Unroofed coronary sinus syndrome is a continuum of venous abnormalities consisting of partial or complete absence of the common wall between the coronary sinus and left atrium. All patients have an interatrial communication. A left SCV is usually but not always present. In most cases, operative intervention becomes necessary owing to a large left to right atrial shunt and cyanosis owing to a persistent left SCV into the left atrium. These operative solutions are presented later in this chapter. Figure 18.4 shows a coronal biatrial view of bilateral SCVs and complete unroofing of the coronary sinus and a coronary sinus atrial septal defect (ASD). Figure 18.5 shows left SCV to the left atrium with complete unroofing of the coronary sinus and absence of the interatrial septum. In a minority of cases, an unroofed coronary sinus is not associated with a left SCV (Fig. 18.6). The atrial communication is through a coronary sinus ASD. Another variation of unroofed coronary sinus is depicted in Fig. 18.7 and shows partial unroofing of the midportion of the coronary sinus with a coronary sinus ASD and absence of a left SCV. Figure 18.8 shows partial unroofing of the distal portion of the coronary sinus with an ostium primum defect in confluence with the coronary sinus ASD and absence of the left SCV. Figure 18.9 shows partial unroofing of the distal portion of the coronary sinus with intact right atrial coronary sinus orifice and coronary sinus ASD, with absence of a left SCV.
18.1.3 Right Superior Caval Vein to the Left Atrium
A right SCV that drains to the left atrium is an extremely rare venous anomaly that requires surgical repair owing to the associated systemic cyanosis resulting from inappropriate mixing in the left atrium. Figure 18.10 shows the right SCV draining into the left atrium. This condition must be differentiated from sinus venosus type ASD with the SCV overriding the interatrialseptum, which can also cause cyanosis.
18.1.4 Inferior Caval Vein into the Left Atrium
In rare instances, the ICV can connect to the left atrium and cause cyanosis. This can occur as an isolated lesion or in association with other cardiac anomalies. Figure 18.11 shows the ICV with a fenestrated opening into the left atrium.
18.1.5 Indirect Inferior Caval Vein Connections
Indirect ICV connections to the right atrium or one of its tributaries occurs when the ICV does not connect directly to the atrium from below but instead continues as an extension of either the azygos or hemiazygos veins. In the case of azygos continuation, the ICV traverses superiorly in the right paravertebral gutter and arches over to join the right SCV in the form of a dilated azygous vein (Fig. 18.12). Hemiazygous continuation occurs on the opposite side; the ICV courses superiorly along the left paravertebral gutter to join the left SCV as a dilated hemiazygos vein (Fig. 18.13). The hepatic veins always connect directly to the right atrium in these anomalies. These anomalies are generally found in patients with heterotaxy syndrome or atrial isomerism. Patients may or may not have situs inversus. These anomalies do not complicate two ventricular repairs, except that proper venous drainage techniques require creative intraoperativecannulation methods. Most of these patients have functionally single ventricles in association with double outlet right ventricle, anomalous pulmonary venous connection, complete atrioventricular canal, and other extracardiac anomalies. Creation of a bidirectional Glenn shunt in these patients results in over 80% of systemic venous return to the pulmonary arteries. The hepatic veins drain to the right atrium. If the Glenn shunt is left in place too long, pulmonary arteriovenous fistulas may occur and cause cyanosis because of the absence of hepatic factor to the lungs. Fontan completion is necessary to provide hepatic factor to the lungs to treat this unusual complication.
18.2 Surgical Management of Systemic Venous Route Abnormalities
Venous route abnormalities generally do not require surgical attention because the connections are physiologic, unless they are associated with cardiac abnormalities that require cardiopulmonary bypass to repair. Under these circumstances, the choice of venous drainage strategies becomes paramount for a successful cardiopulmonary bypass interval. The most common systemic venous route abnormality is the left SCV that drains unobstructed into the coronary sinus. In the majority of cases, it is wise to insert a venous catheter into this vein in preparation for cardiopulmonary bypass, to ensure proper drainage and avoid cerebral venous hypertension. Care must be taken to identify and preserve the phrenic nerve, which lies on the left side of the left SCV. Snugger control of this structure is best achieved in the intrapericardial portion of the left SCV to avoid injury to the phrenic nerve. Other challenging anatomic variations of systemic venous route return are the conditions of azygos or hemiazygos continuation of the ICV. Cannulation of this structure can be problematic. We have found that the best drainage technique is achieved with a large, straight catheter, the tip of which is advanced slightly (2 mm) into the orifice of the azygos or hemiazygos vein. The other nearby tributaries will be drained effectively in this manner, and the SCV snugger can be comfortably applied to ensure complete and unencumbered drainage. In general, hepatic veins that connect from below the diaphragm to the right atrium can be directly cannulated with small, angled venous cannulas. Care must be taken not to advance the catheters too far; doing so may result in poor drainage because the hepatic vein tributaries are closely aligned. In rare instances, the hepatic veins are large in number, small in caliber, and present a difficult cannulation dilemma. Under these circumstances, the surgeon may elect to institute cardiopulmonary bypass with a single-catheter technique and establish deep hypothermic circulatory arrest (DHCA) for the repair. This is an excellent option if individual cannulation of the hepatic veins involves increased risks.
18.2.1 Surgical Management of Systemic Venous Destination Abnormalities
126.96.36.199 Left Superior Caval Vein to the Left Atrium without a Coronary Sinus
This anomaly is usually clinically suspected from cyanosis and identified by echocardiography. Treatment is not standardized. Ligation of the left SCV can be entertained and accomplished if temporary occlusion does not result in upstream venous hypertension. If ligation is not an option, the left SCV to the left atrium must be routed to the right atrium by an interatrial pericardial baffle. This surgical technique can be accomplished by atrial septum resection and placement of a pericardial baffle to reposition the interatrial septum so that the systemic venous orifices lie on the right atrial side of the new interatrial septum, while the pulmonary venous orifices remain on theleft atrial side (Fig. 18.14). Another method to redirect left SCV flow to the right atrium is depicted in Figs. 18.15, 18.16, 18.17, 18.18, 18.19, 18.20, 18.21, 18.22, 18.23, and 18.24; this superior atrial approach requires that a significant amount of interatrial tissue be incised superiorly from the coronary sinus toward the right SCV orifice. Figure 18.15 shows the lines of incision that result in a medially hinged interatrial flap. With the flap retracted by a suture, a pericardial tunnel can be reconstructed to form an orifice in the right atrial cavity (Fig. 18.16). The remaining interatrial defect is closed with the autologous interatrial tissue flap that was initially created (Fig. 18.17). Pericardium or prosthetic material may be used if there is inadequate autologous tissue. A coronal view of the completed repair is shown in Fig. 18.18. When the surgeon is concerned that the interatrial baffle can cause stenosis of the left pulmonary veins, the left SCV can be detached from the left atrium and reimplanted into the roof of the left atrium closer to the plane of thenative interatrial septum. The native interatrial septum is then excised and repositioned, with pericardium or other patch material, to direct all of the systemic venous flow to the right atrium. Another ingenious method to redirect the left SCV to the right atrium is the roofing procedure, which can be accomplished with native atrial wall or pericardium. The idea is to create a new roof on the shared wall that divides the coronary sinus from the left atrium. These techniques are shown in Figs. 18.19 and 18.20. Figure 18.19 shows a tunnel being constructed by plication over a measured stent on the posterior wall of the left atrium. Figure 18.20 shows the same tunnel being constructed with a pericardial patch and patch closure of the interatrial septum to complete the repair.