Electrocardiography-gated cardiac CT angiography can differentiate brachycephalic dogs with and without pulmonary valve stenosis and findings differ from transthoracic echocardiography.

Pulmonary valve stenosis (PS) is one of the most commonly diagnosed congenital heart defects in dogs. Currently, transthoracic echocardiography (TTE) is the standard modality used to evaluate PS. Image acquisition by TTE can be challenging in some brachycephalic breeds of dogs. The use of echocardiographic-gated CT angiography (ECG-gated CTA) in veterinary medicine is limited. This retrospective method comparison study investigated right and left ventricular outflow diameters by sedated ECG-gated CTA and unsedated TTE in 14 brachycephalic dogs with PS and 12 brachycephalic dogs without PS. Measurements of ventricular outflow structures were made in early systole and end diastole for both modalities and then compared for significance between systolic and diastolic phases, as well as between the two modalities. Ratios of the pulmonary trunk diameter to the aorta at different locations (aortic valve, aortic annulus, and ascending aorta) and in different planes (transverse, sagittal) were compared between dogs with PS and without PS, as well as within dogs, by both TTE and ECG-gated CTA. Transthoracic echocardiography and ECG-gated CTA both detected significantly greater pulmonary trunk to aorta ratios in dogs with PS at all aortic locations (P < 0.05). Pulmonary valve to aortic valve ratios were significantly smaller in dogs with PS (P < 0.05). Pulmonary trunk to aorta and pulmonary valve to aorta ratios were achieved with good anatomic detail using ECG-gated CTA. Ratios of the pulmonary trunk and pulmonary valve relative to the aorta may be useful to evaluate for PS using a modality that is underutilized for cardiac assessment.

Equine Congenital Heart Disease.

Congenital heart disease (CHD) represents a small proportion of horses undergoing clinical evaluation; however, both simple and complex defects occur during cardiac development leading to many unique malformations. This article reviews cardiac development and the fetal circulation, describes the morphologic method and the sequential segmental approach to CHD analysis, presents a summary of CHD in horses, and offers an overview of lesions that should be considered during evaluation of horses suspected to have CHD. For many forms of equine CHD, therapies are limited because cardiac interventions and cardiac surgery are not routinely pursued in this species.

A retrospective review of 146 active and passive fixation bradycardia lead implantations in 74 dogs undergoing pacemaker implantation in a research setting of short term duration.

BACKGROUND: Canine veterinary patients increasingly benefit from implantation of transvenous pacemakers for bradyarrhythmias. No published data exist examining procedural outcomes of pacemaker implantation performed in the preclinical laboratory. The purpose was to review short term complication, infection, dislodgement, penetration rates, plus overall morbidity following pacemaker implantation in the research setting. A retrospective review of 74 Class A purpose-bred mongrels implanted with active (n = 89) and passive fixation (n = 57) intracardiac leads for dual (n = 72) or single (n = 2) chamber pacing was performed. RESULTS: All leads were implanted successfully, meeting electrical implant criteria. Follow-ups typically occurred every 7 days (first month), then at 30 day intervals. Seroma formation was 1.4% and 10.8% at the venotomy and pulse generator site respectively. Overall infection rate was 1.4%. Overall dislodgement rate was 2.1%, (2 passive atrial leads, 1 passive ventricular lead). Overall fractures and insulation defects were zero. Two helix penetrations were noted incidentally post mortem, one at the right atrial appendage and one at the right ventricle (64 dogs, 128 leads evaluated), a 1.6% event rate. Major in-life adverse events were 5.4% (4 of 74 dogs), including 1 infection and 3 lead dislodgements. CONCLUSIONS: This review demonstrates a low complication rate with bradycardia lead implants in the short term (up to 180 days), in a high volume research setting. Lead type, implant technique, surgeon experience, healthy patient population, patient size and follow-up care play a role. This review also suggests active fixation leads in the right atrial appendage of dogs are safe and reliable.

Use of an intravenous sclerosing foam (3% sodium tetradecyl sulfate) for treatment of orbital varix in a dog.

A 6-month-old intact male Standard Dachshund was referred for evaluation of a soft tissue swelling above the right eye. Examination of the right eye revealed mild lateral deviation of the globe, normal vision, and a dorsonasal soft tissue swelling. Examination of the posterior segment was normal. Dual-phase computed tomography angiography was consistent with an orbital varix of the angularis oculi and right dorsal external ophthalmic veins with no evidence of arterial involvement. Treatment involved fluoroscopically guided coil embolization of the venous outflow with nine platinum microcoils, followed by sclerotherapy of the varix using 1.5 mL of 3% sodium tetradecyl sulfate foam. Moderate-to-marked swelling was noted at the treatment site in the weeks following therapy, which gradually resolved. At final reexamination 3 months post-therapy, complete sclerosis and resolution of the orbital varix were documented. To the authors' knowledge, this is the first reported case involving the use of a sclerotic agent for successful treatment of a venous malformation in a dog.

Arterial anomalies of the celiac trunk and median arcuate ligament compression in dogs and cats assessed by computed tomography angiography.

OBJECTIVE: To identify abnormalities of the celiac artery (CA) and major branches in dogs and cats by computed tomography angiography (CTA). STUDY DESIGN: Multi-institutional retrospective case series. ANIMALS: Two hundred fifty-four dogs and 13 cats. METHODS: Abdominal CTA images from 2009 to 2017 were reviewed. Logistic regression models were used to evaluate the relationship between CA abnormalities and sex, age, size of dog, concurrent venous anomaly, or presence of gastrointestinal signs. RESULTS: Abnormalities in the CA were observed in 32 animals (11.9%) including 9 with abnormal branching (3.4%) and 23 with CA compression (8.6%). A celiacomesenteric trunk was observed in 8 (2.9%; 6 dogs, 2 cats). The splenic artery originated from the cranial mesenteric artery in 1 dog; the hepatic arterial branches originated from the left gastric artery in another. Four out of 32 animals (12.5%) with an arterial anomaly had another vascular abnormality. Large breed dogs were more likely to have an arterial anomaly (OR 4.3, 95% CI: 1.18-15.5, P = .02) and 12 times more likely to have CA compression (OR 12.0, 95% CI: 1.4-97.7, P = .02) compared to small breed dogs. Dogs with CA compression were more likely to present for gastrointestinal signs (OR 3.6, 95% CI: 1.2-10.3, P = .01). CONCLUSION: Anomalies of the celiac trunk are apparent on CTA and may impact surgical or image-guided intervention. Compression at the origin of the CA was apparent on imaging, similar to the median arcuate ligament syndrome in people, although the significance of this finding in dogs is unknown.

Quantification of nasal airflow resistance in English bulldogs using computed tomography and computational fluid dynamics.

Stenotic nares, edematous intranasal turbinates, mucosal swelling, and an elongated, thickened soft palate are common sources of airflow resistance for dogs with brachycephalic airway syndrome. Surgery has focused on enlarging the nasal apertures and reducing tissue of the soft palate. However, objective measures of surgical efficacy are lacking. Twenty-one English bulldogs without previous surgery were recruited for this prospective, pilot study. Computed tomography was performed using conscious sedation and without endotracheal intubation using a 128 multidetector computed tomography scanner. Raw multidetector computed tomography data were rendered to create a three-dimensional surface mesh model by automatic segmentation of the air-filled nasal passage from the nares to the caudal soft palate. Three-dimensional surface models were used to construct computational fluid dynamics models of nasal airflow resistance from the nares to the caudal aspect of the soft palate. The computational fluid dynamics models were used to simulate airflow in each dog and airway resistance varied widely with a median 36.46 (Pa/mm)/(l/s) and an interquartile range of 19.84 to 90.74 (Pa/mm)/(/s). In 19/21 dogs, the rostral third of the nasal passage exhibited a larger airflow resistance than the caudal and middle regions of the nasal passage. In addition, computational fluid dynamics data indicated that overall measures of airflow resistance may significantly underestimate the maximum local resistance. We conclude that computational fluid dynamics models derived from nasal multidetector computed tomography can quantify airway resistance in brachycephalic dogs. This methodology represents a novel approach to noninvasively quantify airflow resistance and may have utility for objectively studying effects of surgical interventions in canine brachycephalic airway syndrome.

Coil embolization of a palatine artery pseudoaneurysm in a gelding.

OBJECTIVE: To describe successful transarterial coil embolization of a palatine artery pseudoaneurysm that extended into the caudal maxillary sinus of a gelding. STUDY DESIGN: Clinical report. ANIMAL: A 24-year-old Morgan gelding with right-sided epistaxis. METHODS: The right maxillary sinus was imaged by radiography, computed tomography, and sinoscopy. Angiography was performed to locate the source of bleeding, and transarterial coil embolization of a right palatine artery pseudoaneurysm was performed. RESULTS: There was some mucoid nasal discharge and an intermittent cough postoperatively. No epistaxis was seen after embolization. There was moderate swelling of the surgical incision over the mid-cervical common carotid artery. The horse was discharged from the hospital 4 days after surgery, and had been doing well, with no signs of bleeding, for 2 months postoperatively. The horse had acute colic secondary to a strangulating lipoma at 2 months and was euthanatized after exploratory celiotomy. Placement of embolization coils in the right palatine artery was confirmed by CT and necropsy. CONCLUSIONS: Severe epistaxis in the horse may be caused by a ruptured major palatine artery pseudoaneurysm. Occlusion of this vessel can be successfully accomplished by transarterial coil embolization.

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.

The Genetics of Canine Pulmonary Valve Stenosis.

There have been recent advancements in understanding the genetic contribution to pulmonary valve stenosis (PS) in brachycephalic breeds such as the French Bulldog and Bulldog. The associated genes are transcriptions factors involved in cardiac development, which is comparable to the genes that cause PS in humans. However, validation studies and functional follow up is necessary before this information can be used for screening purposes.

Right atrial thrombus formation in a dog after successful electrical cardioversion for atrial fibrillation.

Right atrial masses in dogs are commonly diagnosed as malignant tumors. This report describes a dog with a right atrial mass that appeared after successful electrical cardioversion of atrial fibrillation and resolved with antithrombotic treatment. A 9-year-old mastiff was presented for acute vomiting, and occasional cough of several weeks' duration. Ultrasonographic and radiographic examinations of the abdomen and chest identified mechanical ileus, as well as pleural effusion and pulmonary edema, respectively. Echocardiography indicated a dilated cardiomyopathy phenotype. During anesthetic induction for laparotomy, atrial fibrillation developed. Electrical cardioversion successfully restored sinus rhythm. An echocardiogram performed 2 weeks later disclosed a right atrial mass, which had not been apparent before cardioversion. Repeat echocardiography after 2 months of clopidogrel and enoxaparin treatment failed to detect the mass. Intra-atrial thrombus formation is possible after successful cardioversion of atrial fibrillation and should be considered as a differential diagnosis for echocardiographically detected atrial masses.

Utility of vertebral left atrial size and vertebral heart size to aid detection of congestive heart failure in dogs with respiratory signs.

BACKGROUND: Differentiating cardiogenic vs noncardiogenic causes of respiratory signs can be challenging when echocardiography is unavailable. Radiographic vertebral left atrial size (VLAS) and vertebral heart size (VHS) have been shown to predict echocardiographic left heart size, with VLAS specifically estimating left atrial size. HYPOTHESIS/OBJECTIVES: Compare the diagnostic accuracy of VLAS and VHS to predict left-sided congestive heart failure (CHF) in dogs presenting with respiratory signs. ANIMALS: One-hundred fourteen dogs with respiratory signs and radiographic pulmonary abnormalities. METHODS: Retrospective cross-sectional study. Dogs had to have an echocardiogram and thoracic radiographs obtained within 24 hours. Diagnosis of CHF was confirmed based on the presence of respiratory signs, cardiac disease, LA enlargement, and cardiogenic pulmonary edema. RESULTS: Fifty-seven dogs had CHF and 57 did not have CHF. Compared to VHS (area under the curve [AUC] 0.85; 95% confidence interval [CI], 0.77-0.91), VLAS was a significantly (P = .03) more accurate predictor of CHF (AUC, 0.92; 95% CI, 0.85-0.96). Optimal cutoff for VLAS was >2.3 vertebrae (sensitivity, 93.0%; specificity, 82.5%). Murmur grade (P = .02) and VLAS (P < .0001) were independently associated with CHF and VHS was not. Increased VHS (54%) was significantly (P = .01) more common than increased VLAS (24%) in dogs without CHF. Results were similar in a subsample of older and smaller dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: When echocardiography is unavailable, VLAS and murmur grade have clinically utility to aid in differentiating cardiogenic from noncardiogenic respiratory signs. These findings might be especially useful to help rule out CHF in dogs with increased VHS that present with respiratory signs.

The classical and alternative circulating renin-angiotensin system in normal dogs and dogs with stage B1 and B2 myxomatous mitral valve disease.

BACKGROUND: The behavior of the comprehensive circulating renin-angiotensin system (RAS) in dogs with myxomatous mitral valve disease (MMVD) before to the onset of congestive heart failure remains largely unexplored. HYPOTHESIS/OBJECTIVES: The classical and alternative RAS activity and aldosterone concentrations will be significantly higher in dogs with American College of Veterinary Internal Medicine (ACVIM) stage B2 MMVD compared to normal dogs and dogs with ACVIM stage B1 MMVD. ANIMALS: One-hundred seventeen client-owned dogs (normal = 60; B1 = 31; B2 = 26). METHODS: Prospective observational study. Angiotensin peptides (AP) and aldosterone concentrations were measured using liquid chromatography and mass spectrometry. Angiotensin converting enzymes 1 and 2 (ACE, ACE2) and renin activity surrogates were calculated from AP concentrations. Equilibrium dialysis (ED) and immediate protease inhibition (PI) methods of AP quantification were compared in 14 healthy dogs. RESULTS: Core RAS activity and aldosterone concentrations did not differ among the 3 groups. However, the balance between the alternative and classical RAS differed, with dogs with stage B2 MMVD having significantly higher ACE2 activity surrogate (ACE2surr ) when compared to normal dogs (adjusted P = .02; ratio of medians for ACE2surr [B2:normal], 1.89; 95% confidence interval [CI]: 1.4-2.6). The ED and PI methods of AP quantification were highly correlated (AngI, r = .9, P < .0001; AngII, r = .8, P = .001). CONCLUSIONS AND CLINICAL IMPORTANCE: Circulating alternative RAS activity, specifically the surrogate measure of ACE2 activity, was increased in dogs with stage B2 MMVD as compared to normal dogs. Equilibrium dialysis results are analogous to immediate protease inhibition in dogs.

Effect of a specially formulated diet on progression of heart enlargement in dogs with subclinical degenerative mitral valve disease.

BACKGROUND: Previous studies in dogs with degenerative mitral valve disease (DMVD) have identified altered myocardial energy metabolism and oxidation, which might contribute to cardiac hypertrophy. Diets rich in medium chain fatty acids and antioxidants are a potential means of treatment. A previous clinical study found significantly smaller left atrial diameter (LAD) and left atrium-to-aorta diameter ratio (LA : Ao) in dogs with subclinical DMVD fed a specially formulated diet vs control diet for 6 months. HYPOTHESIS/OBJECTIVES: A specially formulated diet will slow or arrest left heart enlargement in dogs with subclinical DMVD over 365 days. ANIMALS: One hundred twenty-seven dogs with unmedicated subclinical DMVD; 101 dogs in the per protocol cohort. METHODS: Randomized double-blinded controlled multicenter clinical trial. RESULTS: The study's primary composite outcome measure was the sum of percentage change in LAD and left ventricular internal dimension at end-diastole (LVIDd) at day 365. In the per protocol cohort, the outcome measure increased by 8.0% (95% confidence interval [CI], 2.9%-13.1%) in dogs receiving the test diet vs 8.8% (95% CI, 5.1%-12.5%) in dogs receiving control diet (P = .79). Neither component of the primary outcome measure was significantly different between groups (LAD, P = .65; LVIDd, P = .92). No difference was found in mitral valve E wave velocity (P = .36) or the proportion of dogs withdrawn from the study because of worsening DMVD and heart enlargement (P = .41). CONCLUSIONS AND CLINICAL IMPORTANCE: Feeding a specially formulated diet for 365 days was not associated with a significantly different rate of change of left heart size in dogs with subclinical DMVD as compared to control.

Bilateral lysis of aortic saddle thrombus with early tissue plasminogen activator (BLASTT): a prospective, randomized, placebo-controlled study in feline acute aortic thromboembolism.

OBJECTIVES: The aim of this study was to investigate the impact of tissue plasminogen activator (TPA) on the treatment of feline aortic thromboembolism (FATE). METHODS: Cats diagnosed with FATE involving ⩾2 limbs were enrolled in a prospective, multicenter, double-blinded, randomized, placebo-controlled study within 6 h of an event. Diagnosis was made by clinical findings and one confirmatory criterion. Cats received placebo or TPA (1 mg/kg/h with the first 10% by bolus). All cats received pain control and thromboprophylaxis. The primary outcome was a change from baseline in a published limb score at 48 h. Secondary outcomes included 48 h survival, survival to discharge and complication proportions. Statistical analyses included pattern-mixture models, logistic regression and Fisher's exact, Student's t- and Mann-Whitney-Wilcoxon tests. RESULTS: Based on a power analysis, 40 cats were enrolled; however, only 20 survived to 48 h (TPA, n = 12; placebo, n = 8 [P = 0.34]). There was a statistically significant improvement in limb scores compared with baseline for both groups (P <0.001). Limb score at 48 h was 1 point lower (better) in the TPA group (P = 0.19). Thrombolysis had no statistically significant effect on 48 h survival (P = 0.22). Lower affected limb lactate was associated with better 48 h survival (odds ratio 1.53, 95% confidence interval 1.08-2.17; P = 0.02). The survival to discharge rates were 45% (TPA) and 30% (placebo; P = 0.51). Complications in the TPA and placebo groups included acute kidney injury (22% and 19%, respectively; P = 1.00) and/or reperfusion injuries (33% and 19%, respectively; P = 0.45). CONCLUSIONS AND RELEVANCE: Survival and complication rates of acute FATE were not different with or without thrombolysis. High in-hospital mortality decreased the statistical power to detect a statistically significant difference between treatments with regard to our primary outcome.

Transatrial stenting for long-term management of cardiac tumor obstruction of the right atrium in 3 dogs.

BACKGROUND: Venous obstruction in dogs caused by large intracardiac masses can result in severe morbidity with few safe treatments. HYPOTHESIS/OBJECTIVES: Retrospective study to report results after transatrial stent placement in dogs with naturally occurring cardiac masses causing venous obstruction. ANIMALS: Three client-owned dogs diagnosed with large cardiac masses. METHODS: Retrospective study of patients that received transatrial stents extending from the caudal vena cava, across the right atrium, and into the cranial vena cava (CrVC). Procedures, complications, and outcomes were recorded based upon medical records, referring veterinarians, and client communications. RESULTS: Two dogs had similar clinical signs suggestive of congestive hepatopathy including marked ascites and lethargy. One dog had clinical signs of CrVC syndrome including head and neck swelling with pitting edema and pleural effusion. After stent placement, venous pressure gradients were decreased and repeat angiography confirmed that vascular patency was reestablished. Resolution of clinical signs was marked in all 3 dogs with only mild complications including tachyarrhythmias and hypertension in 1 dog during the perioperative period. Two dogs that required additional transatrial stent placement for reobstruction 6 and 14 months later improved after the second stent implantation. Survival times poststenting for the dogs were 3, 21, and 37 months, with cause of death related to the cardiac tumor in all dogs. CONCLUSIONS AND CLINICAL IMPORTANCE: Endovascular transatrial stenting may provide a long-term palliative treatment option for dogs with clinical signs attributable to tumor-induced venous obstruction when more traditional treatments are declined or not indicated.

Surgical repair for canine tricuspid valve dysplasia: Technique and case report.

Tricuspid valve dysplasia (TVD) is a congenital malformation of the right atrioventricular valve characterized by restricted leaflet motion, annular dilation, and tricuspid regurgitation (TR). Severe cases typically exhibit progressive right-sided congestive heart failure, affecting the quality of life and survival. This article describes a technique for surgical repair of TVD and a case report with long-term follow-up. A 1.5-year-old intact male Labrador retriever with severe TR underwent surgical repair for TVD. Valve repair was performed under cardiopulmonary bypass and consisted of neochord mobilization of the valve leaflets and partial band annuloplasty. Transthoracic echocardiogram performed 5 days after surgery showed mild TR, a 93% decrease in anatomic regurgitant orifice area, and decreased right chamber dimensions. Forty-eight months after repair, the patient was free of clinical signs, did not have a heart murmur, and was receiving no cardiac medications. Based on this case, surgical repair of TVD is feasible with long-term durability, and the outcome suggests that the described technique may be a viable treatment option for patients with severe TVD.

Self-reported radiation safety behaviors among veterinary specialists and residents performing fluoroscopic procedures on small animals.

OBJECTIVE: To describe the radiation safety behaviors of veterinary specialists performing small animal fluoroscopic procedures and examine potential risk factors for these behaviors, including knowledge of radiation risk and training regarding machine operating parameters. SAMPLE: 197 veterinary specialists and residents in training. PROCEDURES: An electronic questionnaire was distributed to members of the American Colleges of Veterinary Internal Medicine (subspecialties of cardiology and small animal internal medicine), Veterinary Radiology, and Veterinary Surgery. RESULTS: The overall survey response rate was 6% (240/4,274 email recipients). Of the 240 respondents, 197 (82%) had operated an x-ray unit for a small animal fluoroscopic procedure in the preceding year and fully completed the questionnaire. More than 95% of respondents believed that radiation causes cancer, yet approximately 60% of respondents never wore hand or eye protection during fluoroscopic procedures, and 28% never adjusted the fluoroscopy machine operating parameters for the purpose of reducing their radiation dose. The most common reasons for not wearing eye shielding included no requirement to wear eyeglasses, poor fit, discomfort, and interference of eyeglasses with task performance. Respondents who had received training regarding machine operating parameters adjusted those parameters to reduce their radiation dose during procedures significantly more frequently than did respondents who had not received training. CONCLUSIONS AND CLINICAL RELEVANCE: On the basis of the self-reported suboptimal radiation safety practices among veterinary fluoroscopy users, we recommend formal incorporation of radiation safety education into residency training programs. All fluoroscopy machine operators should be trained regarding the machine operating parameters that can be adjusted to reduce occupational radiation exposure.

Use of a unique method for removal of a foreign body from the trachea of a cat.

CASE DESCRIPTION: A 2.96-kg (6.5-lb) 9-month-old spayed female domestic longhair cat was admitted for removal of a tracheal foreign body. CLINICAL FINDINGS: The cat had moderate respiratory distress but otherwise appeared to be healthy. Thoracic radiography revealed a foreign body in the trachea. TREATMENT AND OUTCOME: The cat was anesthetized and endoscopy of the trachea was performed in an attempt to retrieve the foreign body. Endoscopic removal was unsuccessful because of the shape and smooth texture of the foreign body. Surgical removal of the foreign body was not considered ideal because of its location and the risks associated with tracheotomy. Fluoroscopic-guided placement of an over-the-wire balloon catheter caudal to the foreign body was followed by inflation of the balloon and gradual traction in an orad direction, which resulted in successful removal of the foreign body (identified as a piece of landscaping gravel). The cat required supplemental oxygen and supportive care following removal of the foreign body. CLINICAL RELEVANCE: A fluoroscopic technique was used as a minimally invasive alternative to endoscopy or open-chest surgery for removal of a foreign body from the trachea of a cat. Use of this technique allowed uninterrupted ventilation of the cat throughout the procedure.

ACVIM consensus statement guidelines for the diagnosis, classification, treatment, and monitoring of pulmonary hypertension in dogs.

Pulmonary hypertension (PH), defined by increased pressure within the pulmonary vasculature, is a hemodynamic and pathophysiologic state present in a wide variety of cardiovascular, respiratory, and systemic diseases. The purpose of this consensus statement is to provide a multidisciplinary approach to guidelines for the diagnosis, classification, treatment, and monitoring of PH in dogs. Comprehensive evaluation including consideration of signalment, clinical signs, echocardiographic parameters, and results of other diagnostic tests supports the diagnosis of PH and allows identification of associated underlying conditions. Dogs with PH can be classified into the following 6 groups: group 1, pulmonary arterial hypertension; group 2, left heart disease; group 3, respiratory disease/hypoxia; group 4, pulmonary emboli/pulmonary thrombi/pulmonary thromboemboli; group 5, parasitic disease (Dirofilaria and Angiostrongylus); and group 6, disorders that are multifactorial or with unclear mechanisms. The approach to treatment of PH focuses on strategies to decrease the risk of progression, complications, or both, recommendations to target underlying diseases or factors contributing to PH, and PH-specific treatments. Dogs with PH should be monitored for improvement, static condition, or progression, and any identified underlying disorder should be addressed and monitored simultaneously.