients. Two main groups were identified among 110 patients undergoing total extracardiac cavopulmonary connection: type 1, those with leftsided inferior vena cava anastomosis, and type 2, those with facing superior and inferior vena cava anastomoses. Flow measurements, a power dissipation study and a finite-element numerical simulation were carried out.
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Conclusion
A total extracardiac cavopulmonary connection with left-sided diversion of the inferior vena caval conduit anastomosis was characterised by a central vortex and a weakly dissipative recirculating zone regulating the caval flow partitioning and modulating the flow distribution into the pulmonary arteries. This ‘beneficial vortex’ provides a more favourable energy-saving pattern than is seen with the total extracardiac cavopulmonary connection with directly opposed cavopulmonary anastomoses.37,38
In the four decades of its history, the Fontan operation has undergone an impressive number of technical, clinical and philosophical advancements and has become established as the only and very reasonable conventional surgical option for patients with highly complex congenital heart anomalies, particularly those with a univentricular heart. Many groups, including ours, have more or less significantly contributed to progress in this field, based on a mix of clinical experience, surgical ingenuity and parallel laboratory work. The issue in the future will be to see how much we can further improve the longterm functional outcome of these patients, relying on a pumpless cavopulmonary circulation.
Effect of unbalanced pulmonary resistances on hydrodynamic performance In the presence of unbalanced pulmonary resistances, a slight flow acceleration with recirculation may be observed due to the increased flow rate in one of the two pulmonary arteries. Therefore, in the asymmetrical total extracardiac cavopulmonary connection, the collision and interaction of caval flows results in kinetic energy losses and viscous dissipation that decreases fluid dynamic efficiency. The results of our numerical investigations showed that a higher resistance in the left pulmonary artery caused the greater loss of hydraulic power for the total cavopulmonary connection under study, while a minimum loss was seen after balancing the pulmonary resistances and, consequently, the flow repartition towards the lungs. Based on this observation, we endorse the use of the transvenous stenting technique in the cases with branch pulmonary artery stenosis, particularly of the left pulmonary artery.39
Conflict of interest None of the authors of this paper has a financial or personal relationship with other people or organisations that could inappropriately influence or bias the content of the paper. A
REFERENCES 1 Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971; 26: 240e8. 2 Sade RM, Castaneda AR. The dispensable right ventricle. Surgery 1975; 77: 624e31. 3 Glenn WW. Circulatory bypass of the right side of the heart. IV. Shunt between superior vena cava and distal right pulmonary artery; report of clinical application. N Engl J Med 1958; 259: 117e20. 4 de Leval MR, Kilner P, Gewillig M, Bull C. Total cavopulmonary connection: a logical alternative to atriopulmonary connection for complex Fontan operations. Experimental studies and early clinical experience. J Thorac Cardiovasc Surg 1988; 96: 682e95. 5 Marcelletti C, Mazzera E, Olthof H, et al. Fontan’s operation: an expanded horizon. J Thorac Cardiovasc Surg 1980; 80: 764e9. 6 Corno A, Becker AE, Bulterijs AH, et al. Univentricular heart: can we alter the natural history? Ann Thorac Surg 1982; 34: 716e27. ¨ren DR, Schuilenburg RM, Becker AE. Fontan’s 7 Marcelletti C, Du operation for Ebstein’s anomaly. J Thorac Cardiovasc Surg 1980; 79: 63e6. 8 Di Donato RM, Becker AE, Nijveld A, et al. Ventricular exclusion during Fontan operation: an evolving technique. Ann Thorac Surg 1985; 39: 283e5. 9 Gale AW, Danielson GK, McGoon DC, Mair DD. Modified Fontan operation for univentricular heart and complicated congenital lesions. J Thorac Cardiovasc Surg 1979; 78: 831e8. 10 Di Donato RM. The Fontan operation 30 years later. Cardiol Young 2004; 14(Suppl 3): 66e70. 11 Haller JA, Adkins JC, Rauenhorst J. Total bypass of the superior vena cava into both lungs. Surg Forum 1964; 15: 264e5. 12 Azzolina G, Eufrate S, Pensa P. Tricuspid atresia: experience in surgical management with a modified cavopulmonary anastomosis. Thorax 1972; 27: 111e5. 13 Hopkins RA, Armstrong BE, Serwer GA, Peterson RJ, Oldham Jr HN. Physiological rationale for a bidirectional cavo-pulmonary shunt. J Thorac Cardiovasc Surg 1985; 90: 391e8. 14 Kawashima Y, Kitamura S, Matsuda H, et al. Total cavopulmonary shunt operation in complex cardiac anomalies. A new operation. J Thorac Cardiovasc Surg 1984; 87: 74e81.
Rationale for the management of systemic venous anomalies in single-ventricle patients The reported application of two innovative surgical techniques for the enhanced management of systemic venous anomalies in single-ventricle patients was supported by computational fluid dynamic studies, currently in publication. From these studies, we derived two basic principles: 1. The venous unifocalisation principle, achieved by side-byside anastomosis between transected bilateral superior venae cavae, or by end-to-side anastomosis between the hepatic veins and the nearby segment of azygos vein, essentially reproduces the normal anatomical pattern of the systemic venous system in which all tributaries converge, at a more or less acute angle, into vessels of progressively larger calibre. Furthermore, it presumably takes advantage of the ensuing flow enhancement effect in the downstream vessels, typically characterised by increased flow output, streamlined flow pattern and possibly increased flow velocity rate. 2. The cavopulmonary polarisation principle pursues the best spatial arrangement of opposite caval channels connecting to the pulmonary arteries, by avoiding fluid collision and minimising power dissipation. The rationale for a unifocal bilateral BCPA is that a single and centrally located cavopulmonary connection provides an unopposed and symmetrical bilateral distribution of pulmonary blood flow, allowing growth of the central pulmonary arteries and preventing thrombus formation. In the case of a direct hepato-azygous connection, the ‘unifocalisation’ of the hepatic venous return and the ‘unipolarisation’ of the whole systemic venous return (i.e. the single cavopulmonary anastomosis) prevent the problem of flow unbalance and collision that is typically seen in the old-fashioned hepatic vein-to-pulmonary artery conduit.
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15 Mazzera E, Corno A, Picardo S, et al. Bidirectional cavopulmonary shunts: clinical applications as staged or definitive palliation. Ann Thorac Surg 1989; 47: 415e20. 16 Rychik J, Jacobs ML, Norwood Jr WI. Acute changes in left ventricular geometry after volume reduction operation. Ann Thorac Surg 1995; 60: 1267e73. discussion 1274. 17 Albanese SB, Carotti A, Di Donato RM, et al. Bidirectional cavopulmonary anastomosis in patients under two years of age. J Thorac Cardiovasc Surg 1992; 104: 904e9. 18 Di Donato R, Di Carlo DC, Giannico S, Marcelletti C. Palliation of complex cardiac anomalies with subaortic obstruction: new operative approach. J Am Coll Cardiol 1989; 13: 406e12. 19 Di Donato RM, Amodeo A, di Carlo DD, et al. Staged Fontan operation for complex cardiac anomalies with subaortic obstruction. J Thorac Cardiovasc Surg 1993; 105: 398e404. discussion 404e5. 20 Amodeo A, Di Donato R, Carotti A, Marino B, Marcelletti C. Pulmonary arteriovenous fistulas and polysplenia syndrome. J Thorac Cardiovasc Surg 1994; 107: 1378e9. 21 McElhinney DB, Reddy VM, Tworetzky W, Petrossian E, Hanley FL, Moore P. Incidence and implications of systemic to pulmonary collaterals after bidirectional cavopulmonary anastomosis. Ann Thorac Surg 2000; 69: 1222e8. 22 Ikai A, Riemer RK, Ma X, Reinhartz O, Hanley FL, Reddy VM. Pulmonary expression of the hepatocyte growth factor receptor c-Met shifts from medial to intimal layer after cavopulmonary anastomosis. J Thorac Cardiovasc Surg 2004; 127: 1442e9. 23 Di Donato RM. Invited commentary. Ann Thorac Surg 2005; 79: 36e7 [on: Berdat PA, Belli E, Lacour-Gayet F, Planche C, Serraf A. Additional pulmonary blood flow has no adverse effect on outcome after bidirectional cavopulmonary anastomosis. Ann Thorac Surg 2005; 79: 29e36.]. 24 Marcelletti C, Corno A, Giannico S, Marino B. Inferior vena cavapulmonary artery extracardiac conduit. A new form of right heart bypass. J Thorac Cardiovasc Surg 1990; 100: 228e32. 25 Shiraishi S, Uemura H, Kagisaki K, Koh M, Yagihara T, Kitamura S. The off-pump Fontan procedure by simply cross-clamping the inferior caval vein. Ann Thorac Surg 2005; 79: 2083e7. discussion 2087e8. 26 Giannico S, Corno A, Marino B, et al. Total extracardiac right heart bypass. Circulation 1992; 86(5 Suppl): II110e7. 27 Amodeo A, Galletti L, Marianeschi S, et al. Extracardiac Fontan operation for complex cardiac anomalies: seven years’ experience. J Thorac Cardiovasc Surg 1997; 114: 1020e30 [discussion 1030e1]. 28 Giannico S, Hammad F, Amodeo A, et al. Clinical outcome of 193 extracardiac Fontan patients: the first 15 years. J Am Coll Cardiol 2006; 47: 2065e73.
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29 Amodeo A, Di Donato RM. The unifocal bilateral bidirectional cavopulmonary anastomosis. Ann Thorac Surg 2007; 84: 2134e5. 30 Amodeo A, Di Carlo D, Grigioni M, De Santis M, Di Donato RM. Early primary Kawashima operation combined with direct hepatic vein-toazygos vein connection: a new logical approach. J Thorac Cardiovasc Surg 2005; 129: 949e50. 31 Baskett RJ, Ross DB, Warren AE, Sharratt GP, Murphy DA. Hepatic vein to the azygous vein anastomosis for pulmonary arteriovenous fistulae. Ann Thorac Surg 1999; 68: 232e3. 32 Michielon G, Parisi F, Di Carlo D, et al. Orthotopic heart transplantation for failing single ventricle physiology. Eur J Cardiothorac Surg 2003; 24: 502e10 [discussion 510]. 33 Michielon G, Parisi F, Squitieri C, et al. Orthotopic heart transplantation for congenital heart disease: an alternative for high-risk Fontan candidates? Circulation 2003; 108(Suppl 1): II140e9. 34 de Leval MR, Dubini G, Migliavacca F, et al. Use of computational fluid dynamics in the design of surgical procedures: application to the study of competitive flows in cavo-pulmonary connections. J Thorac Cardiovasc Surg 1996; 111: 502e13. 35 Sharma S, Goudy S, Walker P, et al. In vitro flow experiments for determination of optimal geometry of total cavopulmonary connection for surgical repair of children with functional single ventricle. J Am Coll Cardiol 1996; 27: 1264e9. 36 Bove EL, de Leval MR, Migliavacca F, Balossino R, Dubini G. Toward optimal hemodynamics: computer modeling of the fontan circuit. Pediatr Cardiol 2007; 28: 477e81. 37 Amodeo A, Grigioni M, Oppido G, et al. The beneficial vortex and best spatial arrangement in total extracardiac cavopulmonary connection. J Thorac Cardiovasc Surg 2002; 124: 471e8. 38 Amodeo A, Grigioni M, D’Avenio G, Daniele C, Di Donato RM. The patterns of flow in the total extracardiac cavopulmonary connection. Cardiol Young 2004; 14(Suppl 3): 53e6. 39 Grigioni M, Amodeo A, Daniele C, D’Avenio G, Formigari R, Di Donato RM. Particle image velocimetry analysis of the flow field in the total cavopulmonary connection. Artif Organs 2000; 24: 946e52. 40 Amodeo A, Grigioni M, Filippelli S, et al. Improved management of systemic venous anomalies in single ventricle: new rationale. J Thorac Cardiovasc Surg, in press.
Acknowledgment We are indebted to Dr Carlo Marcelletti, who started and contributed greatly to our achievements in the quest for the ‘ideal’ Fontan operation.
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