Feline hypertrophic cardiomyopathy: Does the microRNA-mRNA regulatory network contribute to heart sarcomeric protein remodelling?

Feline primary hypertrophic cardiomyopathy (HCM) is an intrinsic myocardial disease characterized by concentric hypertrophy of the left ventricle. In the present study, we investigated the microRNA-mRNA regulatory network in feline myocardial tissue affected by primary (HCMI) and secondary HCM (HCMII). MRNA expression levels of sarcomeric genes, including, TNNT2, TNNI3, MYH7, MYBPC3, TPM1 and ACTC1 were assessed in the FFPE myocardial tissues. FFPE tissues from healthy cats were sequenced by the NGS, to explore, in the entire non-deposited miRNome, the expression level of microRNAs targeting the complementary sequences of selected sarcomeric mRNAs. The sarcomeric genes TNNT2, MYH7, MYBPC3 and TPM1 showed a statistically significant upregulation in HCMI compared to HCMII (p < .01), except ACTC1 which was downregulated (p < .01); TNNI3 showed no statistically significant difference. In HCMII miR-122-5p, miR-338-3p, miR-484, miR-370-3p, miR-92b-3p, miR-375 and miR-370-3p showed a significant upregulation (p < .01) compared to control. The exception was miR-30a-5p which showed downregulation. Worthy of note is the 4-fold higher expression of miR-370-3p, a key regulator of MYBPC3, in HMCI compared to HMCII. This research does not solve the aetiological mystery of HCM, but it may help to find a way to help diagnose and define the prognosis of HCM in cats.

Imaging diagnosis--transesophageal ultrasound-guided removal of a migrating grass awn foreign body in a dog.

A 3-year-old English Setter dog was presented for an acute onset of coughing. Tracheobronchoscopic examination allowed localization and removal of one grass awn foreign body. A second migrated grass awn was suspected to be present in the left caudal lung lobe. Transesophageal ultrasound revealed an area of pulmonary consolidation in the dorsomedial portion of left caudal lobe and a linear hyperechoic structure consistent with a grass awn foreign body within the area of consolidation. Transesophageal ultrasonography was also used to provide anatomical landmarks that facilitated successful thoracoscopic removal of the foreign body.

Dumon silicone stents can improve respiratory function in dogs with grade IV tracheal collapse: 12 cases (2019-2023).

OBJECTIVE: To evaluate the efficacy, complications, and outcome of Dumon silicone stent placement for dogs with grade IV tracheal collapse. ANIMALS: 12 client-owned dogs. CLINICAL PRESENTATION: Each dog was diagnosed with grade IV TC unresponsive to medical therapy and had severe obstructive respiratory failure. RESULTS: 12 dogs were included in the study. By the end of the study, 5 of 12 (41.7%) remained alive, while 7 of 12 (58.3%) dogs died. Survival times after stent placement ranged from 97 to 1,310 days (mean, 822.43 days; median, 810 days). Three of the 12 (25%) dogs died spontaneously, while 4 of 12 (33.3%) were euthanized. The cause of death was determined for 6 of 7 (85.7%) dogs and was TC related for 3 of 7 (50%). Causes of death related to TC were progressive airway collapse (2/3 [66.6%]) and incoercible cough (1/3 [33.4%]). Complications occurred in 9 of 12 (75%) cases and included granulation tissue growth (3/12 [25%]), incoercible cough (2/12 [16.7%]), stent migration (1/12 [8.3%]), and stent deformation (1/12 [8.3%]). Reduction of obstructive dyspnea and episodes of asphyxiation was achieved after Dumon silicone stent placement. CLINICAL RELEVANCE: The placement of an intraluminal Dumon silicone stent was a successful salvage treatment for TC in dogs that did not respond to medical management. Disease progression is inevitable, but substantial improvement of respiratory function may be achieved for months to years.

Prognostic indicators for canine parvoviral enteritis in a Teaching Hospital in Italy: a retrospective study of 76 cases.

Potential prognostic indicators have been associated with decreased survival during canine parvoviral enteritis (CPE), such as body weight, sex, and clinicopathological parameters. Few studies reported the prognostic factors for CPE in Italy; therefore, the aim of this study was to identify prognostic factors associated with the survival of dogs admitted to the Veterinary Teaching Hospital of Perugia University, naturally infected with canine parvovirus. Seventy-six medical records of dogs with a definitive diagnosis of parvoviral infection admitted from 2017 to 2021 have been reviewed and included in the study. From medical records were extracted data on signalment, history, clinical examination, hematology, serum biochemistry, treatments, progression of clinical signs during hospitalization and outcome. The data have been subjected to univariate and multivariate statistical analysis. Our results showed winter season, male sex, dog ownership, small breed, normal sensory status, normal heart rate, normal hydration status, abdominal pain, increased capillary reperfusion time, and normal white blood cell count as positive prognostic factors. The survival model confirmed that parameters such as male sex, small breed, and ownership increased the survival rate during hospitalization. Data reported in the present study are partially in agreement with previous studies and added new information on the possible prognostic factors in dogs affected by CPE in Italy.

Serum D-Lactate Concentrations in Dogs with Inflammatory Bowel Disease.

The D-enantiomer of lactic acid (D-lactate) is normally produced from bacterial fermentation in the gastrointestinal tract in mammals. In humans, increased D-lactate concentrations are related to gastrointestinal disease, including short bowel syndrome and malabsorptive syndrome. Similarly, increased D-lactate concentrations have been described in calves affected by diarrhea, in cats with gastrointestinal diseases, and in dogs with parvoviral enteritis. The purpose of the present study was to measure the serum D-lactate concentrations in dogs with inflammatory bowel disease (IBD). We retrospectively reviewed data from the database of the VTH of Perugia University, and dogs affected by IBD with serum samples stored at -80 °C were considered eligible for inclusion. A total of 18 dogs with IBD and 10 healthy dogs were included in the study. The dogs with IBD were divided into three subcategories based on the severity of the disease. Serum D-lactate concentrations (µM) were determined using a commercially available colorimetric assay kit (D-Lactate Colorimetric Assay Kit; Catalog #K667-100, BioVision Inc., Milpitas, CA, USA). Our results showed no significant difference (p > 0.05) in the serum concentrations of D-lactate between dogs with various degrees of IBD and healthy dogs. However, the wide variability of the D-lactate concentrations in dogs with IBD and evidence of increased serum D-lactate concentrations in dogs with confirmed dysbiosis encourage further studies on this topic to understand potential factors influencing the serum D-lactate concentrations in dogs affected by IBD.

Factors related to longevity and mortality of dogs in Italy.

Besides its translational value, an improved understanding of dog longevity and mortality is necessary to guide health management decisions, breed selection, and improve dog welfare. In order to analyse the lifespan of dogs in Italy, identify the most common causes of death, and evaluate possible risk factors, anonymised medical records were collected from 9 veterinary teaching hospitals and 2 public health institutions. Data regarding breed, sex, neuter status, age, diagnosis, and mechanism of death were retrieved. Cause of death (COD) was classified by pathophysiologic process (PP) and organ system (OS). Of the 4957 dogs that died between 2004 and 2020 included in the study, 2920 (59.0%) were purebred, 2293 (46.2%) were female, 3005 (60.6%) were intact, 2883 (58.2%) were euthanised. Overall median longevity was 10.0 years. Median longevity was significantly longer for crossbreds, females, neutered dogs, and small-sized breeds. The breeds with the highest median age at death were the Yorkshire terrier, English cocker spaniel, West Highland white terrier, Italian volpino, and Shih Tzu, whilst the American bulldog, English bulldog, American pit bull terrier, Bernese mountain dog and the Maremma and the Abruzzes sheepdog had the lowest median age at death. The most frequent COD by PP was neoplasia (34.0%), which occurred more frequently in large breeds, namely German shepherd, Labrador retriever and Boxer. Degenerative diseases mostly affected small-sized dogs like Miniature pinscher and Dachshund. Regarding the OS involved, diseases of the renal/urinary system were most frequently responsible for COD (15.0%), prevalently degenerative and inflammatory/infectious. Substantial variation in median longevity according to causes of death by PP and OS was observed. These data are relevant for breeders, veterinary practitioners, and owners, to assist breed selection, facilitate early diagnosis, guide choice when purchasing a purebred dog and making health management decisions, and ultimately improve dog welfare.

Endoscopic Retrieval of Esophageal and Gastric Foreign Bodies in Cats and Dogs: A Retrospective Study of 92 Cases.

Esophageal and gastric foreign bodies (FBs) commonly occur in small animal practices, and their endoscopic removal has been previously reported. However, few studies reported the endoscopic instruments used for the retrieval attempt and the time spent for endoscopic removal. Therefore, the aim of this study is to evaluate the factors that can influence the success rate and timing of the endoscopic retrieval of FBs. The medical records of 92 animals undergoing endoscopic removal of esophageal (n = 12) and gastric (n = 84) FBs have been reviewed. Two dogs had FBs in both the esophagus and stomach. From medical records and video recordings, there were extrapolated data on signalment, clinical signs, endoscopic devices used, success of retrieval, and duration of endoscopy. Endoscopic removal of FBs was successful in 88% cases, and the mean time spent for the extraction was 59.74 min (range, 10-120 min). The success rate and timing for the removal of endoscopic foreign bodies (EFBs) are influenced by several factors in our population: medium-breed dogs, adult animals, and localization of FBs in the body of the stomach increased the probability of failure during the endoscopic retrieval attempt. Conversely, the success and timing of the retrieval of EFBs were higher in puppies and with increasing operator's experience. Moreover, the use of combination devices such as polypectomy snare and grasping forceps negatively influenced the success of extraction of FBs. Further prospective and comparative studies in a large and multicentric population of patients can be useful to create interventional endoscopic guidelines, as in human medicine.

Risk factors for atrial fibrillation in dogs with dilated cardiomyopathy.

Introduction: Atrial fibrillation secondary to dilated cardiomyopathy (DCM) frequently affects large-breed dogs. The aim of the present study was to identify risk factors for the development of atrial fibrillation in dogs of different breeds with an echocardiographic diagnosis of DCM. Methods: In this multicenter retrospective study, we searched the electronic databases of five cardiology referral centers for dogs with an echocardiographic diagnosis of DCM. A comparison of clinical and echocardiographic variables was performed between dogs developing atrial fibrillation and those not developing atrial fibrillation and the ability to distinguish between these two groups of dogs was evaluated by receiver operating characteristic curve analysis. Univariate and multivariable logistic regression analysis estimated the odds ratio (OR) with 95% confidence interval (CI) of developing atrial fibrillation. Results: We included 89 client-owned dogs with occult and overt echocardiographic DCM. Of these, 39 dogs (43.8%) had atrial fibrillation, 29 dogs (32.6%) maintained a sinus rhythm, and 21 dogs (23.6%) showed other cardiac arrhythmias. Left atrial diameter had high accuracy (area under the curve = 0.816, 95% CI = 0.719-0.890) to predict the development of atrial fibrillation at the cut-off of >4.66 cm. After multivariable stepwise logistic regression analysis, only increased left atrial diameter (OR = 3.58, 95% CI = 1.87-6.87; p < 0.001) and presence of right atrial enlargement (OR = 4.02, 95% CI = 1.35-11.97; p = 0.013) were significant predictors of atrial fibrillation development. Discussion: Atrial fibrillation is a common complication of DCM in the dog and is significantly associated with increased absolute left atrial diameter and right atrial enlargement.

Intracardiac Porcupine Quill Migration in a Dog: Multimodality Imaging Findings and Surgical Management.

The porcupine is a nocturnal quill-bearing rodent common throughout Italy. When threatened, it defends itself by erecting its quills, rattling its tail, and running sideways or backyard into predators. The quills are released upon contact with assailants and tend to migrate into several body tissues or cavities due to the unique inverted cuticles (crenate) directed downwards to the quill base (a sort of "harpoon effect"). Intracardiac migration of porcupine quills has been reported in a few dogs with severe clinical signs. This case report describes a single porcupine quill [Hystrix cristata, (HC)] migration through the heart in a dog and the use of multimodality imaging for the diagnosis and surgical approach. A 4-year-old 25 kg female mixed-breed dog was presented for evaluation of recurrent fever. Transthoracic echocardiographic examination showed a linear, hyperechoic foreign body traversing the interventricular septum from the heart base to the cardiac apex. Computed tomography and transesophageal echocardiography confirmed the presence of a single structure resembling a quill; a later esophageal endoscopy showed no anatomical alterations or mucosal injuries. Following median sternotomy and after accurate localization by intraoperative ultrasound, the quill was successfully removed. The dog had a good recovery without evidence of severe cardiac injury secondary to an intracardiac quill. To the best of the authors' knowledge, the identification of an intracardiac HC quill by ultrasonography and CT and its successful removal by ultrasound guide has not been previously reported.

A Pleistocene Fight Club revealed by the palaeobiological study of the Dama-like deer record from Pantalla (Italy).

Here, we report on the exceptionally well-preserved deer record from the locality of Pantalla (central Italy), dated in the Early Pleistocene (ca. 2.1-2.0 million years ago). The fossils show a combination of characters that allows an unambiguous attribution to 'Pseudodama' nestii, of which they represent one of the most informative collections to date. Our comparisons-also conducted through CT-based methods on endocranial structures-reveal that the cranial and postcranial skeleton of 'P.' nestii displays a mosaic of intermediate characters between extant Dama and Cervus, but also that the affinities with Dama are prevalent. Some Cervus-like features especially in cranial morphology, can be interpreted as plesiomorphic characters supporting a basal position of 'Pseudodama' among the Cervini. Interestingly, three bone anomalies are described in the two male crania of 'P.' nestii from Pantalla and are interpreted as palaeotraumatological evidence resulting from different injuries suffered by the deer during their life. This allows opening a treasure trove of information on paleobiological aspects, including ontogeny and antler cycle and function.

Reference intervals for transthoracic echocardiography in the American Staffordshire Terrier.

This study reports the echocardiographic reference intervals in the American Staffordshire Terrier (AST). The echocardiographic variables obtained in 57 healthy adult AST were compared with published data from the general canine population and other breeds. In the AST, the left ventricular volumes were lower than values reported in Boxers and Dobermans (P<0.0001), but higher than in small breeds (P<0.0001). The left ventricular ejection fraction was higher than Boxers and Dobermans (P<0.0001), but lower than small breed dogs (P=0.027). The aortic peak velocity values were similar to Boxers (P=0.55) but higher than the general canine population (P<0.0001). The reference intervals presented in this study are clinically useful for an accurate echocardiographic interpretation and screening in the AST.

Left Atrial Mural Thrombosis and Hemopericardium in a Dog with Myxomatous Mitral Valve Disease.

A 14-year-old mixed-breed dog with a 2-year history of myxomatous mitral valve disease was examined for collapse and lethargy. At the presentation, pale oral mucous membranes, rapid and weak femoral pulses, and muffled heart sounds with a moderate left apical systolic murmur were revealed. Echocardiographic examination showed pericardial effusion with organized echogenic material originating from the left atrial wall. Tamponade of the right atrium and severe left atrial enlargement were also observed. Multiple views of the left atrium and left auricle allowed to visualize a hyperechoic mass adherent to the endocardium of the left atrial wall. Contrast-enhanced ultrasonography study allowed to rule out active intrapericardial hemorrhages, and echo-guided pericardiocentesis was performed. No recurrence of pericardial effusion was observed, but the dog suddenly died after 10 days. The postmortem examination confirmed multifocal left atrial thrombosis attached to the endomyocardial tears.

Double-Outlet Right Ventricle in a Chianina Calf.

Congenital heart defects have been occasionally reported in cattle and ventricular septal defect represents the most frequently encountered anomaly. The double-outlet right ventricle is a rare congenital ventriculoarterial malformation reported only in certain cattle breeds. We describe this rare and complex congenital cardiac malformation observed in a 10-day-old male Chianina calf. Clinical examination showed tachycardia, tachypnea, jugular pulses, cyanotic mucous membranes and a right apical systolic murmur. Transthoracic echocardiography revealed severe dilation of the right-sided cardiac chambers with a markedly hypoplastic left ventricle. Both aorta and pulmonary artery leaving the right ventricle in parallel alignment with the tricuspid valve were suggestive of a dual-outlet right ventricle. Interventricular and interatrial septal defects were also visualized. Post-mortem examination confirmed the echocardiographic findings. To the authors' knowledge, a similar complex congenital cardiac malformation has not been reported in calves of the Chianina breed to date.

Assessment of Longitudinal Left Ventricle Deformation by 2-Dimensional Speckle Tracking Echocardiography Obtained from Different Views in Cats.

Two-dimensional speckle tracking echocardiography (STE) is a novel, angle-independent imaging technique useful to assess myocardial function by strain and strain rate analysis in human and veterinary medicine. Commonly, the left apical four-chamber (LAP4Ch) view is used to assess left ventricular (LV) longitudinal deformation in dogs and cats. However, the right parasternal four-chamber (RP4Ch) view is often more easily obtained than the LAP4Ch view in cats. No studies exist comparing longitudinal strain and strain rate values using STE from different echocardiographic views in cats. Therefore, we examined the agreement between RP4Ch and LAP4Ch for assessment of LV longitudinal strain and strain rate in cats. We acquired 2D echocardiographic cineloops from RP4Ch and LAP4Ch views and analyzed LV longitudinal strain and strain rate in 50 cats (31 healthy cats and 19 cats with different disease states) using XstrainTM software. Peak systolic strain and strain rate values of endocardial and epicardial border were used for the analysis. The two echocardiographic views were compared using limits-of-agreement analyses and intra-observer measurement variability was assessed. We could obtain longitudinal strain and strain rate from the RP4Ch view in all cats. Strain, but not strain rate, had good intra-observer measurement variability (<10% vs. <20%). However, only endocardial strain values obtained with the two views agreed sufficiently to be used interchangeably (95% limits of agreement: -3.28, 2.58). Epicardial strain/strain rate and endocardial strain rate values did not agree sufficiently to be used interchangeably (95% limits of agreement: -11.58, 9.19; -2.28, 1.74; -1.41, 1.36, respectively). Our study suggests that RP4Ch view was feasible for assessment of the LV longitudinal deformation analysis by STE in cats, but only endocardial longitudinal strain values obtained from the two different views were interchangeable.

Transverse Right Ventricle Strain and Strain Rate Assessed by 2-Dimensional Speckle Tracking Echocardiography in Dogs with Pulmonary Hypertension.

Right ventricular (RV) strain analysis using 2-dimensional speckle tracking echocardiography (2D STE) permits practitioners to assess regional and global deformation of the myocardium. Recently, assessment of the longitudinal right ventricle (RV) strain and strain rate using 2D STE has been reported in dogs. Although longitudinal deformation is the dominant component of the RV systole, RV myocardial fibers of the superficial layer are oriented circumferentially and these contribute to the RV pump function (radial deformation). Because this strain component has not been investigated in dogs, we have assessed radial RV strain and strain rate using 2D STE in healthy dogs and dogs with pulmonary hypertension (PH). We have recruited 74 dogs (40 healthy dogs and 34 dogs with PH) in which we have analyzed radial RV free wall strain and strain rate using XstrainTM software. We have used the left apical 4-chamber view optimized for the RV for analysis of the radial strain and strain rate variables (XstrainTM software denoted radial strain as "transverse"). Seven dogs were excluded during the analysis for low quality images. Transverse strain and strain rate obtained in healthy dogs showed no relationship with heart rate, body weight or age (r2 < 0.09 and p > 0.05 for all variables). Moreover, no relationship between transverse strain/strain rate variables and left atrial-to-aortic ratios was observed (r2 < 0.06 and p = 0.2, for both). Transverse strain and strain rate obtained in dogs with PH, showed weak negative relationships with tricuspid regurgitation velocity (r2 < 0.25 and p = 0.006, for both). Transverse RV strain and strain rate using 2D STE is feasible in most dogs and decrease with worsening of the PH, but these advanced echocardiographic indices do not help in identifying dogs with PH.

Prostatic Localization of a Migrating Grass Awn Foreign Body in a Dog.

A 13-year-old male mixed-breed dog was examined because of hematuria and pyrexia. Ultrasonographic examination of the genitourinary tract showed the presence of a migrating grass awn in the right prostatic lobe. Laparotomy allowed, under ultrasonographic guidance, to remove entirely the migrating grass awn from the prostatic parenchyma. The recovery was uneventful and four months after the surgery the owner reported that the dog showed the complete resolution of the clinical signs and full return to normal activity. To our knowledge, this case report describes for the first time the clinical presentation, imaging findings, management and outcome for a dog with prostatic localization of a migrating grass awn.

Severe Pleural Effusion in a Dog Affected by Larval Mesocestodiasis.

A 4-year-old, 20 kg, female mixed breed dog was referred to our Veterinary Teaching Hospital for severe respiratory distress. Thoracic ultrasonography revealed severe pleural effusion with multiple anechoic cystic structures within the fluid. Abdominal cavity presented few small and irregular cystic structures. Diagnosis of infection by larval stages of Mesocestoides spp. on the basis of a PCR approach was performed and therapy with oral fenbendazole was started. Due to an incomplete clinical response, the dog underwent to remove metacestodes cysts by surgical debridement. The dog showed no recurrence of clinical signs for 12 months after the surgery. Pleural larval cestodiasis should be added as a differential diagnosis in the list of diseases causing pleural effusion in dogs.

Ultrasonographic assessment of abdominal aortic elasticity in hypertensive dogs.

BACKGROUND: Systemic hypertension (SH) is a persistent and pathological increase in arterial blood pressure (BP). Chronic SH leads to an increase in aortic (Ao) stiffness, and measuring Ao elasticity is useful for estimating Ao stiffness in humans. Currently, no literature in veterinary medicine describes noninvasive assessment of abdominal Ao elasticity in dogs with SH. OBJECTIVE: Compare ultrasonographic-derived abdominal Ao strain (AoSt) between hypertensive (HT) and normotensive (NT) dogs. ANIMALS: Fifty privately-owned dogs with clinical signs, conditions, or both potentially associated with SH. METHODS: Prospective observational case-control study. Aortic stiffness was estimated by calculating AoSt as follows: AoSt = ([AoDs - AoDd]/AoDd) × 100, where AoDs and AoDd are the Ao diameter in systole and in diastole, respectively. Aortic stiffness was calculated from 2 different Ao transverse sections, the first caudal to the left renal artery (K_AoSt), and the second cranial to the external iliac arteries (I_AoSt). RESULTS: Thirty-two dogs were included in the HT group and 18 in the NT group. Both K_AoSt and I_AoSt in HT dogs were significantly lower (P < .05) than in NT dogs (7.4 ± SD 3.6) vs 10.3 (±3.8) and 5.7 (interquartile range [IQR], 3.9-7.5) vs 8.1 (IQR, 7-10.3), respectively. Only K_AoSt was significantly influenced by age. CONCLUSIONS AND CLINICAL IMPORTANCE: Ultrasonographic Ao elasticity assessment was feasible to compare HT and NT dogs. Results indicated that K_AoSt and I_AoSt indices can be used to assess SH-related Ao stiffness, especially when indirect BP measurements are inconsistent or inaccurate. Additional studies to assess the AoSt in healthy dogs of various ages are needed.

Bacterial colonization of non-permanent central venous catheters in hemodialysis dogs.

Non-permanent central venous catheters (CVCs), are the most commonly used vascular access in veterinary patients undergoing hemodialysis. In human dialysis patients, CVC infection represents a common cause of morbidity and mortality. The aim of this retrospective observational study was to evaluate the prevalence of bacterial colonization of CVCs in dogs submitted to hemodialysis treatment at time of CVC removal. The CVCs of all dogs submitted to hemodialysis (n = 23) at the Veterinary Teaching Hospital ''Mario Modenato'' of the University of Pisa between January 2015 and December 2016 were considered. For all dogs, data regarding signalment, reason for hemodialysis treatment, duration of catheterization (≤15 or >15 days), CVC complications, and 30-day survival were considered. Statistical analysis was performed using Graph Pad Prism™. Five over 23 dogs (22%) showed positive bacterial culture of CVC (+), and 18/23 dogs (78%) negative culture of CVC (-). The most prevalent microorganism was Staphylococcus Spp (3/5; 60%). No significant difference was found in the prevalence of CVC infection according to age, gender, reason for hemodialysis, CVC complications, duration of catheterization, and outcome. No statistically significant difference (p = 0.64) in survival curves was reported at log rank analysis between dogs with CVC - and CVC +. The prevalence of bacterial CVC contamination in our dialysis dogs showed relatively low. Exclusive use of CVC for hemodialysis, good hygiene practice during CVC management, and use of chlorhexidine as an antiseptic should be strongly encouraged.

Transthoracic M-mode echocardiographic assessment of pulmonary vein-to-pulmonary artery ratio in healthy horses.

Equine cardiovascular structures and function are routinely assessed by transthoracic echocardiography. Recently, investigators have described the echocardiographic visualization of equine pulmonary vein ostia. In companion animals, the right pulmonary vein (RPV) to right pulmonary artery (RPA) ratio has been used as an index to estimate the severity of cardiac diseases resulting in left ventricular volume overload. We sought to assess the feasibility of measuring RPV and RPA dimensions, and sought to provide various previously examined RPV and RPA variables in clinically healthy horses that could be used to assess cardiopulmonary disease status. Echocardiographic examination was prospectively performed in 70 healthy horses. The RPV and RPA were visualized using a modified right parasternal long-axis view and maximum and minimum diameters of both vessels were measured from 2D guided M-mode traces. The aortic diameter (Ao) was measured from the right parasternal short-axis view in early diastole. These measurements were then used to produce various ratio indices. RPV and RPA were imaged in all 70 horses. Median of the minimum and maximum RPV/RPA was 0.51 and 0.60, respectively. Median fractional dimensional change of vessels was 33% for RPV and 22% for RPA. The medians of the minimum and maximum RPV/Ao and RPA/Ao were 0.18, 0.28, 0.35 and 0.46, respectively. No relationships between either bodyweight or heart rate and any of the vein or artery variables were identified (maximum r2 = 0.04). Inter- and intra-observer measurement variability was very good for all RPV and RPA measurements. Measuring of RPV and RPA diameters using M-mode transthoracic echocardiography is feasible in healthy horses. Further studies of these variables in horses with cardiac diseases are needed to determine the clinical applicability and utility.