Partial and Total Anomalous Pulmonary Venous Connection, Surgical Treatment Treatment & Management

Obstructed total anomalous pulmonary venous connection (TAPVC) presents immediately after birth with severe cyanosis and poor systemic perfusion and constitutes a medical and surgical emergency.^{[19, 20]} The anatomic lesions limit the extent of hemodynamic and metabolic resuscitation obtainable with conventional noninvasive treatment. These are intended to stabilize the patient's conditions and provide the best possible preoperative status prior to surgical repair, which still represents the criterion standard of care for this otherwise fatal condition.

Sedation, ventilation, or hyperventilation with 100% oxygen and maintenance of pCO2 levels below 30 mm Hg contribute to improve effective pulmonary blood flow. Administration of prostaglandin E₁ (eg, alprostadil, PGE₁) may allow some right-to-left shunting at the level of the ductus arteriosus. This may increase systemic cardiac output, although it may do so at the expense of pulmonary blood flow. Aggressive correction of systemic acidosis with sodium bicarbonate is mandatory, as well as optimization of hematocrit to improve oxygen-delivery capacity.

In neonates or infants with unobstructed TAPVC, medical therapy is directed at compensating right ventricular failure, hypoxia, and congestive heart failure. In these cases, mild inotropic support, diuresis, and low levels of inspired oxygen are often used. Assisted ventilation is rarely needed. In selected cases, α-blockade can be used to reduce the incidence of pulmonary hypertension.

Partial anomalous pulmonary venous connection (PAPVC) is most commonly diagnosed as a result of an incidental finding of murmur or abnormal chest radiographs during routine medical examination. Those who present with primary arrhythmia or right heart failure may benefit from antiarrhythmic agents or management of right heart failure while the diagnostic workup is being completed and before surgical correction is considered.

Balloon atrial septostomy (BAS) has been used with some success to decompress the venous circuit and improve cardiac output in cases of a restrictive interatrial communication.

More recently, stenting of obstructed vein has emerged as a valid aid to provide immediate relief of pulmonary hypertension and cardiogenic shock allowing a more effective hemodynamic stabilization prior to surgical intervention.^{[21, 22, 23, 24, 25]}

Similarly some centers have advocated the use of extracorporeal membrane oxygenation (ECMO) during resuscitation. In few cases, ECMO has been adopted after the repair to support neonates with residual pulmonary hypertension.^{[26, 27]}

Several techniques have been proposed for the surgical repair of both PAPVC and TAPVC. Whereas the first is normally corrected without complications, TAPVC still carries significant morbidity and mortality in low volume centers, due to the severe hemodynamic and metabolic compromise at presentation. Moreover, 10-15% of patients undergoing repair of TAPVC require multiple interventions due to recurrent stenosis after initial successful correction, with an increasingly poor outcome at each representation.^{[19, 28]}

Most recently, a technique aimed at eliminating any suturing to the vein wall, called sutureless technique, was proposed to relieve postrepair stenosis and avoid recurrence. At present, indications for using this technique are being extended to the correction of primary venous anomalies.^[29]

The goal of surgical repair is to recreate an unobstructed venous inflow to the left side chambers and repair of the associated anomalies, such as closure of atrial septal defect (ASD).

Preoperative echocardiographic definition of the pulmonary venous anatomy and associated defects is important in planning the appropriate cannulation technique and surgical approach. This point is especially pertinent in PAPVC, in which the location of the anomalous pulmonary venous drainage influences the use of a minimally invasive sternotomy incision and placement of venous cannulae. A high insertion of the anomalous vein in the superior vena cava (SVC) makes a minimally invasive approach considerably more difficult.

In patients with obstruction resulting in cyanosis and acidosis, resuscitative correction should be attempted while emergency surgical correction is being organized.

Total anomalous pulmonary venous connection

Aorto-bicaval cannulation offers flexibility to repair all forms of TAPVC. Cardiopulmonary bypass is instituted and the patient is cooled to mild-to-moderate hypothermia. The ductus arteriosus is ligated at this point. The aorta is cross-clamped, and cold antegrade cardioplegia is administered.

Many surgical techniques have been proposed to correct different types of TAPVC, but none has really succeeded in avoiding in as many as 15% of the cases relentless pulmonary vein stenosis, often recurrent, which complicates the recovery of these children.

A novel technique, introduced a decade ago, named the sutureless technique seems to offer some benefit from this troublesome complication. Initially introduced to treat the subsiding restenosis in children who already underwent primary repair with the traditional anastomotic techniques, it has been adopted and developed in the author's center as the preferred primary repair for most cases of TAPVC, congenital pulmonary vein stenosis, and complex cases of mixed types with encouraging results.

In supracardiac TAPVC, the vertical vein is usually ligated next to its connection to the systemic vein.^{[30, 31]} The exposure of the vein confluence can vary. The pulmonary venous confluence can be seen in the posterior pericardium by retracting the heart rightward and anteriorly or by a superior access between the ascending aorta and SVC.^[32] Alternatively, it can be accessed in the right pericardial fossa by a vertical incision through the right atrium, the interatrial septum, and the left atrium (LA). Generally, an incision is created in the pulmonary venous confluence to match a corresponding incision in the posterior wall of LA and extending into the LA appendage.

With care to avoid distortion, a pulmonary confluence–to-LA anastomosis is created using fine sutures in order to minimize the degree of intimal hyperplasia and potential restenosis. The use of absorbable suture material (polydioxanone [PDS]) versus nonabsorbable suture material (eg, Prolene) and running versus interrupted stitches are controversial. However, neither of these techniques has demonstrated a clear advantage over the others. The primary goal is a large, unobstructed anastomosis. Although deep hypothermic arrest is only seldom necessary,^[28] a short period of low-flow cardiopulmonary bypass may be desirable for a meticulous anastomosis.

Repair of cardiac TAPVC involves unroofing the coronary sinus through an incision between the coronary sinus and the fossa ovalis, thus creating a large ASD. The pulmonary vein ostia are visualized through the coronary sinus and its connection with the confluence. Then, a patch is used to reconstruct the atrial septum, leaving the pulmonary venous drainage to flow through the unroofed coronary sinus into the LA. When the anomalous veins drains directly into the right atrium (RA), the interatrial septum is detached posteriorly and reattached to the right of the right side pulmonary vein ostia.^[33]

For infracardiac TAPVC, the technique is similar to that described for supracardiac TAPVC. The pulmonary venous confluence tends to be oriented vertically, typically in a Y -shape and is extrapericardial. As a consequence, the incision into the LA is relatively vertical or Y- shaped. Some surgeons do not ligate the vertical vein to provide access to a low pressure system in cases of a particularly small and restrictive LA. Others ligate the connecting vein immediately above the diaphragm and use the intrapericardial portion of this vein to produce a larger anastomosis.^[34]

Surgical correction of mixed TAPVC depends on the exact anatomy and site of pulmonary venous connections. A combination of the aforementioned procedures is usually required to completely redirect pulmonary venous blood to the LA.^{[35, 36]}

When a sutureless technique is used, the pulmonary vein confluence is incised through the posterior pericardium, and the LA is opened through a long incision extending from the atrioventricular groove to the appendage. This is then sutured onto the pericardium surrounding the venous confluence. Pulmonary blood then flows from the vein directly into the atrial cavity, and hemostasis is secured by the fibrous continuity between the pericardium and the pulmonary veins.

Careful visualization of the phrenic nerve is mandatory in this technique because the suture line is often juxtaposed to its course on the left side. The resulting anastomosis requires no suture placement into the pulmonary vein, minimizing direct surgical trauma and intimal fibrosis and hyperplasia secondary to suturing.^[19] Moreover, the incision of the pulmonary veins can be extended into the hilar portion and even into the distal portion of their intraparenchymal tract due to the continuity offered by the layers of the mediastinal pleura and areolar tissues around the veins, thus creating a lung-to-atrium continuum to the blood flow.

Partial anomalous pulmonary venous connection

The position of the anomalous pulmonary vein determines the site of cannulation in the SVC. In most patients, the SVC or the innominate vein is cannulated to provide venous drainage for the upper extremities. After cardioplegic arrest, systemic normothermia is maintained. The RA is opened, and the pulmonary veins and any ASDs are identified.

A double-patch technique with glutaraldehyde-treated autologous pericardium is typically used to create a baffle which redirects pulmonary venous blood from the anomalous right upper pulmonary vein beneath the baffle through the ASD into the LA. The second patch is used to augment the SVC on top of the baffle to prevent obstruction to RA inflow.^[5]

A single-patch technique has been proposed. This involves a transverse atriotomy extending along the lateral aspect of the RA and across the cavoatrial junction along the SVC to just proximal to the point of inflow of an anomalous right superior pulmonary vein. A single pericardial patch is then fashioned to close the sinus venosus type of ASD and to create a baffle through the posterior SVC and over the origin of the right superior pulmonary vein. The atriotomy is then closed by incorporating the lateral limit into the suture line.

As an alternative, a new SVC-RA junction (Warden operation) is established by dividing the SVC just distal to the anomalous pulmonary venous entry and translocating the cephalic end of the SVC to a site at the RA appendage, where a SVC-to-RA anastomosis is performed. Take care to resect the trabeculations in the appendage to prevent obstruction of systemic venous drainage. The divided cardiac end of the SVC (bearing the anomalous pulmonary venous connection) is closed, and in the RA, a baffle is created from the site of the anomalous pulmonary vein to the ASD and LA.

Poor hemodynamic performance following repair of PAPVC or TAPVC should raise concern of potential obstruction at the site of repair. In those cases, chest radiography often reveals pulmonary edema, although this finding is nonspecific because it seen in many patients with preoperative pulmonary venous obstruction despite normal hemodynamics. Any suspicion of residual postoperative pulmonary venous obstruction should prompt echocardiography to interrogate the pulmonary venous anastomosis.^[37] When possible MRA is indicated to refine diagnosis.

Patients with obstructed TAPVC often have a difficult postoperative course secondary to high pulmonary vascular resistance and poor lung compliance. Some centers advocate the routine use of ECMO after surgical correction in these patients.

Pulmonary venous obstruction may arise in as many as 15% of patients after repair of TAPVC.

Most patients represented by obstruction at the site of anastomosis, presumably as a result of postoperative scar formation or distortion of the veno-atrial junction. Repeat surgery in these cases produces generally favorable results. However, in a smaller number of patients, a diffuse stenotic process involving the whole length of the pulmonary veins including their intrapulmonary course occurs. This process may progress to almost complete vein occlusion. When the lesion is bilateral, prognosis is poor. Sutureless techniques and/or lung transplantation may improve the outlook in this difficult subgroup.

Patients with PAPVC should also be followed up for evidence of stenosis at the site of pulmonary venous repair, although the diffuse stenosis described after repair of TAPVC is rare. See the image below.

Residual obstruction at the site of pulmonary venous repair is manifested by poor cardiac output and chest radiographic findings of pulmonary congestion. The principle diagnostic feature is turbulence at the pulmonary venous anastomotic site, as noted on echocardiography. Residual turbulence may create a cycle of local injury, hyperplasia, and increasing turbulence, perpetuating a process of diffuse pulmonary vein stenosis. Pulmonary vein stenosis may remain localized to the site of anastomosis, may progress unilaterally with diffuse pulmonary vein stenosis or may progress with bilateral diffuse pulmonary vein stenosis.

TAPVC is associated with hospital mortality ranging from 2% to 20%. Risk factors include poor preoperative status (eg, acidosis), obstruction, high pulmonary vascular resistance, young age, small left ventricle, and single-ventricle anatomy^{[38, 39, 40, 41, 42, 43, 44]}

Long-term prognosis after successful repair of TAPVC is favorable. Approximately 10-15% of patients have evidence of late pulmonary-vein obstruction. For this reason, long-term surveillance is important. Postoperative stenosis can be recurrent and progressive^{[45, 46]} . Among patients with post-repair pulmonary vein stenosis, ‘sutureless’ repairs are associated with superior freedom from recurrent stenosis.

Long-term prognosis for patients after repair of PAPVC is excellent in the absence of irreversible pulmonary hypertension. In children, closure of an associated atrial septal defect (ASD) almost eliminates the risk of the late development of atrial arrhythmias. In the older population the presence of preoperative arrhythmias represent a risk factor for persistent arrhythmias and mortality after the repair.^{[47, 48]}

Improved neonatal care and surgical techniques have greatly improved, reducing perioperative mortality to below 10% in most centers. However, in particular subsets of patients, the risk of surgical death is still extremely high. In particular, neonates with single ventricle circulations and obstructed total anomalous pulmonary venous connection (TAPVC) requiring emergency repair have a high rate of surgical mortality despite optimal medical management and prompt surgical repair.

A second frontier in the treatment of TAPVC is represented by postsurgical vein obstruction. Improved understanding of the vascular biology responsible for diffuse pulmonary vein stenosis in this group is required. At present, the wide adoption of a sutureless technique for postrepair stenosis as well as primary repair seems to offer the most promising result and long term patency.^{[49, 50, 51, 52, 53, 54]}