Patent ductus arteriosus (PDA)

Closed loop catheter position in patent ductus arteriosus (PDA) with video

PA view of fluroscopic image showing closed loop catheter position in patent ductus arteriosus (PDA).

The catheter is seen emerging from the inferior vena cava into the right atrium (RA) above the right hemidiaphragm and crossing the mid line across the tricupsid valve into the right ventricle. In the right ventricle, it does not go into the apical region, but goes straight to the right ventricular outflow (RVOT) region. From the RVOT it crosses the pulmonary valve into the main pulmonary artery (MPA). From the MPA, it enters the descending aorta through the PDA which is situated at the junction of the left pulmonary artery and the MPA. Ao: aorta; Desc Ao: descending aorta. The closed loop catheter position in PDA has to be differentiated from the open loop catheter position which occurs in aorto pulmonary window. In aorto pulmonary window, the catheter enters the ascending aorta to the right of the main pulmonary artery without curving further to the left as in PDA. This produces an open loop appearance rather than a closed loop appearance. Open loop appearance can also rarely be seen in PDA, especially in slightly tilted views when the pulmonary artery is dilated.

Catheter passing below the diaphragm through PDA into descending aorta.

When a right heart catheter passes from main pulmonary artery down the lung fields, it could be either in the left pulmonary artery or the descending aorta. If it passes very close to the left border of the spine, it is more likely to be in the descending aorta. A more definite way to confirm that it is in the aorta is to pan the table so that the course of the catheter dipping below the diaphragm can be documented as in this image. Catheter tip pressure tracing is helpful when the pulmonary arterial pressures are not elevated as the pressure rises abruptly on entering the aorta from the pulmonary artery. But in severe pulmonary hypertension as in a large PDA, the pulmonary and aortic pressures may be nearly equal. Another way to confirm is to draw out a sample of blood and check the oxygen saturation, which will be higher in the aorta. There can be a problem in this case also, if there is a right to left shunt across the ductus. Hence the usual method of confirmation is simply by panning the table to see that the catheter tip can be passed below the level of the diaphragm.

Lateral view of catheter position in patent ductus arteriosus (PDA)

Lateral view of the fluroscopic image shows the catheter emerging from the inferior vena cava into the right atrium above the right hemidiaphragm. The anterior course of the catheter documents its position in the right ventricle (RV), which is just beneath the sternum. The catheter further curves posteriorly as it crosses the pulmonary artery into the PDA. The location of the PDA is identified by the overlapping tracheal air column. Further the catheter passes down in the descending aorta which has a course adjacent to the spine. In the lateral view also, the course below the diaphragm can be documented by moving the table up and showing the catheter tip.

Angiographic video -posteroanterior (PA) and lateral views demonstrating the closed loop catheter position. The catheter is seen coursing down the descending aorta well below the diaphragm.

Device closure of patent ductus arteriosus (PDA)

PDA angio prior to device closure

Though small PDAs can be closed by coils, large PDAs require a device to close them. Initially an angiogram is taken to confirm the size of the PDA to choose the size of the device. The angiogram above shows pigtail catheter in the descending aorta and the dye passing from the descending aorta to pulmonary artery through the PDA. The PDA is superimposed on the tracheal air column in this view.

PDA device in position

A guide wire is introduced into the femoral vein and guide through inferior vena cava into right atrium. From right atrium it is passed into the pulmonary artery through the right ventricle. From the pulmonary artery, the guide wire is passed into the descending aorta across the PDA. A long sheath is threaded over the guide wire. Then the PDA device is loaded under water and introduced into the sheath. The device is pushed out of the sheath in the aorta and the assembly is withdrawn so that the device is deployed in the PDA.

PDA angio with device in position

PDA device delivered

Once the position of the device is fine, and the shunt obliterated, the delivery cable is unscrewed and the device released. Delivery cable and sheath are withdrawn, as well as the pigtail. Hemostasis is achieved by compression over the puncture site. Follow up echocardiograms are obtained to document the absence of residual flow.

More on coil closure of PDA (patent ductus arteriosus)

Before closing patent ductus arteriosus (PDA), make sure that it is not an obligatory PDA  which is needed for maintaining a ductus dependent circulation which could be either systemic, pulmonary or combined. Closure of PDA in a ductus dependent circulation can be catastrophic.

Trans catheter closure of PDA can be either by a device specifically made for the purpose or using embolisation coils. Coil closure can be either a direct delivery of a coil or a bioptome assisted delivery. Special coils with delivery systems have also been used for closure of PDA.

In any case, the PDA is first confirmed by an angiogram. If an arterial puncture is made, the angiogram can be from the descending aorta using a pigtail catheter. If only venous entry is made to facilitate early hospital discharge, ductus can be crossed and check injections made. Coil delivery can be made from the venous side as well as the arterial side. In the venous route, the femoral vein is puncture by the standard percutaneous technique and sheath introduced. A multipurpose catheter with a guide wire can be used to cross the ductus from the pulmonary side. The standard guide wire is then replaced by a stiffer wire to guide the long sheath across the PDA. Once the sheath is across the PDA, the guide wire can be withdrawn. Then the embolisation coils are loaded either into a catheter for direct delivery or on a bioptome. In the direct delivery method, once the catheter loaded with the coil is across the PDA, it is withdrawn into the ampulla and the coil pushed out turn by turn so that most of it compacts in the ampulla and a portion is across the ductus and a short segment may even jut into the pulmonary artery. In bioptome assisted method the coil is allowed to fall out of the sheath by pushing and then the whole assembly is withdrawn so that most of coil compacts in the ampulla of the ductus while a short segment is across the ductus and into the pulmonary artery. Once the position is confirmed by check angio, which also confirms the proper closure of the ductus, the coil is released from the bioptome and the sheath withdrawn. Residual shunts can be closed by the delivery of additional coils. If needed, more than one coil can attached to the bioptome electively and delivered, if it is anticipated that one coil may not be enough to close the ductus. Residual shunts, unless trivial, should be closed to prevent hemolysis, which can occasional occur. Urine colour is observed on follow up to look for discolouration suggesting hemoglobinuria due to hemolysis, which may occur rarely due to the jet across a residual PDA.

Aortogram for visualising the PDA

Aortogram is taken in the lateral view or the RAO (right anterior oblique) view for visualising the PDA. The pigtail catheter tip is kept just above the duct to obtain a good view of the ductus. Some operators keep a multipurpose catheter across the duct during angiography for calibration to assess the duct size. Other operators are concerned about potential ductal spasm and avoid entering the duct before the angio for fear of inducing spasm and consequent undersizing of the duct. If the duct size is underestimated, it is theoretically possible to have a small coil slipping out of the duct after deployment or incomplete closure of the duct. Similarly, some operators keep the pigtail catheter tip just below the duct as the duct rather sucks the dye into the pulmonary artery during injection. If the pigtail tip is kept too much high into the arch, the arch and ascending aorta gets opacified and may interfere with the proper visualisation of the duct and pulmonary artery. The minimum diameter of the duct at the pulmonary artery side has to be assessed or even measured. Ampulla size also has to be assessed. Occasionally, the coil is cut short to be compatible for a shallow ampulla. Overlap with the descending aorta may sometimes make this difficult and require oblique views. The relation of the pulmonary artery and the duct to the trachea has to be noted as only fluroscopy will be available during deployment of the coil and the tracheal shadow is a useful landmark.

Coil selection for PDA closure

At least one coil (if multiple coils are used) should be more than twice the size fo the duct. At least 2.5 to 3 loops of the coil should be there in the ampulla. This is calculated from the duct size and the coil size using simple mathematical formula for the circumference of a circle. 0.052″ coils are less likely to embolize, but they do not pack well. While using multiple coils of the same length, one coil of smaller loop diameter is chosen for better packing within the other.

Direct deployment of the PDA coil

Direct deployment is seldom used, that too only in a small duct which will not allow a bioptome to pass through. Coil is loaded in a multipurpose or Judkins right coronary artery catheter, beyond the tip of teflon guide wire and gradually pushed into the PDA.

Bioptome assisted PDA coil delivery

Hardwire required:

Exchange length guide wire, Balken long sheath – 6F, 7F or 8F, depending the number and size of coils to be used, bioptomes of 3F and 5F size, loader of 1 size smaller than the sheath. Initial crossing of the PDA is with a teflon coated straight tip wire. Vertically oriented duct may be difficult to cross from the venous side and require crossing from the arterial side.

Procedure:

Amplatzer guide wire is introduced into the descending aorta and Balken sheath threaded over it 2-3 cm beyond the duct, before the coil/s are introduced, loaded at the tip of a bioptome.

Multiple coil delivery:

When more than one coils are needed to close the duct, two coils can be tied together at the proximal end using a silk strand. To facilitate the tying, the ball at the tip of the coil is stretched using a hemostat. The coils are then loaded into the loader and the assembly introduced into the Balken sheath. The coil is pushed out of the sheath into the aorta before the assembly is withdrawn to position the coil in the duct. Too much of coil into the pulmonary artery can cause left pulmonary artery stenosis later. When the coil position is deemed suboptimal, the coil is withdrawn into the sheath and the procedure is redone. This requires the removal of the bioptome coil assembly out and reintroduction of the Amplatzer wire and threading the Balken sheath across the PDA before reintroduction of the bioptome coil assembly. For residual shunts, further coils may be deployed from the arterial side. A stiff coil may stent the duct and sometimes require the delivery of a PDA closure device within the coil for complete closure, in very rare situations. On the other hand, coil delivery can be used to close residual shunts after the delivery of a device as well.

Complications of PDA coil closure:

Complications of PDA coil closure include embolisation (into the pulmonary artery or aorta), residual shunt and rarely hemolysis with hemoglobinuria and anemia. Embolised coils can be retrieved with a 10 mm snare. Poor compaction can lead to embolisation. Usually the coil is held in position by the aortic pressure. Redeplyoment of a retrieved coil is also feasible. Embolisation of coil into a mesentric vessel may make retrieval difficult. Some authors prefer devices over coils for these reasons. But coils are cheaper and also gets preference over devices in smaller children with small tubular ducts which are difficult to close.

Venous side only deployment:

Venous side only deployment is considered in very small infants to avoid loss of patency of femoral artery. In this case angio is taken from the venous side. But the downside is a poor ductal opacification with this angio, unlike the aortogram from the arterial access. The problem with arterial access in small infants is that it may cause arterial problems requiring the use of heparin, which in turn can lead to non-clotting of the coiled segment and residual PDA.

PDA jet in Tetralogy of Fallot

Patent ductus arerious jet in Tetralogy of Fallot on Colour Doppler imaging

Colour flow imaging shows high velocity jet in the pulmonary artery arising distally, form the descending aorta, suggesting a patent ductus arteriosus (PDA). This is one of the compensatory mechanisms to improve pulmonary flow in Tetralogy of Fallot. Another mechanism is major aorto pulmonary collateral arteries (MAPCA). Intra pulmonary collaterals can also occur in Tetralogy of Fallot. Desc Ao: descending aorta. The image is in the parasternal short axis view.

PDA jet in Tetralogy of Fallot

Continuous wave Doppler interrogation of the jet guided by colour flow mapping picks up the continuous flow with a peak gradient of 61.5 mm Hg. The gradient is calculated from the velocity measured by the device using the formula: V = 4 V². Ao: aorta; PA: pulmonary artery

PDA in TOF Video from Cardiophile MD

The video shows the mosaic jet originating from the distal portion of the pulmonary artery from the descending aorta through the PDA.