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Original report |
1
Department of Diagnostic Imaging, Hospital for Sick Children and University of
Toronto, 555 University Ave., Toronto M5G 1X8, Canada.
2
Division of Cardiology, Hospital for Sick Children and University of Toronto,
Toronto M5G 1X8, Canada.
3
Department of Critical Care Medicine, Hospital for Sick Children and
University of Toronto, Toronto M5G 1X8, Canada.
4
Department of Pediatrics, Hospital for Sick Children and University of
Toronto, Toronto M5G 1X8, Canada.
Received November 18, 1999;
accepted after revision April 3, 2000.
Address correspondence to I. Adatia.
Abstract
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CONCLUSION. We recommend that inferior venacavography be performed in routine assessment before surgery of patients with azygos or hemiazygos continuation of the inferior vena cava, in whom redirection of systemic venous blood to the pulmonary artery is contemplated.
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The practical importance of diagnosing persistence of the hepatic venous plexus is twofold. First, the diversion of blood flow away from the hepatic IVC may lead to the incorrect diagnosis of IVC stenosis. Second, after surgery to redirect systemic venous blood to the pulmonary artery, commonly used to palliate patients with left atrial isomerism and complex congenital heart disease [7], the diversion of desaturated blood away from the pulmonary circulation with retrograde flow in the azygos vein through the persistent hepatic venous plexus to the atrium may lead to unexplained and profound hypoxemia after surgery.
Therefore, we present the angiographic features in eight patients with these latter rare systemic venous anomalies with emphasis on the practical implications of the diagnosis and the importance of low inferior venacavography in routine assessment of patients with certain forms of congenital heart disease.
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Three patients were previously reported [3, 8].
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We divided the patients into two groups. Group 1 (three patients) had pulmonary vein anomalies in addition to persistence of the hepatic venous plexus with a patent, albeit underdeveloped, IVC (Figs. 1,2,3). In one patient (Fig. 1) the initial venogram suggested IVC stenosis with secondary decompression through the hepatic venous channels and the azygos. The error in diagnosis became apparent after surgery to augment the IVC. Cardiac catheterization after surgery showed the absence of a pressure gradient from the IVC to the right atrium and a patent surgical reconstruction of the IVC, without resolution of the hepatic venous channels [3]. Similar appearances in the two other children (Figs. 2 and 3) prompted us to follow them without surgical intervention. Neither child has developed signs or symptoms of IVC stenosis or a pressure gradient from low IVC to right atrium.
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Group 2 (five patients) (Figs. 4,5A,5B,6,7,8A,8B) had complex congenital heart disease (characterized by mixing of systemic and pulmonary venous blood at both atrial and ventricular levels) associated with left atrial isomerism or polysplenia syndrome and azygos or hemiazygos continuation of the IVC. All were candidates for palliation of the cardiac defect by anastomosis of the azygos or hemiazygos vein into the pulmonary artery to increase effective pulmonary blood flow, decrease physiologic right-to-left shunt, and thus improve systemic arterial oxygenation [7].
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In group 2, the diagnosis was made during cardiac catheterization in five patients with left atrial isomerism (Figs. 4, 5A, 6, and 8A,8B) to assess unexpected and, in one patient (Figs. 8A and 8B), profound arterial oxygen desaturation shortly after surgical anastomosis of the superior vena cava and azygos or hemiazygos to the pulmonary artery. Three patients underwent coil embolization of persistent hepatic venous fistula, and one patient underwent coil embolization of the underdeveloped IVC to decrease the right-to-left shunt with improvement of arterial oxygen saturation from 65-80% to 80-93%. Three of the four patients underwent subsequent completion of the total cavopulmonary anastomosis with hepatic vein redirection. In one of five patients with left atrial isomerism (Fig. 7), the presence of the hepatic venous fistula was detected by venography performed with the catheter low in the IVC before surgical systemic venous redirection. We elected not to undertake occlusion of the venous fistula but rather to follow the patient with early transcatheter embolization if problematic hypoxemia occurred after surgery. She underwent a successful Kawashima operation [7] with arterial oxygen saturation in the low 80% range after surgery. Although an arterial oxygen saturation greater than 90% is expected after the Kawashima procedure, she remained clinically well. We followed her without further intervention until she underwent total cavopulmonary anastomosis with redirection of the hepatic veins and thus the decompression of the fistula into the pulmonary artery. Subsequently, her systemic arterial oxygen saturation was 99%.
In all patients with left atrial isomerism, we confirmed low pulmonary artery pressures (< 12 mm Hg mean pressure) and the absence of anastomotic or pulmonary artery stenosis.
The angiographic appearances of the hepatic venous plexus differed between groups 1 and 2. In group 1, the inferior venacavograms showed an extensive racemose network of middle-size venous channels connecting the infrahepatic IVC to the hepatic veins and to the right atrium. In group 2, low inferior venacavography identified a large tortuous venous circuit arising from the infrahepatic IVC and renal vein connecting to the portal venous system and draining into the hepatic veins through a plexus of intrahepatic venous channels.
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We described the angiographic appearance of two anomalies of the hepatic segment of the inferior vena cava. Each anomaly has an important influence on treatment and requires low inferior venacavography for definitive diagnosis. The first anomaly consists of an uninterrupted, albeit underdeveloped, hepatic segment of the inferior vena cava with a persistent hepatic venous fistula connecting the IVC to the right atrium. We observed this pattern of venous drainage in four of our patients (one with complex congenital heart disease and three with pulmonary vein abnormalities). Underdevelopment of the hepatic segment of the inferior vena cava, in our experience, may occur with or without continuation of part of the venous return through the azygos or hemiazygos system. This underdevelopment has been described in children with complex congenital heart disease [3,4,5].
The importance of recognizing the anomaly is twofold. First, the persistence of a venous channel from the infrahepatic IVC through the liver to the right atrium reduces flow through the upper IVC and may suggest the diagnosis of IVC stenosis, also described in the scimitar syndrome [11]. The persistence of the hepatic plexus despite successful surgical augmentation of the small IVC in one of our patients (Fig. 1) suggests true underdevelopment of the IVC, rather than stenosis with subsequent decompression.
Second, in patients with complex heart disease and azygos continuation of the IVC, it is not sufficient to assume intrahepatic IVC interruption if the patient is to receive cardiac palliation with redirection of systemic venous return directly into the pulmonary artery.
After anastomosis of the azygos or hemiazygos vein to the pulmonary artery, only pulmonary and hepatic venous blood should return to the atrium, resulting in arterial oxygen saturation in the low 90% range. However, when the hepatic portion of the IVC persists, profound arterial oxygen desaturation ensues after surgery as a result of steal from the pulmonary circulation with reversal of flow in the hemiazygos vein and increased return of desaturated blood to the common atrium (Fig. 8A,8B).
The second anomaly is associated particularly with left atrial isomerism and is characterized by azygos continuation of the IVC and an extensive venous plexus originating at the renal vein and draining to the right atrium via connections with the portal and hepatic veins.
We suggest that the dilatated intrahepatic venous channels that connect the infrahepatic IVC azygos to the right atrium represent a primary developmental anomaly rather than the consequence of elevated venous pressure. Abnormal venous channels, particularly intrahepatic ones, have been described as a cause of persistent cyanosis and right-to-left shunt after bidirectional or total cavopulmonary anastomosis as palliation for complex congenital heart disease, especially with hepatic vein exclusion [8, 12]. It has been suggested that generally the abnormal venous channels open up in response to high venous pressures occurring after palliative cardiac surgery involving rerouting of systemic venous return to the pulmonary arteries [8, 12]. However, we suggest that hepatic venous channels, such as we describe, are present before surgery yet remain undiagnosed until the circulation is rerouted with production of a right-to-left shunt.
Indeed, four reasons add credence to the concept that the hepatic venous plexus and an underdeveloped hepatic IVC may exist before surgery: first, the identification of the hepatic venous plexus in two patients (one described by Jolly et al. [6] and one in this report [Fig. 7]), with azygos continuation of an interrupted IVC, who had not undergone cavopulmonary surgery; second, the documentation of persistence of an underdeveloped hepatic IVC to a right atrial connection in patients with left atrial isomerism, and azygos continuation of the IVC again in patients who had not undergone cavopulmonary shunts [1, 2, 4, 5]; third, the finding of venous pressures of less than 12 mm Hg without anastomotic or pulmonary artery stenosis; and fourth, the rapidity (immediately after surgery) with which the unexpected degree of cyanosis was noted in our patients.
Failure to visualize the persistent IVC or renal portohepatic venous plexus before surgery, as noted by Anderson et al. [1], occurs because low inferior venacavography is not performed as part of the routine diagnostic evaluation. Usually decompressing venous vessels after the bidirectional superior cavopulmonary anastomosis or Kawashima operation [7] (if there is azygos or hemiazygos continuation of the IVC) are diagnosed before surgery during investigation of unexpectedly low systemic arterial oxygen saturation [8, 12].
The practical importance of recognizing such anomalies before surgery is shown by four of our patients, in whom decompression of the superior vena caval flow from the pulmonary artery to the right atrium via the azygos or hemiazygos vein and hepatic venous plexus produced significant and unexpected systemic oxygen desaturation. Diagnosis after surgery of persistence of the hepatic venous plexus or underdeveloped hepatic IVC, despite azygos or hemiazygos continuation, provides an explanation for arterial desaturation after the Kawashima operation [7] and provides the opportunity for timely and precise intervention if symptomatic cyanosis occurs, without the need for exhaustive investigation of a fragile patient in the early period after surgery. Indeed, recognition of this venous anomaly may alter treatment to include coil embolization of the venous fistula either before the Kawashima procedure or early after surgery. Alternatively, earlier referral for hepatic vein redirection in the patient with good hemodynamics for conversion to a total cavopulmonary anastomosis may be considered. We elected to follow the latter course in our patient. However, in the patient with risk factors for conversion to a total cavopulmonary connection in whom more extended palliation from the Kawashima operation is anticipated, careful consideration of occlusion of the hepatic vein connection before surgery is warranted. Angiography to exclude a left superior vena cava is routine in patients under consideration for bidirectional superior cavopulmonary anastomosis. However, rarely is angiography performed with the catheter low in the inferior vena cava. We recommend and routinely perform inferior venacavography as part of the elective assessment before surgery of all patients with developmental cardiac defects associated with abnormalities of the IVC in whom redirection of systemic venous blood to the pulmonary artery is contemplated.
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  M. Bret-Zurita, I. Pinilla, E. Cuesta-Lopez, and M. Burgueros Magnetic resonance imaging findings of persistent primitive hepatic venous plexus with complex congenital cardiac disease Eur. J. Cardiothorac. Surg., January 1, 2008; 33(1): 119 - 120. [Abstract] [Full Text] [PDF]
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