Palliative Treatment: Pulmonary Artery Banding

PAB - A summary

Pulmonary artery banding –PAB: It is a technique of palliative surgical therapy that is used by congenital heart surgeons as a staged approach to operative correction of congenital heart defects. This was widely used in the past as an initial surgical intervention for children born with cardiac defects characterized by left-to-right shunting and pulmonary over circulation. In the last decade, early definitive intracardiac repair has been replaced largely by palliation with PAB. This trend has evolved because many centers have demonstrated improved results with primary corrective surgery as an initial intervention in the neonate with congenital heart condition. Although the use of PAB has recently decreased significantly, it continues to maintain a therapeutic role in certain sects of patients with congenital heart condition.

The main objective of performing PAB is to reduce excessive pulmonary blood flow and safeguard the pulmonary vasculature from hypertrophy and irreversible pulmonary hypertension. Recently, PAB has played a role in the preparation and training of the left ventricle (LV) in patients with d-transposition of the great arteries (d-TGA) that are evaluated for a delayed arterial switch medical procedure.

INDICATIONS

Presently, the patients selected for PAB and staged cardiac repair are determined based on the experience and philosophy of the pediatric cardiologists and congenital heart surgeons at any institution. Most of them fall into 2 broad categories: 1. the ones with pulmonary over circulation and left-to-right shunting who require reduction of PBF as a staged approach to more definitive repair and 2. The ones with d-TGA who require training of the LV as a staged approach to the arterial switch procedure.

• The first category patients who are reckoned for PAB include those with the following diagnosis:
• Single or multiple VSDs with coarctation of the aorta or interrupted aortic arch
• Single ventricle defects (e.g., tricuspid atresia) that are associated with increased PBF in the neonate
• Cardiac defects that require a homograft conduit (e.g., d-TGA with Subpulmonic stenosis requiring a Rastelli-type repair) for complete repair: Use of PAB may allow time for growth of the patient before the complete repair. The interim growth of the patient permits placement of a larger conduit at the time of repair and potentially increases the longevity of the conduit and the length of freedom from reoperation. With current clinical practice, most patients with d-TGA pulmonary stenosis (PS) undergo a Rastelli procedure and placement of a right ventricle (RV)–to–pulmonary artery (PA) conduit. In case a staged repair is indicated, a PAB is not normally performed because of already decreased pulmonary blood flow. In a situation like this, a systemic-to-pulmonary shunt will be performed.
• Multiple muscular VSDs with a "Swiss cheese" septum which is technically difficult to repair in the neonate or requires a Ventriculotomy
• Unbalanced AVC defects where the LV is hypo plastic however, the potential exists for a 2-ventricle repair with further growth and developmen

• Patients in the second category who are considered for PAB include those with the following diagnosis:
• D-TGA that requires preparation of the LV for an arterial switch procedure following a previous Mustard or Senning procedure with the development of right ventricular failure
• D-TGA that requires preparation of the LV for an arterial switch procedure following initial late presentation or diagnosis in patients older than 1 month

MEDICAL TREATMENT:

Therapy (Medical): Preoperative treatment of patients with pulmonary overcirculation and CHF need to focus on minimizing left-to-right shunting, improving cardiac function with inotropic support, systemic afterload reduction, and aggressive diuresis. To maintain adequate ventilation and oxygenation in the setting of pulmonary edema Mechanical ventilator support may be necessary. Maintaining higher carbon dioxide levels and lower fraction of inspired oxygen (FIO2) during ventilation may assist in reducing PBF and pulmonary edema. Attempts should be made to reduce or close it with medical therapy (e.g., indomethacin) to reduce this source of PBF,that is if a PDA is present.

Therapy (Surgical): In this treatment of congenital heart defects, PAB is a palliative intervention which is performed as a structured approach to a more conclusive surgical procedure. PAB goals include reduction of PBF to reduce left-to-right shunting and CHF, protect the pulmonary vasculature from hypertensive changes, and training of the LV in anticipation of an arterial switch procedure.

RESULT AND FORECAST

This procedure will result in improved hemodynamic and an overall improvement in the patients. The symptoms of CHF should be solved or should become medically manageable, cardiomegaly need to decrease, and the pulmonary vascular resistance need to decrease. PAB expend protection to the pulmonary vasculature against fixed irreversible pulmonary hypertension secondary to elevated PA pressures and pulmonary overcirculation.

The death rate of PAB is clearly associated more with the complexity of the heart defect and the total condition of the patients than with the procedure. Patients who are opting for PAB and a staged repair are often chosen as they are considered to fall under high risk to undergo definitive repair. Hence, the death rates from earlier groups have been high (at around 25%). A decreasing death rate with PAB could be related to improved operative skills and better patient selection and timing of intervention. Adding to this, there are gradual improvements in anesthetic and postoperative management. This has also resulted in a decreased death rate. The present mortality rates for PAB are reported to be as low as 3-5%.