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Percutaneous Closure of Patent Ductus Arteriosus: State of the Art
Patent ductus arteriosus (PDA) may be an isolated lesion or may be present in association with other defects. Isolated PDA constitutes 6–11% of all congenital heart defects. The configuration of PDA varies considerably, but most often it has a conical or funnel shape. The aortic end (ampulla) is wide and gradually narrows towards the pulmonary end. The narrowest segment is usually at the pulmonary end. PDA morphology can vary and the ductus may be short and tubular, have multiple constrictions, or have a bizarre configuration. Some order was brought to classifying the PDAs by the work of Krichenko and his colleagues.1
Since the description of the first successful surgical ligation of a PDA by Gross and Hubbard2 in 1939, surgery has been extensively used in the treatment of PDA. Although surgical treatment has been shown to be safe and effective, with only occasional complications, cardiologists have been attempting to develop less invasive transcatheter methods for closure of PDA. The initial efforts of Porstmann3 and Rashkind4 and their associates paved the way for the development of a number of other PDA closure devices. Most of these devices have been tested in animal models followed by human use. The devices which did not reach the stage of human clinical trials, as well as those used in human clinical trials, were reviewed elsewhere.5,6 Of these, Gianturco coils (both free and detachable),7–9 the Gianturco-Grifka vascular occlusion device (GGVOD),10 the Amplatzer duct occluder (ADO)11 and the Amplatzer vascular plug12 are currently available for routine clinical use. The remaining devices at the time of this writing have not received approval from the U.S. Food and Drug Administration, but are available for use only at institutions that are participating in clinical trials.
Atiq et al13 in this issue of the Journal present their experience with transcatheter closure of PDA in 98 consecutive patients, ages 7 months to 54 years (64 ± 11 months) during a 6-year period ending in 2006. The PDAs measured 1.1–11.0 mm (3.1 ± 1.4) at their narrowest. The mean fluoroscopy time was 9.2 ± 5.5 minutes (range: 3.4–26). Seven (7.1%) patients were thought to have unfavorable size or shape, and transcatheter occlusion was not attempted. Detachable coils were used in 37 patients with minimal ductal diameter < 2.5 mm, and ADOs were implanted in 53 patients with larger PDAs (≥ 2.5 mm). Two patients with systemic-level systolic pulmonary artery pressure had an Amplatzer muscular ventricular septal defect (VSD) occluder implanted. Successful implantation of the device was achieved in all but 1 patient. In the lone exception, the Amplatzer muscular VSD occluder embolized into the right pulmonary artery 12 hours following device deployment, requiring surgical retrieval. Complete occlusion of the PDA was demonstrated by angiography in 83% patients who had detachable coils implanted, and 94% with ADO. Echo- Doppler studies 1 week following device placement showed complete occlusion of 95% and 99% with coils and Amplatzer device, respectively. By 6 months, complete closure was demonstrated in 99% patients in both groups. Follow up for 2–16 months revealed no evidence for reopening of any PDA and no evidence for obstruction in the left pulmonary artery. A gradient of 10 mmHg in the descending aorta was noted in 1 patient. The authors conclude that transcatheter closure of PDA is a preferred alternative to surgical therapy.
This is a well-written report documenting the utility of detachable coils and ADOs in closing PDAs in a large series of patients. Although the authors set criteria of minimal ductal diameter of 2.5 mm for the use of detachable coil versus ADO, they did not strictly adhere to the set limits. Also, the criteria for not performing coil/device closure, but instead referring to surgical closure, were not clearly defined. The follow-up duration was short, and it is not clear how many patients underwent follow-up studies. Finally, this is a retrospective, descriptive study, which is a drawback similar to many studies reported to date. Despite these limitations, the authors’ work is of value to the interventional cardiologist. Furthermore, this gives us an opportunity to discuss some issues germane to percutaneous occlusion of PDA.
Indications for Percutaneous Closure
Patients with clinical and echo-Doppler evidence of PDA who are ordinarily candidates for surgical closure are candidates for transcatheter occlusion. The procedure is indicated only in patients with continuous murmur suggestive of PDA with echo-Doppler confirmation. Closure is not recommended in the so-called “silent ductus” detected incidentally without typical auscultatory features.14 Very small and small PDAs without hemodynamic overload are candidates for closure because of the risk of subacute bacterial endocarditis. Medium- and large-sized ductus should be closed to prevent further volume overloading of the left ventricle, to treat congestive heart failure and to prevent pulmonary vascular obstructive disease apart from eliminating the endocarditisrisk. Patients with ductal-dependent congenital cardiac anomalies and those associated with pulmonary vascular obstructive disease should not undergo closure.
Results
The feasibility of implantation of coils and devices is close to 100%. Residual shunts 24 hours after the procedure were present in 18% of patients with free Gianturco coils, which decreased to 9% at follow up.6 With detachable coils, residual shunts were present in 7–28% immediately after the procedure, which decreased at follow up to 3–12%.6 Residual shunts were present in 9% patients with GGVOD, all spontaneously closed during follow up.6 Following implantation of the Amplatzer device, residual shunts were seen in 0–34%, which decreased to 0–3% at follow up.6 In a multicenter U.S. trial,15 the Amplatzer device was successfully implanted in 435 (99%) of 439 patients. Complete occlusion by angiography was demonstrated in 384 (76%), which increased to 89% patients by echocardiography the following day. At 1- year follow up, 359 (99.7%) of 360 patients had complete closure. Of the 60 consecutive Amplatzer ductal occlusions during a 30-month period ending March 2007, performed by the author, 59 had complete closure demonstrated by echo- Doppler studies the morning following device implantation, and the 60th patient had complete closure at 3-month follow up. At 1-year follow up, no residual shunts were seen. The complications are minimal, although coil/device embolization may occur, requiring transcatheter or occasionally surgical retrieval.
Approaches to PDA Closure
Based on personal experience with PDA closure with a number of methods,5,6,14,16–28 I believe that the choice of the method of closure should be based on the shape of the PDA1 and minimal ductal diameter.
Ductal shape. Earlier descriptions such as conical, tubular, short and long have largely been replaced by classification described by Kriechenko.1 If the ductus is small or very small, the shape may not play an independent role in determining the feasibility or effectiveness of closure. However, if the ductus is moderate-to-large in size, the shape may have a special role on feasibility and effectiveness of device closure. If the ductus is conical in shape (Krichenko type A1, A2, A3 and D), coils or ADOs may be used depending upon the size of the ductus. If it is short (type B), either an ADO or Amplatzer septal occluder may become necessary. Tubular ductus (type C) may need a GGVOD or Amplatzer vascular plug. PDAs with long and bizarre shapes (type E) may be occluded by coils, ADOs or Amplatzer vascular plugs.
Size of the PDA. Silent PDA. Widespread use of color Doppler echocardiographic studies has resulted in identification of a new group of patients, commonly termed “silent ductus”. Nearly 1% of children undergoing color Doppler studies were found to have a PDA.29 These patients without auscultatory (continuous murmur) findings of ductus, but with visualization by color Doppler, fall into the category of silent PDA. Some investigators30,31 recommend closure, while others32 including our group,14,19,24 are opposed to closing such PDAs. The controversy continues but, as more data become available, the weight of evidence should eventually be the deciding factor.
Silent ductus after device/coil occlusion. Residual shunts may be present in a small number of patients following device/coil closure, as reviewed in the preceding section. Most of these have no associated murmur and are technically “silent PDAs”. Can the noninterventional strategy be extended to such PDAs? This issue was examined by Latson et al33 in a piglet model; the PDAs were occluded by Rashkind devices. Their studies suggested that the piglets with no residual and “trivial” shunts were not at a higher risk than controls, whereas those with significant residual shunts were found to be at risk for developing endocarditis. Based on these data, Latson concluded that silent ducts after device occlusion are not at risk for developing endocarditis. But it is not clear how these residual shunts, trivial versus significant, compare with residual shunts without murmurs in human subjects following device/coil closure. In addition, the current practice is to recommend antibiotic prophylaxis for prevention of subacute bacterial endocarditis if residual shunt exists after device/coil occlusion. Therefore, it appears prudent to recommend closure (mostly coil occlusion) if residual shunts are present beyond 6–12 months after initial attempt to occlude by device/coil.
Very small PDA. Our definition of very small PDA is minimal ductal diameter < 1.5 mm with a continuous murmur. These PDAs can easily be occluded with free Gianturco coils, initially described by Cambier et al.8 We prefer 0.038 inch coils with 4–5 loops to effect complete occlusion.20,23 These coils can be delivered transarterially via 4 Fr catheters. The method is relatively simple and inexpensive. The use of snares,34 forceps,35,36 detachable coils,9,37 balloons38, 39 and tapered-tip catheters40 during coil deployment is not necessary, and is likely to increase the cost and fluoroscopic time. The detachable coils that the authors used,13 while giving a sense of safety in that the there is less likely to be embolization, is not truly advantageous since a careful comparison of dislodgement rates between free (9%) and detachable coils (1.5–7%) is essentially similar.6 Furthermore, the wire diameter of the detachable coils is 0.035 inches and has less occluding effect than that of 0.038 inch free coils.
Small PDA. There are PDAs with minimal ductal diameters of 1.5–2.5 mm, again with a continuous murmur. A single 0.038 inch Gianturco coil is likely to result in significant residual shunt, and multiple coils may be required.41 While the multicoil technique is a reasonable approach because of the potential for coil embolization and left pulmonary artery stenosis, we do not recommend such an approach. For these patients, we employ 0.052 inch coils;5 these coils are delivered via long 4 Fr Blue Cook sheaths (Cook, Bloomington, Indiana)with the assistance of a biopsy forceps, a method similar to that described by Hays35 and Grifka.36
Whereas devices may be used to occlude very small and small PDAs, the devices, in my opinion, are not necessary and may be problematic because of the need for larger sheaths to implant the devices and higher cost.
Moderate-to-large PDAs. The ducts with minimal ductal diameter > 2.5 mm may be considered moderate-to-large. Their closure may be accomplished by conventional surgical closure,42 video-assisted thoracoscopic interruption43 and by a number of devices. The Rashkind PDA occluder, Botallo occluder, Clamshell device, polyvinyl alcohol foam plug and folding plug buttoned device have been discontinued or not available for routine clinical use. The usefulness of ductoccluder pfm44 to close moderate-to-large PDAs has not been thoroughly investigated. The Gianturco-Grifka sac10 is available for general clinical use, and is particularly useful in occluding tubular PDAs. However, a relatively large delivery sheath and difficulties in retrieving the dislodged devices are disadvantages with this device. The Amplatzer duct occluder6,11,13,15,45,46 has several favorable features, including a relatively small delivery sheath (5–7 Fr), the facility with which it can be retrieved and repositioned prior to detachment and high closure rates. However, device dislodgement requiring surgery45,46 is of some concern, although the device dislodgement rate (3 of 209 or 1.4%) in large series45 is low. Finally, wireless devices, such as the transcatheter patch,26 may be useful in occluding large PDAs once they become available for clinical use. Thus, a number of devices 5,6,27 have been used to occlude moderate-to-large PDAs; some have been discontinued and others modified. Some are available for general clinical use, and others are under clinical trial protocols. At the current stage of development of device technology, ADO competes, I might add, favorably with conventional surgical closure and video-thoracoscopic closure. The selection of the method for occlusion of a moderate- to-large PDA would largely depend upon the availability of a particular device or method at a given institution at a given time. When several devices become available for general clinical use, an opportunity to perform randomized clinical trials may arise, and such data may help determine the best method of PDA closure.
In summary, most of the PDAs can be occluded by percutaneous methodology, and the selection of an appropriate type and size of the device is largely based on the minimal ductal diameter and shape of the ductus.
References
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