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Abstract Background Reliability of echocardiographic calculations for stroke volume and mitral regurgitant fraction (RFMR) are affected by observer variability and lack of a gold standard. Variability is used to calculate critical change values (CCVs) that are thresholds representing real change in a measure not associated with observer variability. Hypothesis Observed intra‐ and interobserver accuracy and variability in healthy dogs help model CCV for RFMR. Animals Reliability cohort of 34 healthy dogs; allometric scaling cohort of 99 dogs with heart disease and 25 healthy dogs. Methods Accuracy, variability, and CCV of 2 observers using geometric and flow‐based echocardiography were prospectively compared against a standard of RFMR = 0% and extrapolated across a range of expected RFMR values in the reliability cohort partly derived from cardiac dimensions predicted by the allometric cohort. Results Accuracy of methods to determine RFMR in descending order was 4‐chamber bullet (Bullet4CH), mitral inflow, cube formula, and Simpson's method of disks. Intraobserver variability was relatively high. The CCV for RFMR ranged from 28% to 88% and was inversely related to RFMR when extrapolated for use in affected dogs. For both observers, the Bullet4CH method had the lowest intraobserver CCV (Operator 1:28%, Operator 2:41%). Interobserver strength of agreement was low with intraclass correlation coefficients ranging from 0.210 to 0.413. Conclusions and Clinical Importance Echocardiographic volumetric methods used to calculate stroke volume and RFMR have low accuracy and high variability in healthy dogs. Extrapolation of observed CCV to a range of expected RFMR suggests observers and methods are not interchangeable and variability might hinder routine clinical usage. Individual observers should be aware of their own variability and CCV.

Abstract Background Differentiation of the subclinical phases of myxomatous mitral valve disease (MMVD) in dogs relies heavily on echocardiography. Focused cardiac ultrasonography (FCU) is a point‐of‐care technique that can assess heart size. Hypothesis/Objectives Veterinary students trained in FCU can differentiate dogs with subclinical MMVD based on left ventricular (LV) and left atrial (LA) dimensions. Animals Forty‐eight dogs with subclinical MMVD. Methods Veterinary students were trained to measure LV dimension and LA‐to‐aortic root dimension ratio (LA : Ao) using FCU. Dogs were categorized into 2 cohorts based on whether or not the LV normalized internal diastolic dimension was ≥1.7 and LA : Ao was ≥1.6. Agreement between FCU and echocardiographic studies performed by cardiologists was evaluated. Results One‐hundred and forty‐six FCU examinations were performed by 58 veterinary students on 48 dogs. Overall agreement between students and cardiologists was moderate (Fleiss' kappa, 0.54; 95% confidence interval [CI], 0.39‐0.69; P

Abstract Background Poor natriuresis is a potential marker of diuretic resistance in dogs with acute congestive heart failure (CHF) but little is known about the relationship between urine sodium concentration (uNa) and frequency of successful decongestion. Supplemental O2 is a common treatment in dogs with severe CHF. The time from start to discontinuation of supplemental O2 therapy (DCSO2) typically reflects the time course and ease of decongestion. Hypothesis/Objectives Urine Na concentration after IV administration of furosemide will be correlated with duration of treatment with supplemental O2 (timeO2) and the cumulative frequency of successful DCSO2 during hospitalization. Animals Fifty‐one dogs with acute CHF. Methods Retrospective observational single center study. Results Dogs with low uNa had significantly longer mean timeO2 than dogs with high uNa (uNa