Echocardiographic evaluation of regurgitant fraction in dogs with subclinical myxomatous mitral valve disease: Method comparison, effects of pimobendan, and reproducibility.

INTRODUCTION/OBJECTIVES: To evaluate regurgitant fraction (RF) using Simpson's method of discs to estimate total stroke volume (RFSMOD_TSV) and using Motion-mode to estimate total stroke volume (RFM-modeTSV) in dogs with subclinical myxomatous mitral valve disease (MMVD). We also sought to evaluate the effects of pimobendan on RF, and to determine the reproducibility of RFSMOD_TSV and RFM-modeTSV. ANIMALS, MATERIALS, AND METHODS: Echocardiography was performed on 57 dogs with MMVD (30 stage B1 and 27 stage B2). Ten dogs received pimobendan for 7-10 days and had a second echocardiogram. Nine dogs underwent six repeated echocardiographic examinations by two operators on three nonconsecutive days within one week for reproducibility analysis. RESULTS: Both RFSMOD_TSV and RFM-modeTSV exhibited a curvilinear relationship with left atrium-to-aortic root ratio. Both RFSMOD_TSV and RFM-modeTSV varied considerably within stage B1 (minimum-maximum: -9.1%-58.2% and -35.7%-66.2%, respectively) and B2 (13.6%-76.2% and 20.1%-85.7%, respectively). Method comparison showed RFSMOD_TSV and RFM-modeTSV were not interchangeable with proportional bias. Pimobendan significantly reduced RFSMOD_TSV (-32.0% ± 23.3%) and RFM-modeTSV (-19.2% ± 10.9%) within the same dog and relative to controls. Good inter-day and between-operator reproducibility was observed for RFSMOD_TSV and RFM-modeTSV based on intraclass correlation coefficients 0.86-0.90 and 0.83-0.90, respectively. Reproducibility coefficients were 19.6%-24.1% and 24.1%-27.0%, respectively. CONCLUSIONS: Use of RF using the total stroke volume method to aid the assessment of dogs with subclinical MMVD might be of clinical value. However, further study is warranted. Based on response to pimobendan and reproducibility analysis, RF SMOD_TSV might be a more reliable technique to quantify RF.

Three-dimensional activation maps of sinus rhythm and focal atrial tachycardia in a dog.

A five-year-old, female-spayed boxer was referred for frequent and medically refractory paroxysmal supraventricular tachycardia. Diagnostic evaluation found no underlying structural heart or systemic diseases. Three-dimensional electroanatomical mapping and radiofrequency ablation were pursued. Activation mapping of normal sinus rhythm demonstrated the location of the sinus node in the posterolateral region of the right atrium. Activation mapping of the tachyarrhythmia identified a centrifugal activation pattern originating from the right atrium at the posterolateral aspect of the tricuspid valve orifice, suggestive of focal atrial tachycardia. A total of 10 ablation lesions were delivered to the earliest activation site. The dog recovered without complications and no recurrence of supraventricular tachycardia was noted on subsequent follow-ups.

Three-dimensional electroanatomic mapping and radiofrequency catheter ablation of ventricular arrhythmia in a dog without structural heart disease.

A 1.5-year-old, female-spayed mix-breed dog was presented with recurrent episodes of shaking and excessive panting attributed to drug-refractory ventricular arrhythmia (VA) characterized predominantly by incessant periods of ventricular bigeminy. The VA had a narrow QRS morphology, suggestive of an origin near the His bundle or fascicular system. Diagnostic evaluation found no structural heart disease or underlying etiology. Three-dimensional electroanatomic mapping and radiofrequency catheter ablation were pursued. Voltage mapping demonstrated normal bi-ventricular voltage (≥1.5 mV) without any fractionated or multicomponent electrograms, indicating the absence of ventricular myocardial scar. Pace mapping identified an endocardial origin of the VA at the basal anterior septum of the left ventricle, distal to the His bundle and near the left bundle branch. Two ablation lesions were delivered to this site, and a left bundle branch block was temporarily induced. The dog recovered uneventfully. One month later, the owners reported a remarkable improvement in clinical signs, and follow-up 48-h Holter monitor found complete resolution of VA.

Aorto-left atrial fistula secondary to infective aortic endocarditis and endarteritis in a cat with valvular aortic stenosis.

A cat previously diagnosed with valvular aortic stenosis developed acute respiratory distress. A new continuous heart murmur was noted on physical exam. Echocardiographic examination revealed vegetative lesions on the aortic valve and continuously shunting blood flow from the aorta into the left atrium. Despite initial treatment for left-sided congestive heart failure, the cat died suddenly. In addition to confirming aortic valve endocarditis and an acquired aorto-left atrial shunt, pathological examination identified vegetative lesions on the luminal surface of the ascending aorta. Although antemortem aerobic blood culture, 16s bacterial ribosomal DNA PCR, and Bartonella PCR failed to identify causative organisms, Escherichia coli was identified on postmortem tissue culture of the aortic lesion. This represented a unique case of primary valvular aortic stenosis with secondary infective aortic endocarditis, infective aortic endarteritis, and aorto-left atrial fistula in a cat. It highlighted potential adverse outcomes of aortic stenosis that are more commonly recognized in humans and dogs.

Echocardiographic assessment of right heart size and function in dogs with pulmonary valve stenosis.

INTRODUCTION/OBJECTIVES: We sought to determine the prevalence and clinical significance of right heart remodeling and right ventricular (RV) dysfunction in dogs with pulmonary valve stenosis (PS). We also sought to evaluate repeatability of several measurements of severity of PS, right heart size, and RV function in dogs with PS. ANIMALS, MATERIALS AND METHODS: Several indices of right atrial (RA) size and RV size and function were prospectively evaluated in 48 dogs with PS. Regression analysis was used to determine if indices of right heart size and function were independently associated with maximum transpulmonary pressure gradient (max PG) and adverse clinical findings (exercise intolerance, syncope, or right heart failure). Eight dogs underwent a second echocardiogram performed by the same operator to assess repeatability of the echocardiographic indices, which was quantified by coefficient of variation (CV) and repeatability coefficient. RESULTS: Increased RA size (81%), increased RV wall thickness (83%), and decreased tricuspid annular plane systolic excursion (TAPSE [81%]) were common. Right atrial size, end-diastolic RV area, and RV wall thickness were independently associated with max PG. Decreased TAPSE was independently associated with adverse clinical findings. All indices except RA area (18.6%) and RV systolic velocity (20.7%) had CVs <15%. Repeatability coefficients are available to help distinguish a true change versus measurement variability during serially obtained exams. CONCLUSIONS: Right heart remodeling and RV dysfunction are common in dogs with PS and are associated with echocardiographic and clinical severity. Results support the quantitative assessment of right heart size and function in dogs with PS.