Patent arterial duct

Abstract

Patent arterial duct (PAD) is a congenital heart abnormality defined as persistent patency in term infants older than three months. Isolated PAD is found in around 1 in 2000 full term infants. A higher prevalence is found in preterm infants, especially those with low birth weight. The female to male ratio is 2:1. Most patients are asymptomatic when the duct is small. With a moderate-to-large duct, a characteristic continuous heart murmur (loudest in the left upper chest or infraclavicular area) is typical. The precordium may be hyperactive and peripheral pulses are bounding with a wide pulse pressure. Tachycardia, exertional dyspnoea, laboured breathing, fatigue or poor growth are common. Large shunts may lead to failure to thrive, recurrent infection of the upper respiratory tract and congestive heart failure. In the majority of cases of PAD there is no identifiable cause. Persistence of the duct is associated with chromosomal aberrations, asphyxia at birth, birth at high altitude and congenital rubella. Occasional cases are associated with specific genetic defects (trisomy 21 and 18, and the Rubinstein-Taybi and CHARGE syndromes). Familial occurrence of PAD is uncommon and the usual mechanism of inheritance is considered to be polygenic with a recurrence risk of 3%. Rare families with isolated PAD have been described in which the mode of inheritance appears to be dominant or recessive. Familial incidence of PAD has also been linked to Char syndrome, familial thoracic aortic aneurysm/dissection associated with patent arterial duct, and familial patent arterial duct and bicuspid aortic valve associated with hand abnormalities. Diagnosis is based on clinical examination and confirmed with transthoracic echocardiography. Assessment of ductal blood flow can be made using colour flow mapping and pulsed wave Doppler. Antenatal diagnosis is not possible, as PAD is a normal structure during antenatal life. Conditions with signs and symptoms of pulmonary overcirculation secondary to a left-to-right shunt must be excluded. Coronary, systemic and pulmonary arteriovenous fistula, peripheral pulmonary stenosis and ventricular septal defect with aortic regurgitation and collateral vessels must be differentiated from PAD on echocardiogram. In preterm infants with symptomatic heart failure secondary to PAD, treatment may be achieved by surgical ligation or with medical therapy blocking prostaglandin synthesis (indomethacin or ibuprofen). Transcatheter closure of the duct is usually indicated in older children. PAD in preterm and low birth weight infants is associated with significant co-morbidity and mortality due to haemodynamic instability. Asymptomatic patients with a small duct have a normal vital prognosis but have a lifetime risk of endocarditis. Patients with moderate-to-large ducts with significant haemodynamic alterations may develop irreversible changes to pulmonary vascularity and pulmonary hypertension.

Figure 1

Echocardiography, a high parasternal long axis view demonstrating a large patent duct (PDA). Colour flow demonstrates shunting from 'left to right', from the descending aorta (DAO) to the pulmonary arteries (MPA).

Figure 2

Lateral angiogram demonstrating a large tubular type duct (type C) with aortic (AO) to pulmonary flow (MPA). The catheter can be seen entering the MPA from the right ventricle, a second pigtail catheter is positioned in the descending aorta from which contrast is delivered.

Figure 3

Diagrammatic representation of the configuration of the ductus as demonstrated on the lateral angiogram can be classified as described by Krichenko. Type A or conical duct with well defined aortic ampulla and constriction near the pulmonary artery end. Type B is a large duct with window like structure which is very short in length. Type C is a tubular duct without any constriction. Type D is the complex duct with multiple constrictions and the type E or elongated duct with constriction remote from the edge of the trachea as viewed on lateral angiography (figure adapted from Amplatzer™ manufacturer information).

Figure 4

a) Lateral angiogram showing a Cook™ flipper coil with complete occlusion of the duct on angiography; b) The same patient as demonstrated in figure 2 that has been successfully closed using an Amplatzer ductal occluder™ (ADO); c) Successful closure of the patent duct demonstrated in figure 1 with an Amplatzer ductal occluder II ™ (ADO II).

Figure 5

Echocardiogram following closure of patent duct with an Amplatzer ductal occluder II™. This image is taken from the same patient as figure 3c. This high parasternal long axis clearly shows the device fixed in the duct between left pulmonary artery and descending aorta.