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Pulmonary arteries (PAs) distend to accommodate increases in cardiac output. PA distensibility protects the right ventricle (RV) from excessive increases in pressure. Loss of PA distensibility plays a critical role in the fatal progression of pulmonary arterial hypertension (PAH) toward RV failure. However, it is unclear how PA distensibility is distributed across the generations of PA branches, mainly because of the lack of appropriate in vivo methods to measure distensibility of vessels other than the large, conduit PAs. In this study, we propose a novel approach to assess the distensibility of individual PA branches. The metric of PA distensibility we used is the slope of the stretch ratio-pressure relationship. To measure distensibility, we combined invasive measurements of mean PA pressure with angiographic imaging of the PA network of six healthy female dogs. Stacks of 2D images of the PAs, obtained from either contrast enhanced magnetic resonance angiography (CE-MRA) or computed tomography digital subtraction angiography (CT-DSA), were used to reconstruct 3D surface models of the PA network, from the first bifurcation down to the sixth generation of branches. For each branch of the PA, we calculated radial and longitudinal stretch between baseline and a pressurized state obtained via acute embolization of the pulmonary vasculature. Our results indicated that large and intermediate PA branches have a radial distensibility consistently close to 2%/mmHg. Our axial distensibility data, albeit affected by larger variability, suggested that the PAs distal to the first generation may not significantly elongate in vivo, presumably due to spatial constraints. Results from both angiographic techniques were comparable to data from established phase-contrast (PC) magnetic resonance imaging (MRI) and ex vivo mechanical tests, which can only be used in the first branch generation. Our novel method can be used to characterize PA distensibility in PAH patients undergoing clinical right heart catheterization (RHC) in combination with MRI.

Introduction/objective: Transcatheter therapeutics have revolutionized treatment of patent ductus arteriosus (PDA). Greater understanding of corrective interventions across species can advance best practices, protocols, and outcomes while minimizing adverse events. The objective of this study was to describe characteristics and outcomes in children and dogs undergoing transcatheter PDA occlusion., Animals, Materials and Methods: This was a multicenter, retrospective cohort study from two pediatric and three veterinary centers. Demographics, procedural characteristics, and outcomes were assessed., Results: Data included 202 children and 106 dogs treated from July 2019 to June 2021. Forty-five (23%) children and 19 (18%) dogs had congestive heart failure prior to catheterization. Transvenous and transarterial approaches for deployment were most used in children and dogs, respectively. All children had percutaneous vascular access compared to 17 (16%) dogs. Intraprocedural anticoagulation was standard for children (100% of 165 reported), but not for dogs (2/103). The median (interquartile range) pulmonary ostium diameter in children was 2.2 mm (1.5-3.0 mm) and 3.0 mm (2.0-4.2 mm) in dogs when all body sizes were considered (P<0.001). Amplatzer™ Duct Occluder was most commonly used in children (64/202, 32%); the Amplatz® Canine Duct Occluder was used in dogs (96/100, 96%). Closure was manual compression in all children, whereas vessel ligation was most used in dogs (74/104, 73%). Successful device deployment was achieved in 197 (98%) children and 98 (93%) dogs (P=0.03). Major reasons for failure included device embolization in six (2.9%) children and PDA morphology concerns in four (3.8%) dogs., Conclusions: Transcatheter PDA occlusion is successful in children and dogs. Study data might be useful for optimizing transcatheter therapeutics and animal models for interventional cardiology., Competing Interests: Conflict of Interest Statement The authors do not have any conflicts of interest to disclose., (Copyright © 2024 The Author(s). Published by Elsevier B.V. All rights reserved.)

A dog with immune-mediated thrombocytopenia and a new heart murmur had an echocardiogram in 2016 and was found to have a suspected aorto-left atrial fistula. The echocardiogram findings remained relatively static from 2016 to 2022. This report highlights the use of cardiac-gated computed tomography angiography to allow further understanding of a complex anomaly in a patient with a ruptured sinus of Valsalva aneurysm causing a fistulous connection with the left atrium., Competing Interests: Conflict of Interest Statement The authors do not have any conflicts of interest to disclose., (Copyright © 2024 Elsevier B.V. All rights reserved.)

Background: Echocardiographic reference intervals have not been reported for North American whippets, or for whippets that have undergone pet-level athletic training., Objectives: To develop normal echocardiographic reference intervals for North American whippets and investigate differences in echocardiographic parameters based on athletic conditioning in pet whippets engaged in competitive sports., Animals: One-hundred healthy North American whippets., Methods: Dogs were examined at national shows between 2005 and 2009. Echocardiographic reference intervals were constructed and the effect of athletic conditioning on parameters of structure and function was assessed., Results: Two dimensional, M-mode, Doppler and tissue Doppler reference ranges for healthy North American whippets are presented. Measures of left ventricular (LV) chamber diameter were larger in conditioned whippets (N = 25) and remained significantly larger than in unconditioned whippets (N = 16) when normalized for weight using allometric equations. Calculated LV mass was higher in conditioned dogs than in unconditioned dogs, and this difference persisted when LV mass was normalized by weight. Mitral E velocity was higher in conditioned dogs than in unconditioned dogs, whereas E/A and measures related to systolic function were not different., Conclusions and Clinical Importance: Pet whippets in peak athletic condition have larger hearts than do less conditioned whippets, but measures of systolic function are similar. Whippet pet athletes may show eccentric LV hypertrophy at peak condition. Normal values for cardiac size and function in North American whippets might be considered abnormal if population-specific whippet reference intervals are not used in analysis., (© 2023 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals LLC on behalf of American College of Veterinary Internal Medicine.)

Introduction: The objective of this retrospective study was to describe the indications, complications, and long-term outcomes in a group of cats that received an epicardial pacing (EP) system., Animals: Twenty client-owned cats., Materials and Methods: Medical records were reviewed for signalment, presenting complaint, primary electrocardiogram (ECG) diagnosis, presence of structural heart disease, presence of congestive heart failure (CHF), presence of major or minor complications, and survival time., Results: The majority of cats were presented for syncope (n = 11), and the most common ECG diagnosis was advanced second-degree atrioventricular block (n = 9). Fifteen cats (15/20, 75%) had one or more major or minor complications. One cat died in the perioperative period as a result of a major complication. None of the variables evaluated were associated with a statistically significant increase in the occurrence of major or minor complications. The most common major complication was loss of ventricular capture (seven instances in six cats), which was successfully treated in all cases by increasing pacemaker output or replacing both the lead and the pulse generator. The most common minor complications were arrhythmias (n = 7) and sensing issues (n = 8). The overall median survival time (MST) was 948 days. No statistical difference in survival time was identified between cats that experienced a major complication and those that did not., Conclusions: Although complications were common in this feline population after EP, major and minor complications were successfully treated., Competing Interests: Conflict of Interest Statement The authors do not have any conflicts of interest to disclose., (Copyright © 2021 Elsevier B.V. All rights reserved.)

The updated VCOG-CTCAE v2 guidelines contain several important updates and additions since the last update (v1.1) was released in 2011 and published within Veterinary and Comparative Oncology in 2016. As the Veterinary Cooperative Oncology Group (VCOG) is no longer an active entity, the original authors and contributors to the VCOG-CTCAE v1.0 and v1.1 were consulted for input, and additional co-authors sought for expansion and refinement of the adverse event (AE) categories. VCOG-CTCAE v2 includes expanded neurology, cardiac and immunologic AE sections, and the addition of procedural-specific AEs. It is our intent that, through inclusion of additional authors from ACVIM subspecialties and the American College of Veterinary Surgery, that we can more comprehensively capture AEs that are observed during clinical studies conducted across a variety of disease states, clinical scenarios, and body systems. It is also our intent that these updated veterinary CTCAE guidelines will offer improved application and ease of use within veterinary practice in general, as well as within clinical trials that assess new therapeutic strategies for animals with a variety of diseases. Throughout the revision process, we strived to ensure the grading structure for each AE category was reflective of the decision-making process applied to determination of dose-limiting events. As phase I trial decisions are based on these criteria and ultimately determine the maximally tolerated dose, there is impact on standard dosing recommendations for any new drug registration or application. This document should be updated regularly to reflect ongoing application to clinical studies carried out in veterinary patients., (© 2021 The Authors. Veterinary and Comparative Oncology published by John Wiley & Sons Ltd. This article has been contributed to by US Government employees and their work is in the public domain in the USA.)

A 2-month-old male Holstein calf was presented for evaluation of a continuous systolic murmur. A grade V/VI left basilar continuous murmur and a grade IV/VI right basilar continuous murmur was auscultated upon evaluation with increased respiratory effort, wheezes, and crackles. Multimodality diagnostics were performed on this patient for further workup and included transthoracic and transesophageal echocardiography, fluoroscopy guided angiography, and gross necropsy with histopathology. An aortopulmonary window with continuous left-to-right shunting was identified at the level of the left aortic sinus of Valsalva with a severely dilated left coronary artery and left-sided congestive heart failure. This case report outlines the diagnostic workup of a rare congenital heart defect and secondary cardiac abnormalities not previously identified in veterinary literature., Competing Interests: Conflict of interest statement The authors do not have any conflicts of interest to disclose., (Copyright © 2021 Elsevier B.V. All rights reserved.)

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., (© 2020 The Authors. Journal of Veterinary Internal Medicine published by Wiley Periodicals, Inc. on behalf of the American College of Veterinary Internal Medicine.)

Objectives: The objective of this study was to report the signalment, presentation, clinical and imaging findings, interventions, and outcomes in a group of dogs with cor triatriatum dexter (CTD)., Animals: Seventeen client-owned dogs., Methods: Medical records were reviewed retrospectively for signalment, history, physical examination findings, imaging and diagnostic findings, presence of concurrent congenital cardiac defects, description of interventional procedures, therapy information, and outcomes., Results: Age at presentation ranged from two to 110 months, with 10 of 17 dogs (59%) aged <12 months. There was an equal distribution between the sexes. Peritoneal effusion was the most common presenting complaint, in 10 of 17 dogs (59%). The CTD was an isolated finding in 3 of 17 dogs (18%); the remaining 14 of 17 (82%) dogs had concurrent cardiac disease, with congenital anomalies present in 12 of 17 (70%). All except one of these 12 dogs had at least one additional condition affecting the right heart. Tricuspid valve dysplasia was the most common congenital comorbidity, present in 9 of 17 dogs (53%). Seven dogs (41%) underwent interventional treatment of their CTD. In 7 of 17 (41%) cases, the CTD was considered to be incidental and the dogs were asymptomatic; therefore, no interventions were performed. The remaining three cases were euthanized or lost to follow-up., Conclusions: Cor triatriatum dexter in dogs is commonly seen in association with other right-sided congenital cardiac anomalies and may be an incidental finding. Dogs with CTD obstructing right atrial inflow can have a good outcome after intervention. Dogs with no clinical signs associated with the CTD may remain asymptomatic into adulthood., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Four dogs, referred for management of heartworm (HW) disease, were found to have HWs entangled in their tricuspid valve apparatus. None of the dogs were actively hemolyzing or showed signs of acute cardiovascular collapse that would have necessitated emergency transvenous HW extraction, and surgery was not performed at time of presentation. The dogs received pimobendan and sildenafil within 24 h of identifying HW in the tricuspid valve apparatus, and the HW moved to the pulmonary arteries within 2 days in most cases (median 2 days, range 1-14 days). All dogs survived to discharge from the original hospital admission and were subsequently treated with adulticide (melarsomine) without complication. All dogs were HW antigen negative 6 months after their last melarsomine injection. Four dogs appeared to respond positively to medical management aimed at decreasing pulmonary arterial pressure and improving the right ventricular function, but movement of HW out of the heart for other reasons cannot be excluded. This therapeutic option is not advised when dogs with HW disease are presented for acute collapse, ongoing hemolysis, and hypotension as surgical extraction is still considered the best option in these cases. It remains unknown if medical management is a safe option for all dogs with intracardiac HW without clinical signs of caval syndrome. Controlled prospective studies are required to determine the efficacy and safety of this treatment regimen in comparison with surgical extraction., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Abscess formation in the pericardial space has been described as a rare complication of trauma, congenital defects, penetrating foreign body, or extension of local myocardial infection in the dog. Presented here is a case of a juvenile dog with septic pericardial effusion secondary to an isolated intrapericardial abscess. Surgical pericardiectomy was successful in removing the abscess and nidus for septic effusion in this patient, and histopathology of the abscess tissue was suggestive of foreign plant material migration as the nidus for abscess formation. Recheck echocardiogram at the six-month postoperative period showed no recurrence of pericardial effusion or abscessation. Although abscess formation and septic pericarditis secondary to foreign body migration is an uncommon cause for large volume pericardial effusion, this should be considered as a differential particularly in a young and previously healthy dog., (Copyright © 2019 Elsevier B.V. All rights reserved.)

Chronic thromboembolic pulmonary hypertension (CTEPH) is a debilitating disease that progresses to right ventricular (RV) failure and death if left untreated. Little is known regarding the progression of RV failure in this disease, greatly limiting effective prognoses, and therapeutic interventions. Large animal models enable the use of clinical techniques and technologies to assess progression and diagnose failure, but the existing large animal models of CTEPH have not been shown to replicate the functional consequences of the RV, i.e., RV failure. Here, we created a canine embolization model of CTEPH utilizing only microsphere injections, and we used a combination of right heart catheterization (RHC), echocardiography (echo), and magnetic resonance imaging (MRI) to quantify RV function. Over the course of several months, CTEPH led to a 6-fold increase in pulmonary vascular resistance (PVR) in four adult, male beagles. As evidenced by decreased cardiac index (0.12 ± 0.01 v. 0.07 ± 0.01 [L/(min * kg)]; p < 0.05), ejection fraction (0.48 ± 0.02 v. 0.31 ± 0.02; p < 0.05), and ventricular-vascular coupling ratio (0.95 ± 0.09 v. 0.45 ± 0.05; p < 0.05), as well as decreased tricuspid annular plane systolic excursion (TAPSE) (1.37 ± 0.06 v. 0.86 ± 0.05 [cm]; p < 0.05) and increased end-diastolic volume index (2.73 ± 0.06 v. 2.98 ± 0.02 [mL/kg]; p < 0.05), the model caused RV failure. The ability of this large animal CTEPH model to replicate the hemodynamic consequences of the human disease suggests that it could be utilized for future studies to gain insight into the pathophysiology of CTEPH development, following further optimization.

Introduction: To determine whether oral l-arginine increases plasma [l-citrulline] in dogs., Animals: Eleven healthy staff-owned dogs were used in this study., Materials and Methods: Dogs (n = 3) were given l-arginine (50mg/kg PO q8h) for 7 days, and plasma [l-arginine] and [l-citrulline] were analyzed by high performance liquid chromatography at baseline (BL), steady state trough, and 0.5, 1, 1.5, 2, 4, 6, and 8 h after final dosing on day 7. Eleven dogs were then treated with 100mg/kg l-arginine PO q8h for 7 days, and [l-arginine] and [l-citrulline] were measured at BL, steady state trough, and at peak 4 hrs after dosing (T4 hrs)., Results: - Plasma [l-arginine] and [l-citrulline] peaked at T4 hrs on the 50mg/kg dosage. Target outcome, modeled after human study results, of a doubling of [l-arginine] and a 25-30% increase in [l-citrulline] from BL were not reached. After the 100mg/kg dosage, plasma [l-arginine] increased from a BL median of 160.1 μM (range, 100.2-231.4 μM) to a peak of 417.4 μM (206.5-807.3 μM) at T4 hrs, and plasma [l-citrulline] increased from a BL median of 87.8 μM (59.1-117.1 μM) to peak of 102.2 μM (47.4-192.6 μM) at T4 hrs. Ten of eleven dogs showed a doubling of plasma [l-arginine] and 4/11 dogs achieved 25-30% or greater increases in plasma [l-citrulline]. No adverse effects on heart rate or blood pressure were noted., Conclusions: - Oral l-arginine dosage of 100mg/kg q8h doubles plasma [l-arginine] in healthy dogs, but conversion to l-citrulline is quite variable. Further evaluation of this dosage regimen in dogs with pulmonary hypertension is warranted., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objectives: To assess the prevalence of functional ejection murmurs and murmurs of mitral regurgitation (MR) due to myxomatous mitral valve disease in healthy whippets; to assess the diagnostic value of auscultation to detect MR; and investigate the relationship between age and presence of echocardiographically documented MR (MR echo )., Animals: A total of 200 healthy client-owned Whippets, recruited at national shows between 2005 and 2009 were involved in this study., Methods: Cross-sectional study. Dogs were examined by auscultation by one examiner and Doppler echocardiography by another, and results were compared. Prevalence of types of murmurs and MR echo were calculated and correlated to age. Accuracy of auscultation to predict MR echo was calculated., Results: Left-sided systolic heart murmurs were detected in 185/200 (93%) of dogs. Left apical systolic murmurs (L apex ) were detected in 57/200 (29%) and left basilar systolic murmurs (L base ) in 128/200 of the dogs (64%). MR echo was present in 76/200 (38%) dogs. Prevalence MR echo was correlated with age (r = 0.96, p=0.0028). Mitral regurgitation detected by echocardiography was present in 12/78 (15%) of the dogs ≤ 2 years of age and in 59% of the dogs at 7-8 years old. Detection of L apex predicted MR echo with sensitivity 65%, specificity 94%, positive predictive value 86%, and negative predictive value 81%; and accuracy improved when only dogs with more intense L apex (grade ≥ 3/6) were considered., Conclusions: Systolic murmurs are common in North American Whippets and this breed exhibits a high prevalence of MR echo , which may be documented at a relatively early age. Whippets with non-clinical MR echo may not be identifiable by auscultation alone; echocardiographic examination may be required to exclude a diagnosis of MR. Louder heart murmurs allow more accurate localization in this population., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Objectives: To evaluate survival time in dogs with persistent atrial standstill after pacemaker implantation and to compare the survival times for cardiac-related vs. non-cardiac deaths. Secondary objectives were to evaluate the effects of breed and the presence of congestive heart failure (CHF) at the time of diagnosis on survival time., Animals: Twenty dogs with persistent atrial standstill and pacemaker implantation., Methods: Medical records were searched to identify dogs diagnosed with persistent atrial standstill based on electrocardiogram that underwent pacemaker implantation. Survival after pacemaker implantation was analyzed using the Kaplan-Meier method., Results: The median survival time after pacemaker implantation for all-cause mortality was 866 days. There was no significant difference (p=0.573) in median survival time for cardiac (506 days) vs. non-cardiac deaths (400 days). The presence of CHF at the time of diagnosis did not affect the survival time (P=0.854). No difference in median survival time was noted between breeds (P=0.126)., Conclusions: Dogs with persistent atrial standstill have a median survival time of 866 days with pacemaker implantation, though a wide range of survival times was observed. There was no difference in the median survival time for dogs with cardiac-related deaths and those without. Patient breed and the presence of CHF before pacemaker implantation did not affect median survival time., (Copyright © 2017 Elsevier B.V. All rights reserved.)

Pulmonary hypertension (PH) is a debilitating vascular disease that leads to pulmonary artery (PA) stiffening, which is a predictor of patient mortality. During PH development, PA stiffening adversely affects right ventricular function. PA stiffening has been investigated through the arterial nonlinear elastic response during mechanical testing using a canine PH model. However, only circumferential properties were reported and in the absence of chronic PH-induced PA remodeling. Remodeling can alter arterial nonlinear elastic properties via chronic changes in extracellular matrix (ECM) content and geometry. Here, we used an established constitutive model to demonstrate and differentiate between strain-stiffening, which is due to nonlinear elasticity, and remodeling-induced stiffening, which is due to ECM and geometric changes, in a canine model of chronic thromboembolic PH (CTEPH). To do this, circumferential and axial tissue strips of large extralobar PAs from control and CTEPH tissues were tested in uniaxial tension, and data were fit to a phenomenological constitutive model. Strain-induced stiffening was evident from mechanical testing as nonlinear elasticity in both directions and computationally by a high correlation coefficient between the mechanical data and model (R 2 =0.89). Remodeling-induced stiffening was evident from a significant increase in the constitutive model stress parameter, which correlated with increased PA collagen content and decreased PA elastin content as measured histologically. The ability to differentiate between strain- and remodeling-induced stiffening in vivo may lead to tailored clinical treatments for PA stiffening in PH patients., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

A 3-month-old, 9.9 kg, male pit bull cross was referred for evaluation of collapse. A left basilar systolic heart murmur graded V/VI and a grade IV/VI right basilar systolic heart murmur were ausculted. Echocardiography showed severe pulmonic stenosis characterized by annular hypoplasia, leaflet thickening, and leaflet fusion. After 1 month of atenolol therapy, a pulmonic valve balloon valvuloplasty procedure was performed, and the intra-operative right ventricular pressure was reduced by 43%. Echocardiography, performed the following day, showed apparent rupture of a pulmonary valve leaflet and a membranous structure within the pulmonary artery consistent with a dissecting membrane. Short-term follow-up has shown no apparent progression of the pulmonary artery dissection and the patient remains free of clinical signs., (Copyright © 2016 Elsevier B.V. All rights reserved.)

A 10-year old Lhasa Apso dog was presented for an acute history of exercise intolerance and hind limb weakness. High grade second degree atrioventricular block with an atrial rate of 200 beats per minute, ventricular rate of 40 beats per minute and an intermittent ventricular escape rhythm, was diagnosed on electrocardiograph. A transdiaphragmatic, unipolar, epicardial pacemaker was implanted without immediate surgical complications. Severe vomiting was noted 12 h post-operatively. Abdominal ultrasound and a barium study supported a diagnosis of pyloric outflow obstruction and exploratory abdominal surgery was performed. The pyloric outflow tract appeared normal and no other causes of an outflow obstruction were identified. The epicardial generator was repositioned from the right to the left abdominal wall. Pyloric cell pacing was presumed to be the cause for the pyloric obstruction and severe vomiting, and this was thought to be due to close proximity of the pacemaker generator to the pylorus situated in the right abdominal wall. Repositioning of the pulse generator to the left abdominal wall resulted in resolution of vomiting., (Copyright © 2016 Elsevier B.V. All rights reserved.)

Objectives: To evaluate the echocardiographic variables and sedation after two dosages of dexmedetomidine combined with butorphanol in healthy dogs., Animals: Fourteen healthy dogs., Methods: The dogs received dexmedetomidine 5 mcg/kg IM and butorphanol 0.4 mg/kg (low dose (LD), n = 6) or dexmedetomidine 10 mcg/kg IM and butorphanol 0.4 mg/kg (recommended dose (RD), n = 8). Sedation scoring, noninvasive blood pressure measurement, and echocardiography were performed before sedation at baseline, at 20 minutes (T20), and 60 minutes (T60) after drug administration., Results: The median sedation scores were increased at both T20 and T60 in the RD group, and at T60 in the LD group, compared with baseline (p < 0.0001, p = 0.012). At T60, the RD dogs were more sedated than the LD dogs (p = 0.0093). The median cardiac output (CO) decreased at both T20 (63%) and T60 (65%) in the RD group and at T60 (42%) in the LD group, compared with baseline (p = 0.0011, p = 0.0055). The median heart rate (HR) was decreased at both T20 and T60 in the RD group and at T60 in the LD group, compared with baseline (p = 0.0009, p = 0.0001). In both RD and LD dogs, valvular regurgitation developed and was identified by color Doppler imaging., Conclusions: There were significant hemodynamic changes, mainly related to HR and indices of systolic function, following administration of dexmedetomidine in these healthy dogs. The changes also included decreases in systolic function and CO, as well as appearance of 'new' valvular regurgitation. Caution should be used when considering dexmedetomidine for sedation in dogs with, or being screened for, cardiovascular disease., (Copyright © 2015 Elsevier B.V. All rights reserved.)

A 6-month old Labrador retriever was presented with an acute history of collapse during exercise. A grade III/VI left basilar systolic murmur and thoracic radiographs showing severe right heart enlargement with an enlarged main pulmonary artery were most consistent with a clinical diagnosis of pulmonic stenosis. Echocardiography revealed an intracardiac mass partially obstructing the right ventricular outflow tract. The mass was surgically excised, and histopathology diagnosed a benign vascular hamartoma of the right ventricle. Short-term follow-up showed resolution of clinical signs with no evidence of local recurrence. Intracardiac masses should be considered a differential diagnosis for patients with acute-onset syncope., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Objective: To describe clinical canine patients with naturally occurring pulmonary hypertension and radiographic pulmonary alveolar infiltrates before and after treatment with sildenafil., Animals: Ten client-owned dogs., Methods: A retrospective analysis of dogs with echocardiographically-determined pulmonary hypertension and pulmonary alveolar infiltrates on thoracic radiographs was performed before (PRE) and after (POST) sildenafil therapy. Clinical scores, pulmonary alveolar infiltrate scores and tricuspid regurgitation gradients were analyzed PRE and POST sildenafil., Results: Pulmonary alveolar infiltrates associated with pulmonary hypertension developed in a diffusely patchy distribution (10/10). Sixty percent of dogs had a suspected diagnosis of interstitial pulmonary fibrosis as the etiology of pulmonary hypertension. Median PRE clinical score was 4 (range: 3-4) compared to POST score of 0 (0-2) (p = 0.005). Median alveolar infiltrate score PRE was 10 (5-12) compared to POST score of 4 (0-6) (p = 0.006). Median tricuspid regurgitation gradient PRE was 83 mmHg (57-196) compared to 55 mmHg POST (33-151) (p = 0.002)., Conclusions: A subset of dogs with moderate to severe pulmonary hypertension present with diffuse, patchy alveolar infiltrates consistent with non-cardiogenic pulmonary edema. The typical clinical presentation is acute dyspnea and syncope, often in conjunction with heart murmurs suggestive of valvular insufficiency. This constellation of signs may lead to an initial misdiagnosis of congestive heart failure or pneumonia; however, these dogs clinically and radiographically improve with the initiation of sildenafil., (Copyright © 2015 Elsevier B.V. All rights reserved.)

Objectives: To compare noninvasive estimates of pulmonary artery pressure (PAP) obtained via echocardiography (ECHO) to invasive measurements of PAP obtained during right heart catheterization (RHC) across a range of PAP. To examine the accuracy of estimating right atrial pressure via ECHO (RAPECHO) compared to RAP measured by RHC (RAPRHC), and determine if adding RAPECHO improves the accuracy of noninvasive PAP estimations., Animals: 14 healthy female beagle dogs., Methods: Comparison of ECHO and RHC measures of PAP, both at normal PAP and increased PAP generated by microbead embolization., Results: Noninvasive estimates of PAP were moderately but significantly correlated (r of 0.68-0.78; p < 0.0006) with invasive measurements of PAP. Wide variance was noted for all estimations, with increased variance at higher PAP. The addition of RAPECHO improved correlation and bias in all cases. RAPRHC was significantly correlated with RAPECHO (r = 0.38; p = 0.04) as estimated by the ellipse area method. Median RAPRHC was significantly different between 3 subjective assessments of right atrial size (p = 0.037)., Conclusions: Spectral Doppler assessments of tricuspid and pulmonic regurgitation are imperfect methods for predicting PAP as measured by catheterization despite an overall moderate correlation between invasive and noninvasive values. Noninvasive measurements may be better utilized as part of a comprehensive assessment of PAP in canine patients. RAPRHC appears best estimated based on subjective assessment of RA size. Including estimated RAPECHO in estimates of PAP improves the correlation and relatedness between noninvasive and invasive measures of PAP, but notable variability in accuracy of estimations persists., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Background: Cardiac biomarkers provide objective data that augments clinical assessment of heart disease (HD)., Hypothesis/objectives: Determine the utility of plasma N-terminal pro-brain natriuretic peptide concentration [NT-proBNP] measured by a 2nd generation canine ELISA assay to discriminate cardiac from noncardiac respiratory distress and evaluate HD severity., Animals: Client-owned dogs (n = 291)., Methods: Multicenter, cross-sectional, prospective investigation. Medical history, physical examination, echocardiography, and thoracic radiography classified 113 asymptomatic dogs (group 1, n = 39 without HD; group 2, n = 74 with HD), and 178 with respiratory distress (group 3, n = 104 respiratory disease, either with or without concurrent HD; group 4, n = 74 with congestive heart failure [CHF]). HD severity was graded using International Small Animal Cardiac Health Council (ISACHC) and ACVIM Consensus (ACVIM-HD) schemes without knowledge of [NT-proBNP] results. Receiver-operating characteristic curve analysis assessed the capacity of [NT-proBNP] to discriminate between dogs with cardiac and noncardiac respiratory distress. Multivariate general linear models containing key clinical variables tested associations between [NT-proBNP] and HD severity., Results: Plasma [NT-proBNP] (median; IQR) was higher in CHF dogs (5,110; 2,769-8,466 pmol/L) compared to those with noncardiac respiratory distress (1,287; 672-2,704 pmol/L; P < .0001). A cut-off >2,447 pmol/L discriminated CHF from noncardiac respiratory distress (81.1% sensitivity; 73.1% specificity; area under curve, 0.84). A multivariate model comprising left atrial to aortic ratio, heart rate, left ventricular diameter, end-systole, and ACVIM-HD scheme most accurately associated average plasma [NT-proBNP] with HD severity., Conclusions and Clinical Importance: Plasma [NT-proBNP] was useful for discriminating CHF from noncardiac respiratory distress. Average plasma [NT-BNP] increased significantly as a function of HD severity using the ACVIM-HD classification scheme., (Copyright © 2014 by the American College of Veterinary Internal Medicine.)

Objective: To prospectively evaluate the diagnostic accuracy of a point-of-care (POC) N-terminal pro-B-type natriuretic peptide (NT-proBNP) ELISA to assess the likelihood of moderate to severe occult heart disease (OcHD) in a clinical population of cats suspected to have heart disease., Animals: One hundred and forty-six asymptomatic client-owned cats with a heart murmur, gallop rhythm, arrhythmia, or cardiomegaly., Methods: Physical examination, blood pressure measurement and echocardiography were performed prospectively. Point-of-care ELISA was visually assessed as either positive or negative by a reader blinded to the echocardiographic results., Results: Forty-three healthy cats, 50 mild OcHD, 31 moderate OcHD, 6 severe OcHD, and 16 cats equivocal for OcHD were examined. Cats with OcHD included 65 with hypertrophic cardiomyopathy, 6 with restrictive or unclassified cardiomyopathy, 1 with arrhythmogenic right ventricular cardiomyopathy, and 15 with non-cardiomyopathic forms of heart disease. Point-of-care ELISA differentiated cats with moderate or severe OcHD with sensitivity/specificity of 83.8%/82.6% and overall accuracy of 82.9%. Positive POC ELISA increased likelihood of moderate or severe OcHD by a factor of 4.8 vs. those that tested negative. Point-of-care ELISA differentiated cats with moderate or severe cardiomyopathic OcHD with sensitivity/specificity of 88.6%/81.3% and overall accuracy of 83.2%., Conclusion: In a select sample of cats referred for cardiac evaluation, positive POC NT-proBNP ELISA increases likelihood of moderate to severe OcHD while negative POC NT-proBNP ELISA result excludes moderate to severe OcHD., (Copyright © 2014 Elsevier B.V. All rights reserved.)

A low relative area change (RAC) of the proximal pulmonary artery (PA) over the cardiac cycle is a good predictor of mortality from right ventricular failure in patients with pulmonary hypertension (PH). The relationship between RAC and local mechanical properties of arteries, which are known to stiffen in acute and chronic PH, is not clear, however. In this study, we estimated elastic moduli of three PAs (MPA, LPA and RPA: main, left and right PAs) at the physiological state using mechanical testing data and correlated these estimated elastic moduli to RAC measured in vivo with both phase-contrast magnetic resonance imaging (PC-MRI) and M-mode echocardiography (on RPA only). We did so using data from a canine model of acute PH due to embolization to assess the sensitivity of RAC to changes in elastic modulus in the absence of chronic PH-induced arterial remodeling. We found that elastic modulus increased with embolization-induced PH, presumably a consequence of increased collagen engagement, which corresponds well to decreased RAC. Furthermore, RAC was inversely related to elastic modulus. Finally, we found MRI and echocardiography yielded comparable estimates of RAC. We conclude that RAC of proximal PAs can be obtained from either MRI or echocardiography and a change in RAC indicates a change in elastic modulus of proximal PAs detectable even in the absence of chronic PH-induced arterial remodeling. The correlation between RAC and elastic modulus of proximal PAs may be useful for prognoses and to monitor the effects of therapeutic interventions in patients with PH., (Copyright © 2014 Elsevier Ltd. All rights reserved.)

A 1-year-old male German shorthaired pointer was referred for evaluation of tachypnea and hemoptysis. A grade VI/VI left basilar continuous murmur was ausculted. Multimodality imaging consisting of thoracic radiographs, transthoracic and transesophageal echocardiography, fluoroscopy-guided selective angiography, computed tomography angiogram (CTA) and magnetic resonance angiogram (MRA), was performed on this patient. The defect included a left-to-right shunting anomalous vessel between the ascending aorta and main pulmonary artery, along with a dissecting aneurysm of the main and right pulmonary artery. An MRA post-processing technique (PC VIPR) was used to allow for high resolution angiographic images and further assessment of the patient's hemodynamics prior to surgical correction. This case report describes the clinical course of a canine patient with a rare form of congenital cardiac disease, and the multiple imaging modalities that were used to aid in diagnosis and treatment., (Copyright © 2014 Elsevier B.V. All rights reserved.)

Pulmonary hypertension (PH) can impact right ventricular (RV) function and alter pulmonary artery (PA) stiffness. The response of the RV to an acute increase in pulmonary pressure is unclear. In addition, the relation between total pulmonary arterial compliance and local PA stiffness has not been investigated. We used a combination of right heart catheterization (RHC) and magnetic resonance imaging (MRI) to assess PA stiffening and RV function in dogs before and after acute embolization. We hypothesized that in moderate, acute PH the RV is able to compensate for increased afterload, maintaining adequate coupling. Also, we hypothesized that in the absence of PA remodeling the relative area change in the proximal PA (RAC, a noninvasive index of local area strain) correlates with the total arterial compliance (stroke volume-to-pulse pressure ratio). Our results indicate that, after embolization, RV function is able to accommodate the demand for increased stroke work without uncoupling, albeit at the expense of a reduction of efficiency. In this acute model, RAC showed excellent correlation with total arterial compliance. We used this correlation to assess PA pulse pressure (PP) from noninvasive MRI measurements of stroke volume and RAC. We demonstrated that in acute pulmonary embolism MRI estimates of PP are remarkably close to measurements from RHC. These results, if confirmed in chronic PH and clinically, suggest that monitoring of PH progression by noninvasive methods may be possible.

Pulmonary hypertension secondary to degenerative mitral valve disease has been recognized clinically for many years in veterinary medicine, and clinical diagnosis of this syndrome in dogs has been enhanced greatly by widespread use of echocardiography and Doppler echocardiography. Medical therapy is now available to treat this clinical complication of mitral valve disease, making timely diagnosis even more important to patient longevity and quality of life., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Objective: To identify risk factors for first-onset congestive heart failure (CHF) in dogs with degenerative mitral valve disease (DMVD)., Animals: Eighty-two dogs with and without CHF secondary to DMVD were retrospectively assigned to a derivation cohort. Sixty-five dogs with asymptomatic DMVD were recruited into a prospective validation cohort., Methods: Variables associated with risk of CHF in dogs were identified in a derivation cohort and used to construct a predictive model, which was then prospectively tested through longitudinal examination of a validation cohort., Results: Logistic regression analysis of the derivation cohort yielded a predictive model that included the left atrial to aortic root dimension ratio (LA:Ao) and plasma concentration of N-terminal pro-B-type natriuretic peptide (NT-proBNP). When this model was prospectively applied to the validation cohort, it correctly predicted first-onset of CHF in 69.2% of cases. Analysis of the validation cohort revealed that plasma NT-proBNP concentration and indexed left ventricular end-diastolic diameter (LVIDd:Ao) were independent risk factors for development of first-onset CHF in dogs with DMVD (NT-proBNP ≥ 1500 pmol/L, odds ratio (OR), 5.76, 95% confidence interval (CI), 1.37-24.28, P = 0.017; LVIDd:Ao ≥ 3, OR, 6.11, 95% CI, 1.09-34.05, P = 0.039)., Conclusions: Measures of left heart size and plasma NT-proBNP concentration independently estimate risk of first-onset of CHF in dogs with DMVD. These parameters can contribute to the management of dogs with DMVD., (Copyright © 2012 Elsevier B.V. All rights reserved.)

Background: B-type natriuretic peptide concentrations reliably distinguish between cardiac and respiratory causes of dyspnea, but its utility to detect asymptomatic cats with occult cardiomyopathy (OCM) is unresolved., Hypothesis/objectives: Determine whether plasma N terminal probrain natriuretic peptide (NT-proBNP) concentration can discriminate asymptomatic cats with OCM from normal cats, and whether NT-proBNP concentration correlates with clinical, biochemical, and echocardiographic parameters., Animals: One hundred and fourteen normal, healthy cats; 113 OCM cats., Methods: Prospective, multicenter, case-controlled study. NT-proBNP was prospectively measured and cardiac status was determined from history, physical examination, and M-mode/2D/Doppler echocardiography. Optimal cut-off values were derived using receiver operating characteristic (ROC) curve analysis., Results: NT-proBNP was higher (median, interquartile range [25th and 75th percentiles]) in (1) OCM (186 pmol/L; 79, 478 pmol/L) versus normal (24 pmol/L; 24, 32 pmol/L) (P < .001); and (2) hypertrophic obstructive cardiomyopathy (396 pmol/L; 205, 685 pmol/L) versus hypertrophic cardiomyopathy (112 pmol/L; 48, 318 pmol/L) (P < .001). In OCM, NT-proBNP correlated (1) positively with LVPWd (ρ = 0.23; P = .01), LA/Ao ratio (ρ = 0.31; P < .001), LVs (ρ = 0.33; P < .001), and troponin-I (ρ = 0.64; P < .001), and (2) negatively with %FS (ρ = -0.27; P = .004). Area under ROC curve was 0.92; >46 pmol/L cut-off distinguished normal from OCM (91.2% specificity, 85.8% sensitivity); >99 pmol/L cut-off was 100% specific, 70.8% sensitive., Conclusions and Clinical Importance: Plasma NT-proBNP concentration reliably discriminated normal from OCM cats, and was associated with several echocardiographic markers of disease severity. Further studies are needed to assess test performance in unselected, general feline populations, and evaluate relationships between NT-proBNP concentrations and disease progression., (Copyright © 2011 by the American College of Veterinary Internal Medicine.)

Objectives: To compare [NT-proBNP], [NT-proANP] and [cTnI] between control dogs with respiratory disease without pulmonary hypertension (PH) and dogs with pre-capillary PH, and to assess the accuracy of [NT-proBNP], [NT-proANP], [cTnI] to predict Doppler-derived peak tricuspid regurgitation (TR) gradient., Animals: 20 dogs. 8 control dogs with respiratory disease with no PH and 12 with pre-capillary PH., Methods: [NT-proBNP], [NT-proANP] and [cTnI] were compared between the 2 groups and simple linear regression analysis was used to predict peak TR gradients from various blood biomarkers., Results: Median [NT-proBNP] was higher in the dogs with PH (2011 pmol/L, 274-7713 pmol/L) compared to control dogs (744 pmol/L; 531-2710 pmol/L) (p = 0.0339). [NT-proBNP] was associated with peak TR gradient (R(2) = 0.7851, p = 0.0001). Median [NT-proANP] did not differ between dogs with PH (1747 fmol/L; 894-2884 fmol/L) and control dogs (1209 fmol/L; 976-1389 fmol/L (p = 0.058). [NT-proANP] was not associated with peak TR gradient (R(2) = 0.2780, p = 0.0781). Median [cTnI] did not differ between dogs with PH (0.2850 ng/mL; 0.19-1.13 ng/mL) and control dogs (0.2 ng/mL; 0.19-0.82 ng/mL, p = 0.3051). Median [TnI] was not associated with peak TR gradient (R(2) = 0.024, p = 0.6307)., Conclusions: [NT-proBNP] concentration is significantly higher in dogs with pre-capillary PH when compared to dogs with respiratory disease without PH, and [NT-proBNP] may be useful to predict the severity of estimated PH. Elevations in [NT-proBNP] due to pre-capillary PH may complicate the interpretation of [NT-proBNP] elevations in patients presenting with cardiorespiratory abnormalities. [NT-proANP] and [cTnI] were not elevated in dogs with pre-capillary PH., (Copyright © 2011 Elsevier B.V. All rights reserved.)

Background: Identification of the bacterial organism in dogs with endocarditis is challenging. Human studies have reported the utility of the polymerase chain reaction (PCR) to amplify and identify bacterial nucleic acid from infected valvular tissue and blood., Hypothesis/objectives: We hypothesized that PCR using primers designed to amplify the bacterial 16s gene would identify circulating bacteria in dogs with suspected bacterial endocarditis more consistently than standard blood culture techniques., Animals: Eighteen dogs with suspected bacterial endocarditis based upon clinical and echocardiographic findings. Fifteen clinically normal dogs served as negative controls., Methods: Prospective study of dogs evaluated for suspect endocarditis at 6 veterinary hospitals. A blood sample was drawn from all dogs and evaluated with both a single-sample PCR and standard 3-sample blood culture techniques., Results: Blood culture identified noncontaminant bacteria in 6/18 study animals (33%) and 1 control dog; PCR identified noncontaminant bacteria in 7/18 study animals (39%). There were no study animals in which the 2 tests identified different bacteria (κ = 1.0). However, bacteria were identified by both techniques in only 2/18 study animals. When results from both PCR and blood culture were considered together, a noncontaminant bacterial organism was identified in 11/18 study animals (61%)., Conclusion and Clinical Importance: The results of this study suggest that although single sample PCR with 16s primers was not more sensitive than blood culture for detection of bacteremia in dogs with suspect endocarditis, performing both techniques simultaneously did increase the likelihood of identification of bacteria in blood., (Copyright © 2011 by the American College of Veterinary Internal Medicine.)

Objective: To determine whether plasma cardiac troponin I (cTnl) concentrations can be used to identify cardiac involvement in dogs with hemangiosarcoma, exclude cardiac hemangiosarcoma in dogs with noncardiac hemangiosarcoma, and identify cardiac hemangiosarcoma in dogs with pericardial effusion., Design: Cohort study., Animals: 57 dogs (18 with confirmed [5 dogs] or suspected [13] cardiac hemangiosarcoma, 14 with confirmed hemangiosarcoma involving sites other than the heart [noncardiac hemangiosarcoma], 10 with pericardial effusion not caused by hemangiosarcoma, and 15 with noncardiac nonhemangiosarcoma neoplasms)., Procedures: Plasma cTnl concentration was measured, and thoracic radiography, abdominal ultrasonography, and echocardiography were performed in each dog. The cTnl concentration was compared among groups., Results: Median plasma cTnl concentration in dogs with cardiac hemangiosarcoma was significantly higher than the concentration in each of the other groups. A plasma cTnl concentration > 0.25 ng/mL could be used to identify cardiac involvement in dogs with hemangiosarcoma at any site (sensitivity, 78%; specificity, 71 %). A plasma cTnl concentration > 0.25 ng/mL could be used to identify cardiac hemangiosarcoma in dogs with pericardia effusion (sensitivity, 81%; specificity, 100%)., Conclusions and Clinical Relevance: The median plasma cTnl concentration was higher in dogs with cardiac hemangiosarcoma, compared with the median concentration in dogs with hemangiosarcoma at other sites, dogs with other neoplasms, and dogs with pericardial effusion not caused by hemangiosarcoma. The plasma cTnl concentration may be used to identify cardiac involvement in dogs with hemangiosarcoma and to identify cardiac hemangiosarcoma in dogs with pericardial effusion.

Pulmonary hypertension (PH) has been recognized as a clinical syndrome for many years in veterinary medicine, but routine accurate clinical diagnosis in dogs was greatly enhanced by widespread use of echocardiography and Doppler echocardiography. Most cases of PH in veterinary medicine can be categorized as precapillary or postcapillary. These subsets of patients often differ with regard to clinical presentation, response to therapy, and prognosis. Effective medical therapy is now available to treat this often-devastating clinical complication of common chronic diseases, making accurate diagnosis even more important to patient longevity and quality of life.

Objectives: Cardiac arrhythmias as a cause of syncope, collapse, or intermittent weakness can be challenging to diagnose. The purpose of this paper is to retrospectively review the diagnosis and outcome of 23 cases of syncope or collapse in dogs that had a Reveal Plus ILR recorder placed as part of the diagnostic evaluation., Animals, Materials and Methods: Medical records of 23 client-owned dogs that were presented for evaluation of syncope, collapse, or intermittent weakness were retrospectively reviewed., Results: Recurrent syncope occurred in 13/23 (57%) and a positive diagnosis of the cause of the event was made in 11/13 (48% of all dogs). Diagnoses included 6/11 with prolonged periods of sinus arrest with slow ventricular escape rate and one each of sub-optimal fixed heart rate by endocardial pacing, high grade second degree atrioventricular block, supraventricular tachycardia, normal ECG during multiple episodes, and high grade second degree atrioventricular block or sinus arrest., Conclusions: The Reveal Plus ILR device was successful in diagnosing a high percentage of cases of syncope or collapse in which signs recurred and implantation had a low complication rate. The Reveal Plus ILR device is a useful tool to diagnose the etiology of recurrent syncope, collapse, or intermittent weakness in the dog., (Copyright 2010 Elsevier B.V. All rights reserved.)

Objectives: To determine the weekly variability of serum and plasma N-terminal pro-B-type natriuretic peptide (NT-proBNP) concentrations in healthy dogs., Animals, Materials and Methods: Fifty-three normal dogs were examined prospectively. Serum (n=25) or plasma (n=28) samples were obtained for NT-proBNP assay at one week interval for 3 consecutive weeks., Results: Median serum or plasma NT-proBNP concentration did not change over 3 consecutive weeks. Twenty-two of 53 dogs (42%) had at least one NT-proBNP value >500 pmol/L, including 14 dogs with at least one serum NT-proBNP concentration >500 pmol/L and 8 dogs with at least one plasma NT-proBNP concentration >500 pmol/L during the 3-week sampling period. The difference between the maximum and minimum NT-proBNP value obtained over the 3-week sampling period was <100 pmol/L in 40% of dogs, between 100 and 200 pmol/L in 40% of dogs, and >200 pmol/L in 20% of dogs. Of the 19 dogs with a value >500 pmol/L on either week 1 or 2, 11 dogs (58%) had a subsequent NT-proBNP value <500 pmol/L on either week 2 or 3., Conclusions: There is a high degree of variability in weekly serum and plasma NT-proBNP values in healthy dogs. Individual variability should be considered when interpreting NT-proBNP results in dogs.

Background: Circulating plasma N-terminal pro-brain natriuretic peptide (NT-proBNP) concentration facilitates emergency diagnosis of congestive heart failure (CHF) in people. Its utility to discriminate between dyspneic cats with CHF vs. primary respiratory disease requires further assessment. Our objectives were to determine if NT-proBNP (1) differentiates dyspneic cats with CHF vs. primary respiratory disease; (2) increases with renal insufficiency; (3) correlates with left atrial dimension, radiographic cardiomegaly, and estimated left ventricular filling pressure (E/E(a))., Methods: NT-proBNP was measured in 167 dyspneic cats (66 primary respiratory disease, 101 CHF) to evaluate (1) relationship with clinical parameters; (2) ability to distinguish CHF from primary respiratory disease; (3) optimal cut-off values using receiver operating characteristic (ROC) curve analysis., Results: NT-proBNP (1) was higher (median and inter-quartile [25th-75th] percentile) in CHF (754 pmol/L; 437, 1035 pmol/L) vs. primary respiratory disease (76.5 pmol/L; 24, 180 pmol/L) cohorts (P<0.001); (2) positively correlated in CHF cats with increased inter-ventricular septal end-diastolic thickness (rho=0.266; P=0.007) and LV free wall thickness (rho=0.218; P=0.027), but not with radiographic heart size, left atrial size, left ventricular dimensions, E/E(a) ratio, BUN, creatinine, or thyroxine; (3) distinguished dyspneic CHF cats from primary respiratory disease at 265 pmol/L cut-off value with 90.2% sensitivity, 87.9% specificity, 92% positive predictive value, and 85.3% negative predictive value (area under ROC curve, 0.94)., Conclusions: NT-proBNP accurately discriminated CHF from respiratory disease causes of dyspnea.