Echocardiography, a non-invasive method for the investigation of heart morphology and function in laboratory dogs: 1. Method and reference values for M-mode parameters.

We have set up M-mode echocardiographic (EC) recording in beagles in our laboratory and generated reference values for EC indicators of left ventricle function and morphology. Additionally we assessed the effects of sex, strain and body weight on these parameters and the correlation between parameters. M-mode EC under two-dimensional guidance in longitudinal section was performed on 59 male and 49 female beagles from Marshall (USA) and 13 males and 13 females from Harlan (France). The following parameters were measured or calculated: left ventricle internal diameter in diastole and systole (LVIDd and LVIDs), left ventricle and diastolic and end systolic and stroke volumes (EDV, ESV and SV), cardiac output and index (CO and CI), fractional shortening (FS), ejection fraction (EF), the thickness of the septum and left ventricle posterior wall in diastole (STd and LVPWd) and systole (STs and LVPWs), the percentage of thickening of the septum and left posterior wall (PST and PWT), and the mean and maximal velocities of the left ventricle posterior wall (PWVm and PWVM). Heart rate (HR) was measured by cardiac auscultation. Marshall dogs have higher left ventricle dimensions but lower amplitude and velocity of contraction than Harlan dogs. There were also statistically significant differences between sexes for a number of EC parameters mainly those relating to the size of the left ventricle walls or cavity in diastole. Overall these differences were explained by the correlation between these parameters and body weight. Heart rate correlated only with PWVm and PWVM. There were positive correlations between PST, PWT and EF or FS and between velocities and FS or EF. EDV correlates negatively with EF, FS, PST or PWT.