Echocardiographic reference intervals and cut-off values to diagnose dilated cardiomyopathy in guinea pigs (Cavia porcellus)

Abstract

The objective of this study was to establish reference intervals in healthy guinea pigs and to calculate optimal cut-off values for several M-Mode parameters to diagnose dilated cardiomyopathy (DCM) phenotype. This prospective study included 146 guinea pigs. The apparently healthy group included 92 animals and was used to create reference intervals for left ventricular internal diameter in diastole (LVIDd), left ventricular internal diameter in systole (LVIDS), E-point-to-septal separation (EPSS), diastolic wall thickness and left atrium and aorta. Allometric scaling was used to normalize LVIDd(-n) and LVIDs(-n) to body weight with a scaling exponent (BWexp). The DCM phenotype group included 54 subjects and was used to calculate optimal cut-off values of several M-mode parameters. Guinea pigs with DCM phenotype had significantly larger measurements of LVIDd, LVIDs and EPSS, as well as lower FS and wall thicknesses compared to apparently healthy guinea pigs. Allometric scaling exponents to normalize LVIDd and LVIDs to BW (g) were 0.336 and 0.346, respectively. The highest area under the curve (AUC) to diagnose DCM were found for LVIDs-n (cut-off value >0.74 mm, AUC 0.996), FS (cut-off value <29%, AUC 0.995), LVIDd-n (cut-off value >1.07 mm, AUC 0.980) and EPSS (cut-off value >1.4 mm, AUC 0.944). M-mode and 2D reference intervals for guinea pigs are presented, including lower and upper limits. Diagnosis of DCM phenotype in guinea pigs can be established using parameters known to be useful in other species, namely LVIDs, LVIDs-n, FS, LVIDd, LVIDd-n and EPSS.