Pulmonary Artery Banding (PAB)

Pulmonary artery banding (PAB) is a simple surgical technique to reduce pulmonary over-circulation in some congenital heart disease. In the beginning, when the use of cardiopulmonary bypass was affected by many deleterious effects, this technique played a fundamental role in the treatment of patients with congenital heart defects and an intracardiac left-to-right shunt.

The use of PAB has decreased during the last two decades, due to the increasing popularity of early complete intracardiac repair, which results have shown to be superior to staged repair, even in low body weight patients. Moreover, several authors have emphasized the negative effects of PAB such as pulmonary arterial branch distortion, abnormal right ventricular hypertrophy, pulmonary valve insufficiency, sub-aortic obstruction and decreased ventricular compliance in patients with univentricular heart.

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Indications

Many factors should be taken into account in a patient who is considered for PAB: the type of cardiac defect, the type of intracardiac shunt, the foreseen resolution of the main congenital defect in the setting of a staged approach and, finally, the experience of the team.

Classical indications

1.  Univentricular hearts, including neonates with ‘single ventricle’ defects;

2. Patients with balanced or even unbalanced ventricles and a large left-to-right shunt are potentially suitable for high-risk biventricular repair and may require a staged correction;

3. Congenital heart defects requiring LV retraining.

New indications

1. Hypoplastic left heart ventricle: critical neonates unsuitable for conventional surgery, or as a staged procedure

2. Early prophylactic PA banding for congenitally corrected TGA: to preserve an optimal cardiac status even when a double-switch procedure is not scheduled

From a physiopathological point of view, we can assess three different situations:

1.  Heart diseases with increased pulmonary flow requiring a palliative procedure for the protection of the pulmonary system until complete repair or a cavo-pulmonary connection;

2.  Heart diseases with an LV unfit to support the systemic pressure, thus requiring retraining;

3.  Hypoplastic left heart syndrome (HLHS) requiring a staged procedure.

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Limiting factors

Nowadays, the use of the PAB procedure represents ∼2% of all cardiac operations for congenital heart diseases. Although the role of the banding is accepted worldwide, some issues are still debated.

1. The main problem of performing a PAB is represented by the optimal intraoperative adjustment of band tightness. This is because, as ruled by Poiseuille's law, minimal changes to the pulmonary diameter have a high impact on resistance and flow. Furthermore, the effects of banding on pulmonary pressure are influenced by several hemodynamic, respiratory and individual variables like systemic and pulmonary resistances, type of congenital heart defect, heart rate, heart contractility, mechanical ventilation and weight of the patient.Difficulty of assessing the optimal tightness of the band: 

2. Changing situation: The rapid patient outgrowth, the patient-related response to banding in terms of hypertrophy or cyanosis, the rapid evolution of the pressure gradient, the appearance and progression of sub-aortic obstruction are many factors that require an earlier surgical repair or any kind of other surgical procedure when complete repair is not feasible.

3. Additional procedures: One of the most recurrent problems of PAB is pulmonary branch distortion or a upravalvular pulmonary stenosis that needs to be addressed at the time of corrective surgery. Furthermore, in cases of compulsory debanding, as in spontaneous closure of muscular VSDs, it is impossible to avoid the use of cardiopulmonary bypass for pulmonary reconstruction.

Source: https://mmcts.org/tutorial/16

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