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Aortic-Pulmonary Septal Defect
Aortic-Pulmonary Septal Defect JOHN W. KIRKLIN F. HENRY ELLIS, JR. O. THERON CLAGETT
AORTIC-PULMONARY septal defect is a rare congenital anomaly. In general, it results in a condition which has many similarities to that due to a large patent ductus arteriosus and it sometimes can be distinguished from patent ductus arteriosus only with difficulty. DEFINITION
Aortic-pulmonary septal defect, sometimes referred to as "partial persistent truncus arteriosus," is a congenital malformation which results in communication between the ascending aorta and the main pulmonary trunk. This communication has no length but, indeed, is a fistulous opening between these two great vessels. In some instances this fistulous opening is located immediately above the semilunar valve, and the aorta and pulmonary trunk may have a common wall between this fistula and the rings of the semilunar valve. In other instances, the fistula is removed approximately 1 cm. from these rings, and the pulmonary trunk and aorta may have separate walls between the fistula and the valve. Like patent ductus arteriof)us, this fistula allows free communication between the aorta and pulmonary trunk. The location of the communication in the two conditions, however, is quite different. PATHOLOGIC PHYSIOLOGY
The pathologic physiology of aortic-pulmonary septal defect is similar to that of a large patent ductus arteriosus. There is free communication between the aorta and pulmonary trunk and most often a large amount of blood is shunted from the aorta to the pulmonary trunk. Although this malformation has not been observed in a sufficient number of cases to allow conclusions to be drawn with certainty, it is probable that pulmonary hypertension is associated more often with this malformation than with patent ductus arteriosus. This is probably related to the huge flow of blood which occurs across this large, short communication. In some instances, the pulmonary hypertension may be so severe that the 975
976
John W. Kirklin, F. Henry Ellis, Jr., O. Theron Clagett
pressures in the pulmonary trunk and aorta are approximately equal. Under these conditions, blood is usually shunted from the pulmonary trunk to the aorta as well as from the aorta to the pulmonary artery. There is then some reversal of flow. DIAGNOSIS
Often patients with aortic-pulmonary septal defect are considered on clinical grounds to have patent ductus arteriosus. Classically a continuous murmur is heard in the region of the left second or third interspace. There may be a wide systemic pulse pressure. Certain features in a case of aortic-pulmonary septal defect may lead the clinician to suspect that the patient does not have a typical patent ductus arteriosus. Under these conditions, cardiac catheterization is carried out and the proper diagnosis can be suspected from certain of the findings recorded at this study. Occasionally angiocardiography will pinpoint the lesion as an aortic-pulmonary septal defect. Without doubt, certain patients still will come to operation with the diagnosis of patent ductus arteriosus. It is, therefore, important that the surgeon be aware of the fact that a patient suspected of having patent ductus arteriosus may well have an aortic-pulmonary septal defect if patency of the ductus cannot be demonstrated at thoracotomy. In this condition one may fail even to identify a ligamentum arteriosum. The pericardium should then be opened and the true defect may be seen. INDICATIONS FOR OPERATION
Since the shunt of blood from the aorta to the pulmonary artery in cases of aortic-pulmonary septal defect is nearly always large and since pulmonary hypertension is an ever-present threat in these conditions, the suspicion that this anomaly is present or the diagnosis of its presence must be an indication for operation. SURGICAL TECHNIQUES
Aortic-pulmonary septal defect presents a formidable challenge to the surgeon undertaking its repair. The exposure of the defect is accomplished in our hands by means of the posterolateral approach through the fourth interspace. The incision must be carried a little farther anteriorly than usual for adequate exposure. The pericardium is widely opened anterior to the phrenic nerve and the ascending aorta and the pulmonary trunk are identified. A tremendous thrill is present over the base of the pulmonary trunk and the fistula can be palpated by indenting the lateral wall of the pulmonary trunk against the defect in the aorticpulmonary septum. The first stage in the operation is the determination of the feasibility of repair. The all-important item is the nature of the aorta and pulmonary trunk between the fistula and the semilunar valve. In some
Aortic-Pulmonary Septal Defect
977
instances, a common wall is found at this level and complete division of the fistula seems impossible under these circumstances by presently available techniques. We have encountered this in one instance. Perhaps some type of suture-ligation technique could be employed to close the defect in this type of case. On occasions, careful dissection allows the development of a plane of cleavage between the aorta and pulmonary trunk proximal to the fistula. By pursuing such a plane of cleavage the surgeon can actually separate the two great vessels between the fistula and the rings of the semilunar valve. Then the surgeon can completely encircle the fistula by carefully dissecting posterior and cephalad to it. After such complete dissection, it is possible to place appropriate clamps across the side of the aorta and pulmonary trunk in the region of the fistula. Since the fistula itself has no length, the actual walls of the great vessels must be clamped in order that the fistula can be disconnected. After the fistulous tract is disconnected, the resultant defects in the aorta and pulmonary trunk are oversewn with fine silk sutures. The execution of this technical procedure may be extremely difficult. Complete co-operation of the anesthesiologist with the surgeon and his team is necessary in order that patients may be safely escorted through this procedure. RESULTS OF OPERATION
We have operated on too few patients and too few cases have been reported in the literature to allow sweeping statements as to the results of operation; however, complete repair of the malformation should result in a virtually normal cardiovascular system even though significant pulmonary hypertension existed prior to operation. In one of our cases in which complete preoperative and postoperative data are available, severe pulmonary hypertension existed prior to operation with virtually equal pressures in the aorta and pulmonary trunk. Six months after complete division of the fistula, the pressure in the pulmonary trunk had decreased markedly and it is anticipated that a permanent and virtually complete return to normal will be accomplished.
AORTIC-PULMONARY septal defect is a rare congenital anomaly. In general, it results in a condition which has many similarities to that due to a large patent ductus arteriosus and it sometimes can be distinguished from patent ductus arteriosus only with difficulty. DEFINITION
Aortic-pulmonary septal defect, sometimes referred to as "partial persistent truncus arteriosus," is a congenital malformation which results in communication between the ascending aorta and the main pulmonary trunk. This communication has no length but, indeed, is a fistulous opening between these two great vessels. In some instances this fistulous opening is located immediately above the semilunar valve, and the aorta and pulmonary trunk may have a common wall between this fistula and the rings of the semilunar valve. In other instances, the fistula is removed approximately 1 cm. from these rings, and the pulmonary trunk and aorta may have separate walls between the fistula and the valve. Like patent ductus arteriof)us, this fistula allows free communication between the aorta and pulmonary trunk. The location of the communication in the two conditions, however, is quite different. PATHOLOGIC PHYSIOLOGY
The pathologic physiology of aortic-pulmonary septal defect is similar to that of a large patent ductus arteriosus. There is free communication between the aorta and pulmonary trunk and most often a large amount of blood is shunted from the aorta to the pulmonary trunk. Although this malformation has not been observed in a sufficient number of cases to allow conclusions to be drawn with certainty, it is probable that pulmonary hypertension is associated more often with this malformation than with patent ductus arteriosus. This is probably related to the huge flow of blood which occurs across this large, short communication. In some instances, the pulmonary hypertension may be so severe that the 975
976
John W. Kirklin, F. Henry Ellis, Jr., O. Theron Clagett
pressures in the pulmonary trunk and aorta are approximately equal. Under these conditions, blood is usually shunted from the pulmonary trunk to the aorta as well as from the aorta to the pulmonary artery. There is then some reversal of flow. DIAGNOSIS
Often patients with aortic-pulmonary septal defect are considered on clinical grounds to have patent ductus arteriosus. Classically a continuous murmur is heard in the region of the left second or third interspace. There may be a wide systemic pulse pressure. Certain features in a case of aortic-pulmonary septal defect may lead the clinician to suspect that the patient does not have a typical patent ductus arteriosus. Under these conditions, cardiac catheterization is carried out and the proper diagnosis can be suspected from certain of the findings recorded at this study. Occasionally angiocardiography will pinpoint the lesion as an aortic-pulmonary septal defect. Without doubt, certain patients still will come to operation with the diagnosis of patent ductus arteriosus. It is, therefore, important that the surgeon be aware of the fact that a patient suspected of having patent ductus arteriosus may well have an aortic-pulmonary septal defect if patency of the ductus cannot be demonstrated at thoracotomy. In this condition one may fail even to identify a ligamentum arteriosum. The pericardium should then be opened and the true defect may be seen. INDICATIONS FOR OPERATION
Since the shunt of blood from the aorta to the pulmonary artery in cases of aortic-pulmonary septal defect is nearly always large and since pulmonary hypertension is an ever-present threat in these conditions, the suspicion that this anomaly is present or the diagnosis of its presence must be an indication for operation. SURGICAL TECHNIQUES
Aortic-pulmonary septal defect presents a formidable challenge to the surgeon undertaking its repair. The exposure of the defect is accomplished in our hands by means of the posterolateral approach through the fourth interspace. The incision must be carried a little farther anteriorly than usual for adequate exposure. The pericardium is widely opened anterior to the phrenic nerve and the ascending aorta and the pulmonary trunk are identified. A tremendous thrill is present over the base of the pulmonary trunk and the fistula can be palpated by indenting the lateral wall of the pulmonary trunk against the defect in the aorticpulmonary septum. The first stage in the operation is the determination of the feasibility of repair. The all-important item is the nature of the aorta and pulmonary trunk between the fistula and the semilunar valve. In some
Aortic-Pulmonary Septal Defect
977
instances, a common wall is found at this level and complete division of the fistula seems impossible under these circumstances by presently available techniques. We have encountered this in one instance. Perhaps some type of suture-ligation technique could be employed to close the defect in this type of case. On occasions, careful dissection allows the development of a plane of cleavage between the aorta and pulmonary trunk proximal to the fistula. By pursuing such a plane of cleavage the surgeon can actually separate the two great vessels between the fistula and the rings of the semilunar valve. Then the surgeon can completely encircle the fistula by carefully dissecting posterior and cephalad to it. After such complete dissection, it is possible to place appropriate clamps across the side of the aorta and pulmonary trunk in the region of the fistula. Since the fistula itself has no length, the actual walls of the great vessels must be clamped in order that the fistula can be disconnected. After the fistulous tract is disconnected, the resultant defects in the aorta and pulmonary trunk are oversewn with fine silk sutures. The execution of this technical procedure may be extremely difficult. Complete co-operation of the anesthesiologist with the surgeon and his team is necessary in order that patients may be safely escorted through this procedure. RESULTS OF OPERATION
We have operated on too few patients and too few cases have been reported in the literature to allow sweeping statements as to the results of operation; however, complete repair of the malformation should result in a virtually normal cardiovascular system even though significant pulmonary hypertension existed prior to operation. In one of our cases in which complete preoperative and postoperative data are available, severe pulmonary hypertension existed prior to operation with virtually equal pressures in the aorta and pulmonary trunk. Six months after complete division of the fistula, the pressure in the pulmonary trunk had decreased markedly and it is anticipated that a permanent and virtually complete return to normal will be accomplished.