PDA coil closure
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 fluoroscopy 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 of 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
Exchange length guidewire, 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.
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. Redeployment of a retrieved coil is also feasible. Embolisation of coil into a mesenteric 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.