Aortopulmonary window in infants.

One of the rarest congenital heart diseases that results from a defect between the main pulmonary artery and the proximal aorta is named aortopulmonary window (APW). Such abnormality could be isolated, but in fifty percent of patients may be associated with other cardiac abnormalities, including arch abnormalities, specifically coarctation of the aorta, interrupted aortic arch, tetralogy of fallot, and atrial septal defect (ASD). Surgical closure or catheter-delivered devices is recommended in all patients with APW and should be performed after diagnosis as soon as possible to prevent irreversible pulmonary vascular disease. In the current era, early mortality following repair of simple APW is low and depends on the presence of associated lesions, especially interrupted aortic arch. We report an 8-month-old boy with APW who was referred to our center by respiratory symptoms and heart murmurs.

INTRODUCTION

Aortopulmonary window (APW) or aortopulmonary septal defect, first described by Elliotson in third decade of last century,[1] is a cardiac abnormality that results from abnormal communication between the proximal aorta and the main pulmonary artery in the presence of two normally separated aortic and pulmonary valves. APW is a relatively rare cardiac lesion representing approximately 0.2% to 0.6% of all cardiac malformation.[2-4] APW could be isolated, but in half of patients, may be associated with other cardiac malformations. The most common associated malformations are arch abnormalities, specifically coarctation of the aorta, type A interruption of aortic arch, ASD, tetralogy of fallot, and aortic origin of the right pulmonary artery.[5] More rarely, it is associated with ventricular septal defect, pulmonary or aortic atresia, transposition of great arteries and tricuspid atresia.[6-9] APW can be classified into 3 types: proximal, distal and total defects.[10]

Classifications of the APW have been described differently in literature by investigators.[111] Proximal defects are the most common and are located in proximal aorta above the sinus of Valsalva. Distal types are located in the upper portion of the ascending before the aortic branches. Finally, total defects are large and involve the majority of the ascending aorta between valsalva and aortic branches.

The clinical features of APW are not specific, but majority of patients have the manifestations of a large left to right shunt. Patients with small defects may be asymptomatic. Patients with large APW usually have symptoms of pulmonary hypertension and congestive heart failure (tachypnea, diaphoresis, failure to thrive, and recurrent respiratory difficulty) in the first weeks of life. Severe pulmonary vascular hypertension can occur in the first months of life.[12] Two-dimensional and Doppler echocardiography could diagnose APW and could describe associated anomalies in majority of patients.

Closure of the defect is offered in all patients with APW and should be performed as soon as possible. Without surgical correction, 40-50% of patients will die due to congestive heart failure during the first year of life, and a large number of survivors will suffer from sequels of congestive heart failure or pulmonary vascular disease in their lives.[13] Gross first reported surgical ligation of an APW through left thoracotomy in 1952.[14] Wright et al. described first transaortic closure of an APW after cardiopulmonary bypass use in 1968.[15] Deverall et al. described using a patch to close of an APW.[16] In this report, we have presented an 8-month-old boy with APW who was referred to our center by respiratory symptoms and heart murmurs.

CASE REPORT

An 8-month-old boy, 6 kg, was referred to our hospital with a history of recurrent upper and lower respiratory infections, progressive tachypnea, and obvious chest retraction at rest and heart murmurs. In last examination his specialist hearing a suspicious moderate continious murmur and refer him to us. Cardiomegaly and pulmonary congestion were seen in chest X-ray. His cardiothoracic ratio was near 65% in chest X-ray. Transtorasic echocardiography showed moderate degree of mitral regurgitation (MR), dilated left atrium and left ventricle, severe turbulence flow in pulmonary artery and large APW (7-8 mm) and “T” artifact at the edge of the defect that distinguishes it from normal dropout [Figure 1].

Figure 1

High parasternal short-axis echocardiogram is showing the aortopulmonary window between the ascending aorta (Ao) and main pulmonary artery (PA)

At cardiac catheterization we found a large APW with pulmonary to aortic flow ratio above 3 and elevated pulmonary pressure (70% of systemic arterial pressure) [Figure 2].

Figure 2

Aortic angiography is showing filling of the main pulmonary artery through the aortopulmonary window (arrow)

The patient was operated after diagnosis by transaortic approach using a median sternotomy and cardiopulmonary bypass. The patient had good recovery from operation. His respiratory symptoms decreased after surgery. Echocardiography was performed and showed normal left ventricular function, and no residual aortopulmonary defect. No evidence of narrowing or stenosis of aorta and pulmonary arteries and no distortion of semilunar valve were found by echocardiographic study. Our patient had trivial to mild MR after operation. He is active and asymptomatic at follow-up period (one year). His mild mitral regurgitation is decreased to trivial regurgitation and cardiac function is normal.

DISCUSSION

At the fetal life, abnormal growth of aorticopulmonary septum, due to one of the rarest congenital heart defects, APW[1718] APW is a defect between two main great arteries in the presence of two separate aortic and pulmonary semilunar valves.[11] Truncus Arteriosus can be differentiated from this anomaly by absence of two separated normally aortic and pulmonary valves. In large defects this lesion often mimics as a large intra or extracardic shut such as ventricular septal defect, atrioventricular septal defect or patent ductus arteriosus (PDA) and resulting in congestive heart failure, pulmonary hypertension and progressive of pulmonary vascular disease.[21213]

Nearly 50-70% of all patients with APW were associated with other cardiac malformations.[19-21] Several cardiac malformation could be seen include coarctation of the aorta, type A interruption of aortic arch, ventricular septal defect, atrial septal defect (ASD), PDA, transposition of the great arteries, and tetralogy of Fallot.[231322]

Several classifications of APW have been presented. One of these classifications separates APW into 3 types, proximal or type A, distal or type B, and total or type C.[10] Proximal defect which is the most common type is a small defect located between the semilunar valves and the pulmonary bifurcation. Distal defects are located in the upper portion of the ascending aorta before aortic branches near the pulmonary biforcation. The rarest type or total defects consist of the entire aortopulmonary septum.

In the past, the diagnostic approach to APW was with cardiac catheterization.[21] By progressing non-invasive approach, techniques and 2-dimensional echocardiography diagnosis of APW and associated anomalies is facilitated.[2131922] The defect can be best visualized from a different views by echocardiographic study, including parasternal short and long-axis views, high parasternal short-axis view and subcostal coronal view. Echocardiographic study helps us to identify the morphological features and typing of the defect, exact location, sizing of defect, and associated cardiac anomalies. At Doppler echocardiography, abnormal continuous forward flow in the pulmonary arteries indicates the presence of an aortopulmonary communication.[23] Cardiac catheterization is indicated for estimating pulmonary vascular resistance and pulmonary artery pressure.

Closure of APW is indicated in all patients and it should be performed as soon as possible after diagnosis. Successful repair of an APW was reported from several years ago and many authors have reported their results.[14] First successful repair of an APW using cardiopulmonary bypass was reported in 1957.[24] Putnam and Gross described the transpulmonary approach in 1966.[25] Transaortic direct closure of an APW was first reported by Wright and coworkers in 1968.[15] In 1969, Deverall et al. described the first use of a patch to close an APW.[16] Currently, several patients have had successful closure using various catheter-delivered devices.[26-29] Transaortic approach using a median sternotomy and cardiopulmonary bypass was performed for our patient. Neither pulmonary stenosis or distortion nor coronary artery injury was found. During the follow-up period (one year), no reintervention was needed and he had trivial MR.

CONCLUSION

Most patients with APW develop severe clinical symptoms such as congestive heart failure or pulmonary hypertension during early stages of life. Early surgical closure or device employment is indicated as soon as the diagnosis is established to prevent congestive heart failure and pulmonary hypertension. Other cardiovascular defects should be repaired. Repair of APW have good results and indicated as soon as possible, even in early infancy. The outcome of these patients is excellent if correction is performed before complication of disease such as pulmonary hypertension.