Ann Thorac Surg 1995;59:201-204
© 1995 The Society of Thoracic Surgeons
Left Ventricular Outflow Tract Obstruction in TGA: Treatment With LV-to-PA Valved Conduit
Franz X. Schmid, MD,
Mark Morales, MD,
Jaroslav Stark, MD
Cardiothoracic Unit, Great Ormond Street Hospital for Children, London, England
Accepted for publication August 26, 1994.
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Abstract
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Progressive or recurrent left ventricular outflow tract obstruction after a previous Mustard or Senning operation represents a rare but challenging problem. The obstruction can be resected in some patients, but abnormal attachment of the mitral valve or a long fibromuscular tunnel represents a difficult surgical problem. Between 1979 and 1993, we encountered this type of left ventricular outflow tract obstruction in 10 patients, 4 to 13 years after the atrial repair. They ranged in age from 5 to 15 years (mean, 8.8 years) and weighed between 11.5 and 47 kg (mean, 25.3 kg). Operations were performed through a left thoracotomy with the patient on hypothermic cardiopulmonary bypass but without aortic cross-clamping. The left atrial appendage and descending aorta were cannulated. Good relief of the gradient was obtained in all patients (mean residual gradient, 14.8 mm Hg). All patients survived the operation. One patient died suddenly at home 6 months later; 2 patients required conduit replacement. All 9 long-term survivors are asymptomatic as of 6 months to 8 years after their conduit placement or replacement. We recommend the placement of a left ventricle-to-pulmonary artery valved conduit for the relief of severe left ventricular outflow tract obstruction arising after a Senning or Mustard operation that cannot be managed by other means.
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Introduction
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Left ventricular outflow tract obstruction (LVOTO) in a patient with transposition of the great arteries (TGA) may preclude the use of an arterial switch operation. Several causes of LVOTO have been described [1]. Some causes, such as pulmonary valve or supravalvar stenosis, a subvalvar shelf, or aneurysm of the membranous part of the interventricular septum, can be treated surgically. Obstruction caused by the bulging septum may become insignificant after an arterial switch operation when the pressure relationship between the right and left ventricles changes. Other causes, such as an abnormal attachment of the mitral valve or a long fibromuscular tunnel, are not amenable to direct relief. For such patients, the placement of a valved conduit to bypass the obstruction presents an excellent solution.
It is important to realize that not all gradients measured between the left ventricle (LV) and the pulmonary artery (PA) signify the existence of an anatomic obstruction [2]. The gradient may be due to an increased pulmonary blood flow, which is common in patients with TGA. The gradient diminishes or disappears after atrial or arterial repair.
Bypassing the obstruction was suggested by McGoon [3] and ourselves [4]. Originally we placed an LV-to-PA conduit at the time of atrial repair in those patients with a severe nonresectable obstruction. However, the results in 13 patients treated at the Mayo Clinic and at our institution were disappointing, as there were five hospital and two late deaths [5].
In later years, we changed our policy, accepting an increased pressure in the LV at the time of the Mustard or Senning operation. We considered an LV-to-PA conduit to be indicated only when the left ventricular pressure was at a systemic or suprasystemic level. In this paper, we review our overall experience with conduit interposition for the relief of LVOTO arising 4 to 13 years after the atrial repair.
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Patients and Methods
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An LV-to-PA conduit was inserted in 10 patients between 1979 and 1993. Operations were performed at the Hospital for Sick Children, Great Ormond Street, and at Harley Street Clinic, London. Four patients had previously undergone a Mustard operation and 6, a Senning operation. The patients ranged in age from 5 to 15 years (mean, 8.6 years) and their weight ranged between 11.5 and 47 kg (mean, 26.5 kg). The interval between the atrial repair and the insertion of the conduit was 4 to 13 years. Two patients had mild to moderate congestive heart failure with dysfunction of the LV and an increased left ventricular end-diastolic pressure (>20 mm Hg). The other patients had only minimal symptoms. The cardiothoracic ratio on the chest x-ray study was greater than 0.5 in 6 patients. All 10 had electrocardiographic evidence of biventricular hypertrophy.
The diagnosis was made on the basis of the cross-sectional and Doppler echocardiography findings. It was also confirmed by cardiac catheterization and angiography findings. An anomalous attachment of the mitral valve (Fig 1
) was found in 7 patients. One patient had an aneurysm of the membranous septum associated with an anomalous attachment of the mitral valve and 2 had a long fibromuscular tunnel (Fig 2). The LV-to-PA gradients ranged from 63 to 173 mm Hg (mean, 110 mm Hg). The left ventricular peak systolic pressure ranged from 90 to 200 mm Hg (mean, 127 mm Hg). Two patients suffering from heart failure had an elevated left ventricular end-diastolic pressure (22 mm Hg in one and 25 mm Hg in the other). In the remaining 8 patients, the left ventricular end-diastolic pressure was within the normal range (Table 1).
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Fig 1. . Left ventricular angiogram demonstrating obstruction to flow due to the abnormal attachment of the mitral valve (arrows). (LV = left ventricle; PA = pulmonary artery.)
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Fig 2. . Left ventricular angiogram demonstrating obstruction to flow due to the long fibromuscular tunnel. (LV = left ventricle; PA = pulmonary artery.)
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Surgical Technique
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The operation can be easily performed through a left thoracotomy made in the fifth intercostal space [6]. The pericardium is opened longitudinally about 2 cm in front of the phrenic nerve. Adhesions in this region are usually minimal. The LV is freed, and the left atrial appendage and the main and left PAs are dissected. The descending aorta is visualized after the lungs are retracted medially. A pursestring suture is placed on the descending aorta, which is easily cannulated for the purpose of arterial return (Fig 3). The lung is then retracted laterally and a pursestring suture placed on the left atrial appendage, which is cannulated with a large, single right-angled cannula for the purpose of venous return.
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Fig 3. . Left thoracotomy view. The arterial cannula (AC) is placed into the descending aorta (DA). The venous cannula (VC) is placed into the left atrial appendage. (AO = aorta; LV = left ventricle; PA = pulmonary artery.) (Reprinted from [6] by permission of Springer-Verlag.)
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The operation is performed with the patient on partial bypass at moderate hypothermia (25° to 27°C). If there is no atrial or ventricular communication, the operation can be performed on the beating heart; otherwise, the heart is electrically fibrillated. A left ventriculotomy is performed near the apex between the two stay stitches. When doing this, care must be taken not to injure the left anterior descending coronary artery or its branches. The edges of the ventriculotomy can be thinned and the small button of muscle excised. We do not use a rigid tube as an intraventricular extension of the conduit. We prefer instead to use a cryopreserved homograft, usually a pulmonary homograft. It is trimmed and sutured to the junction of the main and left PAs. If it is easier, it can be sutured to the left PA.
A matching Gore-Tex tube (W.L. Gore, Flagstaff, AZ) is then trimmed obliquely and sutured to the ventriculotomy. The suture line is buttressed with two strips of Teflon felt (Fig 4). If the heart was fibrillated, it is now defibrillated and the patient is rewarmed. The conduit is trimmed to an appropriate length before it is sutured to the homograft. Hemostasis is achieved, rewarming is completed, bypass is discontinued, and the cannulas are removed. Protamine is given, temporary pacing wires are placed, and the chest is closed with drains in place.
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Fig 4. . Completed conduit from the left ventricle to the pulmonary artery. (DT = Dacron tube [currently Gore-Tex tube is preferred]; HO = homograft; PA = pulmonary artery.)
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The postoperative care given these patients does not differ from the care usually given after other open heart procedures. Patients can be extubated early.
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Results
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All 10 patients survived. Gradients were measured intraoperatively in 9, and ranged between 8 and 20 mm Hg (mean, 14.8 mm Hg) (Table 2). Eight patients had an uncomplicated recovery and were extubated early. They were discharged from the hospital between 7 and 21 days (mean, 13.7 days) after operation. Two patients with a preoperatively elevated left ventricular end-diastolic pressure experienced a prolonged postoperative course. A 9-year-old girl required prolonged support on inotropic agents and ventilation. She underwent recatheterization but no gradient was found. Her left ventricular function gradually improved and she was discharged from the hospital 42 days after operation on a regimen of angiotensin-converting enzyme inhibitors. The second patient, a 15-year-old girl, suffered repeated respiratory tract infections and septicemia. Fortunately, her conduit did not get infected and she was discharged 29 days after operation.
Follow-up ranged from 6 months to 14 years (mean, 5.6 years). One patient died suddenly at home 6 months after operation. A postmortem examination was not performed. Although he had no history of arrhythmias, we presume that the most likely cause of his death was arrhythmia.
Reoperation for the relief of conduit stenosis was required in 2 patients, in one 9 and in the other 11 years after the original conduit placement. The original conduits were a Carpentier-Edwards (25 mm) and an aortic homograft extended with a Dacron tube (17 mm). The indication for reoperation was progression of the gradient from the LV to the PA (90 and 103 mm Hg). Reoperations were performed through the left thoracotomy. Exposure was easy and the patients' postoperative course uneventful. Both patients received cryopreserved 24-mm pulmonary homografts extended with a Gore-Tex tube.
All 9 survivors are asymptomatic 6 months to 8 years after their conduit placement or replacement. Doppler echocardiography has shown only minimal LV-PA gradients (8 to 20 mm Hg).
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Comment
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The surgical approach to LVOTO in patients with TGA depends on the nature of the underlying anatomic condition. Idriss and associates [7] resected an LVOTO directly in 12 patients. Oelert and colleagues [8] recommended a transatrial or transmitral resection of an LVOTO. Both groups of authors reported that residual gradients were present in their patients, and, in patients with an abnormal mitral valve, relief of the obstruction was not attempted. Patients with a bulging interventricular septum can be treated with an arterial switch operation. When the left ventricular pressure is increased after an arterial switch procedure, this moves the septum to the right and the gradient is diminished or disappears.
It has been our policy for some time to attempt resection of the obstruction. If it is incomplete or if resection is not possible, such as in the event of an abnormal attachment of the mitral valve, we accept an increased left ventricular pressure if it is subsystemic. In a few patients, we have accepted a systemic pressure in the LV. During follow-up, the gradient has not been observed to increase in most of our patients. A similar experience was reported by Park and associates [9]. It is therefore only a small number of patients, whose left ventricular pressure gradually increases to suprasystemic levels, or patients showing signs of heart failure, who need this operation.
Technically, the operation can be easily done through the left thoracotomy. This facilitates the cannulation and also enables us to choose the appropriate position and curvature of the conduit. The one late death was probably due to arrhythmia, as the child died while apparently in good health. Arrhythmias are well-recognized complications of atrial repairs for TGA [10, 11].
The long-term results will probably depend mostly on the fate of the implanted conduits. However, they should not differ from the results seen for patients with valved conduits implanted for other conditions [12, 13], except that, in the patients with TGA plus LVOTO, a moderate obstruction may be better tolerated. This is partly because the subpulmonary ventricle is the ``strong'' LV, and also because we virtually create a double-outlet LV, the original outlet being obstructed but still patent.
In conclusion, we recommend interposition of a valved conduit between the LV and PA in patients with severe nonresectable LVOTO arising after atrial repair of TGA.
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Footnotes
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Address reprint requests to Mr Stark, Cardiothoracic Unit, Great Ormond Street Hospital for Children, London WC1N 3JH, England.
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References
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- Shrivastava S, Tadavarthy SM, Fukada T, Edwards JE. Anatomic causes of pulmonary stenosis in complete transposition. Circulation 1976;54:154–9.[Abstract/Free Full Text]
- Taylor JFN, Silove ED, Graham GR. Pressure gradients from left ventricle to pulmonary artery in transposition of the great aerteries. In: Proceedings of the Seventh European Congress of Cardiology, Amsterdam, 1976:561.
- McGoon DC. Left ventricular and biventricular extracardiac conduits. J Thorac Cardiovasc Surg 1976;72:7–14.
- Singh AK, Stark J, Taylor JFN. Left ventricle to pulmonary artery conduit in treatment of transposition of the great arteries, restrictive ventricular septal defect and acquired pulmonary atresia. Br Heart J 1976;38:1213–6.[Abstract/Free Full Text]
- Stark J. Concordant transposition and left ventricular outflow tract obstruction. In: Stark J, de Leval M, eds. Surgery for congenital heart defects. London: Grune & Stratton, 1983:361–74.
- Stark J. Reoperations in patients with extracardiac conduits. In: Stark J, Pacifico AD, eds. Reoperations in cardiac surgery. London: Springer-Verlag, 1989:283–4.
- Idriss FS, DeLeon SY, Nikaidoh H, et al. Resection of left ventricular outflow obstruction in d-transposition of the great arteries. J Thorac Cardiovasc Surg 1977;74:343–51.[Medline]
- Oelert H, Borst HG. Transatrial resection of subpulmonary stenosis in transposition of the great arteries. Thorac Cardiovasc Surg 1979;27:58–60.[Medline]
- Park SC, Neches WH, Mathews RA, et al. Hemodynamic function after the Mustard operation for transposition of the great arteries. Am J Cardiol 1983;51:1514–9.[Medline]
- El-Said G, Rosenberg HS, Mullins CE, et al. Dysrhythmias after Mustard's operation for transposition of the great arteries. Am J Cardiol 1972;30:526–32.[Medline]
- Deanfield J, Camm J, Macartney F, et al. Arrhythmia and late mortality after Mustard and Senning operation for transposition of the great arteries: an eight year prospective study. J Thorac Cardiovasc Surg 1988;96:569–76.[Abstract]
- Bull C, Macartney FJ, Horvath P, et al. Evaluation of long-term results of homograft and heterograft valves in extracardiac conduits. J Thorac Cardiovasc Surg 1987;94:12–9.[Abstract]
- Ross DN, Somerville J. Actuarial estimates of the long-term results of homograft valved conduits between right ventricle and pulmonary arteries. In: Kirklin JW, Barratt-Boyes BG, eds. Cardiac surgery. Morphology, diagnostic criteria, natural history, techniques, results and indications. New York: Wiley 1986:800–2.
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Abstract
Introduction
