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Subaortic obstruction in hearts with a univentricular connection to a dominant left ventricle and an anterior subaortic outlet chamber
Subaortic obstruction in hearts with a univentricular connection to a dominant left ventricle and an anterior subaortic outlet chamber Results of a staged approach In 1984 we reported a 56 % mortality after major cardiac operations for patients with univentricular connection to a dominant left ventricle, an anterior subaortic outlet chamber, and subaortic obstruction. Since then we have adopted a staged approach to this repair. Between 1984 and 198932 patients had such operations. The overall mortality has decreased (16%; p < 0.001). The current cohort was divided by subaortic gradient into three subgroups for comparison with the cohort reported in 1984. Staging improved the outcome in patients with gradients greater than 40 mm Hg (mortality of 17 % compared with 67% from 1984; p = 0.05). Patients with gradients from 10 to 25 mm Hg who had a single-stage operation had the best outcome (mortality 6 %). Survival has improved. Many factors, including increased awareness of the detrimental effects of subaortic obstruction, improved surgical techniques, better perioperative care, and the appropriate application of a staged repair, have contributed to this improvement. We recommend simultaneous relief of obstruction and a modified Fontan operation for patients with subaortic gradients less than 25 mm Hg. Those with gradients greater than 40 mm Hg should have repair in two stages. It is unclear whether a one-stage or two-stage approach is better for patients with gradients between these extremes. (J THORAC CARDIOVASC SURG 1992; 104:1231-7) Patrick W. O'Leary, MD, David J: Driscoll, MD, Ann R. Connor, MD, Francisco J. Puga, MD, and Gordon K. Danielson, MD, Rochester, Minn.
Uiventricular connection to a dominant left ventricle (LV) with an anterior subaortic outlet chamber, hereafter referred to as double-inlet LV, is a congenital cardiac malformation that has a poor natural history.' When subaortic obstruction coexists with this malformation, previous attempts at corrective operations have been associated with a particularly high mortality.v? In 1984 Barber and coworkers'' reported the early surgical experience at the Mayo Clinic with this lesion; the surgical mortality in this group was 56%. This poor outcome was From the Section of Pediatric Cardiology and the Division of Thoracic and Cardiovascular Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minn. Received for publication June 3,1991.
similar to the experience of other investigators at that time. 2-7 In addition to the high mortality, Barber and coworkers'' reported that patients with severe subaortic obstruction had a worse surgical outcome than patients with less obstruction. This information prompted many clinicians to change their approach to this lesion.9-!2 Since severe subaortic obstruction is associated with poor outcome.i we hypothesized that prior relief of severe subaortic obstruction might improve survival after the Fontan procedure. Therefore we devised a staged approach to the surgical repair of this malformation and began to apply it in 1984. The purpose of this study is to report and analyze the results of this staged approach.
Accepted for publication Jan. 20, 1992.
Methods
Address for reprints: David J. Driscoll, MD, Section of Pediatric Cardiology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905.
Study patients. The register of all patients operated on at the Mayo Clinic between January 1984 and August 1989 was reviewed. Inclusion criteria were as follows:
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The Journal of Thoracic and Cardiovascular Surgery
I 2 3 2 O'Leary et al.
Table I. Comparison ofpatients reported by Barber
and colleagues' with those in the current study Study group Barber et al.
No. of patients Meanage (yr) Gradient (rnm Hg) Mean Range Pulmonary artery banding (no. of pt) Systemic-to-pulmonary artery shunt (No. of patients)
18 10.5 ± 6.6
64 ± 38* 10-140 13
3
Current study 32 9.9 ± 7.6 30 ± 22* 10-96
27 4
*p
I. The patient had double-inlet LV with an anterior subaortic outlet chamber. Patients with atresia of an atrioventricular (AV) valve were included as long as the AV relationship was consistent with double-inlet LV and an anterior subaortic outlet chamber was present. 2. Resting (directly measured) pressure gradient (from the LV to the ascending aorta) was 10 mm Hg or more. 3. The patient was considered to be a possiblecandidate for the modified Fontan procedure. 4. The subaortic obstruction was relieved by enlargement of the ventricular septal defect (VSD) in all patients. Some patients had additional resection of subaortic myocardium or patch enlargement (or both) of the outlet chamber. Only one patient who had an operation for this malformation was excluded from the study (on the basis of criterion 4). That patient was aged 18 months, had severe obstruction, and an aorta-pulmonary anastomosis was performed; the patient did not survive. This was the only patient with this malformation to have this type of operation during the study period. Surgical approach. Patients with moderately severe or severe subaortic obstruction were considered candidates for a two-stage repair. Two-stage repair consisted of two sequential operations. During the first operation the subaortic obstruction was relieved.The outlet chamber was usually approached transaortically, and the subaortic resection was performed through the retracted aortic valve. If the exposure was inadequate, if the aorta was small (as in infants), or ifthe outlet chamber required enlargement with a patch, the transoutlet chamber approach was employed. All patients had enlargement of the VSD by direct resection of the ventricular septum in an area away from the conduction system. When the outlet chamber was located anteriorly and to the left, the septal incisionwasoriented apically and posteriorly. For patients with a right-sided outlet chamber, the septal incision was oriented apically and anteriorly. Some patients had additional resection of subaortic muscle within the outlet chamber or patch enlargement (or both) of the outlet chamber. This initial procedure was followed by a convalescent period of about 1 year. This interval was chosen to allow time for regression of preexisting ventricular hypertrophy and improvement in ventricular compliance. After this period the patient was reevaluated and the second stage of repair (a modified Fontan operation) was performed if the patient was an acceptable candidate. Patients with this lesion and mild subaortic obstruction were
considered for a one-stage repair, which consisted of VSD enlargement, subaortic resection or outlet chamber patch augmentation (or both if necessary), and a simultaneous modified Fontan procedure. Study procedure. The records of the patients identified by registry review were examined for details of history, preoperative evaluations (both invasiveand noninvasive),operations, and postoperative course. The cohort described in 1984 by Barber and coworkers" was used as a historical control for comparisons of surgical outcome based on age, preoperative subaortic gradient, surgical approach, and year of operation. Statistical methods. Differences between the two cohorts were compared using Student's t test for unpaired groups or, when appropriate, for paired groups. Differences in survival between cohorts and subgroups within the cohorts were compared by X2 analysis. Only differences with two-tailed p values of 0.05 or less were considered significant. All data, when appropriate, were expressed as the mean ± one standard deviation. Results Demographics. Thirty-two patients met the study's inclusion criteria (25 male, 7 female). They were aged I to 26 years at the time of one-stage repair or the first operation of two-stage repair (mean 9.9 ± 7.6 years). The subaortic pressure gradient ranged from 10 to 96 mm Hg (mean 30 ± 22 mm Hg). Previous palliative operations. Of the 32 patients, 27 had had banding of the pulmonary artery. The remaining five had natural pulmonary or subpulmonary stenosis, or both. Four patients had systemic-to-pulmonary artery shunts. Three of these had required shunt placement after pulmonary artery banding. One patient, also with prior pulmonary artery banding, had had a Glenn anastomosis. Four patients had previous attempts at subaortic resection elsewhere with variable success. Five had repair of aortic coarctation. Two patients had balloon atrial septostomy, and one had had a Blalock-Hanlon septectomy. Two patients were pacemaker dependent before entering the study; one of these had had subaortic resection elsewhere. Comparisons between the current group and the cohort reported by Barber and colleagues'' are shown in Table I. Repairs. All patients had VSD enlargement. Ten patients required additional resection of myocardium within the outlet chamber. Two patients had patch enlargement of the outlet chamber. Twenty of the 32 patients had one-stage repair. The remaining 12 patients had two-stage repair. One of the patients who had twostage repair required additional subaortic resection at the time of the modified Fontan procedure for a recurrent gradient of 41 mm Hg (the gradient after the initial resection had been 5 mm Hg). Table II compares available preoperative data of patients having one-stage repair with data of patients having the first stage of two-stage repair. The only significant differences between the two
Volume 104 Number 5 November 1992
Univentricular connection to a double-inlet LV
12 3 3
Table II. Comparison ofpatients having OSR with those having the first stage of TSR OSR No. of patients Mean age (yr) Atresia of one AV valve (no.)
TSR 12 9.8 ± 7.1
20 10.1 ± 8.0
Left Right Previous operations (no.) Pulmonary artery banding Systemic-to-pulmonary artery shunt Coarctation repair Subaortic resection Pacemaker Atrial septostomy or septectomy Hemodynamic variables Mean subaortic gradient (mm Hg) Mean LVEDP (rnm Hg) Mean pulmonary arteriolar resistance (U/m 2 ) Echocardiographic variables Mean LV posterior wall thickness (mm) Mean LV posterior wall thickness ratio#
2 0
0 0
15 2 2 2 3
12 2 3 2 I 0
19.6 ± 13.5 8.9 ± 3.6*,t 1.9 ± 0.9:1:
46.9 ± 22 13.7 ± 5.3t 1.8 ± 2.1§
I
8.1 ± 1.0 ±
11.7 ± 1.6 ±
2·11,~
O·~I
3.4~
0.4
OSR, One-stage repair; TSR, two-stage repair; A V, atrioventricular; LVEDP, left ventricular end-diastolic pressure; LV, left ventricular.
'Eighteen patients.
tp = 0.007. :j:Thirteen patients. §Six patients. IIFifteen patients. 'lIP = 0.006.
#Ratio of observed wall thickness over the upper limit of normal.' J
Table III. Comparison ofpatients having OSR with those having the second stage of TSR OSR Hemodynamic variables Mean subaortic gradient (rnm Hg) Mean LVEDP (mm Hg) Mean pulmonary arteriolar resistance (U/m 2) Echocardiographic variables Mean LV posterior wall thickness (mm) Mean LV posterior wall thickness (ratio)*
TSR
No. of pt
Mean ± SD
No. of pt
Mean ± SD
20 18 13
19.6 ± 13.5 8.9 ± 3.6 1.9 ± 0.9
9 9 9
10.4 ± 13.3 10.9 ± 6.0 2.0 ± 1.7
IS
8.1 ± 2.7 1.0 ± 0.4
6 6
10.5 ± 2.3 1.3 ± 0.4
15
OSR, One-stage repair; TSR, two-stage repair; LVEDP, left ventricular end-diastolic pressure; LV, left ventricular. 'Ratio of observed wall thickness over upper limit of normal. 13
groups were the presence of increased left ventricular end-diastolic pressure (LVEDP) and increased left ventricular posterior wall thickness in patients having twostage repair. When reevaluated after the convalescent period (postsubaortic resection), the two-stage repair group had gradients, LVEDPs, and left ventricular posterior wall thicknesses that were decreased and not significantly different from the preoperative values of patients who had one-stage repair (Table III). Outcome. Within 30 days of the operation, 5 of the 32 patients died. This 15.6%mortality is significantly better
than the 56% reported by Barber and colleagues" (p < 0.001) (Fig. 1). Two of the deaths occurred in patients having one-stage repair, and the other three were in patients having two-stage repair (two after initial resection; one after modified Fontan procedure). Outcome related to age. Barber and coworkersreported an increased risk of death for young patients. In the current group there was no statistically significant difference in the mean ages between the survivors and the nonsurvivors (Fig. 2). In fact, 18 of 23 patients in the current group who were lessthan 10 years of age on entry
The Journal of Thoracic and Cardiovascular Surgery
I 2 3 4 O'Leary et al.
Cu rrent cohort
36 32
J:
c vi
C Q) ~
0-
24
Barbe r at al
20
1973- 1983
Current cohort O SR
120
E E
100
C Q)
80
~
60
28
ci
140
Ol
1984-198 9
'6
16
tn ()
12
e0
40
.0
20
ro
8
:::J (f)
0
56%
16%
Survivor
_
Survivors
No nsurvivor
120
s, ai OJ
«
10
I Barbe r et at,
Current coho rt
1973-1983
1984 - 1989
•II
0 No .
Surv ivo rs
Non survivors
Su rvivo rs
8
10
27
E
E
E Q)
EJ
•
I
P< Q,001
Survivor
•
Survivor
_
Survivors
Nonsurvrvors
27
5
Nonsurvivor
Fig. 3. Effect of severity of obstruction on outcome.
rn
25
15
Nonsurvivors 10 D
Fig. l. Overall outcome. OSR, One-stage repair; TSR, twostage repair.
20
1984- 1989
No .
Mortality rate
o
Current co hort
1973-1983
0
25%
10%
Barber et al,
'6 ro
100
o
c. U> C
60
Q)
40
Q)
20
'"
20
at.
1973- 1983
80
0, c
::i;
Barber et
"16
CL
18
Em
Barbe r et al
16
_
Current co hort
14 12
~
~
10
~ !$1
8 6
~
~
~%
P ",N$
18
32
Patients, no. Nonsurvivors
10-25
26-40
> 40
Gradient range, mm Hg
Fig. 4. Subaortic gradient distribution.
Nonsurvivor
Fig. 2. Effect of age on outcome. to the study survived. None of the eight patients from the report of Barber and colleagues who were less than the age of 10 years survived. Outcome related to left ventricular posterior wall thickness. Twenty-seven of the 32 patients had preoperative echocardiograms. The left ventricular posterior wall was thickened (greater than upper limit of normal! 3) in 17. All patients with normal wall thickness and 5 with thickened walls had one-stage repair. All 12 patients with two-stage repair had a thickened posterior wall. Patients with normal wall thickness had a mortality of 10%.Those with thickened posterior walls had a mortality of 17.6%. There was no significant difference in outcome between these two groups, but patients with thickened walls were much more likely to have had two-stage repair (p = 0.0(01). Outcome related to degree of obstruction. Barber and colleagues/ also reported an increased risk for patients with more severe subaortic obstruction. In the current group there was no statistically significant difference between the subaortic gradients of survivors and nonsurvivors (Fig. 3). The current group, however, had an overall mean subaortic gradient that was significantly
lower than that of the cohort reported by Barber and colleagues. To control for differences in the mean gradient between the current group and the cohort reported by Barber and colleagues, we divided the two cohorts into three subgroups based on the degree of subaortic obstruction (Fig. 4). The mild group had gradients from 10 to 25 mm Hg, the moderate group, between 26 and 40 mm Hg, and the severe group, greater than 40 mm Hg. The outcomes in these subgroups, both overall and by type of repair, are shown in Fig. 5. Because of the small number of patients with mild and moderate obstruction in the report of Barber and colleaguesf we cannot make any valid statistical comparisons for these subgroups. The 6% mortality in the patients with mild obstruction who had one-stage repair is not different from the surgical mortality for all patients with double-inlet LV having the modified Fontan procedure at the Mayo Clinic between 1981 and 1989 (9%).14 In the subgroup of patients with severe obstruction, there was a dramatic improvement in survival. Patients who had two-stage repair in this subgroup had a mortality of 17% compared with the 67% in the subgroup of Barber and colleagues'' (p = 0.05). Complications (early). One patient who had one-stage repair had takedown of the Fontan anastomosis and
Volume 104 Number 5 November 1992
Univentricular connection to a double-inlet LV
Gradients 10-25 mm Hg
Table IV. Complications in patients who had OSR or TSR Earl y Co mplete A V block Persistent effusions Postoper ati ve bleeding requiring reoperation Cardi ac tamponade Wound infection Other Late Atri al arrhythmia Requiring ongoing medication Requiring a ntitachycardia pacemaker Recurrent subaortic obstruction requiring reoperation Atrial patch leak requiring reoperation Other
OSR
TSR
2
6
0 0
2
1
2 2 2
0 0
I 235
Current cohort
20
1984 -1989
16
12 B
0 0%
I
11%
6%
50%
Gradients 26-40 mm Hg 8
3
2
1
2
20
0
16
(/)
12
C
C
2
o
OSR, O ne-stage repair; TSR, two-stage repair; A V, a trioventricular.
placement of a central shunt in the immediate postoperative periodbecauseof an excessive transpulmonary gradient. Progressive cyanosis and polycythemiarequired an additional systemic-to-pulmonary artery shunt 2 years later. The other early complications experiencedby the current group of patients are listed in Table IV. The two patients in whomcomplete AV blockdeveloped had subaortic resection early in the series. Between 1987and the end of this study, 10 patients were operated on with this technique, and there have been no additional cases of complete AV block. Late follow-up. The 27 patients who survived the immediatepostoperativeperiod had been followed up for a meanof 22 months (range I month to 56 months) at the completion of this study. One patient who had two-stage repair had not yet had the modified Fontan procedure performed because of persistently increased pulmonary arteriolar resistance despite adequate relief of the subaortic obstruction. There were two late deaths, one in a patient whohad two-stagerepair and one in a patient who had one-stage repair. The cause of death in the patient whohad two-stagerepair was presumed to be an arrhythmia. The patient was aged 26 years upon entry into this study and even at that time had a history of ventricular arrhythmias and was receiving antiarrhythmic therapy. In the patient who had one-stage repair, protein-losing enteropathydeveloped 2 yearsafter the Fontan procedure despite satisfactory repair and resection (determined by catheterizationafter the diagnosisof protein-losing enter-
~ a...
Currenl cohort 1984-1989
B
CurrenlcohOr1
4
0 67 %
14
12
Barber et at, 1973-1983
17%
0%
25%
Gradients > 40 mm Hg ·Barber vs . TSR P - O OS
10
8 6
2
o
67 %
25%
50 %
17%
Mortality rate ~
Survivor
IlIIlIIIIlIIII Nonsurvivor
Fig. 5. Effect of staging on outcome. OSR, One-stage repair; TSR, two-stage repair,
opathy was made). Four years after the Fontan procedure, severe left AV valve insufficiency and recurrent subaortic obstruction developed. At that time he had AV valve replacement and repeat resection of the VSD at another institution. He died with persistent protein-losing enteropathy 2 months after this operation. Effect of calendar year. Similar to the findings of several previous investigators, 15-17 our results indicated a trend toward improved survival in the later years of this study (Fig. 6). The improvement in survival for patients with severe obstruction who had two-stage repair was apparent, however, evenin the earliest periodof this study (p = 0.02).
The Journal of
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O'Leary et al.
Thoracic and Cardiovascular Surgery
28 24
oc:
20
vl
16
OJ
12
C
~
Q.
Current cohort 1984-1985 1986-1989
Barber et al, 1973-1983
8 4 0
All 10·40 >40
All 10·40
All 10·40
>40
>40
_
_
Nonsurvivor
All Survivor mil 10·40 { c::J >40
Fig. 6. Calendar year effect. OSR, One-stage repair; TSR, two-stage repair. Discussion Survival after cardiac operations for double-inlet LV with subaortic obstruction has improved. Our overall mortality of 16% is significantly better than the 50% to 60% mortality reported in the early 1980s.2-8 The 6% mortality in patients with mild obstruction is, in fact, no different from our current mortality (9%) for an unselected group of patients with double-inlet LV having the Fontan operation.!" Several variables may have favorably affected survival in our cohort. Our patients, as a group, had less severe subaortic obstruction than previous groups, probably because of wider recognition of subaortic obstruction as a significant risk factor and the current trend toward intervention before such obstruction becomes severe. Our patients also had the advantage of increasing surgical experience. In addition, since 1984 we have used a twostage surgical approach for patients with the most significant obstruction. Presumably the advantage of relieving significant subaortic obstruction before attempting the modified Fontan operation was that ventricular afterload was substantially reduced. Consequently, in an unobstructed ventricle, preexisting myocardial hypertrophy could regress and diastolic function could improve. These changes should allow the ventricle to adapt more easily to the unusual hemodynamic circumstances that exist after Fontan operation. This presumption was supported by the decreased subaortic gradient, decreased left ventricular posterior wall thickness, and decreased LVEDP found in patients who had subaortic resection as the first stage of two-stage repair. The most convincing evidence that prior relief of subaortic obstruction was advantageous was the improvement in outcome for patients who had twostage repair and resting subaortic gradients greater than 40 mm Hg, even in the earliest years of the technique's application. The fact that increased left ventricular pos-
terior wall thickness did not affect outcome in our cohort was probably also due to the beneficial effects of two-stage repair. One of the more encouraging findings was the improved outcome for patients younger than 10 years. This improvement may have been due to a combination of improved selection of patients for operation and recent advances in perioperative care, methods of cardiopulmonary bypass, and surgical techniques for the young. These improvements allow relatively safe surgical intervention before severe obstruction develops or subaortic obstruction produces potentially irreversible deleterious changes in the ventricular myocardium. Even with these improvements, cardiac difficulties were still experienced by the survivors of both one-stage repair and two-stage repair. Irrespective of surgical approach, only about 50% (one-stage repair, 8 of 18; two-stage repair, 4 of 8) of the long-term survivors were free of significant cardiac problems (see Table IV). This was not dissimilar to the long-term results seen in an unselected group of patients after the Fontan operation, however.' 8 Several authors 9- 12, 1 9 have advocated a modified Damus-Stansel-Kaye procedure to relieve subaortic obstruction in double-inlet LV. For several reasons we and others/" have advocated direct enlargement of the VSD and outlet chamber to relieve subaortic obstruction. First, patients may develop significant pulmonary ("neoaortic") valve regurgitation after this procedure. This may result from distortion of the main pulmonary artery by a pulmonary artery band.i" Second, the modified Damus-Stansel-Kaye procedure has been associated with high mortality in this group of patients (53% in 34 patientsj.t- 12,20,21 In addition, the present study indicates that direct enlargement of the VSD and subaortic outlet chamber effectively relieves the obstruction. In this series this technique was associated with less morbidity and mortality than has been reported for the Damus-StanselKaye procedure. Bypassing an obstructed subaortic outflow tract with a modified Damus-Stansel-Kaye operation may be a good option, however, in infants with univentricular hearts or in patients with single ventricles of right ventricular morphology. In summary, survival after the modified Fontan operation for double-inlet LV with subaortic obstruction has improved significantly. The previously reported influence of age on outcome was not apparent in our group of patients. In addition, the deleterious influence of severe obstruction was offset by the beneficial effect of two-stage repair. At this time we recommend that patients with mild obstruction (any resting gradient less than 25 mm Hg) have one-stage repair. Those with severe obstruction
Volume 104 Number 5 November 1992
(resting gradients greater than 40 mm Hg) should have two-stage repair. It is not possible to determine from the available data whether one-stage repair or two-stage repair is better for patients with moderate obstruction (resting gradients from 26 to 40 mm Hg). Increasing experience should provide additional data for decision making in this intermediate group.
We thank Eileen M. Nemec for her assistance in collecting the echocardiographic data.
REFERENCES I. Moodie DS, Ritter DG, Tajik AJ, O'Fallon WM. Longterm follow-up in the unoperated univentricular heart. Am J CardioI1984;53:1124-8. 2. Somerville J, Becu L, Ross D. Common ventricle with acquired subaortic obstruction. Am J CardioI1974;34:20614. 3. Freedom RM, Sondheimer H, Dische R, Rowe RD. Development of "subaortic stenosis" after pulmonary arterial banding for common ventricle. Am J Cardiol 1977; 39:78-83. 4. Moreno-Cabral RJ, Miller DC, Oyer PE, Stinson EB, Reitz BA, Shumway NE. A surgical approach for S,L,L single ventricle incorporating total right atrium-pulmonary artery diversion. J THORAC CARDIOVASC SURG 1980;79: 202-9. 5. Como A, Becker AE, Bulterijs AHK, et al. Univentricular heart: Can we alter the natural history? Ann Thorac Surg 1982;34:716-26. 6. McKay R, Pacifico AD, Blackstone EH, Kirklin JW, Bargeron LM Jr. Septation of the univentricular heart with left anterior subaortic outlet chamber. J THORAC CARDIOVASC SURG 1982;84:77-87. 7. Penkoske PA, Freedom RM, Williams WG, Trusler GA, Rowe RD. Surgical palliation of subaortic stenosis in the univentricular heart. J THORAC CARDIOVASC SURG 1984;87:767-81. 8. Barber G, Hagler DJ, Edwards WD, et al. Surgical repair of univentricular heart (double-inlet left ventricle) with obstructed anterior outlet chamber. J Am Coli Cardiol 1984;4:771-8. 9. Lin AE, Laks H, Barber G, Chin AJ, Williams RG. Subaortic obstruction in complex congenital heart disease: management by proximal pulmonary artery to ascending
Univentricular connection to a double-inlet LV
12 37
aorta end to side anastomosis. J Am Coli Cardiol 1986;7: 617-24. 10. Freedom RM, Benson LN, Smallhorn JF, Williams WG, Trusler GA, Rowe RD. Subaortic stenosis, the univentricular heart, and banding of the pulmonary artery: an analysis of the courses of 43 patients with univentricular heart palliated by pulmonary artery banding. Circulation 1986; 73:758-64. II. Park SC, Siewers RD, Neches WH, et al. Surgical management of univentricular heart with subaortic obstruction. Ann Thorac Surg 1984;37:417-21. 12. Rothman A, Lang P, Lock JE, Jonas RA, Mayer JE, Castaneda AR. Surgical management of subaortic obstruction in single left ventricle and tricuspid atresia. J Am Coli CardioI1987;10:421-6. 13. Feigenbaum H. Echocardiography. 4th ed. Philadelphia: Lea & Febiger, 1986. 14. Mair DD, Hagler DJ, Julsrud PR, Puga FJ, Schaff HV, Danielson GK. Early and late results of the modified Fontan procedure for double-inlet left ventricle: the Mayo Clinic experience. J Am Coli CardioI1991;18:1727-32. 15. Kirklin JK, Blackstone EH, Kirklin JW, Pacifico AD, Bargeron LM Jr. The Fontan operation. Ventricular hypertrophy, age, and date of operation as risk factors. J THORAC CARDIOVASC SURG 1986;92:1049-64. 16. Mayer JE Jr, Helgason H, Jonas RA, et al. Extending limits for modified Fontan procedures. J THORAC CARDIOVASC SURG 1986;92:1021-8. 17. Bartmus DA, Driscoll DJ, et al. The modified Fontan operation for children less than four years old. J Am Coli Cardiol 1990;15:429-35. 18. Driscoll DJ, Offord KP, Feldt RH, Schaff HV, Puga FJ, Danielson GK. Five to fifteen year follow up after the Fontan operation. Circulation 1992;85:469-96. 19. Franklin RCG, Spiegelhalter DJ, Anderson RH, et al. Double-inlet ventricle presenting in infancy. II. Results of palliative operations. J THORAC CARDIOVASC SURG 1991;101:917-23. 20. Cheung HC, Lincoln C, Anderson RH, et al. Options for surgical repair in hearts with univentricular atrioventricular connection and subaortic stenosis. J THORAC CARDIOVASC SURG 1990;100:672-81. 21. Franklin RCG, Sullivan ID, Anderson RH, Shinebourne EA, Deanfield JE. Is banding of the pulmonary trunk obsolete for infants with tricuspid atresia and double-inlet ventricle with a discordant ventriculo-arterial connection? Role of aortic arch obstruction and subaortic stenosis. J Am Coli CardioI1990;16:1455-64.
Uiventricular connection to a dominant left ventricle (LV) with an anterior subaortic outlet chamber, hereafter referred to as double-inlet LV, is a congenital cardiac malformation that has a poor natural history.' When subaortic obstruction coexists with this malformation, previous attempts at corrective operations have been associated with a particularly high mortality.v? In 1984 Barber and coworkers'' reported the early surgical experience at the Mayo Clinic with this lesion; the surgical mortality in this group was 56%. This poor outcome was From the Section of Pediatric Cardiology and the Division of Thoracic and Cardiovascular Surgery, Mayo Clinic and Mayo Foundation, Rochester, Minn. Received for publication June 3,1991.
similar to the experience of other investigators at that time. 2-7 In addition to the high mortality, Barber and coworkers'' reported that patients with severe subaortic obstruction had a worse surgical outcome than patients with less obstruction. This information prompted many clinicians to change their approach to this lesion.9-!2 Since severe subaortic obstruction is associated with poor outcome.i we hypothesized that prior relief of severe subaortic obstruction might improve survival after the Fontan procedure. Therefore we devised a staged approach to the surgical repair of this malformation and began to apply it in 1984. The purpose of this study is to report and analyze the results of this staged approach.
Accepted for publication Jan. 20, 1992.
Methods
Address for reprints: David J. Driscoll, MD, Section of Pediatric Cardiology, Mayo Clinic, 200 First St. SW, Rochester, MN 55905.
Study patients. The register of all patients operated on at the Mayo Clinic between January 1984 and August 1989 was reviewed. Inclusion criteria were as follows:
12/1/36843
1 23 1
The Journal of Thoracic and Cardiovascular Surgery
I 2 3 2 O'Leary et al.
Table I. Comparison ofpatients reported by Barber
and colleagues' with those in the current study Study group Barber et al.
No. of patients Meanage (yr) Gradient (rnm Hg) Mean Range Pulmonary artery banding (no. of pt) Systemic-to-pulmonary artery shunt (No. of patients)
18 10.5 ± 6.6
64 ± 38* 10-140 13
3
Current study 32 9.9 ± 7.6 30 ± 22* 10-96
27 4
*p
I. The patient had double-inlet LV with an anterior subaortic outlet chamber. Patients with atresia of an atrioventricular (AV) valve were included as long as the AV relationship was consistent with double-inlet LV and an anterior subaortic outlet chamber was present. 2. Resting (directly measured) pressure gradient (from the LV to the ascending aorta) was 10 mm Hg or more. 3. The patient was considered to be a possiblecandidate for the modified Fontan procedure. 4. The subaortic obstruction was relieved by enlargement of the ventricular septal defect (VSD) in all patients. Some patients had additional resection of subaortic myocardium or patch enlargement (or both) of the outlet chamber. Only one patient who had an operation for this malformation was excluded from the study (on the basis of criterion 4). That patient was aged 18 months, had severe obstruction, and an aorta-pulmonary anastomosis was performed; the patient did not survive. This was the only patient with this malformation to have this type of operation during the study period. Surgical approach. Patients with moderately severe or severe subaortic obstruction were considered candidates for a two-stage repair. Two-stage repair consisted of two sequential operations. During the first operation the subaortic obstruction was relieved.The outlet chamber was usually approached transaortically, and the subaortic resection was performed through the retracted aortic valve. If the exposure was inadequate, if the aorta was small (as in infants), or ifthe outlet chamber required enlargement with a patch, the transoutlet chamber approach was employed. All patients had enlargement of the VSD by direct resection of the ventricular septum in an area away from the conduction system. When the outlet chamber was located anteriorly and to the left, the septal incisionwasoriented apically and posteriorly. For patients with a right-sided outlet chamber, the septal incision was oriented apically and anteriorly. Some patients had additional resection of subaortic muscle within the outlet chamber or patch enlargement (or both) of the outlet chamber. This initial procedure was followed by a convalescent period of about 1 year. This interval was chosen to allow time for regression of preexisting ventricular hypertrophy and improvement in ventricular compliance. After this period the patient was reevaluated and the second stage of repair (a modified Fontan operation) was performed if the patient was an acceptable candidate. Patients with this lesion and mild subaortic obstruction were
considered for a one-stage repair, which consisted of VSD enlargement, subaortic resection or outlet chamber patch augmentation (or both if necessary), and a simultaneous modified Fontan procedure. Study procedure. The records of the patients identified by registry review were examined for details of history, preoperative evaluations (both invasiveand noninvasive),operations, and postoperative course. The cohort described in 1984 by Barber and coworkers" was used as a historical control for comparisons of surgical outcome based on age, preoperative subaortic gradient, surgical approach, and year of operation. Statistical methods. Differences between the two cohorts were compared using Student's t test for unpaired groups or, when appropriate, for paired groups. Differences in survival between cohorts and subgroups within the cohorts were compared by X2 analysis. Only differences with two-tailed p values of 0.05 or less were considered significant. All data, when appropriate, were expressed as the mean ± one standard deviation. Results Demographics. Thirty-two patients met the study's inclusion criteria (25 male, 7 female). They were aged I to 26 years at the time of one-stage repair or the first operation of two-stage repair (mean 9.9 ± 7.6 years). The subaortic pressure gradient ranged from 10 to 96 mm Hg (mean 30 ± 22 mm Hg). Previous palliative operations. Of the 32 patients, 27 had had banding of the pulmonary artery. The remaining five had natural pulmonary or subpulmonary stenosis, or both. Four patients had systemic-to-pulmonary artery shunts. Three of these had required shunt placement after pulmonary artery banding. One patient, also with prior pulmonary artery banding, had had a Glenn anastomosis. Four patients had previous attempts at subaortic resection elsewhere with variable success. Five had repair of aortic coarctation. Two patients had balloon atrial septostomy, and one had had a Blalock-Hanlon septectomy. Two patients were pacemaker dependent before entering the study; one of these had had subaortic resection elsewhere. Comparisons between the current group and the cohort reported by Barber and colleagues'' are shown in Table I. Repairs. All patients had VSD enlargement. Ten patients required additional resection of myocardium within the outlet chamber. Two patients had patch enlargement of the outlet chamber. Twenty of the 32 patients had one-stage repair. The remaining 12 patients had two-stage repair. One of the patients who had twostage repair required additional subaortic resection at the time of the modified Fontan procedure for a recurrent gradient of 41 mm Hg (the gradient after the initial resection had been 5 mm Hg). Table II compares available preoperative data of patients having one-stage repair with data of patients having the first stage of two-stage repair. The only significant differences between the two
Volume 104 Number 5 November 1992
Univentricular connection to a double-inlet LV
12 3 3
Table II. Comparison ofpatients having OSR with those having the first stage of TSR OSR No. of patients Mean age (yr) Atresia of one AV valve (no.)
TSR 12 9.8 ± 7.1
20 10.1 ± 8.0
Left Right Previous operations (no.) Pulmonary artery banding Systemic-to-pulmonary artery shunt Coarctation repair Subaortic resection Pacemaker Atrial septostomy or septectomy Hemodynamic variables Mean subaortic gradient (mm Hg) Mean LVEDP (rnm Hg) Mean pulmonary arteriolar resistance (U/m 2 ) Echocardiographic variables Mean LV posterior wall thickness (mm) Mean LV posterior wall thickness ratio#
2 0
0 0
15 2 2 2 3
12 2 3 2 I 0
19.6 ± 13.5 8.9 ± 3.6*,t 1.9 ± 0.9:1:
46.9 ± 22 13.7 ± 5.3t 1.8 ± 2.1§
I
8.1 ± 1.0 ±
11.7 ± 1.6 ±
2·11,~
O·~I
3.4~
0.4
OSR, One-stage repair; TSR, two-stage repair; A V, atrioventricular; LVEDP, left ventricular end-diastolic pressure; LV, left ventricular.
'Eighteen patients.
tp = 0.007. :j:Thirteen patients. §Six patients. IIFifteen patients. 'lIP = 0.006.
#Ratio of observed wall thickness over the upper limit of normal.' J
Table III. Comparison ofpatients having OSR with those having the second stage of TSR OSR Hemodynamic variables Mean subaortic gradient (rnm Hg) Mean LVEDP (mm Hg) Mean pulmonary arteriolar resistance (U/m 2) Echocardiographic variables Mean LV posterior wall thickness (mm) Mean LV posterior wall thickness (ratio)*
TSR
No. of pt
Mean ± SD
No. of pt
Mean ± SD
20 18 13
19.6 ± 13.5 8.9 ± 3.6 1.9 ± 0.9
9 9 9
10.4 ± 13.3 10.9 ± 6.0 2.0 ± 1.7
IS
8.1 ± 2.7 1.0 ± 0.4
6 6
10.5 ± 2.3 1.3 ± 0.4
15
OSR, One-stage repair; TSR, two-stage repair; LVEDP, left ventricular end-diastolic pressure; LV, left ventricular. 'Ratio of observed wall thickness over upper limit of normal. 13
groups were the presence of increased left ventricular end-diastolic pressure (LVEDP) and increased left ventricular posterior wall thickness in patients having twostage repair. When reevaluated after the convalescent period (postsubaortic resection), the two-stage repair group had gradients, LVEDPs, and left ventricular posterior wall thicknesses that were decreased and not significantly different from the preoperative values of patients who had one-stage repair (Table III). Outcome. Within 30 days of the operation, 5 of the 32 patients died. This 15.6%mortality is significantly better
than the 56% reported by Barber and colleagues" (p < 0.001) (Fig. 1). Two of the deaths occurred in patients having one-stage repair, and the other three were in patients having two-stage repair (two after initial resection; one after modified Fontan procedure). Outcome related to age. Barber and coworkersreported an increased risk of death for young patients. In the current group there was no statistically significant difference in the mean ages between the survivors and the nonsurvivors (Fig. 2). In fact, 18 of 23 patients in the current group who were lessthan 10 years of age on entry
The Journal of Thoracic and Cardiovascular Surgery
I 2 3 4 O'Leary et al.
Cu rrent cohort
36 32
J:
c vi
C Q) ~
0-
24
Barbe r at al
20
1973- 1983
Current cohort O SR
120
E E
100
C Q)
80
~
60
28
ci
140
Ol
1984-198 9
'6
16
tn ()
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e0
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ro
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0
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_
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No nsurvivor
120
s, ai OJ
«
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I Barbe r et at,
Current coho rt
1973-1983
1984 - 1989
•II
0 No .
Surv ivo rs
Non survivors
Su rvivo rs
8
10
27
E
E
E Q)
EJ
•
I
P< Q,001
Survivor
•
Survivor
_
Survivors
Nonsurvrvors
27
5
Nonsurvivor
Fig. 3. Effect of severity of obstruction on outcome.
rn
25
15
Nonsurvivors 10 D
Fig. l. Overall outcome. OSR, One-stage repair; TSR, twostage repair.
20
1984- 1989
No .
Mortality rate
o
Current co hort
1973-1983
0
25%
10%
Barber et al,
'6 ro
100
o
c. U> C
60
Q)
40
Q)
20
'"
20
at.
1973- 1983
80
0, c
::i;
Barber et
"16
CL
18
Em
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16
_
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14 12
~
~
10
~ !$1
8 6
~
~
~%
P ",N$
18
32
Patients, no. Nonsurvivors
10-25
26-40
> 40
Gradient range, mm Hg
Fig. 4. Subaortic gradient distribution.
Nonsurvivor
Fig. 2. Effect of age on outcome. to the study survived. None of the eight patients from the report of Barber and colleagues who were less than the age of 10 years survived. Outcome related to left ventricular posterior wall thickness. Twenty-seven of the 32 patients had preoperative echocardiograms. The left ventricular posterior wall was thickened (greater than upper limit of normal! 3) in 17. All patients with normal wall thickness and 5 with thickened walls had one-stage repair. All 12 patients with two-stage repair had a thickened posterior wall. Patients with normal wall thickness had a mortality of 10%.Those with thickened posterior walls had a mortality of 17.6%. There was no significant difference in outcome between these two groups, but patients with thickened walls were much more likely to have had two-stage repair (p = 0.0(01). Outcome related to degree of obstruction. Barber and colleagues/ also reported an increased risk for patients with more severe subaortic obstruction. In the current group there was no statistically significant difference between the subaortic gradients of survivors and nonsurvivors (Fig. 3). The current group, however, had an overall mean subaortic gradient that was significantly
lower than that of the cohort reported by Barber and colleagues. To control for differences in the mean gradient between the current group and the cohort reported by Barber and colleagues, we divided the two cohorts into three subgroups based on the degree of subaortic obstruction (Fig. 4). The mild group had gradients from 10 to 25 mm Hg, the moderate group, between 26 and 40 mm Hg, and the severe group, greater than 40 mm Hg. The outcomes in these subgroups, both overall and by type of repair, are shown in Fig. 5. Because of the small number of patients with mild and moderate obstruction in the report of Barber and colleaguesf we cannot make any valid statistical comparisons for these subgroups. The 6% mortality in the patients with mild obstruction who had one-stage repair is not different from the surgical mortality for all patients with double-inlet LV having the modified Fontan procedure at the Mayo Clinic between 1981 and 1989 (9%).14 In the subgroup of patients with severe obstruction, there was a dramatic improvement in survival. Patients who had two-stage repair in this subgroup had a mortality of 17% compared with the 67% in the subgroup of Barber and colleagues'' (p = 0.05). Complications (early). One patient who had one-stage repair had takedown of the Fontan anastomosis and
Volume 104 Number 5 November 1992
Univentricular connection to a double-inlet LV
Gradients 10-25 mm Hg
Table IV. Complications in patients who had OSR or TSR Earl y Co mplete A V block Persistent effusions Postoper ati ve bleeding requiring reoperation Cardi ac tamponade Wound infection Other Late Atri al arrhythmia Requiring ongoing medication Requiring a ntitachycardia pacemaker Recurrent subaortic obstruction requiring reoperation Atrial patch leak requiring reoperation Other
OSR
TSR
2
6
0 0
2
1
2 2 2
0 0
I 235
Current cohort
20
1984 -1989
16
12 B
0 0%
I
11%
6%
50%
Gradients 26-40 mm Hg 8
3
2
1
2
20
0
16
(/)
12
C
C
2
o
OSR, O ne-stage repair; TSR, two-stage repair; A V, a trioventricular.
placement of a central shunt in the immediate postoperative periodbecauseof an excessive transpulmonary gradient. Progressive cyanosis and polycythemiarequired an additional systemic-to-pulmonary artery shunt 2 years later. The other early complications experiencedby the current group of patients are listed in Table IV. The two patients in whomcomplete AV blockdeveloped had subaortic resection early in the series. Between 1987and the end of this study, 10 patients were operated on with this technique, and there have been no additional cases of complete AV block. Late follow-up. The 27 patients who survived the immediatepostoperativeperiod had been followed up for a meanof 22 months (range I month to 56 months) at the completion of this study. One patient who had two-stage repair had not yet had the modified Fontan procedure performed because of persistently increased pulmonary arteriolar resistance despite adequate relief of the subaortic obstruction. There were two late deaths, one in a patient whohad two-stagerepair and one in a patient who had one-stage repair. The cause of death in the patient whohad two-stagerepair was presumed to be an arrhythmia. The patient was aged 26 years upon entry into this study and even at that time had a history of ventricular arrhythmias and was receiving antiarrhythmic therapy. In the patient who had one-stage repair, protein-losing enteropathydeveloped 2 yearsafter the Fontan procedure despite satisfactory repair and resection (determined by catheterizationafter the diagnosisof protein-losing enter-
~ a...
Currenl cohort 1984-1989
B
CurrenlcohOr1
4
0 67 %
14
12
Barber et at, 1973-1983
17%
0%
25%
Gradients > 40 mm Hg ·Barber vs . TSR P - O OS
10
8 6
2
o
67 %
25%
50 %
17%
Mortality rate ~
Survivor
IlIIlIIIIlIIII Nonsurvivor
Fig. 5. Effect of staging on outcome. OSR, One-stage repair; TSR, two-stage repair,
opathy was made). Four years after the Fontan procedure, severe left AV valve insufficiency and recurrent subaortic obstruction developed. At that time he had AV valve replacement and repeat resection of the VSD at another institution. He died with persistent protein-losing enteropathy 2 months after this operation. Effect of calendar year. Similar to the findings of several previous investigators, 15-17 our results indicated a trend toward improved survival in the later years of this study (Fig. 6). The improvement in survival for patients with severe obstruction who had two-stage repair was apparent, however, evenin the earliest periodof this study (p = 0.02).
The Journal of
I 236
O'Leary et al.
Thoracic and Cardiovascular Surgery
28 24
oc:
20
vl
16
OJ
12
C
~
Q.
Current cohort 1984-1985 1986-1989
Barber et al, 1973-1983
8 4 0
All 10·40 >40
All 10·40
All 10·40
>40
>40
_
_
Nonsurvivor
All Survivor mil 10·40 { c::J >40
Fig. 6. Calendar year effect. OSR, One-stage repair; TSR, two-stage repair. Discussion Survival after cardiac operations for double-inlet LV with subaortic obstruction has improved. Our overall mortality of 16% is significantly better than the 50% to 60% mortality reported in the early 1980s.2-8 The 6% mortality in patients with mild obstruction is, in fact, no different from our current mortality (9%) for an unselected group of patients with double-inlet LV having the Fontan operation.!" Several variables may have favorably affected survival in our cohort. Our patients, as a group, had less severe subaortic obstruction than previous groups, probably because of wider recognition of subaortic obstruction as a significant risk factor and the current trend toward intervention before such obstruction becomes severe. Our patients also had the advantage of increasing surgical experience. In addition, since 1984 we have used a twostage surgical approach for patients with the most significant obstruction. Presumably the advantage of relieving significant subaortic obstruction before attempting the modified Fontan operation was that ventricular afterload was substantially reduced. Consequently, in an unobstructed ventricle, preexisting myocardial hypertrophy could regress and diastolic function could improve. These changes should allow the ventricle to adapt more easily to the unusual hemodynamic circumstances that exist after Fontan operation. This presumption was supported by the decreased subaortic gradient, decreased left ventricular posterior wall thickness, and decreased LVEDP found in patients who had subaortic resection as the first stage of two-stage repair. The most convincing evidence that prior relief of subaortic obstruction was advantageous was the improvement in outcome for patients who had twostage repair and resting subaortic gradients greater than 40 mm Hg, even in the earliest years of the technique's application. The fact that increased left ventricular pos-
terior wall thickness did not affect outcome in our cohort was probably also due to the beneficial effects of two-stage repair. One of the more encouraging findings was the improved outcome for patients younger than 10 years. This improvement may have been due to a combination of improved selection of patients for operation and recent advances in perioperative care, methods of cardiopulmonary bypass, and surgical techniques for the young. These improvements allow relatively safe surgical intervention before severe obstruction develops or subaortic obstruction produces potentially irreversible deleterious changes in the ventricular myocardium. Even with these improvements, cardiac difficulties were still experienced by the survivors of both one-stage repair and two-stage repair. Irrespective of surgical approach, only about 50% (one-stage repair, 8 of 18; two-stage repair, 4 of 8) of the long-term survivors were free of significant cardiac problems (see Table IV). This was not dissimilar to the long-term results seen in an unselected group of patients after the Fontan operation, however.' 8 Several authors 9- 12, 1 9 have advocated a modified Damus-Stansel-Kaye procedure to relieve subaortic obstruction in double-inlet LV. For several reasons we and others/" have advocated direct enlargement of the VSD and outlet chamber to relieve subaortic obstruction. First, patients may develop significant pulmonary ("neoaortic") valve regurgitation after this procedure. This may result from distortion of the main pulmonary artery by a pulmonary artery band.i" Second, the modified Damus-Stansel-Kaye procedure has been associated with high mortality in this group of patients (53% in 34 patientsj.t- 12,20,21 In addition, the present study indicates that direct enlargement of the VSD and subaortic outlet chamber effectively relieves the obstruction. In this series this technique was associated with less morbidity and mortality than has been reported for the Damus-StanselKaye procedure. Bypassing an obstructed subaortic outflow tract with a modified Damus-Stansel-Kaye operation may be a good option, however, in infants with univentricular hearts or in patients with single ventricles of right ventricular morphology. In summary, survival after the modified Fontan operation for double-inlet LV with subaortic obstruction has improved significantly. The previously reported influence of age on outcome was not apparent in our group of patients. In addition, the deleterious influence of severe obstruction was offset by the beneficial effect of two-stage repair. At this time we recommend that patients with mild obstruction (any resting gradient less than 25 mm Hg) have one-stage repair. Those with severe obstruction
Volume 104 Number 5 November 1992
(resting gradients greater than 40 mm Hg) should have two-stage repair. It is not possible to determine from the available data whether one-stage repair or two-stage repair is better for patients with moderate obstruction (resting gradients from 26 to 40 mm Hg). Increasing experience should provide additional data for decision making in this intermediate group.
We thank Eileen M. Nemec for her assistance in collecting the echocardiographic data.
REFERENCES I. Moodie DS, Ritter DG, Tajik AJ, O'Fallon WM. Longterm follow-up in the unoperated univentricular heart. Am J CardioI1984;53:1124-8. 2. Somerville J, Becu L, Ross D. Common ventricle with acquired subaortic obstruction. Am J CardioI1974;34:20614. 3. Freedom RM, Sondheimer H, Dische R, Rowe RD. Development of "subaortic stenosis" after pulmonary arterial banding for common ventricle. Am J Cardiol 1977; 39:78-83. 4. Moreno-Cabral RJ, Miller DC, Oyer PE, Stinson EB, Reitz BA, Shumway NE. A surgical approach for S,L,L single ventricle incorporating total right atrium-pulmonary artery diversion. J THORAC CARDIOVASC SURG 1980;79: 202-9. 5. Como A, Becker AE, Bulterijs AHK, et al. Univentricular heart: Can we alter the natural history? Ann Thorac Surg 1982;34:716-26. 6. McKay R, Pacifico AD, Blackstone EH, Kirklin JW, Bargeron LM Jr. Septation of the univentricular heart with left anterior subaortic outlet chamber. J THORAC CARDIOVASC SURG 1982;84:77-87. 7. Penkoske PA, Freedom RM, Williams WG, Trusler GA, Rowe RD. Surgical palliation of subaortic stenosis in the univentricular heart. J THORAC CARDIOVASC SURG 1984;87:767-81. 8. Barber G, Hagler DJ, Edwards WD, et al. Surgical repair of univentricular heart (double-inlet left ventricle) with obstructed anterior outlet chamber. J Am Coli Cardiol 1984;4:771-8. 9. Lin AE, Laks H, Barber G, Chin AJ, Williams RG. Subaortic obstruction in complex congenital heart disease: management by proximal pulmonary artery to ascending
Univentricular connection to a double-inlet LV
12 37
aorta end to side anastomosis. J Am Coli Cardiol 1986;7: 617-24. 10. Freedom RM, Benson LN, Smallhorn JF, Williams WG, Trusler GA, Rowe RD. Subaortic stenosis, the univentricular heart, and banding of the pulmonary artery: an analysis of the courses of 43 patients with univentricular heart palliated by pulmonary artery banding. Circulation 1986; 73:758-64. II. Park SC, Siewers RD, Neches WH, et al. Surgical management of univentricular heart with subaortic obstruction. Ann Thorac Surg 1984;37:417-21. 12. Rothman A, Lang P, Lock JE, Jonas RA, Mayer JE, Castaneda AR. Surgical management of subaortic obstruction in single left ventricle and tricuspid atresia. J Am Coli CardioI1987;10:421-6. 13. Feigenbaum H. Echocardiography. 4th ed. Philadelphia: Lea & Febiger, 1986. 14. Mair DD, Hagler DJ, Julsrud PR, Puga FJ, Schaff HV, Danielson GK. Early and late results of the modified Fontan procedure for double-inlet left ventricle: the Mayo Clinic experience. J Am Coli CardioI1991;18:1727-32. 15. Kirklin JK, Blackstone EH, Kirklin JW, Pacifico AD, Bargeron LM Jr. The Fontan operation. Ventricular hypertrophy, age, and date of operation as risk factors. J THORAC CARDIOVASC SURG 1986;92:1049-64. 16. Mayer JE Jr, Helgason H, Jonas RA, et al. Extending limits for modified Fontan procedures. J THORAC CARDIOVASC SURG 1986;92:1021-8. 17. Bartmus DA, Driscoll DJ, et al. The modified Fontan operation for children less than four years old. J Am Coli Cardiol 1990;15:429-35. 18. Driscoll DJ, Offord KP, Feldt RH, Schaff HV, Puga FJ, Danielson GK. Five to fifteen year follow up after the Fontan operation. Circulation 1992;85:469-96. 19. Franklin RCG, Spiegelhalter DJ, Anderson RH, et al. Double-inlet ventricle presenting in infancy. II. Results of palliative operations. J THORAC CARDIOVASC SURG 1991;101:917-23. 20. Cheung HC, Lincoln C, Anderson RH, et al. Options for surgical repair in hearts with univentricular atrioventricular connection and subaortic stenosis. J THORAC CARDIOVASC SURG 1990;100:672-81. 21. Franklin RCG, Sullivan ID, Anderson RH, Shinebourne EA, Deanfield JE. Is banding of the pulmonary trunk obsolete for infants with tricuspid atresia and double-inlet ventricle with a discordant ventriculo-arterial connection? Role of aortic arch obstruction and subaortic stenosis. J Am Coli CardioI1990;16:1455-64.