BACKGROUND:Pimobendan might affect mitral annular dynamics (MAD) in dogs with myxomatous mitral valve disease (MMVD); in humans, alterations in MAD are known to increase the severity of mitral regurgitation (MR). HYPOTHESIS/OBJECTIVES:To investigate the short-term effect of pimobendan on MAD, severity of MR, and systemic arterial compliance in dogs with MMVD. ANIMALS:Twenty dogs with newly diagnosed ACVIM stage B2 MMVD. METHODS:Prospective, open-label, longitudinal study. All dogs underwent echocardiographic and cardiac computed tomographic (CCT) examinations before and 2 weeks after oral administration of pimobendan. Changes in MAD, leaflet-to-annulus index, left heart volumes, regurgitant volume/fraction, and aortic distensibility index were evaluated on CCT. RESULTS:All dogs completed the study without major adverse events. Pimobendan decreased normalized end-systolic mitral annular area (mean difference of 1.38 cm2/m2; 95% CI, 0.79-1.97 cm2/m2; P < .001), aortoparietal distance (mean difference of 1.03 mm/kg1/3; 95% CI, 0.54-1.53 mm/kg1/3; P < .001), and intercommissural distance (mean difference of 0.75 mm/kg1/3; 95% CI, 0.44-1.06 mm/kg1/3; P < .001). Mean leaflet-to-annulus index increased (mean difference of 0.06; 95% CI, 0.02-0.09; P = .002). Changes in left ventricular end-diastolic and end-systolic volumes, left atrial end-diastolic and end-systolic volumes, regurgitant volume (mean reduction of 0.31 mL/kg; 95% CI, 0.13-0.5 mL/kg), and regurgitant fraction (mean reduction of 9.8%; 95% CI, 5.2%-14.3%) were detected (all P < .05) with administration of pimobendan. There was no detectable difference in aortic distensibility index (P = .6). CONCLUSIONS AND CLINICAL IMPORTANCE:Short-term pimobendan administration decreases MR severity by augmenting systolic contraction of the mitral annulus. The study provides new insight into the mechanism of action of pimobendan in dogs with MMVD.

INTRODUCTION/OBJECTIVES:Short-term results of mitral transcatheter edge-to-edge repair (TEER) with the canine V-Clamp device have been promising; however, longer-term outcome data are needed. This prospective study evaluated survival and echocardiographic outcomes in dogs with severe mitral regurgitation (MR) following TEER performed at one referral center. ANIMALS, MATERIALS AND METHODS:Dogs in American College of Veterinary Internal Medicine stages B2, C, and D meeting criteria for severe MR were treated by TEER. The procedure was performed via transapical approach and guided by transesophageal echocardiography and fluoroscopy. RESULTS:One hundred eleven dogs underwent TEER between January 2021 and January 2025. Technical feasibility for placing one clamp was 97.3%, with a single clamp placed in 80 of 108 / (74%) and two clamps placed in 28 of 108 (26%) dogs. In-hospital mortality was 6.3%, and 3-month survival was 86.4%. Freedom from all-cause and cardiac-related mortality was 75% and 80% at one year and 67% and 78% at two years, respectively. Mean (standard deviation) regurgitant fraction decreased from 60.6 (13.3)% to 35 (23)% post procedure and was 30.7 (24.1)% at one year. Normalized left ventricular diastolic dimension decreased from 2.07 (0.24) to 1.84 (0.3) and short-axis left atrial-to-aortic ratio decreased from 2.31 (0.41) to 2.08 (0.45) immediately post procedure; these variables remained decreased at 1.79 (0.28) and 1.94 (0.46), respectively, at 1-year follow-up (P < 0.001). STUDY LIMITATIONS:Follow-up echocardiograms were obtained by multiple centers. CONCLUSIONS:Intermediate outcomes after TEER demonstrated a likely benefit in dogs with severe MR as adjunct to medical therapy. Future goals include improving consistency of MR reduction, decreasing procedural complications through experience and refined case selection, and prospectively comparing to medical therapies.

Introduction/objectives: Quantitative assessment of mitral regurgitation (MR) severity has become increasingly important as procedural therapies for MR reduction become available. This study aimed to obtain quantitative measures of MR severity across stages of degenerative mitral valve disease (DMVD) and evaluate agreement between two echocardiographic methods. Animals, materials and methods: Fifty-one client-owned dogs were included across three DMVD stages (ACVIM B 1, B2, and C). Regurgitant volume (RVol) and fraction (RF) were measured on echocardiograms prospectively acquired by a single cardiologist using volumetric (using Simpson's method of discs) and proximal isovelocity surface area (PISA) methods. Results were compared across stages. Agreement between methods over the range of MR severity was determined by Bland-Altman analyses. Intra- and inter-observer measurement variability assessments were performed via intraclass correlation coefficients (ICC). Results: Median differences (25th percentile, 75th percentile) for volumetric and PISA-derived RVol and RF were as follows, respectively: B1:0.19 mL/kg (-0.02 mL/kg, 0.25 mL/kg), 13.6% (-2.17%, 20.6%); B2:1.49 mL/kg (1.09 mL/ kg, 2.12 mL/kg), 55.6% (45.0%, 70.5%); C:2.72 mL/kg (1.76 mL/kg, 3.13 mL/kg), 67.2% (61. 8%, 78.5%); B1:0.39 mL/kg (0.22 mL/kg, 0.69 mL/kg), 34.3% (19.0%, 56.1%); B2:1.6 7 mL/kg (1.33 mL/ kg, 2.15 mL/kg), 58.8% (49.8%, 73.9%); C:3.1 mL/kg (1.91 mL/kg, 3.57 mL/kg), 75.2% (66.4%, 92.0%). All were different (P<0. 0001) across stages. There was no proportional bias for RVol or RF (P-0.79, P-54). Intra- and inter-observer variability assessments showed ICC greater than 0.75 except PISA RF. Conclusions: Measures of MR severity correlate with disease stage, although their accuracy remains unknown. Volumetric and PISA methods are not interchangeable. (c) 2025 Elsevier B.V. All rights are reserved, including those for text and data mining, AI training, and similar technologies.

ObjectiveTo determine procedural feasibility, safety, and short-term efficacy in dogs with severe degenerative mitral regurgitation (MR) undergoing transcatheter edge-to-edge repair (TEER) with a canine-specific device.DesignProspective, single-arm (uncontrolled), single-institution clinical feasibility study.AnimalsFifty client-owned dogs with severe degenerative MR operated over a 28-month period.MethodsTEER was performed using the canine mitral V-Clamp via a transapical approach using transesophageal echocardiographic and fluoroscopic guidance. Indices of MR severity were determined by echocardiography the day before and 2 to 3 days after the procedure.ResultsProcedural feasibility was 96% based on delivery of at least one device in 48 of 50 dogs. There were no procedural deaths. Procedural safety was 96% based on survival to hospital discharge in 48 of 50 dogs. Euthanasia in 2 dogs prior to hospital discharge was due to damage of the mitral valve and worsened MR after the procedure. Device-related adverse event rate was 6.3% based on 3 events (single-leaflet device detachment, locking failure, locking failure with device embolization) in 59 implanted devices. All three events were nonfatal and successfully treated with a second device. Median regurgitant volume (mL/kg) decreased (p < 0.001) from 2.3 [1.9, 3.1] to 1.1 [0.3, 1.8]. Median effective regurgitant orifice area (cm2/m2) decreased (p < 0.001) from 0.60 [0.40, 0.80] to 0.25 [0.10, 0.50].Conclusion and clinical importanceInitial feasibility results support continued development of TEER as a procedurally feasible, relatively low-risk, and low morbidity treatment for degenerative MR in dogs. Operator experience and case selection are likely to be important components of success of this technique. Evidence of short-term efficacy is promising but needs to be verified with longer-term follow up.

BackgroundPulmonary hypertension (PH) is a common complication of cardiopulmonary disease. In dogs, PH commonly occurs secondary to myxomatous mitral valve disease (MMVD). Red blood cell and platelet indices including mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration (MCHC), red cell distribution width (RDW), mean platelet volume (MPV) and platelet distribution width (PDW), have previously been found to be indicators for predicting and prognosing PH in humans. Therefore, this study aimed to investigate whether these indices are associated with MMVD and/or PH in dogs.MethodsTwo hundred and forty-six dogs were retrospectively recruited for the study and classified into 4 groups: normal (n = 49), MMVD (n =102), PH (n =17), MMVD+PH (n =78). A sub-analysis was performed in dogs with MMVD without evidence of PH according to stage B1 (n =20), stage B2 (n =15), stage C (n =67). The data are expressed as median (interquartile range).Results and discussionNo significant differences (p < 0.05) were found in MCV, RDW and MPV among all groups (normal, MMVD, PH and MMVD+PH). However, decreases in MCH and MCHC were found in MMVD [22.40 (20.90-23.50) pg and 35.25 (33.08-36.90) g/dL], MMVD+PH [22.25 (20.85-23.98) pg and 35.65 (33.30-37.33) g/dL] and PH groups [21.20 (20.60-22.20) pg and 33.80 (32.75-35.70) g/dL] compared to the normal dogs [24.29 (23.55-24.90) pg and 38.20 (37.50-39.05) g/dL] (p < 0.001). Decreases in PDW were found in dogs in the MMVD+PH [15.10 (14.98-15.30) %] groups compared to dogs in the normal group [15.30 (15.10-15.50) %] (p = 0.004). Sub-analysis of MMVD dogs without PH showed a decrease in MCH in dogs with stage B2 MMVD [21.00 (20.50-22.90) pg] and stage C MMVD [22.40 (20.90-23.20) pg] compared to normal dogs [24.29 (23.55-24.90) pg] (p < 0.001). MCHC of dogs with stage B1 [36.55 (33.53-37.78) g/dL] (p = 0.004), B2 [32.90 (32.00-35.00) g/dL] (p < 0.001) and C MMVD [35.30 (33.30-36.80) g/dL] (p < 0.001) were lower than those of normal dogs [38.20 (37.50-39.05) g/dL]. PDW in the stage C MMVD group [15.10 (15.00-15.30) %] was reduced compared to the normal group [15.30 (15.10-15.50) %] (p = 0.042) and the stage B1 MMVD group [15.35 (15.23-15.68) %] (p = 0.002). MCH, MCHC and PDW were negatively correlated with the left atrial and left ventricular size.ConclusionDecreases in MCH and MCHC are related to MMVD, precapillary PH and postcapillary PH while PDW are associated with MMVD severity but not with the presence of PH.

Introduction To evaluate microcirculation and endothelial glycocalyx (eGC) variables using sidestream darkfield (SDF) videomicroscopy in canine cardiopulmonary bypass (CPB). Methods Dogs undergoing CPB for surgical correction of naturally-occurring cardiac disease were prospectively included. Variables collected included patient demographics, underlying cardiac disease, red blood cell flow (Flow), 4-25 μm vessel density (Density), absolute capillary blood volume (CBVabs), relative capillary blood volume (CBVrel) and eGC width assessed by perfused boundary region (PBR). Anesthetized healthy dogs were used as control. Microcirculation and eGC variables were compared at baseline under anesthesia (T0), on CPB prior to cross clamping (T1), after cross clamp removal following surgical correction (T2) and at surgical closure (T3). Results Twelve dogs were enrolled, including 10 with a complete dataset. Median Flow was 233.9, 79.9, 164.3, and 136.1 μm/s at T0, T1, T2, and T3, respectively, (p = 1.00). Median Density was 173.3, 118.4, 121.0 and 155.4 mm/mm2 at T0, T1, T2, and T3, respectively, (p = 1.00). Median CBVabs decreased over time: 7.4, 6.6, 4.8 and 4.7 103μm3 at T0, T1, T2, and T3, respectively, (p < 0.01). Median CBVrel increased over time: 1.1, 1.5,1.1, and 1.3 103μm3 at T0, T1, T2, and T3, respectively, (p < 0.001). Median PBR increased over time: 1.8, 2.1, 2.4, 2.1 μm at T0, T1, T2, and T3, respectively, (p < 0.001). Compared to control dogs (n = 8), CPB dogs had lower CBVabs at T0. Conclusion Alterations in eGC thickness and microvascular occur in dogs undergoing CPB for naturally-occurring cardiac disease.

Trifoliate left atrioventricular (AV) valve with common atrioventricular junction is considered part of the spectrum of atrioventricular septal defect. This valve morphology is typically associated with defects in the AV septum resulting in communication at the atrial or ventricular level, but has also been described as an isolated defect in the setting of a common AV junction without AV septal defect. Trifoliate left AV valve exhibits a line of apposition between the bridging leaflets that is directed toward the inlet interventricular septum, distinguishing it from isolated mitral valve cleft in which the orientation of the bridging leaflets are toward the left ventricular outflow tract. The echocardiographic findings of four dogs with trifoliate left AV valve are described; two with intact septal structures and two with large ostium primum defects. Three dogs underwent open surgical repair using different approaches depending on the presence or absence of a septal defect. One of these underwent concurrent surgical repair for right AV valve dysplasia. One dog with intact septal structures underwent interventional closure of a concurrent patent ductus arteriosus. Current terminology associated with trileaflet left AV valve malformations is reviewed.

INTRODUCTION:Systemic administration of tissue plasminogen activator (tPA) is seldomly reported in dogs and cats. ANIMALS:Client-owned animals receiving tPA (2010-2020). MATERIALS AND METHODS:Medical records of dogs and cats receiving tPA for distant known/suspected thrombus were reviewed. Fourteen dog visits (24 injections) and five cat visits (six injections) were included. RESULTS:Canine known/suspected thrombus included pulmonary thromboembolism (n=6), intracardiac thrombus (n=4), aortic thrombus (n=1), cranial vena cava thrombus (n=2), and femoral and iliac veins thrombus (n=1). Various canine primary diseases were represented, but open-heart surgery was the most common cause. Median time between diagnosis/suspicion of thrombus and tPA injection was 24.5 h (range, 3-150 h). Mean total tPA dose was 1.0±0.78 mg/kg. Clinical improvement occurred in 93% of dogs. Non-fatal complications were reported in 14% of dogs. Dogs' survival to discharge was 78.6% without identifiable non-survivor characteristics. Feline known/suspected thrombus included unilateral feline aortic thromboembolism (FATE) (n=2), bilateral FATE (n=2), and right renal artery thrombus. Feline primary diseases included cardiomyopathy (n=5). Median time between diagnosis/suspicion of thrombus and tPA injection was 4 h (range, 2-17 h) and median total tPA dose was 1.0 mg/kg (range, 0.6-1.4 mg/kg).Clinical improvement occurred during 40% of the visits. All cats (n=3) with acute kidney injury (AKI) at admission developed worsening AKI and reperfusion injury. Of the remaining two visits, one developed a non-fatal AKI. Cats' survival to discharge was 40%. CONCLUSIONS:Systemic thrombolysis with tPA seems to be effective and safe in dogs. More investigation is needed in cats.

Introduction: Combining an antiplatelet drug, clopidogrel, with the direct oral Factor Xa inhibitor, apixaban, could provide an effective antithrombotic strategy in dogs. Thus, a limited 3 thorn 3 phase I dose-escalation clinical trial in healthy dogs was conducted to evaluate bleeding (primary end-point) and pharmacodynamic (PD)/pharmacokinetic (PK) parameters (secondary end-point). Animals: Eleven beagle dogs, median body weight 10.2 kg (9.7-10.9 kg), were enrolled. Methods: Four doses of apixaban (three dogs/dose) administered for eight days. Clopidogrel dose was fixed at 18.75 mg per os (PO) q 24 h with escalation of apixaban dose at 5 mg PO q 12 h, 5 mg PO q 8 h, 10 mg PO q 12 h, and 10 mg PO q 8 h. Laboratory testing included fecal occult blood, coagulation parameters, Factor X activity, apixaban concentration, platelet aggregometry, and thromboelastography on days 1, 3, and 8. Results: Evidence of bleeding was not observed at any dosage. Dose-dependent changes in PD/PK parameters between baseline and 3 h post-medication were observed including a prolongation of prothrombin time, a prolongation of activated partial thromboplastin time, a decrease of Factor X activity level, and increased apixaban concentration.

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.

Pulmonary artery banding (PAB) is a viable but underreported palliative option for hemodynamically significant ventricular septal defect in small animals. A significant challenge associated with PAB is judging the degree of band tightening, which can be further complicated when animals are immature and still growing at the time of PAB. If a pulmonary artery band is overtightened or becomes progressively too tight after surgery, the result can be reversal of shunt flow with potentially devastating consequences. Placement of a band that could be percutaneously dilated using a balloon catheter affords a minimally invasive option for partially or completely relieving the band should it become too tight after PAB. This report describes a surgical technique for placement of a dilatable pulmonary artery band, reviews guidelines for tightening the band, and reports the outcome of three cats undergoing the procedure. All three cats showed evidence of reduced hemodynamic load after PAB for a period of up to three years after PAB.

Epicardial pacemaker implantation can be performed as a lone procedure or in combination with another thoracic or abdominal surgery. This article reviews the current literature and describes a minimally invasive approach for epicardial pacemaker implantation in small animals. The principal advantage of epicardial pacing is that it avoids contact with blood and intracardiac structures and thereby avoids uncommon but potentially devastating complications associated with endocardial pacemaker implantation. Epicardial pacing as a lone procedure can be accomplished via an abdominal transdiaphragmatic or minimal incision thoracotomy approach (minithoracotomy). A minithoracotomy offers the advantages of being less invasive and providing more direct access to the cardiac surface for suturing of epicardial electrodes. Epicardial pacing is a viable option for smaller animals, animals with pre-existing infections, animals at risk for thrombotic complications, or animals undergoing another thoracic or abdominal surgery.

Cardiac surgery strategies include surgeries performed on the beating heart, surgeries performed with brief circulatory arrest during venous inflow occlusion, surgeries performed with the aid of cardiopulmonary bypass (CPB), and hybrid cardiac surgeries that combine image-guided interventional techniques with minimal-incision cardiac approaches. Many cardiac surgeries can be performed on a beating heart without circulatory or cardiac arrest. Venous inflow occlusion is a strategy that provides a brief period of circulatory arrest, allowing for open cardiac repairs that can be performed in a short period of time, generally less than 2 minutes. CPB is a strategy where the patient is connected to an extracorporeal system that provides flow of oxygenated blood to the patient allowing the heart to be stopped for surgical repair. Hybrid cardiac surgery is an emerging option for correction of congenital and acquired structural cardiac defects.

A comprehensive reference for the small animal surgeon, covering all aspects of thoracic surgical conditions. Taking a full perioperative approach, it covers: anaesthesia and complications; critical care; cardiology; cancer; swallowed objects and colour doppler echocardiography.

The pulmonary outflow tract consists of the outflow portion of the right ventricle, pulmonary valve, pulmonary artery and the branch pulmonary arteries. Valvular pulmonary stenosis (PS) represents a constellation of pathologic malformations of the pulmonary valve. PS and other pulmonary outflow obstructions cause pressure overload on the right ventricle. Diagnosis of PS is confirmed by echocardiography. Interventional options for valvular PS include transvenous balloon valvuloplasty, transventricular pulmonary valvuloplasty, pulmonary patch-graft, and pulmonary valve bypass conduit. Subvalvular aortic stenosis (SAS) is an important congenital defect in dogs accounting for 15% to 25% of congenital defects, depending on the study population. Diagnosis of SAS is confirmed by echocardiography. Interventions for SAS in dogs with SAS include transapical aortic valve dilation, and aortic valve bypass conduit. Aortic insufficiency (AI) is a relatively uncommon structural heart condition in animals; however, its consequences tend to be devastating compared to other valvular heart conditions.