Cardiac Interventions in Small Animals: Areas of Uncertainty

Correlation of transthoracic echocardiographic and angiographic measurements of pulmonary valve annular diameter in dogs with pulmonary stenosis

INTRODUCTION/OBJECTIVES

Dogs with severe pulmonary stenosis (PS) are routinely treated with balloon valvuloplasty. Success and safety of these procedures require an accurate assessment of the pulmonary valve annulus (PVA) diameter for proper balloon catheter selection. PVA diameter is assessed with angiography (PVA-Ang) and transthoracic echocardiography (PVA-TTE), and both may impact procedural planning for balloon valvuloplasty. The objective of this study was to describe the relationship between PVA-Ang and PVA-TTE in dogs with PS.

ANIMALS, MATERIALS AND METHODS

Observational, retrospective study of 59 client-owned dogs. Medical records of dogs diagnosed with PS were reviewed. Images from selective right ventricular angiography and transthoracic echocardiography were reviewed. The PVA diameters were measured at the time of angiography (PVA-Ang) and by a single operator for this study (PVA-TTE). Image quality scores were assigned to echocardiographic images of the PVA based on visualization of PVA margins and valve leaflet hinge points.

RESULTS

In 41/59 (70%) dogs, the diameter of the PVA-Ang was larger than the PVA-TTE, and the median absolute difference between measurements was 1.9 mm (range 0.1-8.4). With worse echocardiographic image quality, the difference in measurement between modalities increased. Dogs with poor echocardiographic image quality had greater differences (range -7.7 to 8.4 mm) between PVA-Ang and PVA-TTE compared to those with excellent image quality (range -2.2 to 3.8 mm), and the absolute differences between poor (median 2.8 mm, range 1.5-8.4 mm) and excellent (median 1.4 mm, 0.2-3.8 mm) image quality were significant (P=0.005).

CONCLUSIONS

Diameters of PVA-Ang are greater than PVA-TTE in most dogs, and these differences are most apparent with worse echocardiographic image quality. These differences may be clinically relevant to interventional procedure planning.

Doppler Ultrasonographic Assessment of Abdominal Aortic Flow to Evaluate the Hemodynamic Relevance of Left-to-Right Shunting Patent Ductus Arteriosus in Dogs

In this multicenter, prospective, observational study, abdominal aortic flow was examined with pulsed-wave Doppler ultrasound in dogs with a left-to-right shunting patent ductus arteriosus (PDA) and in apparently healthy dogs. Forty-eight dogs with a PDA and 35 controls were included. In the dogs with a PDA, 37/48 had hemodynamically significant PDAs (hsPDAs) while 11/48 had non-hsPDAs, based on the presence or absence of echocardiographic signs of left-sided volume overload, respectively. In 12 dogs (4/35 control dogs, 7/37 dogs with an hsPDA and 1/11 dogs with a non-hsPDA), the diastole was too short to visualize the end-diastolic flow. Antegrade end-diastolic flow was observed in 30/35 controls and 6/11 dogs with a non-hsPDA. Absent end-diastolic flow was observed in 1/35 control dogs and 3/11 dogs with a non-hsPDA. Retrograde end-diastolic flow was observed in 30/37 dogs with an hsPDA and 1/11 dogs with a non-hsPDA. Twenty-one dogs (15 with an hsPDA and 6 with a non-hsPDA) were reassessed after PDA closure, and, in 19/21, end-diastolic flow was visualized: 17/19 showed an antegrade flow, 1/19 an absent flow and 1/19 a retrograde flow. Sensitivity and specificity of retrograde end-diastolic flow for detection of hsPDAs were 100% and 90%, respectively. In conclusion, ultrasonographic assessment of abdominal aortic flow was feasible in dogs with PDA. However, end-diastolic flow was not always visualized. The presence of a retrograde end-diastolic flow was an accurate finding for discriminating hsPDAs and non-hsPDAs.

Advances in the Treatment of Pulmonary Valve Stenosis

Pulmonary valve stenosis represents the most common congenital heart defect of dogs and appears to be increasing in prevalence due to the growing popularity of brachycephalic breeds. Current treatments include beta-blockade and balloon pulmonary valvuloplasty, though evidence-based approaches to this disease are lacking. Balloon pulmonary valvuloplasty is most effective for fused, doming valves leaving a large population of dogs with thick, dysplastic valves that fail to respond adequately to balloon dilation. Transpulmonary stent implantation is an emerging therapy to consider for dogs with valve dysplasia or who have failed balloon pulmonary valvuloplasty; current experience with transpulmonary stent implantation is provided.

Transthoracic echocardiography and its limitations in the diagnosis of congenital supernumerary aortic valve in a Thoroughbred

Aortic valve malformation is a common congenital abnormality reported in human medicine. The malformation is characterised by an increased or decreased number of cusps. Anatomical variations of the aortic valve that have been documented in humans include unicuspid, bicuspid, quadricuspid and quinticuspid valves. Two reports described a quadricuspid aortic valve in horses associated with either a ventricular septal defect (VSD) or tetralogy of Fallot. In this case report we describe the clinical and echocardiographic findings of a horse with a quadricuspid aortic valve as single congenital abnormality, referred with history of exercise intolerance and an episode of paroxysmal atrial fibrillation. Limitations and risks of misdiagnosis that can be encountered with transthoracic echocardiography are also discussed. The reported case highlights the importance of echocardiographic screening in asymptomatic patients as congenital heart disease can be present without obvious cardiac signs. As advanced imaging on the equine thorax is still far from future possibilities for adult horses, this report may help to reach an accurate diagnosis with similar cases.

Non-cardiogenic pulmonary oedema complicating balloon valvuloplasty and stent angioplasty of severe pulmonary valve stenosis in four dogs

In dogs, balloon valvuloplasty is considered the treatment of choice for severe pulmonary valve stenosis, and this technique is currently performed routinely in specialist referral practices with low morbidity and mortality. Stent angioplasty has also been recently proposed as a viable treatment option. The present case series describes the clinical course of four dogs with severe pulmonary valve stenosis, treated with balloon valvuloplasty or stent angioplasty at four different institutions, which developed non-cardiogenic pulmonary oedema perioperatively after apparently successful dilation of the pulmonary valve. In three cases, there was evidence of some degree of pulmonary hypertension before ballooning. Despite intensive care, the complication proved fatal in three cases. Clinicians should therefore be aware of this life-threatening complication, previously undescribed in dogs.

Natural history of subaortic stenosis in 166 dogs (1999-2011)

INTRODUCTION

Subaortic stenosis (SAS) is one of the most common congenital cardiac diseases in dogs. The objective of this study was to provide survival times on a large population of dogs with SAS and to propose a redefined pressure gradient (PG) scale to include a mild, moderate, severe and very severe disease group.

ANIMALS, MATERIALS AND METHODS

Dogs were divided into four groups based on the Doppler-derived PG across the stenosis. Disease severity was defined as follows: mild = PG < 50 mmHg; moderate = PG range 50-80 mmHg; severe = PG range 80-130 mmHg; and very severe = PG > 130 mmHg. Over the study period (1999-2011), 166 client-owned dogs were diagnosed with SAS of which 129 had follow-up information available.

RESULTS

Unadjusted median survival time for severity groups were as follows: mild 10.6 years; moderate 9.9 years; severe 7.3 years; and very severe 3.0 years. Univariable analysis examining the effect of the PG, age at diagnosis and sex found only the PG and age at diagnosis had a significant effect on survival. Adjusted survival curves showed that the survival time in the very severe group was decreased compared with all other groups.

CONCLUSION

Based on the results of this study, a revised SAS classification system with four PG groups is appropriate. Dogs with a PG > 130 mmHg were identified as those with the lowest median survival time.

Branham sign in dogs undergoing interventional patent ductus arteriosus occlusion or surgical ligation: A retrospective study

Background:

The Branham sign is a baroreceptor response that follows patent ductus arteriosus (PDA) closure. Although described in dogs following both interventional and surgical ductal closure, a direct comparison of the Branham sign elicited by these two techniques has not been made.

Aim:

Since closure with an Amplatz canine ductal occluder (ACDO) occurs over 10 minutes and surgical ligation (SL) is more rapid, we hypothesized that the Branham sign following occlusion of a PDA with an ACDO would be less severe than following SL.

Methods:

Clinical records of dogs diagnosed with left-to-right shunting PDA between 2008 and 2018 were retrospectively reviewed. Of 139 dogs undergoing PDA occlusion, only 41 dogs (ACDO n = 32, SL n = 9) were included after applying exclusion criteria. Heart rate (HR) and blood pressure (BP) from occlusion time (T₀) until 30 minutes post occlusion (T₃₀) were recorded. Signalment and anesthetic protocol were also recorded. The influence of age and weight on the hemodynamic variations was assessed. Hemodynamic variables and calculations were compared between and within groups using a repeated measures general linear model, and post hoc tests were applied if significance was identified.

Results:

A mild Branham sign was present in both groups, and hemodynamic changes were not significantly different between groups. In both groups, there was a significant decrease in HR (11 bpm, 5.3–16.3; p < 0.001) (10.4%, 5.4–15.5; p < 0.001) and increase in diastolic BP (9.5 mmHg, 3–16; p = 0.002) (23.5%, 7.1–39.9; p = 0.002), but systolic BP did not change significantly (p = 0.824). Age and weight did not influence Branham sign.

Conclusion:

The Branham sign in dogs is mild in both groups, lasts for at least 30 minutes, and is independent of the method of PDA closure.

Balloon valvuloplasty in 2 juvenile alpacas with severe valvular pulmonic stenosis

Two juvenile alpacas, 1 male and 1 female, were presented for evaluation of grade V/VI bilateral basilar systolic heart murmurs. Both animals were ultimately diagnosed with severe valvular pulmonic stenosis and a small ventricular septal defect. Transvenous balloon valvuloplasty was performed in each animal using methods described in the dog. A double balloon technique was employed in the first case, with a balloon‐annulus ratio of ~1.55. For the second case, a high‐pressure dilatation balloon catheter with a balloon‐annulus ratio of ~1.33 was selected. Experience with both procedures indicates that balloon pulmonary valvuloplasty is technically feasible in alpacas using techniques extrapolated from those used in dogs. Furthermore, accepted criteria for procedural success were fulfilled for both alpacas, with more than a 50% reduction in the echocardiographically derived transpulmonic pressure gradient after intervention.

Balloon valvuloplasty of valvular pulmonary stenosis in a neonatal foal

In a 1-day old filly with a loud heart murmur, transthoracic echocardiography revealed right ventricular hypertrophy associated with severe pulmonary valvular stenosis and a transvalvular pressure gradient (between right ventricle and pulmonary artery) of 125 mmHg. Computed tomographic angiography confirmed the finding, with no evidence of other relevant concurrent abnormalities. Balloon valvuloplasty was performed using a single balloon technique. The foal recovered well from anaesthesia. Following the procedure, the right ventricle-pulmonary artery transvalvular gradient decreased to 38 mmHg. At follow up examinations after 1 month, 1 year and 2 years, the filly showed normal exercise capacity and echocardiography confirmed the persistent substantial improvement in the transvalvular outflow gradient.

Transpulmonary Stent Implantation for Dysplastic Pulmonary Valve Stenosis with a Single Left Coronary Ostium and Anomalous Prepulmonary Right Coronary Artery in an English Bulldog

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Coronary artery anomalies may exist with congenital PS.

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PS occurs in both animals and humans.

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Transpulmonary stenting may be considered in dogs with PS and coronary anomalies.

Anaesthetic management and complications of transvascular patent ductus arteriosus occlusion in dogs

OBJECTIVE

To retrospectively analyse the anaesthetic management, complications and haemodynamic changes in a cohort of dogs undergoing transvascular patent ductus arteriosus (PDA) occlusion in a tertiary referral centre (from January 2017 to August 2018).

STUDY DESIGN

Retrospective study.

ANIMALS

A total of 49 client-owned dogs.

METHODS

Anaesthetic records of dogs with PDA that underwent transvascular occlusion of the ductus were reviewed. Anaesthetic complications evaluated included tachycardia [heart rate (HR) > 160 beats minute^-1], bradycardia (HR < 50 beats minute^-1), hypertension [systolic arterial pressure (SAP) > 150 mmHg], hypotension [mean arterial pressure (MAP) < 60 mmHg], hypothermia (<37 °C) and the presence of arrhythmias. Cardiovascular variables [HR and invasive SAP, MAP and diastolic arterial pressure (DAP)] at the time of occlusion device deployment (time 0) were compared with variables at 5 and 10 minutes after deployment. Descriptive statistics, Shapiro-Wilk test and repeated measures analysis of variance followed by a Dunnett's post hoc test were used to analyse the data (p < 0.05).

RESULTS

Crossbreed dogs were the most commonly represented followed by the Cavalier King Charles Spaniel. The median age was 8 (2-108) months, and female dogs were over-represented (65.3%). The most common American Society of Anesthesiologists score was III. Mean duration of anaesthesia was 96 ± 26 minutes and mean surgery time was 58 ± 21 minutes. Acepromazine with methadone was the most commonly used premedication combination (77.6%). Propofol was the most common induction agent (73.5%). General anaesthesia was maintained with isoflurane in oxygen in all dogs. Complications included hypotension (63%), hypothermia (34%), bradycardia (28%), arrhythmias (16%), hypertension (16%) and haemorrhage (2%). MAP and DAP increased significantly 10 minutes after device deployment compared with time 0.

CONCLUSIONS

and clinical relevance: Hypotension was the most common complication reported in dogs undergoing transvascular PDA occlusion. No major adverse events were documented.

A pilot study evaluating cutting and high-pressure balloon valvuloplasty for dysplastic pulmonary valve stenosis in 7 dogs

INTRODUCTION

This case series describes early experience and technical aspects of cutting balloon dilation followed by high-pressure balloon pulmonary valvuloplasty in dogs with dysplastic pulmonary valve stenosis.

ANIMALS

Seven client-owned dogs were enrolled in this study.

METHODS

Dogs were prospectively enrolled based on echocardiographic diagnosis of severe pulmonary valve dysplasia, defined as marked valve thickening with variable degrees of annular hypoplasia or subvalvar fibrous obstruction and a peak echocardiography-derived transpulmonary pressure gradient higher than 100 mmHg. Preinterventional and postinterventional hemodynamic data and transthoracic pressure gradients were obtained for all dogs. Recheck echocardiography varied in timing by client convenience, with maximum follow-up 35 months after intervention.

RESULTS

No intraprocedural or periprocedural mortality was observed. The only major complication was partial avulsion of a cutting blade related to exceeding recommended burst pressure of the device, which was not associated with obvious clinical consequence. Invasive hemodynamic measurements demonstrated an average reduction of 46% in peak systolic right ventricular-to-pulmonary artery pressure gradient (range, 31-77%). The echocardiographic results 24 h after procedure demonstrated an average reduction in pressure gradient of 43% (range, 20-66%), with late follow-up demonstrating an average reduction of 35% (range, 10-57%) compared with preprocedural echocardiography.

CONCLUSIONS

This procedure is a feasible therapeutic transcatheter intervention for dogs with dysplastic pulmonary valves and appears safe in this small cohort. The ideal selection criteria and rate of restenosis for this procedure is under investigation, and long-term follow-up and a large, randomized, controlled study are necessary to demonstrate efficacy.

Balloon valvuloplasty in a dog with congenital bicuspid aortic valve and supravalvar aortic stenosis (atypical Shone's complex)

An 8-month-old intact female pug was presented for evaluation and possible balloon valvuloplasty (BV) for severe aortic stenosis. A bicuspid, severely stenotic aortic valve of type 3 morphology with a supravalvar stenosis component was diagnosed, consistent with the diagnosis of atypical Shone's complex. There was severe concentric hypertrophy of the left ventricle, with increased echogenicity of the myocardium nearest to the endocardial border. Mild left atrial enlargement was observed. Selective angiography and transesophageal echocardiography revealed an enlarged and relatively tortuous ascending aorta. The changes to the ascending aorta and the anatomy of the lesion made retrograde access to the left ventricle challenging. Ultimately, BV was successful using a pediatric valvuloplasty balloon catheter and rapid right ventricular pacing, and the pressure gradient across the aortic valve was decreased by more than 50% compared with preoperative measurements. Although valvar aortic stenosis is rare in veterinary medicine, this report highlights the potential challenges and feasibility of BV for this disease.