When, why, and how to perform cardiac radiofrequency catheter ablation

Radiofrequency catheter ablative techniques provide a unique opportunity to cure dogs of certain supraventricular tachyarrhythmias, rather than simply controlling the rhythm with drug therapy. Accessory pathways, which can participate as one limb of a rapid, narrow complex tachyarrhythmia circuit, have a particularly high cure rate with radiofrequency catheter ablation. Focal atrial tachycardias also provide a substrate that can be amenable to ablation. Tachycardia-induced myocardial dysfunction resulting from frequent tachyarrhythmic episodes will resolve after a successful ablation. This report outlines the indications, equipment, and techniques used in dogs for performing catheter ablation with temperature-controlled radiofrequency energy delivery.     

Coil embolization of patent ductus arteriosus via the carotid artery in seven dogs

This study was designed to evaluate the feasibility and limitations of transcatheter embolization coil occlusion of patent ductus arteriosus in dogs using a carotid artery approach. Seven dogs examined at the University of California, Davis Veterinary Medical Teaching Hospital in 2002-2003 for evaluation of heart disease had congenital patent ductus arteriosus diagnosed by characteristic physical, electrocardiographic, radiographic, and anatomic and Doppler echocardiographic findings. Dogs were anesthetized for transesophageal echocardiography and transcatheter coil embolization of the ductus via the right external carotid artery. Coil embolization was achieved in all seven cases, using one to four detachable embolization coils. There were no major complications. Minor complications occurred in two dogs (additional coils placed using a femoral arterial approach and coil embolization of a left femoral artery branch). One dog was examined only 24 h post-operatively and had no murmur and trivial residual ductal flow by Doppler echocardiography. The other 6 dogs were clinically healthy when examined up to three years post-intervention. One dog had a very soft continuous murmur and mild residual ductal flow; the other five had no audible continuous murmur, with only one dog having trivial residual ductal flow identified by Doppler echocardiography. Although technically challenging, coil embolization via the carotid artery is a viable alternative approach for transcatheter closure of patent ductus arteriosus in some dogs.     

Transcatheter closure of congenital ventricular septal defects in 3 dogs with a detachable coil

The purpose of this study was to evaluate the feasibility, safety, and efficacy of transcatheter closure in dogs with a congenital perimembranous ventricular septal defect (VSD) by using a detachable coil. No dogs showed any symptoms, and results of chest X-rays and ECGs were normal. The diameters of VSD ranged from 2 to 4 mm on echocardiogram. The defect was 2-2.5 mm from the aortic valve. A detachable coil (size 5 mm with 5 loops) designed for patent ductus arteriosus was delivered via the transarterial route. The device was successfully employed in all dogs. A minimal residual shunt was observed in all dogs even though Qp/Qs decreased. Hemolysis and a rate-dependent right-bundle branch block were observed in 1 dog, but there was no clinical significance. No major complication was noted. Pathologic examination after 1 year revealed that the coils were covered with tissue without significant damage to the His-Purkinje conduction system. In conclusion, transcatheter closure of a small perimembranous VSD with a detachable coil can be achieved without major complications or significant pathologic damage at the lesion site.     

Long-term follow-up after transvenous single coil embolization of patent ductus arteriosus in dogs

Background: Long‐term follow‐up studies after interventional therapy of patent ductus arteriosus (PDA) in dogs are rare. Hypothesis: Transvenous PDA embolization with a single detachable coil is a highly effective method in patients with an angiographically determined PDA ≤ 4.0 mm. Animals: Twenty‐eight dogs with an angiographic PDA ≤ 4.0 mm were included. Methods: Prospective follow‐up study after PDA coil embolization. Results: The median follow‐up time was 792 days (range, 2–3, 248 days). The rate of complete closure demonstrated by Doppler color flow was 54% at day 3 after intervention and the final cumulative rate was 71%. The rate of complete closure was significantly different between small and moderately sized PDA over the study period (P < .0001) and finally was 100 and 50%, respectively. In 16 dogs with complete closure, no recanalization was found. Disappearance of the continuous heart murmur was found in 89% after 3 days, and this increased to a final cumulative rate of 96%. Indexed left ventricular internal diameter in diastole (LVDd‐I) decreased significantly (P < .0001). In the group with moderately sized PDA, a significant difference (P= .0256) was seen in LVDd‐I between patients with and without residual shunt after exclusion of patients with persistent severe mitral valve regurgitation. Conclusion and Clinical Importance: Long‐term follow‐up after single coil embolization showed complete closure in all small PDA but a residual shunt with mild hemodynamic consequences was present in half of the moderately sized PDA.     

The Use of Ultrasound to Assess the Thrombogenic Properties of Teflon and Polyurethane Catheters for Short-Term Use in Systemically Healthy Horses

The objective of this study was to establish an ultrasound scoring system to assess the degree of fibrin tag and clot formation associated with jugular catheters in horses. A second objective was to test the hypothesis that, in healthy horses undergoing short-term anesthesia, polyurethane (PU) catheters have a different ultrasound score compared with polytetrafluoroethylene (Teflon) catheters. Twenty-three systemically healthy horses requiring anesthesia were randomly assigned PU or Teflon catheters. The mean catheter dwell time was 5 hours. Ultrasound was used to examine the jugular vein before catheter placement, before catheter removal (mean, 4 hours 45 minutes), and approximately 24 hours after catheter insertion (mean, 24 hours 42 minutes). The repeatability of the ultrasound scoring system was assessed by producing a series of randomly ordered selected still images for independent evaluation by four radiologists on two separate occasions. The interobserver and intraobserver repeatability was determined using a weighted kappa statistic, with substantial intraobserver repeatability mean κ .77 (range, .59–.91) and moderate interobserver repeatability mean κ .53 (range, .33–.67). The proportion of positive bacteriologic cultures in the polyurethane (PU) and Teflon groups was compared using Fisher's exact test, with no significant difference (P > .99) between the two groups. The distribution of the scores from the PU and Teflon groups was compared using the Mann-Whitney test, with no evidence of a difference between groups at the time of catheter removal (P = .23) and 24 hours after catheter insertion (P = .20). Further studies with a larger sample of systemically healthy horses are required to substantiate this preliminary finding.     

Transvenous embolization of small patent ductus arteriosus with single detachable coils in dogs

Transvenous embolization of small patent ductus arteriosus (PDA; < or = 4 mm) with a single detachable coil was attempted in 24 dogs (median age 5.7 months, range, 2.6-65.5 months; median body weight 5.5 kg, range, 1.5-30.0 kg). Angiographic imaging of the duct and pressure measurements were made before and after embolization. The minimal ductal diameter was 2.7 +/- 0.7 mm. In all dogs, a single coil was employed regardless of residual shunting. Ten dogs (PDA minimal diameter range, 1.5-2.2 mm) received a 5-mm coil, and 14 dogs (PDA minimal diameter range, 2.9-3.6 mm) received a 8-mm coil. After coil embolization the angiographic shunt grade decreased significantly (n = 20, P < .001). Residual shunts were assessed by angiography 15 minutes after and by Doppler echocardiography 1-3 days and 3 months after the intervention. In the dogs treated with the 5-mm coils the residual shunt rate was low (0%, 10%, and 0% for angiography and Doppler echocardiography at 1-3 days and 3 months, respectively), in contrast to the dogs treated with the 8-mm coils (91%, 79%, and 67% for angiography and Doppler echocardiography at 1-3 days and 3 months, respectively). After 3 months, no residual murmur was found in dogs treated with the 5-mm coils (0/7), in contrast to murmurs in 5 of 12 (42%) dogs treated with the 8-mm coils. Despite incomplete closure in these dogs, volume loading of the left heart decreased in all dogs. Pulmonic or aortic coil embolism did not occur. Analysis of initial results shows that single detachable coil embolization is possible in all dogs with a small PDA (< or = 4 mm), but only very small PDA (< or = 2.5) could be treated effectively, and for the moderate PDA (2.6-4.0 mm) longer coils or multiple coils may be necessary to achieve complete occlusion.     

The use of Amplatzer vascular plug II in 32 consecutive dogs for transvenous occlusion of patent ductus arteriosus

ObjectivesTo describe the use of the Amplatzer vascular plug II (AVPII) for transvenous occlusion of patent ductus arteriosus in a non-selective population of dogs, with a focus on the surgical technique, short term outcome and associated complications.Animals, materials and methodsRetrospective study. Records of thirty-two consecutive dogs treated for a left-to-right shunting patent ductus arteriosus with the AVPII were reviewed.ResultsDuctal occlusion with an AVPII occlusion device was attempted in 32 dogs weighing 1.1–53.8 kg. Transvenous occlusion was successful in 30 dogs. One dog required a transarterial approach for occlusion. One dog died during catheterisation of the right heart but prior to transductal catheterisation. Mean ductal ampulla diameter was 7.9 mm (range, 4.1–15.4 mm) and median size of deployed devices was 10 mm (range 4–20 mm). Mean device to ampulla ratio was 1.34 ± 0.15. Device was positioned in situ with no residual flow on follow-up echocardiographic assessment (> one month) in all dogs where deployment was attempted. Occlusion success rate was 96.9% and mortality rate was 3.1%. Four dogs (13.3%) demonstrated minor complications, with none having long-term significance.ConclusionsThe use of AVPII device via a transvenous approach is a feasible and effective method for occlusion of a left-to-right shunting patent ductus arteriosus in dogs of a wide range of weight. The method described may complement existing catheter-based occlusion methods.