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Ann Thorac Surg 1998;66:659-663
© 1998 The Society of Thoracic Surgeons
a Department of Pathology, University of Padua, Padua, Italy
b Department of Cardiovascular Surgery, University of Padua, Padua, Italy
Address reprint requests to Dr Thiene, Istituto di Anatomia Patologica, Via A. Gabelli, 61, 35121 Padova, Italy
e-mail: (cardpath{at}ux1.unipd.it)
Presented at the Workshop on "One and One-Half Ventricle Repairs," Gubbio, Italy, Dec 6–7, 1996.
Abstract
Background. A review of the history and practice of cavopulmonary connections in staging toward Fontan operation and the pathologic experience at Padua University is presented.
Methods. Gross and histologic assessment of the heart-lung blocks removed at autopsy in the cases in which the cause of death could be related to a dysfunction of the cavopulmonary anastomosis were performed.
Results. The main complications were distortion of the intraatrial tunnel and thrombosis of the pulmonary branches of the cavopulmonary anastomosis.
Conclusions. The cavopulmonary anastomosis remains a widespread procedure, both as a preliminary step to a Fontan operation and as an integral part of a Fontan or modified Fontan procedure in all those cardiac malformations characterized by a hypoplastic right or left ventricle in which these ventricles are too small to support the whole circulation.
Current surgical approaches to patients with congenital heart disease characterized by a functionally single ventricle derive from the idea that systemic venous blood can pass through the lungs without the action of a ventricular pump. Carlon, a surgeon working at the University of Padua, first developed the technique for performing an anastomosis between the superior vena cava and the right pulmonary artery in cases of cyanosis associated with cardiovascular disease. In their original work published in 1951 [1] he and his associates suggested that " ... it would be possible and much more convenient to increase pulmonary blood flow with venous blood instead of arteriovenous blood as used by Blalock, through a convenient anastomosis between that great venous trunk and the capillary region of the right lung." They performed the procedure on 11 dogs, and in some of them the operation was successful. In Figure 1, reproduced from the original article, the final step of the operation is illustrated with the end-to-end anastomosis between the azygos vein and the right pulmonary artery. "The superior vena cava is tied short of its opening into the right auricle and the blood from the superior part of the body flowing into the right lung and returning to the left side of the heart through the right pulmonary veins, avoids the right side of the heart" [1]. The evidence of a successful right heart bypass was produced. However, Carlon’s name has been overshaded by Glenn who, in the United States, carried out much of the experimental and clinical work on the application of the procedure. Glenn and Patino’s first experimental work with cavopulmonary anastomosis in dogs was published in 1954 [2] and the clinical application was attempted in 1958 [3] on a 7-year-old boy with single ventricle and pulmonary stenosis. The decade from 1950 to 1960 witnessed other surgeons’ attempts to perform complete or partial right heart bypass. Worthwhile to mention, even though unsuccessful, are the applications in humans of the cavopulmonary anastomosis as early as 1954 by Shumacker [4] in the United States, and the major contributions in the understanding of the physiologic consequences, the indications, and the merits and disadvantages of this procedure given by the group of Robicsek and Sanger [5, 6]. A contribution to this group [6] was also made by Vincenzo Gallucci, at that time a young research fellow who continued Carlon’s pioneering studies in the cardiovascular field, and who later became the chief director of the Cardiovascular Surgery Department at the University of Padua. In Russia also, a great deal of work was carried out at the same time both in dogs and humans. In 1956 Meshalkin [7] reported his large experience in 24 children, with 21 successes. The classic Glenn technique remained standard for many years.
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In 1992 Norwood and coworkers [12] incorporated the cavopulmonary anastomosis between the superior vena cava, the root of the right atrium, and the right pulmonary artery in the second step of the "Norwood" procedure for the hypoplastic left heart syndrome in which the hypoplastic ventricle is the left one and the right, well-developed ventricle is used to support the systemic circulation. Indeed, they stated that total cavopulmonary connection could be better managed in two steps to allow better diastolic function of the single ventricle [13].
In more recent years the cavopulmonary anastomosis has been included as a part of the total right heart bypass in both the intracardiac [14, 15] and the extracardiac procedures [16–18]. In this setting the superior vena cava–pulmonary artery anastomosis could be considered both as an intermediate step and as a part of the procedure of total right heart bypass.
The main indications for the cavopulmonary anastomosis remain cardiac diseases characterized by a single-ventricle physiology, in other words, all those malformations that have the common feature of providing a sole functional ventricular chamber to support the systemic circulation and in which the blood to the lungs could be provided by a systemic–pulmonary shunt (Blalock-Taussig) or by a partial or total cavopulmonary anastomosis.
From an anatomic standpoint these cardiac malformations are atresia of an atrioventricular valve, double-inlet ventricle, pulmonary atresia with intact septum, complex transposition of the great arteries, or double-outlet right ventricle, hypoplastic left heart syndrome, straddling atrioventricular valves, and malalignment atrioventricular septal defect.
Atrioventricular valve atresia, both left and right, is characterized by a well-developed ventricle on one side and a small ventricle on the other. Often this ventricle is rudimentary or severely hypoplastic, and a muscular bar is present at the atrioventricular junction at the site of the absent connection (or valve). In double-inlet ventricle, often the main chamber is of left morphology with a rudimentary right ventricle located anterior to the main ventricular chamber. The two atrioventricular valves open into the main chamber. Although in some cases of double inlet the anatomy could suggest the option for surgical repair by septation, nowadays the best treatment seems to be a modified Fontan procedure. In the setting of pulmonary atresia, we are faced with a right ventricle of different sizes. In the case of intact septum the rudimentary ventricle could present with only an inlet or outlet component with an absent trabecular part. This is mainly because of the degree of myocardial hypertrophy, which can even obliterate the trabecular portion, the outlet portion, or both.
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In the case of hypoplastic left heart syndrome, namely, a group of congenital anomalies such as aortic atresia, mitral atresia, mitral-aortic atresia, and hypoplastic left heart with critical aortic stenosis, the left ventricle is hypoplastic or even virtual. The right ventricle is then used to support the systemic circulation with the creation of a new aorta and a systemic pulmonary shunt. It is in the second step of the palliation that the shunt is closed and the cavopulmonary anastomosis is performed.
In the case of straddling valve, either morphologically tricuspid, mitral, or a common valve in the setting of malalignment atrioventricular septal defects, there is an imbalance between the two ventricles because of the malalignment of the interventricular septum. This is very frequent in the case of atrial isomerism.
Pathologic experience
We present our pathologic experience, confined to the cases in which the cause of death could be related to a dysfunction of the cavopulmonary anastomosis. They consist of cases of tricuspid atresia (Fig 2), pulmonary atresia with intact septum (Figs 3, 4), double-inlet left ventricle, and mitroaortic atresia in patients who underwent the stage III Norwood procedure (Table 1). All cases had a bidirectional cavopulmonary anastomosis, in 2 of them with intracardiac tunneling. The main complications turned out to be distortion of the intraatrial tunnel and thrombosis of the pulmonary arteries or of the cavopulmonary anastomosis (see Table 1).
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In conclusion, the cavopulmonary anastomosis remains a widespread procedure, both as a preliminary step to a Fontan procedure and as an integral part of a Fontan or modified Fontan operation in all those cardiac malformations characterized by a hypoplastic right or left ventricle in which these ventricles are too small to support the whole circulation. Even though mortality and morbidity of cavopulmonary connection have decreased in recent years, problems can still be identified [19, 20].
In some patients a gradual enlargement of collateral venous channels between the superior vena cava and the inferior vena cava occurs with diminished flow through the anastomosis and with an increase in pressure in the superior vena cava. In some patients a coil embolization of multiple venous collaterals at cardiac catheterization is necessary to increase arterial oxygen saturation. However, if all the venous collaterals are not accessible to coil embolization, a take-down of the cavopulmonary anastomosis is required [11].
In addition, there is frequently decreased perfusion of the upper lobe of the right lung relative to the lower one. This problem has been partially resolved by the introduction of the bidirectional cavopulmonary anastomosis.
Pulmonary artery distortion, defined as peripheral pulmonary artery stenosis or hypoplasia or discontinuity of the pulmonary arteries, has remained a risk factor for successful definitive repair.
The classic Glenn operation was never complicated by atrial arrhythmias. On the other hand, the bidirectional Glenn or hemi-Fontan operation produces sinoatrial node dysfunction as a consequence of surgical injury to the sinoatrial node area. The occurrence of altered atrial rhythm after cavopulmonary shunt is itself a risk factor for arrhythmias after the Fontan operation [21].
The most serious late complication remains the development of pulmonary arteriovenous fistula in patients who had a long-standing shunt. In recent series the incidence of pulmonary arteriovenous fistula varied from 11% to 19% [19, 22]. Many of the patients reported were less than 1 year old at the time when the cavopulmonary anastomosis was constructed, suggesting an age factor in the development of this complication. It is interesting to note that Glenn [23] himself stated that in some patients, normally occurring minute arteriovenous connections in the lung may enlarge to become fistulous and cause precapillary shunting of blood with arterial desaturation. The exact mechanism of pulmonary arteriovenous fistula formation is not clear, but the use of a bidirectional cavopulmonary anastomosis with an additional pulsatile pulmonary artery blood flow seems to reduce the risk of such a complication.
Acknowledgments
Supported by Target Project "Congenital Heart Disease" Veneto Region, Venice, Italy.
References
This article has been cited by other articles:
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  C. Mavroudis, C. L. Backer, L. M. Kohr, B. J. Deal, J. Stinios, A. J. Muster, and D. F. Wax Bidirectional Glenn shunt in association with congenital heart repairs: the 1 1/2 ventricular repair Ann. Thorac. Surg., September 1, 1999; 68(3): 976 - 981. [Abstract] [Full Text] [PDF]
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