Procedural technique

The size and shape of ductus were evaluated by CT angiography and aortography in left anterior oblique (LAO) and right anterior oblique (RAO) views. In two cases, PDA was conical shape (Fig 1a) and in three remaining patients, it was tubular (Fig 1b). We chose double disk muscular Occluder device because it fits more for the physiology of pulmonary hypertension.

Figure 1. Conical (1A) and tubular (2A) shapes of PDA in our patients (arrowed).

After local anaesthesia, we started the procedure via femoral approach. First, the right vein and arterial access was obtained and a 5F Occutech sheath was placed. After that, Heparin was injected intravenously based on the patient’s weight. Pulmonary artery; left and right heart pressure chambers were recorded and indicated no obstructions. Then, based on findings of CT angiography and aortography, the device was selected and placed through the femoral vein and the desired sheath. After making sure of the proper device position, sheath was removed and the tubular end of the device was opened in the duct. At the end of the procedure, aortic root injection in the left lateral view was performed to check the proper position of the device and the amount of residual shunt, which showed a small residual shunt in one case. Follow up echocardiography was done immediately and 24 hours after closure for detection of possible complications.

Ethical considerations

The patients were informed about the procedure and we answered any question related to their procedure. Informed written consent for the procedure and for reporting the case was taken from each patient separately.

Diagnostic methods

Primary diagnostic tool for detection of PDA is chest X-ray (CXR) which may show specific radiological features known as the ‘railroad track’. Furthermore, chest radiography might show some complications of the disease for example heart failure or cardiomegaly but none of them are specific and CXR may be normal in spite of having PDA. ^{Reference Schneider and Moore4}

Another diagnostic method for evaluation of PDA is echocardiography which is used for classification of PDA and evaluation of other associated anomalies ^{Reference Arlettaz5} but in cases of increased pulmonary vascular resistance and pulmonary hypertension, diagnosis of even large type PDA is very difficult. ^{Reference Schneider and Moore4}

Multi-planar CT is another tool which provides good information about size, morphology and presence of calcified tunnel which could be helpful for choosing therapeutic option. ^{Reference Morgan-Hughes, Marshall and Roobottom6} When deciding on treatment strategy, factors such as PDA anatomy and proximity to the trachea (which is easily detect by this method) are important for choosing patients for trans-catheter closure. ^{Reference Goitein, Fuhrman and Lacomis7} In addition, we can choose proper device based on CT characteristics of PDA.

Cardiac catheterization is another diagnostic method, which is now the preferred therapeutic method in most centres. This method makes it possible to have complete evaluation of patients, assessment of pulmonary pressure and vascular resistance and various vasodilator tests which may be beneficial in determining advisability of ductus closure. In addition, catheterization provides enough insight on exact anatomy of ductus and choosing appropriate device in terms of type and size. ^{Reference Schneider and Moore4}

Treatment options

PDA is usually detected and treated in childhood, and spontaneous closure is rare in adults and for this reason, it is recommended to close PDA immediately after diagnosis even in asymptomatic patients because of the numerous complications that will cause as the result of ductus which remain open. ^{Reference Schneider and Moore4} But it is important to keep in mind that in patients with irreversible pulmonary hypertension, neither surgery nor a trans-catheter closure is recommended because it increases mortality. ^{Reference Cassidy, Cassidy and Blackshear8,Reference Kalavrouziotis, Kourtesis, Paphitis and Azariades9}

Generally, in patients with PDA, trans-catheter closure of PDA is the preferred therapeutic technique and has many benefits, such as shorter hospital stays and surgical avoidance and is associated with fewer complications compared with surgery. ^{Reference Dries, Luc, Geert, Bert and De Wolf10} Furthermore, in patients with large PDA and pulmonary arterial hypertension, successful PDA closure applying different devices such as Amplatzer Duct Occluder or even Amplatzer Muscular Ventricular Septal Defect Occluder has been reported. ^{Reference García-Montes, Camacho-Castro and Sandoval-Jones11} However, in patients whose anatomical characteristics of the ductus are not acceptable (for example duct with large diameter or short length), the results of using these devices may not be satisfactory.

Catheter intervention

For the first time, trans-catheter closure of PDA was explained by Portsmann et al ^{Reference Porstmann, Wierny and Warnke12} who used a conical Ivalon plug in 1967, and then followed by Rashkind and Cuaso. ^{Reference Fernando, Koranne, Loyalka, Kar and Gregoric1} This technique has been well developed over the years and Krichenko et al ^{Reference Krichenko, Benson, Burrows, Möes, McLaughlin and Freedom13} divided the isolated PDAs into five groups according to anatomical and topological variations, which can affect the technique of catheter occlusion. This classification is based on angiographic appearances in which the narrowest segment of the ductus arteriosus is used as a landmark (Table 2).

Table 2. Krichenko classification of PDA based on shape and orientation

Adapted from Fernando et al. ^{Reference Fernando, Koranne, Loyalka, Kar and Gregoric1}

Today, various devices have been used commercially for trans-catheter closure of PDA, but only five of them have been approved by the Food and Drug Administration: The Gianturco coil (1992); the Cook detachable coil (1994); the Flipper detachable coil (1996); the GianturcoGrifka sac (1996); and the Amplatzer Duct occluder (ADO) I (1996). ^{Reference Rao14} Another off-label device is ADO II (2009) that has two retaining discs on either side to prevent embolization of the device. In addition, it has a flexible waist that makes it fit well with the lumen and alignment of the duct and prevents disc protrusion and obstruction of pulmonary artery or aorta. ^{Reference Thanopoulos, Eleftherakis, Tzannos and Stefanadis15} Furthermore, due to the maximum waist diameter of this device (12 mm), we cannot use it to close large PDA, but in clinical setting, feasibility and efficacy (96–100%) of the ADO II for using in PDA with a minimum diameter >2 mm have been well-known. ^{Reference Thanopoulos, Eleftherakis, Tzannos and Stefanadis15,Reference Dua, Chessa and Piazza16} In some situations, Amplatzer vascular plugs and septal Occluders in an off-label have been used for PDA closure due to the large difference in the size and shape. ^{Reference Meadows and Landzberg3}

Compared with the ADO II, Amplatzer mVSD Occluder device has a different structure that allows it to accommodate a thicker part of the septum. Moreover, it makes a better approximation to the PDA wall due to the larger waist and two concentric discs. The higher waist-to-disc ratio (0.44 for the smallest to 0.69 for the largest compared with 0.33 for the smallest to 0.5 for the largest in ADO II) and larger maximum waist diameter (22 mm in the mVSD Occluder compared with 12 mm in ADO II) of this device, makes it suitable for closure of large PDA such as our patients. This device can cause residual shunting when used in patients similar to our cases with short length and large diameter. In addition, studies have shown that the presence of double discs reduces the chances of complications such as migration of device, and the presence of such a structure in this device makes it very effective in patients with high pulmonary pressures.

An important issue to consider is choosing a device with a suitable waist size for trans-catheter closure of PDA that lead to complete closure of the duct. Studies have shown that 50% of the compressive effects of the device are due to the waist and only 25% of each of the disc. Another point which should be in mind is about retention disk which is designed in the Amplatzer mVSD Occluder device in such a way that is accompanied by an angle and concavity that causes the device to be completely fixed at the end of the aorta. In addition, García-Montes suggested Amplatzer mVSD as the first choice device in patients with large type C (≥8 mm) or some cases with type A (who have diameter of aortic ampulla more than 1.5 times of the pulmonary end). ^{Reference García-Montes, Camacho-Castro and Sandoval-Jones11} In our experience with these five cases, one of the most influential reasons for success in implantation of device is the position of retention aortic disc in duct. If the retention disc is dislodged to duct, the risk of embolization will be very high, as we had it in our last case (Fig 2a–d).

Figure 2. Abnormal position of retention disc in duct (2C) in conical PDA (2B).