Ann Thorac Surg 2002;73:663-664
© 2002 The Society of Thoracic Surgeons
Case report
Pathologic findings in atrial musculature seven years after the intraatrial tunnel Fontan
Yasushi Yoshikawa, MD*a,
Hatsue Ishibashi-Ueda, MDb,
Hideki Uemura, MDa,
Youichi Kawahira, MDa,
Toshikatsu Yagihara, MDa
a Department of Cardiovascular Surgery, National Cardiovascular Center, Osaka, Japan
b Department of Pathology, National Cardiovascular Center, Osaka, Japan
Accepted for publication June 23, 2001.
* Address reprint requests to Dr Yoshikawa, Department of Cardiovascular Surgery, National Cardiovascular Center, 5-7-1, Fujishirodai, Suita, Osaka 565-8565, Japan
e-mail: yayoshikawa{at}hotmail.com
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Abstract
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Surgical specimens of the atrial wall were microscopically investigated 7 years after total cavopulmonary connection. The intima of the morphologically right atrium was thicker in the part used for the high-pressured venous channel than in the other portion placed for the low-pressured atrial cavity supporting the systemic circulation. The number of myocardial cells was smaller, and the area of interstitial fibrosis was greater, in both circumstances, when compared with the normal right atrium.
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Introduction
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We previously employed intraatrial rerouting when achieving total cavopulmonary connection (TCPC) for the Fontan circulation [1]. Our modification was use of the anterior wall of the atrium, being different from the original lateral tunnel technique [2], so as to place the sinus node outside the high-pressured venous channel [1]. A part of the right atrial appendage was used in a rectangular shape together with an intraatrial heterologous pericardial baffle for draining the inferior caval vein. Recently, one of such patients underwent reoperation, and the atrial wall was investigated microscopically.
A girl, having double inlet right ventricle with separate atrioventricular valves in the setting of usual atrial arrangement, underwent TCPC by the intraatrial maneuver [1] at the age of 5 years. Atrioventricular regurgitation became obvious 5 years after the procedure, and progressed to a severe degree. The patient, therefore, underwent orificial closure of the right-sided valve, and plasty to the left-sided one, 7 years after the initial TCPC. Although no atrial arrhythmia had been noted, conversion to extracardiac TCPC was concomitantly employed using a 24-mm diameter extended polytetrafluoroethylene tube, the alternative method being among our current preferences for achieving the Fontan circulation [1].
Consecutive catheterizations demonstrated enlargement of the inferior caval venous channel (Table 1).
Width of the autologous tissue used for the channel, designed initially as 20 mm, became much larger.
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Table 1. Changes in the Venous Channel for the Inferior Caval Vein and Atrial Pressure Supporting the Systemic Circulation
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Histopathologically, the intima of the morphologically right atrium was thicker in the anterior part used for the high-pressured venous channel (600 ± 380 µm) than in the other part placed for the low-pressured atrial cavity supporting the systemic circulation (153 ± 67 µm) (Fig 1).
Computerized microscopic morphometry on the specimens with Masson’s trichrome staining using Winroof software (Nikon, Tokyo, Japan) illustrated that the atrial myocardial cells occupied 56% and 63% of the overall medial layer area for the high-pressured and the low-pressured sites, respectively. Degenerative changes were present in both. These proportions of the myocytes were clearly smaller than the anticipated normal value for the right atrium which was known to be greater than 90% [3]. Electron microscopic examination demonstrated that the mitochondria in the myocytes had increased in number, and that the myofibrils had irregularly been arranged. There were no obvious differences noted in these findings between the high- and the low-pressured parts. The postoperative course after the reoperation has been entirely smooth without arrhythmia or recurrent regurgitation.
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Fig 1. Photomicrographs from the morphologically right atrium. The intima of the high-pressured part of the atrium showed 750 µm in thickness (a), being much thicker than that of the low-pressured part (b). Degeneration and fibrosis of the atrial myocardium were recognized in either circumstance (Masson’s trichrome staining, x25). Electron micrograph of the atrial myocardium from the high- pressured part (c) illustrated that increased mitochondrial proliferation was present among myofilaments. The myofibrillar bundles showed irregular branching and loss of myofibrils (x6,200).
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Comment
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The anterior tunnel technique was chosen in 34 patients undergoing TCPC between 1987 and 1995 at our institution, anticipating possible advantages in less frequent atrial arrhythmia [1, 4] and in growth potential of the inferior caval venous channel. Two patients (6%) have experienced episodes of atrial arrhythmia; paroxysmal supraventricular tachycardia in 1 with situs inversus, and sinus nodal dysfunction in the other with left isomerism. This incidence seems comparable to, or even better than, the previously reported 14% to 22.5% [5, 6] in patients undergoing the lateral tunnel method. As for enlargement of the channel, it was clearly over the anticipated normal growth of the pathway in our present patient. This was most likely because of chronic distention of the atrial appendage posed by the elevated venous pressure. This could be a disadvantage of our anterior tunnel technique. Such prolonged stress can produce unfavorable effects on the structure [5, 6], even if the part of the atrium placed within a high-pressured circumstance is limited.
In this respect, histopathologic changes in atrial musculature, as seen in our present experience, could be a morphologic background of functional abnormalities, even in patients without episodes of arrhythmia. In our patient, similar histological changes were also found in the part placed for the low-pressured cavity, related to volume load, as well as mild pressure load, caused by atrioventricular regurgitation. Probably because of this, a qualitative difference could not be clearly demonstrated between the high-pressured and the low-pressured sites. Nonetheless, adjacent parts of the atrial wall should have precisely the same histologic findings unless the parts of the morphologically right atrium were placed in different circumstances. Accordingly, the results were considered sufficiently important to realize the impact of the circumstances, one for the venous channel and the other for the atrial cavity with atrioventricular regurgitation.
The surgeon should wisely pay attention to the underlying pathologic changes in the atrial wall subsequent to the Fontan procedure. On the basis of our present findings, we preclude use of any part of the atrium for the venous channel. TCPC should better be achieved in extracardiac fashion, and, in case construction of the intraatrial tunnel is mandatory, we recommend use of a prosthetic tube graft so as to avoid exposure of the atrial wall to the high-pressured channel.
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References
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Uemura H., Yagihara T., Kawahira Y., Yoshikawa Y., Kitamura S. Total cavopulmonary connection in children with body weight less than 10 kg. Eur J Cardiothorac Surg 2000;17:543-549.[Abstract/Free Full Text]
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De Leval M.R., Kilner P., Gewillig M., Bull C. Total cavopulmonary connection: a logical alternative to atriopulmonary connection for complex Fontan operations. J Thorac Cardiovasc Surg 1988;96:682-695.[Abstract]
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Davies M.J., Anderson R.H., Becker A.E. Anatomy of the conduction tissues. In: Davies M.J., Anderson R.H., Becker A.E., eds. The conduction system of the heart. London: Butterworths, 1983:9-24.
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Fishberger S.B., Wernovsky G., Gentles T.L., et al. Factors that influence the development of atrial flutter after the Fontan operation. J Thorac Cardiovasc Surg 1997;113:80-86.[Abstract/Free Full Text]
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Abstract
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