Tricuspid atresia versus other complex lesions

J

THoRAc CARDIOVASC SURG

1988;96:204-11

Tricuspid atresia versus other complex lesions Comparison of results with a modified Fontan procedure Several modificatiom of the Fontan principle are currently applied to the treatment of tricuspid atresia with low mortality. The use of these modifications in other rnalformatiom has most frequently been associated with less satisfactory results. At our institution, from June 1977 to October 1986, 35 consecutive patients, whose ages ranged from 8 months to 20 years (median age 3.4 years), wtderwent a modified Fontan procedure. Twenty patients with a median age of 3.2 years (group I) haYing tric~pid atresia (16 patients) or hypoplastic right heart syndrome (four patients) were treated by means of a right atrium-pulmonary artery anastomosis (12 patients) or right atrium-subpulmonary chamber connection (eight patients). FIfteen patients (group II) with a median age of 3.6 years, haYing a single left ventricle (10 patients), left atrieveatricalar valve hypoplasia or atresia (three patients), or double-outlet right ventricle (two patients), wtderwent right atrium-pulmonary artery anastomosis, together with a repositioning of the atrial septum to the right of the right atriovenmcular vabe, which thus left intact the inlet to the l'entricle(s~ The operative mortality rate was 25 % in group I and 0 % in group II. One patient in group I and one in group II died late postoperatively. All the 28 survivors are free of symptoms 3 months to 9 years after correction. According to our results, low risk can be associated with modified Fontan procedures in the treatment of complex heart malformations other than tricuspid or pulmonary atresia. Presening the integrity of the entire inlet to the ventrielets) by repositioning the interatrial septum, as done in group II malformations, might be helpful in improYing the quality of the repair.

Giovanni Stellin, MD, Alessandro Mazzucco, MD, Uberto Bortolotti, MD, Stefano del Torso, MD,a Giuseppe Faggian, MD, Alberto Fracasso, MD, Ugolino Livi, MD, Aldo Milano, MD, Giulio Rizzoli, MD, and Vincenzo Gallucci, MD, Padova, Italy

In 1971, Fontan and Bauder' demonstrated the feasibility of a physiologic correction of tricuspid atresia by means of a total atriopulmonary shunt. Since then, several variations of this principle, the so-called modified Fontan procedures, have been applied to the treatment of an increasing variety of congenital malformations." Although the results of modified Fontan procedures in cases of tricuspid atresia are satisfactory, the use of

such procedures for other complex lesions is, so far, less gratifying. 5-8 This report compares our results with modified Fontan procedures in patients with classic tricuspid atresia and in a separate group of patients with other malformations, mainly single left ventricle, in which the surgical technique was modified to preserve the integrity of the whole atrioventricular (A V) junction. Patients and methods

From the Department of CardiovascularSurgery and the Department of Pediatrics,' University of Padova Medical School, Padova, Italy. Supported in part by National Research Council (C.N.R.), Target Project "Preventive Medicine and Rehabilitation," Subproject "Perinatal Pathology and its Sequelae," Rome, Italy. Received for publication July 2, 1987. Accepted for publication Dec. 2, 1987. Address for reprints: G. Stellin, MD, Istituto di Chirurgia Cardiovascolare, Universita di Padova, Via Giustiniani, 2, 35128 Padova, Italy.

204

Patient population. Over a period of 9.3 years, from June 1977 throughout October 1986, 35 consecutive patients have undergone a modified Fontan procedure at the Department of Cardiovascular Surgery of the University of Padova. There were 18 male and 17 female patients, aged from 8 months to 20 years (median age 3.4 years). Twenty patients were younger than 4 years of age and 15 were older. The patients were divided into two groups according to intracardiac anatomy and physiologic condition. Group I (Table I) included 20 patients with a median age of 3.2 years (range 8 months to II years). Sixteen of these had classic tricuspid atresia: type la in two, Ib in 10, lib in three, and III in one (according to the

Volume 96 Number 2 August 1988

Modified Fontan procedure 205

Table I. Anatomic classification of patients in group I (n = 20) Situs viscerum and atria Solitus Solitus Solitus Solitus Solitus Solitus

Diagnosis TA (type TA (type TA (type TA (type PA+IVS HRHS

Ia) Ib) lIb) III)

Type of AV connection

No. of patients

Concordant (Dvloop) Concordant (D-loop) Concordant (D-loop) Discordant (Lloop) Concordant (D-loop) Concordant (D-loop)

2

10 3 1 3 I

Type of VA connection Concordant (normally Concordant (normally Discordant (TGA) Discordant (TGA) Concordant (normally Concordant (normally

related GA) related GA)

related GA) related GA)

AV. Atrioventricular; VA. vemriculoarterial: D. dextro: L. leva; TGA, transposition of the great arteries; PA + IVS, pulmonary atresia with intact interventricular septum; HRHS, hypoplastic right heart syndrome; GA, great arteries.

Table II. Anatomic classification of patients in group II (n = 15) Situs viscerum and atria Solitus Solitus Solitus Inversus Solitus Ambiguus Inversus

Diagnosis Single LV (univentricular AV connection) Single LV (univentricular AV connection) Single LV (univentricular AV connection) Mitral stenosis with hypoplastic LV Mitral atresia Mitral atresia DORV with noncommitted VSD

No. of patients

Type of AV connection

Type of VA connection

6

Discordant (L-loop)

Discordant (TGA)

3

Concordant (D-loop)

Discordant (TGA)

Concordant (D-loop) Discordant (D-loop)

Concordant (normally related great arteries) DORV (malposition of aorta)

Concordant (Dvloop) ? (D-loop) Concordant (Lvloop)

DORV (malposition of aorta) DORV (malposition of aorta) DORV (malposition of aorta)

1 1

2

AV. Atrioventricular; VA, ventriculoarterial; LV, left ventricle; L, levo; TGA, transposition of the great arteries; D, dextro: DORV,double-outlet right ventricle; VSD, ventricular septal defect.

classification of Edwards and Burchell"). Four of the patients in group I had a critically diminutive hypoplastic tricuspid valve in the setting of right heart hypoplasia: Pulmonary valve atresia was present in three and severe stenosis in one. Group II (Table II) included 15 patients with a median age of 3.6 years (range 15 months to 20 years), Ten of these had a single left ventricle (univentricular A V connection with main left ventricle), with transposed great arteries in nine and normally related great arteries in one (Holmes heart 10); two A V valves were present in all. Five patients had a double-outlet right ventricle type of ventriculoarterial connection. Two of the latter had two well-developed ventricles, a very far "noncommitted" ventricular septal defect, and multiple defects of the muscular septum. The remaining three patients had hypoplasia of the left ventricular chamber with mitral valve atresia or stenosis. The preoperative hemodynamic status was remarkably comparable between the two groups (Table III), as the same criteria were used for selecting candidates for modified Fontan procedures in both. Surgical repair. Moderately hypothermic cardiopulmonary bypass with direct cannulation of the venae cavae was used in all but three infants in whom deep hypothermic circulatory arrest was used. In group I, the mode of right atriumpulmonary artery (RA-PA) connection was modified during the considered time interval: An RA-PA anastomosis was done in 12 patients, with the use of a Hancock conduit in three and a valveless conduit in one. In the remaining eight patients,

a direct RA-PA connection was achieved. In eight patients, the anastomosis incorporated the subpulmonary chamber (Table IV), In the four patients with right heart hypoplasia, the right ventricle was either excluded by suture of the tricuspid valve leaflets (two patients) or used for an A V anastomosis after patch reconstruction of the right ventricular outflow tract. In group II, a direct RA-PA anastomosis together with an atrial partitioning was done in all patients, with the aim of directing the pulmonary venous return into both AV valves. This was achieved by incising the interatrial septum in a trapezoidal fashion, as is usually done in the Senning operation, obtaining a flap that was then lifted upward and sutured anteriorly to the right AV valve anulus, to avoid an anterior A V node. Most often this maneuver required the augumentation of the flap by means of a small semilunar patch of autologous pericardium. The roof of the coronary sinus was cut at its orifice and was left draining into the left atrial cavity (Fig. I). Most commonly, the direct RA-PA connection was obtained by anastomosing the upper aspect of the junction of the superior vena cava and right atrium (RA) to the underface of the right pulmonary artery (PA). In patients with normally related great arteries, such an anastomosis was greatly facilitated by transection of the main PA at its origin and its transferal to the right and posterior to the aorta, as shown in Fig.!. Additional concomitant surgical procedures were necessary in 16 patients (Table IV). Reconstruction of the right PA was

The Journal of Thoracic and Cardiovascular

2 0 6 Stellin et al.

Table

Surgery

m. Preoperative hemodynamic data Group I Tricuspid atresia Pulmonary atresia Group II

(mean values)

Arterial O2 saturation (%)

Mean PAP

LVEDP

(mmHg)

(mmHg)

77 (69-84) 69 (65-74) 80 (66-95)

13 (10-25) 4 (3-5) 10 (3-25)

6 (3-10)

2.0 (1.3-3.8) 1.8 (1.2-2.5) 1.8 (1.0-3.3)

9 (3-18)

7 (3-20)

Range of values given in parentheses. Pulmonary artery was not entered in three patients in group I with tricuspid atresia, in two patients in group I with pulmonary atresia, and in two patients in group II. PAP, Pulmonary artery pressure; PVR, pulmonary vascular resistance; LVEDP, Left ventricular end-diastolic pressure.

Table IV. Surgical technique and results Previous palliation Group I Tricuspid atresia

Pulmonary atresia

BT

No. II

Waterston

4

BT

4

RVOT reconstruction Group II

No.

Associated procedures

RA-PA direct anastomosis RA-SPC anastomosis

6

RP A reconstruction

6

Hancock conduit Valveless conduit

3 I

RPA and LPA reconstruction Intraatrial membrane resection

RA-PA direct anastomosis with tricuspid valve closure RA-R V anastomosis

2

RPA reconstruction

2

R VOT reconstruction

15

RPA reconstruction RPA and LPA reconstruction Damus- Kaye-Stansel

RA-PA direct anastomosis with atrial septum repositioning

BT

PA banding BH

Type of repair

No.

Deaths

7

2

2

2

2 I

BT, Blalock-Taussig shunt; SPC, subpulmonary chamber; RPA, right pulmonary artery; LPA, left pulmonary artery; RV, right ventricle; RVOT, right ventricular outflow tract; BH, Blalock-Hanlon.

performed in 11 (nine in group I and two in group II) and reconstruction of both right and left branches in two (one in group I and one in group 11). Pericardial patch reconstruction of the right ventricular outflow tract was associated to a right atrium-right ventricle anastomosis in one patient with pulmonary atresia with intact ventricular septum. In another patient with single left ventricle, transposed great arteries, and restrictive bulboventricular foramen, a Damus-Kaye-Stansel procedure":" was performed. Finally, in one patient in group I, a hypertrophic eustachian valve that caused cor triatriatum dexter was resected, Twenty-nine patients had undergone a total of 34 palliative procedures before definitive repair: These included 26 BlalockTaussig shunts, four Waterston shunts, two PA bandings, one right ventricular outflow tract reconstruction with a patch of autologous pericardium, and one Blalock-Hanlon atrial septectomy (Table IV). Follow-up. All operative survivors were followed up by

means of direct hospital visit; follow-up was done during a 6-month period that ended in April 1987. A lung perfusion scan with technetium 99m and combined M-mode and two-dimensional Doppler echocardiographic studies were done postoperatively to noninvasively assess pulmonary circulation and ventricular performance.

Results Early mortality and complications. There were five hospital deaths (14%), three in patients younger than 4 years of age (15%, 7% to 28%, 70% confidence limits) and two in patients older than 4 years of age (13%, 4% to 29%, 70% confidence limits) (by x' test, p = 0.9). All five deaths occurred in group I (25%, 15% to 38%, 70% confidence limits); there were none in group II (0%,0%

Volume 96 Number 2

Modified Fontan procedure

August 1988

a

b

c

d

207

e

Fig. 1. Technique of modified Fontan procedure in patients with two AV valves or atresia of the left AV valve. a, Atrial cavity is exposed by incision of RA anterior and parallel to sulcus terminalis. Dotted line shows site of incision into atrial septum. b, Trapezoidal flap of atrial septum is obtained and lifted upward. Roof of coronary sinus is opened into left atrium. c, Flap is then sutured anteriorly to right AV valve anulus. Coronary sinus is left draining into left atrial cavity. Foramen ovale is also closed. d, A small semilunar patch of autologous pericardium is used to augment atrial septum flap. e, Suture is continued on the RA wall around right AV valve anulus, to avoid anterior AV node. Upper aspect of superior vena cava-right atrium junction is incised to prepare anastomosis with main pulmonary artery, which has been transected and moved posteriorly to right of aorta. Additional length of incision is gained in right PA. f, Atrial partitioning is completed, after which a direct RA-PA connection is achieved.

to 12%, 70% confidence limits) (by x' test, p = 0.04) (Table IV). The cause of death was a septic shock complicating mediastinitis in one patient; the others died with signs of

low output syndrome. Among these, necropsy showed an unrelieved left PA branch stenosis in one, a diffuse hypoplasia of the PA tree in another, and no evident cause of death in the third. In the fourth patient, in

The Journal 01 Thoracic and Cardiovascular Surgery

2 0 8 Stellin et al.

whom a postmortem study could not be obtained, an emergency postoperative catheterization before death had shown increased pulmonary vascular resistance (5.5 U 1m2 ) . This patient had undergone a Waterston shunt 8 years before the repair. Pleural effusions occurred in 17 patients, eight of whom required thoracenteses. In three patients, in addition, pericardiocentesis was needed. Chylothorax occurred in two patients 15 and 21 days after operation, respectively: In one it resolved within 45 days after a tetracycline solution was injected into the chest cavity, and in the second it ceased on postoperative day 52 after surgical pleurodesis. Four patients underwent early successful reintervention 3 to 18 hours after the initial operation, two because of excessive postoperative bleeding and two because of arterial blood desaturation. In the latter, a two-dimensional contrast echocardiogram detected a residual right-to-left shunt at the atrial level. A previously unrecognized cribriform septum primum in one and an incomplete atrial septal defect patch closure in the other were found. The last patient underwent a second reoperation 45 days later to relieve a residual right PA stenosis. In two other patients, because of the persistence of a low output state with elevated RA pressure, the RA-PA anastomosis was taken down in an attempt to reestablish the preoperative hemodynamic situation; both of these patients died. Late results and complications. There were two late deaths. One occurred in a 19-month-old girl with double-outlet right ventricle and mitral atresia who underwent a direct RA-PA anastomosis and atrial partitioning: She died at home of an unrecognized pericardia I tamponade 50 days after discharge. Another patient, an 18-year-old boy, died of septic shock at reoperation done to replace a stenotic Hancock conduit that had been inserted 8 years previously for the repair of tricuspid atresia type lb. Two other patients underwent successful reoperation 2 and 6 months, respectively, after the modified Fontan procedure. The first, a 12-year-old girl, was readmitted to our unit because of recurrent chest effusion and heart failure after a right atrium-subpulmonary chamber direct anastomosis and ventricular septal defect patch closure for tricuspid atresia type Ib; hemodynamic investigation disclosed a dehiscence of the ventricular septal defect patch, which was repaired by direct suture. The second, a 6-year-old girl with situs inversus, doubleoutlet right ventricle, and "noncomrnitted" ventricular septal defect, underwent an RA-PA anastomosis together with atrial partitioning; the coronary sinus was left draining into the low-pressure left atrium. Six months

later, reinvestigation prompted by the presence of increasing cyanosis, despite an excellent hemodynamic state, showed a persistent right superior vena cava draining into the coronary sinus. Through a right thoracotomy, the vein was ligated. Two late episodes of arrhythmia occurred: atrial fibrillation in one patient and supraventricular tachycardia in another. Both patients were treated successfully with intravenous verapamil. Follow-up. All of the 28 long-term survivors are free of symptoms 3 months to 9 years after repair. Twentyone of them, 12 in group I and nine in group II, were electively reevaluated from 6 months to 8 years after correction. Preliminary data l3a from lung perfusion and Doppler studies showed perfusion defects or abnormal flow patterns 14. 15 in 10 patients. In three patients, all in group II, major areas of marked underperfusion were present; in four (three in group I, one in group II), only small areas of underperfusion of one lung were detected, whereas three (two in group I, one in group II) had only echocardiographic demonstration of an abnormal flow pattern. These abnormalities were noticed only in patients who had previous palliative procedures and appeared to be related to the side and duration of previous shunts, to preoperative polycythemia, and to postoperative ventricular dysfunction. Discussion In 1951, Carlon, Mondini, and De Marchi," in a canine experimental model, proved that the systemic blood return to the upper part of the body can be freely diverted into the right lung for oxygenation and that "the blood flow is held up by a moderate increase of the venous pressure ... by thoracic suction and by the expansion and collapse of the breathing lungs." Clearly, the principle based on the fact that the lungs can be perfused under venous pressure was in this way established. Seven years later, this principle was successfully applied in humans by Glenn.'? Subsequently, in 1971, Fontan and Bauder' reported the first successful results of total venous blood diversion into the lungs in cases of tricuspid atresia. They believed that the venous blood return from the lower part of the body progressed into the lungs by the pumping power of a hypertrophied right atrium, as typically seen in this anomaly. For this reason, they deemed it necessary to insert a valve at the orifice of the inferior vena cava and a valved conduit between the RA appendage and the main PA to prevent blood reflux into the RA and inferior vena cava, respectively. After this initial report, the procedure was modified-" and extended to some other complex forms of congenital heart defects":" previously thought to be

Volume 96 Number 2 August 1988

uncorrectable. However, most recent series still report a lower risk for modified Fontan procedures after repair of tricuspid atresia than for other cardiac anomalies." To verify the reason for such a difference, we have reviewed our experience with modified Fontan procedures, comparing two groups of patients. The first (group I) included patients with tricuspid atresia or with a similar anatomic and physiologic situation characterized by a hypertrophied high-pressure RA and a complete (or almost complete) right-to-left shunt of the venous return, with normal left AV connection. In group II, we included a variety of lesions unified by the common feature of double-inlet ventricle(s) or atresia of the left AV orifice, which thus led to a low-pressure RA physiologic condition. Anomalies with two well-developed ventricles can be assimilated insofar as a large unrestrictive interventricular communication produces a common pumping system. This experience, even though the patient population is limited, provides data that suggest that repair of cardiac lesions characterized by a double-inlet type of physiologic condition does not involve an increased surgical risk. Paradoxically, the risk in group II is lower than that in group I. In this subset of patients (group II), the most commonly reported surgical approach involves the closureof the right AV valve orifice.5, 2! Because of the high incidence of left AV valve dysplasia observed in patients with this group of malformations" and with the aim of avoiding any interference with the emptying phase of the left atrium, we elected to preserve the anatomic and functional integrity of both inlets to the ventricle(s), simply by repositioning the atrial septum. In addition, because disruption of the right AV valve patch or direct closure remains a serious complication," atrial septum repositioning seems to be an ideal alternative, as also previously described.t'? To obtain a larger atrial flap, we continue our incision in the atrial septum into the coronary sinus, which is left draining into the low-pressure left atrium. With this approach only a small pericardiaI patch is required to augment the atrial flap. This modification, which avoids the need for total atrial reseptation with exogenous tissue," might reduce the incidence of intracavitary thrombosis promoted by the use of a large amount of intraatrial foreign material." According to Choussat and co-workers," young age (under 4 years) was to be considered a contraindication to an RA-PA anastomosis. However, recent reports advocate an earlier repair to avoid the hazard of prolonged cyanosis on ventricular function" and on neurologic development, the long-term effect of volume overload of the ventricle, and the threat of paradoxical

Modified Fontan procedure

209

embolism." In agreement with Kirklin? and Mayer," and their associates, patients in our series operated on before the age of 4 years did not show an incremental risk linked to young age. Indeed our indications to perform a modified Fontan procedure, initially inspired by criteria from Choussat and colleagues," have been modified throughout our experience, and the limits of operability expanded. However, increased pulmonary vascular resistance, above 4 U . rn', and severe uncorrectable hypoplasia of the PA tree have been maintained as absolute contra indications to modified Fontan procedures. Like others," we have experienced the disastrous impact of residual PA branch deformities at the completion of a modified Fontan procedure, even though in most of the patients we could obtain a satisfactory ultimate result. In the data collected from a postoperative radionuelide study of the lungs, there is evidence that perfusion defects occur almost invariably ipsilaterally to a previous systemic-to-pulmonary artery shunt. 13. Distortion of the PA branches and intimal thrombosis or pulmonary emboli caused by prerepair polycythemic status seem to play an important role in causing lung perfusion abnormalities." On the basis of these observations, we believe that, if other conditions are equal, we should proceed with a primary modified Fontan procedure in any child with symptoms, after the first 6 months of life, in the presence of a normal size PA and its branches, to avoid the undesired effects of a systemic-pulmonary shunt. In tricuspid atresia, when possible, we incorporate the subpulmonary chamber, as originally described by Bjork and colleagues.' The importance of the contribution of the subpuimonary chamber to pulmonary blood flow is still uncertain." 30 PA flow profiles after a modified Fontan procedure appear to be uniform and unrelated to whether or not the subpulmonary chamber was used for the repair," and the subpulmonary chamber seems to act simply as a conduit.' Accordingly, we believe that it can be used to facilitate the connection to the RA, in the presence of a well-developed pulmonary valve. Otherwise, our current preference goes to a direct anastomosis of the roof of the RA to the main PA, which, in hearts with normally related great arteries, is transected and shifted rightward posteriorly to the aorta, to facilitate the RA-PA connection. This approach has proved effective in patients in group II and eliminates the use of any prosthetic material, in particular of exogenous valves and conduits, that would expose the patient to the risk of late dysfunction and need for reoperation. Finally, in light of the quality of the short- and

2 10 Stellin et al.

intermediate-term results reported in the literature and confirmed by our data, repair of single ventricle by a modifed Fontan procedure, when feasible, appears to be preferable to a ventricular septation, especially in those patients in whom severe pulmonary valve stenosis or atresia is present. 3 I For the same reason, in agreement with Kirklin and co-workers," we also feel confident in performing a modified Fontan procedure in those patients with double-outlet right ventricle and noncommitted ventricular septal defect, particularly if multiple defects of the ventricular septum are associated. We wish to express our gratitude to Anna Rambaldo and Giancarlo Pengo for their technical assistance. REFERENCES

I. Fontan F, Baudet E. Surgical repair of tricuspid atresia. Thorax 1971;26:240-8. 2. Kreutzer G, Galindez E, Bono H, de Palma C, Laura JP. An operation for the correction of tricuspid atresia. J THORAC CARDIOVASC SURG 1973;66:613-21. 3. Bjork VO, Olin CL, Bjarke BB, Thoren CA. Right atrial-right ventricular anastomosis for correction of tricuspid atresia. J THORAC CARDIOVASC SURG 1979; 77:452-8. 4. Doty D, Marvin W J, Laurer RM. Modified Fontan procedure: methods to achieve direct anastomosis of right atrium to pulmonary artery. J THORAC CARDIOVASC SURG 1981;81:470-5. 5. Laks H, Milliken JC, Perloff JK, et al. Experience with the Fontan procedure. J THORAC CARDIOVASC SURG 1984;88:939-51. 6. de Vivie ER, Rupprath G. Long-term results after Fontan procedure and its modifications. J THORAC CARDIOVASC SURG 1986;91:690-7. 7. Kirklin JK, Blackstone EH, Kirklin JW, Pacifico AD, Bargeron LM. The Fontan operation: ventricular hypertrophy, age, and date of operation as risk factors. J THoRAe CARDIOVASC SURG 1986;92:1049-64. 8. DeLeon SY, I1bawi MN, Idriss FS, et al. Fontan type operation for complex lesions: surgical consideration to improve survival. J THORAC CARDIOVASC SURG 1986; 92:1029-37. 9. Edwards JE, Burchell HB. Congenital tricuspid atresia: a classification. Med Clin North Am 1949;53:1177-82. 10. Holmes AF. Case of malformation of the heart. Trans Med Chir Soc Edin 1824;1:252-9. 11. Damus R. Correspondence. Ann Thorac Surg 1975; 20:724-5. 12. Kaye MP. Anatomic correction of transposition of the great arteries. Mayo Clin Proc 1975;638-40. 13. Stansel HR Jr. A new operation for D-loop transposition of the great vessels. Ann Thorac Surg 1975;19:565-7. 13a. del Torso S, Benetti E, Gui P, et al. Radionuclide evaluation of lung perfusion after the Fontan procedure. Int J Cardiol [In press].

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14. DiSessa TG, Child JS, Perloff JK, et al. Systemic venous and pulmonary arterial flow pattern after Fontan's procedure for tricuspid atresia and single ventricle. Circulation 1984;70:898-902. 15. Hagler DJ, Seward JB, Tajik AJ, Ritter DG. Functional assessment of the Fontan operation: combined M-mode, two-dimensional and Doppler echocardiographic studies. J Am Coli Cardiol 1984;4:756-64. 16. Carlon CA, Mondini PG, de Marchi R. Surgical treatment of some cardiovascular diseases (New vascular anastomosis). J Int Coli Surg 1951;16:1-10. 17. Glenn WWL. 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;259:117-24. 18. Sharrat GP, Sbokos CG, Johnson AM, Anderson RH, Monro JL. Surgical "correction" of solitus-concordant, double-outlet left ventricle with L-malposition, and tricuspid stenosis with hypoplastic right ventricle. J THORAC CARDIOVASC SURG 1976;71:853-8. 19. Lamberti JJ, Thilenius 0, de la Fuente D, Lin CY, Arcilla R, Reploge RL. Right atrial partitioning and right ventricular exclusion: another surgical approach for complex cyanotic congenital heart disease. J THORAC CARDIaVASC SURG 1976;71:386-91. 20. Yacoub MH, Radley-Smith R. Use of valved conduit from right atrium to pulmonary artery for "correction" of single ventricle. Circulation 1987;54(Pt 2):III63-70. 21. Gale AW, Danielson GK, McGoon DC, Mair DD. Modified Fontan operation for univentricular heart and complicated congenital lesions. J THORAC CARDIOVASC SURG 1979;78:831-8. 22. Van Praagh R, Plett JA, Van Praagh S. Single ventricle: pathology, embryology, terminology and classification. Herz 1979;4:113-50. 23. Mayer JE Jr, Jonas RA, Castaneda AR. Modified Fontan procedure. In: Cohn LH, ed. Modern technics in surgery. Mount Kisko, New York: Futura, 1984:751-11. 24. Dobell ARH, Trusler GA, Smallhorn JF, Williams WG. Atrial thrombi after Fontan operation. J THORAC CARDIaVASe SURG 1986;42:664-7. 25. Choussat A, Fontan F, Besse P, Vallot F, Chauve A, Bricaud M. Selection criteria for Fontan's operation. In: Shinebourne EA, Anderson RH, eds. Paediatric cardiology 1977. Edinburg: Churchill Livingstone, 1978:559-66. 26. del Torso S, Kelly MJ, Kalff V, Venables AW. Radionuelide assessment of ventricular contraction at rest and during exercise following the Fontan procedure for either tricuspid atresia or single ventricle. Am J Cardiol 1985;55:1127-32. 27. Mayer JE, Helgason H, Jonas RA, et al. Extending the limits for modified Fontan procedure. J THORAC CARDIaVASe SURG 1986;92:1021-8. 28. Juaneda E, Haworth SG. Pulmonary vascular structure in patients dying after Fontan procedure: the lung as a risk factor. Br Heart J 1984;52:575-80.

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29. Bull C, de Leval MR, Stark J, Taylor JFN, Macartney FJ, McGoon DC. use of a subpulmonary ventricular chamber in the Fontan circulation. J THoRAc CARDI0VASC SURG 1983;85:21-31. 30. Lee CN, Danielson GK, Puga FJ, Driscoll DJ. Comparison of atriopulmonary versus atrioventricular connection for modified Fontan/Kreutzer repair of tricuspid valve atresia. J THoRAc CARDIOVASC SURG 1986;92:1038-48. 31. Stefanelli G, Kirklin JW, Naftel DC, et al. Early and

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intermediate-term (10 year) results of surgery for univentricular atrioventricular connection ("single ventricle"). Am J Cardiol 1984;54:811-21. 32. Kirklin JW, Pacifico AD, Blackstone EH, Kirklin JK, Bargeron LM Jr. Current risk and protocols for operations for double-outlet right ventricle: derivation from an 18-year experience. J THORAC CARDIOVASC SURG 1986; 92:913-30.

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