Echocardiographic evaluation of dogs with dysautonomia

Abstract

Objective - To describe echocardiographic findings in dogs with dysautonomia. Design - Prospective case series. Animals - 20 dogs with dysautonomia (13 confirmed during necropsy and 7 with results of antemortem testing [tear production, pilocarpine response test, atropine response test, and ID histamine response] supportive of the diagnosis). Procedures - Dogs with dysautonomia were evaluated by use of echocardiography, and M-mode measurements were obtained on all dogs. A dobutamine response test was performed on 1 dog, starting at a rate of 1 μg/kg/min and doubling the rate every 15 minutes until fractional shortening (FS) increased to < 2 times the baseline value. Results - Evidence of systolic dysfunction was detected in 17 of 20 dogs with dysautonomia, as determined on the basis of FS (median, 17.9%; range, 4.0% to 31.1 %). Left ventricular internal dimension during diastole or left ventricular internal dimension during systole was enlarged in 4 of 20 and 14 of 20 dogs, respectively. Enlargement of the left atrium or aorta was identified in 3 of 15 and 1 of 15 dogs in which it was measured, respectively. Administration of dobutamine at a rate of 4 μg/kg/min resulted in dramatic improvement in FS (increase from 4% to 17%) in the 1 dog tested. Conclusions and Clinical Relevance - Results suggested that echocardiographic evidence of diminished systolic function was common in dogs with dysautonomia. Whether the diminished function was a result of sympathetic denervation or myocardial hibernation was unclear, aitnougn myocardial hibernation was more likely.