Differences in Left Ventricular Enlargement Secondary to Chronic Volume Loading Between English Springer Spaniels and Two Similar Sporting Breeds

English springer spaniels have larger, rounder ventricles than most other breeds. How this geometry impacts responses to volume overload remains unknown. We compared left ventricular size between English springer spaniels and two similarly sized sporting breeds (Border collies and Labrador retrievers) in naturally occurring chronic left ventricular volume loading conditions (mitral regurgitation and patent ductus arteriosus [PDA]) to examine whether differences in remodelling responses exist between these breeds. We searched records for cases of mitral regurgitation and PDA in three breeds. We recorded age, sex, presence of congestive heart failure (CHF), body weight and specific echocardiographic variables. We compared normalised measures of left ventricular size between breeds. Cases with CHF were further examined as a separate group. One-hundred-and-ninety-one dogs were included: 110 with degenerative mitral valve disease, 42 with mitral dysplasia and 39 with PDA. One third of all cases had CHF. All measures of left ventricular size were larger in English springer spaniels in mitral regurgitation cases (P