The Amplatz canine duct occluder: a novel device for patent ductus arteriosus occlusion

Transesophageal echocardiography using a microprobe for determination of transcatheter procedural candidacy, device selection, and procedural monitoring in small dogs with patent ductus arteriosus

INTRODUCTION

Small dogs with patent ductus arteriosus (PDA) may be unable to undergo transesophageal echocardiography (TEE) with traditional probes.

OBJECTIVES

To report the utility of TEE using a microprobe in dogs weighing less than 4 kg diagnosed with PDA for determination of transcatheter procedural candidacy, device selection, and intraoperative procedural guidance.

ANIMALS

Eight dogs weighing less than 4 kg diagnosed with PDA.

MATERIALS AND METHODS

All dogs had standard transthoracic echocardiography and microprobe TEE imaging. The quality of TEE images was graded as optimal, adequate, or poor. The ability of TEE to assess PDA anatomy, determine procedural candidacy, provide procedural guidance, detect deployed devices, and assess residual flow was recorded.

RESULTS

The median age of included dogs was 6.4 months (range: 3.2-15.7 months) and the median body weight was 2.2 kg (range: 1.4-3.8 kg). Microprobe TEE images were adequate or optimal in all dogs and were integral for guiding procedural candidacy decisions. Transcatheter procedures were not pursued in two dogs based on TEE images. In the other six dogs, TEE procedural guidance was useful during transvenous (n = 5) and transarterial (n = 1) PDA occlusion attempts. Each deployed device (n = 4) was easily detected with the TEE microprobe. Real-time confirmation of adequate device sizing and placement was possible prior to release and residual flow could be monitored after release.

CONCLUSIONS

Transesophageal echocardiography using a microprobe in dogs weighing less than 4 kg diagnosed with PDA allowed for characterization of PDA anatomy and determination of transcatheter procedural candidacy. Microprobe TEE images were integral for PDA device selection and offered valuable intraoperative procedural guidance.

Transjugular Patent Ductus Arteriosus Occlusion in Seven Dogs Using the Amplatzer Vascular Plug II

Simple Summary

This study outlines the authors’ experience using the Amplatzer Vascular Plug II device for occlusion of patent ductus arteriosus (PDA) in dogs through a right transjugular approach, never before described in veterinary medicine for this purpose. The obtained results demonstrate that the use of the Amplatzer Vascular Plug II via a transvenous right jugular approach is a feasible and effective method, even in small-sized patients. The authors’ experience is that the transvenous approach is a safe and effective method for PDA occlusion in dogs. Furthermore, the right jugular approach provides easier and faster vascular access than the femoral one. The authors affirm that this approach, together with the properties of the Amplatzer Vascular Plug II and its wide size selection, potentially provide a novel method that can complement the current available methods for transcatheter PDA occlusion.

Abstract

Although vascular plugs for the closure of patent ductus arteriosus (PDA) have been validated in dogs, studies are lacking on its use as a first-choice device with a transjugular approach. The present case series describes the transvenous right jugular embolization of PDA using an Amplatzer Vascular Plug II in seven dogs of different ages, breeds, and body weights. Complete closure of the PDA was demonstrated in all cases. All dogs showed significant hemodynamic reduction of pulmonary overcirculation and left heart size after the procedure and at following echocardiographic check-ups. Transjugular PDA occlusion using an Amplatzer Vascular Plug II can thus be considered as a safe alternative to the arterial or venous femoral approach using an Amplatzer canine ductal occluder (ACDO), particularly in puppies with small femoral vessels.

Pre-procedural femoral vessel ultrasound in dogs with patent ductus arteriosus: diameter, image quality and relationship with arterial catheterization

INTRODUCTION

/Objectives: Patent ductus arteriosus (PDA) in dogs is often treated via minimally invasive transvascular occlusion using femoral artery access. This study compared ultrasound-derived diameter and image quality of the right femoral artery (RFA) and vein (RFV) in dogs with PDA using a linear ultrasound probe (L-P) and phased-array transthoracic echocardiography probe (TTE-P). The case outcome was assessed.

ANIMALS, MATERIALS & METHODS

Forty-five client-owned dogs with PDA were prospectively enrolled. Ultrasound-measured RFA and RFV diameters were obtained on images acquired with both probes pre-operatively and compared using Bland-Altman plots. The image quality of RFA and RFV was scored on L-P and TTE-P images.

RESULTS

Comparison of RFA and RFV diameter from L-P versus TTE-P images revealed: [Mean difference (limits of agreement): RFA = 0.009 mm (-0.78-0.79 mm), RFV = 0.523 mm (-1.75-2.79 mm)]. Image quality scores were significantly higher for L-P than TTE-P (P < 0.0001). In six small dogs, measurable images were unattainable with TTE-P. Dogs of similar body weight had variable RFA diameters. Twenty-seven dogs had RFA catheterization. In 21/27 dogs, RFA diameter exceeded the external diameter of the introducer used for catheterization, and in 6/27, it was smaller.

CONCLUSIONS

Pre-procedural ultrasound of the RFA in dogs with PDA is useful given variable RFA diameter relative to body weight. Despite poorer image quality, RFA diameters from TTE-P images were very similar to L-P images on average, suggesting TTE-Ps are suitable for pre-procedural planning in most dogs. Vasospasm, hypotension or differences in the location of ultrasound measurement versus catheterization might produce variation in pre-procedural versus intraoperative RFA size.

Late recanalization after complete occlusion of patent ductus arteriosus in a Pembroke Welsh Corgi with von Willebrand disease

A 36‐month‐old female Pembroke Welsh Corgi with a cardiac murmur weighing 12.6 kg was referred to the Matsubara Animal Hospital cardiology service. Echocardiography revealed a patent ductus arteriosus. The dog underwent ductus arteriosus closure using an Amplatz Canine Duct Occluder. After the operation, we suspected coagulation and a platelet disorder because of the slightly increased haemorrhage during the operation, postoperative purpura around the surgical wound inside of the thigh, and dog breed, which is known to be commonly affected with von Willebrand disease (vWD). Subsequently, type 1 vWD was confirmed. Complete occlusion was achieved 1 month after the operation; however, 2 months after the operation, recanalization appeared. Recanalization progressed gradually; cardiac redilation was not detected 6 years after the operation. The late recanalization was most likely associated with vWD. In canine breeds pre‐disposed to developing vWD, pre‐operative testing may be indicated prior to patent ductus arteriosus occlusion, though the prevalence of vWD is rare.

Low profile vascular plug for transarterial occlusion of patent ductus arteriosus in small dogs

Background

Minimally invasive transcatheter occlusion using Amplatz canine duct occluder (ACDO) is the treatment of choice for dogs with left‐to‐right shunting patent ductus arteriosus (PDA). However, in small dogs the femoral artery diameter is often too small to accommodate the guiding catheter required for ACDO deployment.

Objective

Describe the effectiveness of transarterial implantation of Amplatzer Vascular Plug 4 (AVP‐4), the only self‐expandable nitinol mesh occlusion device which can be implanted through a 4 French diagnostic catheter, in small dogs with left‐to‐right shunting PDA.

Animals

Seven client‐owned dogs.

Methods

Descriptive case series. Dogs with hemodynamically relevant left‐to‐right shunting PDA and a femoral artery diameter less than 2.0 mm measured preoperatively with ultrasonography were prospectively enrolled.

Results

Angiography after releasing the device showed complete immediate PDA closure in 5 dogs, where the manufacturers' recommendation were strictly followed (30%‐50% device oversizing of the ductal ampulla's diameter). Trivial residual flow on angiography in the 6th dog, whose device was slightly undersized, had resolved on echocardiography within 2 hours after placement. Marked device undersizing in the 7th dog resulted in severe residual shunting, which necessitated the addition of a coil. In this dog, the AVP‐4 embolized into the pulmonary artery within 2 weeks after placement.

Conclusions and Clinical Importance

Transarterial implantation of AVP‐4 is a safe, effective and technically easy procedure for PDA occlusion in small dogs and offers a valuable alternative to coil implantation. Accurate PDA measurement and device sizing is essential to prevent residual shunting, inadvertent device embolization, and protrusion of the device into the aorta.

Development of Spontaneous Echocardiographic Contrast After Transarterial Occlusion of a Patent Ductus Arteriosus in an Adult Dog With Concurrent Pulmonary Hypertension

An 8-year-old intact female Chihuahua was presented for evaluation and possible occlusion of a previously diagnosed patent ductus arteriosus (PDA). Transthoracic echocardiography revealed left ventricular and left atrial enlargement, enlargement of the main pulmonary artery, and a PDA with bidirectional shunting. Tricuspid regurgitant velocities suggested moderate pulmonary hypertension. The PDA was occluded with an Amplatz® Canine Duct Occluder using a transarterial approach on the following day. No immediate complications were observed other than an acute decrease in left ventricular systolic function. One day after the PDA occlusion transthoracic echocardiography revealed no residual ductal flow, but there was spontaneous echocardiographic contrast in the left ventricle. The patient was discharged with sildenafil, pimobendan, and clopidogrel. Five weeks later when the patient was presented for a recheck examination, the previously documented spontaneous echocardiographic contrast was no longer present. Finding spontaneous echocardiographic contrast in the dog has not previously been reported in association with PDA occlusion.

Complications during catheter-mediated patent ductus arteriosus closure and pulmonary balloon valvuloplasty

OBJECTIVES

To evaluate and illustrate complications of cardiac catheterisation and the associated risk factors of the most common cardiac intervention procedures.

MATERIALS AND METHODS

Retrospective study of clinical records of client-owned dogs presented to a cardiology referral centre between January 2006 and December 2017.

RESULTS

Five hundred and twenty-four dogs were included, 62 of which had complications. Complications were divided into technical complications and those due to unexpected additional anatomical abnormalities. Seven procedures (1.33%) were interrupted; five dogs (0.95%) subsequently underwent surgery, and four dogs died during the interventional procedure, indicating a mortality rate of 0.76% CLINICAL SIGNIFICANCE: There is a low risk of complications following closure of patent ductus arteriosus or pulmonary balloon valvuloplasty when carried out by a trained team using standardised procedures in a referral centre.

Anatomy, baseline characteristics, and procedural outcome of patent ductus arteriosus in German Shepherd dogs

Background

German Shepherd dogs (GSD) are predisposed to developing patent ductus arteriosus (PDA) and are reportedly prone to type III (tubular) PDA anatomy. Dogs with type III anatomy are not considered favorable candidates for device‐based intervention.

Objective

To describe the PDA anatomy, baseline characteristics, and procedural outcome of GSD with PDA.

Animals

Twenty‐eight client‐owned GSD.

Methods

Retrospective review of medical records of 28 GSD diagnosed with PDA that underwent surgical ligation or transcatheter device closure between 2007 and 2017.

Results

German Shepherd dogs with PDA often presented with clinical signs (50%), concurrent congenital heart disease (35.7%), and arrhythmias (29%). Dogs were typically mature at presentation (median age, 12.1 months) and evenly distributed by sex (57% female). The PDA anatomy was classified in 24 of 28 GSD, with type II anatomy being most common (21/24). Three dogs had unusual anatomy (type IV in 1, type V in 2). Median minimal ductal diameter (MDD) in this population was larger than previously reported in a mixed population and ranged between 4.4 and 4.9 mm depending upon imaging modality. Successful closure was achieved using an Amplatz canine duct occluder (ACDO) in 22 dogs or by surgical ligation in 6 dogs. No cases of type III anatomy were confirmed.

Conclusions and Clinical Importance

The majority of GSD in this population had type II PDA anatomy that was amenable to ACDO deployment. Predisposition for large MDD and occasional, unusual PDA anatomy suggests that transesophageal echocardiography may be beneficial for optimal procedural planning in this breed.

A pictorial view of the three-dimensional representation and comparative two-dimensional image orientation derived from computed tomography angiography in a dog with a patent ductus arteriosus

Patent ductus arteriosus (PDA) occlusion is one of the more common cardiovascular procedures performed in dogs. Two-dimensional imaging has been the primary method of visualizing the PDA and is the basis of its morphologic description. Transesophageal echocardiographic imaging has further characterized the three-dimensional (3D) variation in ductal morphology and shape (circle, oval). An accurate assessment of the shape and dimensions of a PDA in an individual dog is important when making decisions about definitive closure. Ductal measurements from angiography and echocardiography have not been found to be interchangeable, likely related in part to the static two-dimensional measurement of a 3D structure. We describe the use of computed tomography angiography (CTA) images imported into three software programs as a tool to provide 3D information about PDA anatomy including a comparison to images obtained from classic two-dimensional imaging modalities. These images provide an example of thorax and heart position related to transducer position and the orientation of image acquisition to demonstrate why measurements do not always compare. Additionally, 3D images are useful as a training tool and in the development of devices and training opportunities. Multidimensional imaging provides a unique representation of the 3D anatomical structure of the ductus arteriosus as displayed in these images from a dog with a PDA.

Effect of calibration methods on the accuracy of angiographic measurements during transcatheter procedures in dogs

Background

Different methods to perform reference calibration of an angiographic image exist; however, a prospective comparison of calibration methods has yet to be investigated in veterinary medicine.

Objective

To compare angiographic measurements using two commonly employed reference calibration methods, an esophageal pigtail marker catheter (EC) versus a radiopaque table ruler (TR).

Animals

Thirty‐five client‐owned dogs undergoing transcatheter intervention.

Methods

Prospective comparison study. Two reference calibration methods, EC and TR, were recorded in dogs undergoing transcatheter procedures from May 2016 to July 2017. Relevant measurements were performed in triplicate and averaged after image calibration to either EC or TR. Comparisons between methods were made by correlation, paired t‐test, the method of Bland and Altman, and Passing‐Bablok regression.

Results

A total of 39 angiographic structures were measured. Interventions included balloon pulmonary valvuloplasty (n = 21), patent ductus arteriosus occlusion (n = 11), subaortic or sub‐pulmonary balloon dilatation (n = 4), and cor triatriatum membranostomy (n = 3). Angiographic measurements were larger when calibrated to EC versus TR (P < .0001). The mean bias was 0.86 mm, with greater bias for larger measurements. The EC measurements were ∼10% greater than TR based on regression analysis. Weight was correlated to the difference between methods (ρ = 0.55, P = .0003).

Conclusions and Clinical Importance

Angiographic image calibration using a ruler placed on the fluoroscopy table underestimates the size of a structure by ∼10% as compared with a marker catheter placed within the esophagus. This effect is greatest when measuring larger structures such as the pulmonary valve annulus and in larger dogs.

Incomplete endothelialization of an intravascular implant and fatal late-onset bacterial ductal arteritis in a dog with occluded patent ductus arteriosus

An 18‐month‐old male Akita Inu dog developed fever and lameness 8 months after successful transcatheter closure of a patent ductus arteriosus with an Amplatz Canine Duct Occluder (ACDO). Corynebacterium species were cultured from 3 blood samples. Echocardiography showed a vegetative process on the aortic valves. The dog died spontaneously 3 days after development of the initial signs. Necropsy confirmed the presence of bacterial ductal arteritis and myocarditis, and revealed an incomplete endothelialization of the intraductal metal implant. The reason for the lack of (neo)endothelialization of the ACDO remains unknown. We conclude that late‐onset bacterial device‐related ductal arteritis can develop in dogs where the implant is incompletely covered by a protective endothelial layer.

Comparative, multidimensional imaging of patent ductus arteriosus and a proposed update to the morphology classification system for dogs

Background

Accurately assessing the morphology and shape of the patent ductus arteriosus (PDA) and obtaining measurements are important to avoid procedural complications.

Objectives

To characterize and compare PDA morphology, shape, and dimensions with angiography and echocardiography.

Animals

25 client‐owned dogs with echocardiographically confirmed PDA.

Methods

Prospective case series. Imaging consisted of single plane angiography, transthoracic echocardiography from the right (TTE‐R) and left (TTE‐L), and two‐dimensional, biplane, and three‐dimensional transesophageal echocardiography (TEE‐2D and TEE‐3D). Measurements included angiographic minimal ductal diameter (MDD), echocardiographic pulmonary ostium in a single dimension (TTE‐R, TTE‐L, and TEE‐2D) and in perpendicular dimensions (TEE‐3D) with similar measurements of the ampulla 3 mm above the MDD or pulmonary ostium. The morphology and shape of the PDA were characterized.

Results

Catheter‐based occlusion (N = 20) and surgical ligation (N = 5) were performed without complication. Angiographic morphology was classified as type II (N = 19), type III (N = 1), and other (N = 1). Angiographic MDD and TEE‐2D pulmonary ostium measurements were significantly (P = .008) but weakly correlated (r = .56); similar relationships were found for ampulla diameter measurements (P < .0001; r = .75). In general, TEE‐2D did not correlate with other imaging modalities measurements. Based on TEE‐3D measurements, the majority of pulmonary ostium (17/24; 71%) and ampulla (19/24; 79%) were oval.

Conclusions and Clinical Importance

Measurements using different imaging modalities are not interchangeable. TEE‐3D provided an en face view of the PDA that cannot be replicated with other echocardiographic techniques and demonstrated an oval shape in the majority of dogs. We propose an update to the current classification system to include additional PDA morphologies.

Speckle-Tracking Echocardiography in Dogs With Patent Ductus Arteriosus: Effect of Percutaneous Closure on Cardiac Mechanics

BACKGROUND

Patent ductus arteriosus (PDA) is 1 of the most common congenital heart defects in dogs and percutaneous closure is effective in achieving ductal closure; PDA closure is associated with abrupt hemodynamic changes.

HYPOTHESIS

A marked decrease in standard parameters of systolic function as assessed by M- or B-mode echocardiography after PDA closure was identified in previous studies. Speckle tracking echocardiography can provide further insight into the effect of PDA closure on cardiac mechanics in dogs affected by PDA.

ANIMALS

Twenty-five client-owned dogs with PDA.

METHODS

Prospective study. Dogs were recruited over a 2-year period. Complete echocardiographic evaluation was performed before and 24 hours after PDA closure, including standard (end-diastolic volumes indexed to body surface area in B- and M-mode [EDVIB /M ], end-systolic volumes indexed to body surface area in B- and M-mode [ESVIB /M ], allometric scaling in diastole [AlloD] and systole [AlloS], pulmonary flow to systemic flow [Qs/Qp], ejection fraction [EF], and fractional shortening [FS]), and advanced speckle-tracking echocardiography (STE): global longitudinal, radial, circumferential and transverse strain (S), and strain rate (SR).

RESULTS

Patent ductus arteriosus closure was associated with statistically significant decreases in EDVIM /B and ESVIM /B , AlloD and AlloS, SI, EF, and FS. A statistically significant decrease in the absolute values of radial, transverse, and circumferential S and SR was observed, whereas longitudinal S and SR did not change significantly.

CONCLUSION AND CLINICAL IMPORTANCE

Patent ductus arteriosus closure by percutaneous approach is associated with marked decreases of conventional echocardiographic parameters as a result of the changes in loading conditions, but no evidence of systolic dysfunction was identified by means of STE, as none of the S and SR values were below reference ranges. In the short term, contractility is enhanced in the long axis (long S/SR values were not statistically different before and after closure) and decreases to normal values in short axis (circumferential, radial, and transversal S/SR decreased to normal reference range).

Relationship between Device Size and Body Weight in Dogs with Patent Ductus Arteriosus Undergoing Amplatz Canine Duct Occluder Deployment

Background

Deployment of the Amplatz Canine Duct Occluder (ACDO) is the preferred method for minimally invasive occlusion of patent ductus arteriosus (PDA) in dogs, with appropriate device sizing crucial to successful closure. Dogs of any body weight can be affected by PDA.

Objectives

To describe the range of ACDO sizes deployed in dogs of various body weights for improved procedural planning and inventory selection and to investigate for correlation between minimal ductal diameter (MDD) and body weight.

Animals

A total of 152 dogs undergoing ACDO deployment between 2008 and 2016.

Methods

Body weight, age, breed, sex, and MDD obtained by angiography (MDD‐A), MDD obtained by transesophageal echocardiography (MDD‐TEE), and ACDO size deployed were retrospectively evaluated.

Results

Correlation between body weight and ACDO size, MDD‐A and MDD‐TEE was poor, with R‐squared values of 0.4, 0.36, and 0.3, respectively. Femoral artery diameter in the smallest population of dogs placed inherent limitations on the use of larger device sizes, with no limitations on the wide range of device sizes required as patient size increased. The most commonly used ACDO devices were size 3 through 6, representing 57% of the devices deployed within the entire study population.

Conclusions and Clinical Importance

Patent ductus arteriosus anatomy varies on an individual basis, with poor correlation between MDD and body weight. Weight‐based assumptions about expected ACDO device size for a given patient are not recommended.

An experimental canine patent ductus arteriosus occlusion device based on shape memory polymer foam in a nitinol cage

Patent ductus arteriosus (PDA) is a congenital cardiovascular defect in which a fetal connection between the aorta and pulmonary artery does not spontaneously close shortly after birth. If left uncorrected serious complications and even death can occur. Surgical ligation is the traditional treatment method; however, it is an invasive procedure, that motivates development of a minimally invasive option. Shape memory polymer (SMP) foams are unique materials that hold promise in the field of minimally invasive occlusion devices. In this work, a prototype nitinol foam cage (NFC) incorporating SMP foams has been designed and evaluated in multiple mechanical and in vitro verification tests. The NFC demonstrated acceptable fatigue resistance in a preliminary strut integrity test, withstanding one million cycles without complete strut fracture. Radial force analysis of both thick- and thin-walled prototype variations generated less vessel distension and wall tension in a vessel mimic compared to a commercial device. The NFCs exhibited negligible in vitro migration, comparable to that of a commercial device, using simplified, ideal models of PDA. Deployment characteristics of the prototypes were evaluated and compared to that of a commercial device when delivered into physiological models of PDA. During mock deployments, a veterinary cardiologist noted that, while deliverable, the thin-walled NFC prototype exhibited poor deployment characteristics, however the thick-walled NFC had deployment characteristics comparable to that of a commercial device. The promising results of this study warrant further investigation of the NFC device for canine PDA closure.

Interventional Closure of a Patent Ductus Arteriosus Using an Amplatz Canine Duct Occluder in an Alpaca Cria

A 6‐month old female alpaca cria presented to The Ohio State University for evaluation of a cardiac murmur. Echocardiography revealed a left‐to‐right shunting patent ductus arteriosus, a restrictive left‐to‐right shunting perimembranous ventricular septal defect, and secondary moderate left atrial and ventricular dilation. Aortic root angiography demonstrated a type IIA patent ductus arteriosus (PDA). Interventional closure of the PDA was successfully performed, without complication, using an Amplatz canine duct occluder. This case report describes the materials and methods used for interventional closure of a PDA in an alpaca cria.

Alternative methods for the measurement of the minimal ductal diameter of a patent ductus arteriosus in a dog

A two and half-year-old, 24 kg, spayed female German Shepherd was presented for evaluation of a suspected patent ductus arteriosus (PDA). Transthoracic echocardiographic examination confirmed a left to right shunting PDA. Closure of the PDA was recommended, and the owners elected to have minimally invasive transcatheter closure of the PDA performed. Standard ductal angiography failed to provide adequate measurements of the minimal ductal diameter (MDD). Alternative methods of measuring the MDD using an angiography catheter and a balloon catheter were performed. The PDA was occluded using an Amplatz^® Canine Ductal Occluder without complication. Further evaluation of these techniques is needed to determine the accuracy, overall clinical efficacy, and safety of using alternative methods for the measurement of the MDD of a PDA.

Chitosan hemostatic dressing for control of hemorrhage from femoral arterial puncture site in dogs

Removal of an introducer-sheath from a femoral artery after completing transarterial embolization of a patent ductus arteriosus can cause life-threatening hemorrhage in dogs. In the present study, the effectiveness of chitosan acetate dressing in 10 experimental dogs was tested. Under general anesthesia, an introducer-sheath was placed into the femoral artery with percutaneous puncture using Seldinger's technique. The outer diameter of the introducer-sheaths varied from 3.0 to 4.0 mm with an introducer/artery ratio of 80 to 123%. The artery's diameter was measured using ultrasonography. Following removal of the introducer-sheath, a chitosan acetate dressing was applied to the wound and held in place with manual compression for 10 min. Successful hemostasis was reached on 12 arteries. However, on two arteries, hemorrhage was uncontrollable and led to a hypovolemic shock during 10 min of manual compression. Possible causes of the negative outcome in two dogs were their old age and an introducer-sheath with a too large diameter. The chitosan acetate dressing was easy to use and the artery remained patent. Dogs could walk directly after recovery from anesthesia and their femoral arteries were saved. In conclusion, the outer diameter of the introducer-sheath should not exceed 3 mm or the inner diameter of the artery.

Mechanical and in vitro evaluation of an experimental canine patent ductus arteriosus occlusion device

Patent ductus arteriosus (PDA) is a congenital cardiovascular malformation in which a fetal connection between the aorta and pulmonary artery remains patent after birth. This defect commonly results in clinical complications, even death, necessitating closure. Surgical ligation is the most common treatment but requires a thoracotomy and is therefore invasive. A minimally invasive option is preferable. A prototype device for PDA occlusion which utilizes shape memory polymer foams has been developed and evaluated using mechanical and in vitro experiments. Removal force and radial pressure measurements show that the prototype device exhibited a lower removal force and radial pressure than a commercially available device. The in vitro experiments conducted within simplified and physiological PDA models showed that the prototype does not migrate out of position into the pulmonary artery at either physiological or elevated pressures in multiple model configurations. While the radial pressure and removal force were lower than commercial devices, the device performed acceptably in the in vitro benchtop experiments warranting further prototype development.

Patent ductus arteriosus occlusion in small dogs utilizing a low profile Amplatz® canine duct occluder prototype

OBJECTIVES

To develop procedural methodology and assess the safety, utility and effectiveness of a low profile Amplatz(®) canine duct occluder (ACDO) prototype in dogs deemed too small to undergo ductal occlusion with the commercially-available ACDO device.

ANIMALS

Twenty-one dogs with left-to-right shunting patent ductus arteriosus (PDA). Dogs were ≥1.5 kg but considered too small to accommodate a 6 Fr catheter or 4 Fr sheath within the femoral artery.

METHODS

Prospective canine study using a low profile ACDO prototype delivered through a 4 Fr catheter via a femoral arterial approach. Procedural methods, fluoroscopy time, perioperative complications, and residual ductal flow were evaluated, and angiographic ductal morphology and dimensions were tabulated.

RESULTS

All 21 dogs underwent successful ductal occlusion using the prototype device, 4 Fr catheter, and right femoral artery approach. No perioperative complications or device embolization occurred. The median minimal ductal diameter was 1.9 mm (range, 0.4-3.4), and the median device size deployed was 4 mm (range, 3-6). Complete ductal occlusion was noted in 17 dogs (81%) on post-deployment angiography. Twenty dogs (95%) had no residual flow on echocardiography performed the following day. In the 17 dogs (81%) that returned for a long-term (≥3months) follow-up evaluation, all had complete ductal occlusion based on echocardiography.

CONCLUSIONS

The low profile ACDO prototype is a safe and effective method of PDA occlusion in the small dog. The deployment procedure appears of similar technical difficulty to the commercially available ACDO.

The history of veterinary cardiology

Throughout civilization, animals have played a pivotal role in the advancement of science and medicine. From as early as 400 BC when Hippocrates recognized that diseases had natural causes, the steadfast advances made by biologists, scientists, physicians and scholars were fueled by timely and important facts and information- much of it gained through animal observations that contributed importantly to understanding anatomy, physiology, and pathology. There have been many breakthroughs and historic developments. For example, William Harvey in the 16th and 17th centuries clarified the importance of the circulatory system, aided by observations in dogs and pigs, which helped to clarify and confirm his concepts. The nineteenth century witnessed advances in physical examination techniques including auscultation and percussion. These helped create the basis for enhanced proficiency in clinical cardiology. An explosion of technologic advances that followed in the 20th century have made possible sophisticated, accurate, and non-invasive diagnostics. This permitted rapid patient assessment, effective monitoring, the development of new cardiotonic drugs, clinical trials to assess efficacy, and multi-therapy strategies. The latter 20th century has marshaled a dizzying array of advances in medical genetics and molecular science, expanding the frontiers of etiologies and disease mechanisms in man, with important implications for animal health. Veterinary medicine has evolved during the last half century, from a trade designed to serve agrarian cultures, to a diverse profession supporting an array of career opportunities ranging from private, specialty practice, to highly organized, specialized medicine and subspecialty academic training programs in cardiology and allied disciplines.

Minimally invasive per-catheter occlusion and dilation procedures for congenital cardiovascular abnormalities in dogs

With ever-increasing sophistication of veterinary cardiology, minimally invasive per-catheter occlusion and dilation procedures for the treatment of various congenital cardiovascular abnormalities in dogs have become not only available, but mainstream. Much new information about minimally invasive per-catheter patent ductus arteriosus occlusion has been published and presented during the past few years. Consequently, patent ductus arteriosus occlusion is the primary focus of this article. Occlusion of other less common congenital cardiac defects is also briefly reviewed. Balloon dilation of pulmonic stenosis, as well as other congenital obstructive cardiovascular abnormalities is discussed in the latter part of the article.

Transthoracic echocardiographic guidance of patent ductus arteriosus occlusion with an Amplatz® canine duct occluder

Placement of an Amplatz canine duct occluder (ACDO) is usually performed by fluoroscopy (Nguyenba and Tobias, 2007). The latter technical approach presents limitations, mostly due to radiation exposure, making this practice dangerous for the patient and operators. In this study, we describe the successful placement of an Amplatz Canine Duct Occluder device by using transthoracic echocardiographic (TTE) guidance, performed on an 11-month-old female mongrel dog with a grade VI/VI continuous heart murmur diagnosed with patent ductus arteriosus (PDA). The TTE is useful in eliminating exposure to radiation and is more versatile than fluoroscopy in conveying real-time detailed information concerning the position of the ACDO.