Performance of Different Echocardiographic Measurements of Left Atrial Size in Dogs by Observers with Different Levels of Experience.

Assessment of left atrial (LA) sizes in dogs informs clinical staging, risk assessment, treatment decisions, and prognosis. The objective of this study was to assess the diagnostic performance of observers with different levels of experience measuring the LA with three different techniques. Echocardiographic images from 36 dogs with different degrees of left atrial enlargement (LAE) were retrospectively retrieved, anonymized and measured in a blinded fashion by a veterinary student, a first-year cardiology resident, a third-year cardiology resident, and two board-certified veterinary cardiologists. The LA to aortic root ratio (LA:Ao), LA antero-postero diameter indexed to body weight (LAiAPD) and left atrial area were measured. Inter- and intra-observer intraclass correlation coefficients (ICCs) were calculated for all three variables. Bland-Altman plots and accuracy in identification of LAE were calculated for the three least experienced observers using LA:Ao and LAiAPD. Intra- and interobserver ICCs were greater than 0.9 for every variable. The observer with least experience had significant positive bias and a tendency to overestimate larger measurements using LA:Ao, but not using LAiAPD. The accuracy of identification of LAE also increased with the increasing level of experience and was higher for LAiAPD compared to LA:Ao. Combining both methods for identification of LAE, further increased accuracy.

Comparison of the mitral valve morphologies of Cavalier King Charles Spaniels and dogs of other breeds using 3D transthoracic echocardiography.

BACKGROUND: Myxomatous mitral valve disease (MMVD) is more prevalent in Cavalier King Charles Spaniels (CKCSs) compared to dogs of other breeds at a given age. Abnormal valvular stress is thought to contribute to the development and progression of MMVD, and a relationship exists between mitral valve (MV) morphology and stress acting on the valve. OBJECTIVES: To determine whether the MV morphology of healthy adult CKCSs differs from the morphology of healthy adult dogs of other breeds determined by RT-3DTTE. ANIMALS: Thirty-five healthy CKCSs and 41 healthy dogs of other breeds. METHODS: Prospective cross-sectional study. Dogs underwent physical examination, conventional echocardiography, and RT-3DTTE. RT-3DTTE datasets were analyzed using dedicated software for MV morphologic analysis. Morphologic variables were compared between CKCSs and dogs of other breeds. RESULTS: The MV of healthy CKCSs had a smaller annulus height (0.46 ± 0.11 vs. 0.56 ± 0.17; P = .0021), tenting height (0.26 ± 0.12 vs. 0.42 ± 0.18; P < .001), tenting area (0.42 ± 0.15 vs. 0.79 ± 0.34; P < .001), normalized tenting volume (0.09 [0.05-0.13] vs. 0.14 [0.10-0.20]; P < .001), and normalized area of the posterior leaflet (0.57 ± 0.15 vs. 0.66 ± 0.18; P = .016) compared to healthy dogs of other breeds; this results in CKCSs having a flatter MV with reduced tenting, compared to the MV of other breeds. CONCLUSIONS AND CLINICAL IMPORTANCE: These morphologic features could confer a mechanical disadvantage and play a role in the predisposition of CKCSs to the early development of MMVD.

Resolution of sustained narrow complex ventricular tachycardia and tachycardia-induced cardiomyopathy in a Quarter Horse following quinidine therapy.

Sustained narrow-QRS tachycardia of three months duration and left ventricular systolic dysfunction were identified in a fifteen-year-old Quarter Horse. No underlying cause for the tachyarrhythmia was found and no predisposing structural cardiac lesions were evident by echocardiography. Intravenous diltiazem and lidocaine were administered without achieving successful conversion of the arrhythmia. Oral quinidine therapy converted the tachyarrhythmia to sinus rhythm. Ventricular systolic dysfunction and chamber dilatation subsequently resolved. As with other species, echocardiographic features of dilated cardiomyopathy can be tachycardia-induced and may resolve following successful control of heart rate and rhythm.

Molecular genetic basis for fluoroquinolone-induced retinal degeneration in cats.

OBJECTIVES: Distribution of fluoroquinolones to the retina is normally restricted by ABCG2 at the blood-retinal barrier. As the cat develops a species-specific adverse reaction to photoreactive fluoroquinolones, our goal was to investigate ABCG2 as a candidate gene for fluoroquinolone-induced retinal degeneration and blindness in cats. METHODS: Feline ABCG2 was sequenced and the consensus amino acid sequence was compared with that of 10 other mammalian species. Expression of ABCG2 in feline retina was assessed by immunoblot. cDNA constructs for feline and human ABCG2 were constructed in a pcDNA3 expression vector and expressed in HEK-293 cells, and ABCG2 expression was analyzed by western blot and immunofluorescence. Mitoxantrone and BODIPY-prazosin efflux measured by flow cytometry and a phototoxicity assay were used to assess feline and human ABCG2 function. RESULTS: Four feline-specific (compared with 10 other mammalian species) amino acid changes in conserved regions of ABCG2 were identified. Expression of ABCG2 on plasma membranes was confirmed in feline retina and in cells transfected with human and feline ABCG2, although some intracellular expression of feline ABCG2 was detected by immunofluorescence. Function of feline ABCG2, compared with human ABCG2, was found to be deficient as determined by flow cytometric measurement of mitoxantrone and BODIPY-prazosin efflux and enrofloxacin-induced phototoxicity assays. CONCLUSION: Feline-specific amino acid changes in ABCG2 cause a functional defect of the transport protein in cats. This functional defect may be owing, in part, to defective cellular localization of feline ABCG2. Regardless, dysfunction of ABCG2 at the blood-retinal barrier likely results in accumulation of photoreactive fluoroquinolones in feline retina. Exposure of the retina to light would then generate reactive oxygen species that would cause the characteristic retinal degeneration and blindness documented in some cats receiving high doses of some fluoroquinolones. Pharmacological inhibition of ABCG2 in other species might result in retinal damage if fluoroquinolones are concurrently administered.

Synovial T-cell lymphoma of the stifle in a dog.

A 6-year-old, 43-kg, spayed female rottweiler was presented for a 1-month history of progressive, left hind-limb lameness. Upon physical examination, a cranial drawer sign and joint distention were present in the left stifle. Radiographically, the stifle had evidence of effusion, remodeling of the patella, and an enlarged popliteal lymph node. Marked synovial thickening and an intact cranial cruciate ligament were noted during surgery. Despite finding a nonspecific, mixed inflammatory response on joint fluid cytopathology, histopathology demonstrated T-cell lymphoma of the synovium. Lameness may be the sole presenting clinical sign in canine lymphoma.