Transcatheter closure of patent ductus arteriosus using occluding spring coils

The purpose of this study is to report our initial experience with the use of spring coils to close the patent ductus arteriosus in the dog. There are few large-patient series reported in the veterinary literature. Coil closure was attempted in 15 dogs (median weight, 6.5 kg; range, 1.2 to 38.7 kg) presenting with a patent ductus arteriosus between May 1997 and May 1999. Arterial catheterization followed by angiography was used to decide if coil placement was adequate. A 5- or 8-mm embolization coil, depending on the angiographic diameter of the ductus, was delivered, with 1 loop in the pulmonary arterial side and the remainder of the coil in the aortic side of the duct. Additional coils were used if a residual shunt was present, and closure was confirmed by aortography. Patients were discharged the day after the procedure. Successful coil closure, without residual shunt on angiography, was achieved in 11 of 13 dogs in which coils were released. In 6 dogs, a coil embolized to the pulmonary artery. Four of these dogs had successful closure with multiple coils, and 2 others had surgery. None of these dogs experienced adverse effects. In 2 dogs with conical patent ductus arteriosus >5 mm in minimal diameter, coil closure was not done. We conclude that the patent ductus arteriosus size and anatomical shape are crucial in deciding whether coil closure is the method of choice. In selected cases, coil closure represents an elegant alternative to surgical ligation. Although pulmonary embolism occurred commonly, it did not cause any obvious clinical problem.

Radiofrequency thermal balloon angioplasty in an experimental model of peripheral arterial stenosis

RATIONALE

To assess the effect of thermal balloon angioplasty on surgically created peripheral arterial stenoses.

METHODS

Unilateral femoral arterial stenoses were created in 17 neonatal lambs (Dorset X Suffolk/Mule), using absorbable sutures. Six to 8 weeks later, the stenoses were dilated using either a standard (N=5), or thermal balloon angioplasty (N=9). Immediate angiography, flow and pressure gradient measurements were made to assess the acute result following either procedure. The survivors were followed up for a further period of 4 to 6 weeks, and a terminal angiographic study performed. The thermally treated segments of vessels were removed for qualitative histologic analysis.

RESULTS

Thermal angioplasty appeared to be acutely successful in eight of nine animals, compared with one of five successful procedures following standard angioplasty. Higher therapeutic temperatures (> or = 80 degrees C) were associated with vascular complications. At the terminal study, stenoses had recurred in four of six survivors successfully treated with thermal angioplasty. Histologic studies demonstrated non-uniform effects of thermal dilation on the vessel wall, with variable changes ranging from partial or full-thickness tears, fibroblastic or myocyte proliferation, and disorganization of the vessel wall layers.

CONCLUSION

Thermal angioplasty appears to be acutely more beneficial compared with standard angioplasty. However there is a significant recurrence of stenoses, and non-uniform changes in the vessel wall.

Exchange of pacing or defibrillator leads following laser sheath extraction of non-functional leads in patients with ipsilateral obstructed venous access

Occlusion of the subclavian or brachiocephalic vein in pacemaker or defibrillator patients prohibits ipsilateral implantation of new leads with standard techniques in the event of lead malfunction. Three patients are presented in whom laser sheath extraction of a non-functional lead was performed in order to recanalise the occluded vein and to secure a route for implantation of new leads. This technique avoids abandoning a useful subpectoral site for pacing or defibrillator therapy. The laser sheath does not affect normally functioning leads at the same site.

[Implantable ECG recorder revealed the diagnosis in a baby with apparent life-threatening events]

A 14-month-old boy went through episodes of cyanosis and brief loss of consciousness. Extensive investigations failed to lead to a diagnosis, until an implanted ECG recorder revealed ECG abnormalities suggestive of strangulation. Interviews with the father and mother showed that this was indeed the case. The diagnosis of 'Münchhausen by proxy' was made. Psychiatric assistance and home help were called in. The child recovered well. If there is a suspicion of arrhythmia as the cause of apparent life-threatening events, prolonged ECG recordings are necessary. In a clinical environment it is possible to make continuous ECG recordings during a limited period. An insertable recorder allows continuous ECG recordings during a syncopal event and can be used for prolonged monitoring. The patient presented is the youngest infant in the world in whom such a device has been implanted.

Homozygous premature truncation of the HERG protein : the human HERG knockout

Background-In long-QT syndrome (LQTS), heterozygosity for a mutation in 1 of the K(+) channel genes leads to prolongation of the cardiac action potential, because the aberrant protein exhibits "loss of function." HERG, which is involved in LQT2, is the gene encoding the rapid component of the delayed rectifier, I(Kr). Methods and Results-In a consanguineous family, a stillbirth was followed by the premature birth of a child in distress due to ventricular arrhythmia in the presence of QT prolongation. LQTS was diagnosed, beta-blocker therapy was begun, and a pacemaker was implanted. She developed well and remained symptom-free for 1.5 years. In the index patient, we identified a duplication of bp 558 to 600 in exon 4 of HERG on both alleles. This will result in a frameshift and a premature stop codon before the S1 domain of the HERG protein. Because it is present on both alleles, no functional I(Kr) is anticipated. The same mutation was found heterozygously in both parents and homozygously in the stillborn brother. Conclusions-It is concluded that absence of I(Kr) gives rise to a severe cardiac phenotype, with no indication of malfunction of any other organ.

Lung perfusion studies after detachable coil occlusion of persistent arterial duct

OBJECTIVE

To evaluate relative lung perfusion following complete occlusion of persistent arterial duct with detachable Cook coils.

METHODS

Ductal occlusion using detachable coils was performed in 35 patients (median age 3.9 years, range 0.5 to 16; 32 native ducts, three patients with previous devices). If the duct could be crossed with a 0.035 inch guidewire and a 4 F catheter after coil implantation, a further coil was implanted. Between one and seven coils were used (median two).

RESULTS

Complete ductal occlusion was confirmed by echocardiography 24 hours after the procedure in all patients. Lung perfusion scans were performed three months after the procedure in 33 of 35 patients (two older patients with a single coil each did not attend). Decreased perfusion to the left lung (defined as < 40% of total lung flow) was observed in only one patient, who had previously had a 17 mm Rashkind umbrella implanted. There was no correlation between left lung perfusion and peak left pulmonary artery Doppler velocities (r = 0.27 and p = 0.125 for the entire group; r = 0.29 and p = 0.124 after excluding patients with previous devices).

CONCLUSIONS

Coil occlusion is effective in achieving complete closure of the duct. An aggressive approach using multiple coils did not compromise perfusion to the left lung.

Sustained high pressure double balloon angioplasty of calcified conduits

OBJECTIVE

To assess the efficacy of prolonged high pressure angioplasty for dilatation of calcified and stenotic cardiac conduits in children.

DESIGN

A prospective study of consecutive patients presenting with calcified and stenotic conduits.

SETTING

Two tertiary paediatric cardiology departments.

METHODS

Sustained (up to five minutes), high pressure (up to 18 atmospheres), double balloon angioplasty was performed in six calcified and stenotic cardiac conduits (five consecutive patients, three male, two female, age 4 to 17 years). Four patients had right ventricle to pulmonary artery (RV-PA) conduits, and one had two venous conduits in a Fontan circulation.

RESULTS

Marked reductions in right ventricle to pulmonary artery gradients, from a median (range) of 48 (40 to 62) mm Hg to 11 (5 to 16) mm Hg, and in right ventricle to femoral artery pressure ratios, from a median of 0.8 (0.72 to 0.86) to 0.4 (0.33 to 0.44), were achieved for all RV-PA conduits. All five patients had sustained clinical improvement at follow up (median follow up 12 months) and none has required reintervention or surgery.

CONCLUSIONS

Prolonged high pressure double balloon angioplasty may have a role in prolonging the interval between conduit replacements in a subset of patients with complex heart defects.

Competitive pulmonary flow in infancy: the effect of respiration

Superior caval flow during positive pressure mechanical ventilation and spontaneous breathing was investigated by Doppler echocardiography in a neonate with a coexisting superior cavopulmonary shunt and an aortopulmonary shunt. During positive pressure ventilation, retrograde systolic flow in the superior vena cava was recorded, with low velocity anterograde flow. This pattern was reversed during spontaneous respiration. Low intrathoracic pressure plays an important role in maintaining anterograde pulmonary blood flow in patients with this physiology.

Junctional ectopic tachycardia evolving into complete heart block

Transition from congenital junctional ectopic tachycardia to complete AV block was observed in an 8 month old girl, over a 36 hour period, during initial hospital admission. Two years later she had evidence of a rapidly increasing left ventricular end diastolic diameter, associated with lowest heart rates during sleep of < 30 beats/min. A transvenous permanent pacemaker was therefore implanted. This finding supports the idea that a pathological process in the area of the AV junction, initially presenting as junctional ectopic tachycardia may later extend to sudden complete atrioventricular block.

Double chambered right ventricle: delineation by multiplane transoesophageal echocardiography

Three consecutive patients (median age 5 years; median weight 15 kg) with double chambered right ventricle (DCRV) were studied by multiplane transoesophageal echocardiography (TOE), using a specially designed paediatric probe. Using a 30 degrees angulation from the longitudinal plane, the body and outflow tract of the right ventricle could be imaged with minimal foreshortening, allowing detailed description of the level and nature of obstruction. In all cases, angiography and subsequent surgical inspection confirmed the TOE findings. Multiplane TOE should avoid the necessity for angiography in the preoperative assessment of this unusual lesion.

Catastrophic transcatheter baffle fenestration for failing Fontan physiology

Transcatheter fenestration and balloon dilation of an atrial baffle created from native atrial tissue was attempted in a 15-year-old girl with failing Fontan physiology and protein-losing enteropathy. After transseptal puncture, initial dilations with a 10-mm and 12-mm diameter balloon resulted in an inadequate fenestration, with no significant decrease of right atrial pressure or systemic arterial saturation. Dilation of the fenestration with a 16-mm-diameter balloon produced a tear of the atrial septum and subsequent death. Balloon dilation of native atrial tissue may result in uncontrolled tears of the atrial septum.

Percutaneous transhepatic dual chamber pacing in children with Fontan circulation

Permanent pacing is often required following the Fontan operation and is usually performed epicardially as there is no direct access to the ventricle from the systemic veins. Dual chamber endocardial pacing was achieved by the transhepatic approach in two children with Fontan circulation. The patients were a 7 year old boy with left atrial isomerism, single ventricle with pulmonary stenosis, interrupted inferior vena caval vein with azygous continuation, and direct drainage of the hepatic veins to the right sided atrium, and a 6 year old girl with tricuspid atresia. This approach to endocardial pacemaker implantation is potentially of considerable value in patients who do not have direct access to the ventricle from the systemic veins.

Intraoperative ultrasonographic troubleshooting after the arterial switch operation

BACKGROUND

Less than perfect coronary artery translocation accounts for the majority of perioperative deaths after the arterial switch procedure for transposition of the great arteries. Some types of coronary arterial anatomy are associated with a higher risk of death.

METHODS

Prospective epicardial ultrasound examination of all neonates with failing left ventricle or difficulty in weaning off cardiopulmonary bypass was performed after completion of the arterial switch operation during a 2-year period from March 1994 to February 1996. The aim was to identify any mechanical, and potentially remediable, factors accounting for ventricular failure.

RESULTS

Four neonates fulfilling the above criteria were identified during a 2-year period when epicardial echocardiography was routinely applied. In 2 patients coronary arterial problems in the form of kinking of the proximal left coronary artery (1 patient) and extrinsic compression of the artery by the neo-pulmonary trunk (1 patient) were identified and successfully corrected. In 2 other patients, supravalvar aortic stenosis was recognized, leading to prompt revision.

CONCLUSIONS

Epicardial echocardiography has an important "troubleshooting" role in the subgroup of patients with a suboptimal hemodynamic result after the arterial switch operation. Patients with unusual coronary anatomy should routinely be candidates for such studies.

Pulmonary atresia, "intact ventricular septum", and aortopulmonary collateral arteries

In muscular pulmonary atresia, major aortopulmonary collateral arteries are characteristic of pulmonary atresia with ventricular septal defect and are rarely seen in pulmonary atresia with intact ventricular septum. Two unusual cases of muscular pulmonary atresia are reported, one with an intact septum and one with a perimembranous ventricular septal defect, closed in utero by aneurysmal tricuspid tissue. In both cases the pulmonary blood supply came entirely from aortopulmonary collaterals. In case 1 a collateral artery connected the left subclavian artery and hypoplastic pulmonary arteries, and several aortopulmonary collaterals arose from the descending aorta, without overlap between these two circulations. In case 2 the pulmonary trunk and arterial duct were absent and the pulmonary blood supply came entirely from collateral arteries. The right ventricle was of normal size and tripartite with a closed perimembranous ventricular septal defect, discovered only at postmortem examination. These observations suggest right ventricular outflow tract obstruction early in fetal development, with involution of the pulmonary trunk and sixth arch derivatives, and persistence of primitive aortopulmonary connections. The morphology in case 1 is at odds with the theoretical division of pulmonary atresia with intact septum and pulmonary atresia with ventricular septal defect into two separate pathological entities that occur at different stages in fetal development.

Metallic stenting of the biliary tree following liver transplant hepatic artery thrombosis in an infant

We report the placement of intrahepatic metallic, balloon-expandable stents in the biliary tree following liver transplantation in a 12-month-old infant who developed biliary strictures secondary to hepatic artery thrombosis. The use of such stents has not previously been reported following transplantation in an infant. Re-transplantation was undertaken 5 months after stenting because of chronic rejection and progressive obstructive jaundice.

Transcatheter occlusion of the patent ductus arteriosus with Cook detachable coils

OBJECTIVE

To report initial experience with a new occlusion device for native and residual patent ductus arteriosus.

DESIGN

Descriptive study of consecutive non-randomised patients undergoing a new method of patent ductus arteriosus closure with detachable coils.

SETTING

Tertiary centres for paediatric cardiology.

PATIENTS

71 consecutive patients, aged 1.2-22 years, with a patent ductus arteriosus (PDA) underwent elective transcatheter closure. 45 had native PDAs (group A) with a minimum diameter of 1.0 mm-5.0 mm (median 2.0 mm). A further 26 had undergone one or more previous occlusion attempts (group B).

INTERVENTIONS

A total of 133 detachable (Cook) spring coils were successfully implanted in 70 patients. The procedure was performed transvenously in 51 patients, retrograde arterially in 13, and by both routes in a further 6 patients. One 5 mm coil migrated but was successfully retrieved.

MAIN OUTCOME MEASURES

In group A colour flow Doppler echocardiography showed that complete occlusion was achieved in 40/45 (89%) at 24 hours, 41/45 (91%) at 1 month, and 44/45 (98%) by 6 months post procedure. Occlusion rates in residual PDAs were 22/25 (88%) occluded at 24 hours, 23/25 (92%) at 1 month, and 24/25 (96%) at 6 months follow up.

CONCLUSIONS

Transcatheter occlusion using detachable (Cook) spring coils is a safe and effective alternative to presently available devices. The delivery system allows full retrieval of the coil until a satisfactory position is obtained.