Simpson's method of discs for measurement of echocardiographic end-diastolic and end-systolic left ventricular volumes: Breed-Specific reference ranges in boxer dogs

Abstract

Background: Boxer dogs are predisposed to congenital and adult onset cardiac diseases. Breed-specific reference values for M-mode and Doppler echocardiographic measurements previously have been established. Left ventricular (LV) end-systolic (ESV) and end-diastolic volumes (EDV) can be measured by M-mode or two-dimensional methods, such as Simpson's method of discs (SMOD). Reference ranges for SMOD-derived LV volumes are lacking. Objectives: To determine reference intervals for EDV and ESV in Boxer dogs. Animals: Previously collected data from 85 healthy Boxers (37 males and 48 females) were used for analysis. Methods: Simpson's method of discs-derived EDV and ESV were measured using offline analysis by 1 observer, in both the right parasternal and the left apical views. Measurements were compared between both views and between male and female dogs using a t-test. Reference intervals were established using the mean + 2 × SD. Results: Measurements obtained from both views showed good agreement, and mean EDVI and ESVI, indexed to body surface area (BSA), were calculated. Reference intervals were 49-93 mL/m2 for EDVI, and 22-50 mL/m2 for ESVI. EDV and ESV were significantly higher in males compared with females, when indexing to BSA, but not when indexing to body weight. Conclusion and Clinical Importance: The upper limit for ESVI exceeds the previously suggested cut-off of 30 mL/m2 for detection of systolic dysfunction. The reference intervals generated in this study should be useful clinically in the assessment of LV size and function in Boxer dogs. © 2013 by the American College of Veterinary Internal Medicine.