The assessment of the severity of left ventricular (LV) hypertrophy in human medicine consists of three main cardiac parameters: LV wall thickness, LV mass (LVM), and LV geometry. The latter is assessed either by LVM/body surface area (BSA) and relative wall thickness, RWT. Based on LV geometry, the LV is classified as normal if LVM/BSA and RWT are within reference ranges, concentric remodelling as normal LVM and increased RWT, concentric hypertrophy as increased LVM and RWT and eccentric hypertrophy as normal/decreased RWT and increased LVM. Data about normal values for LVM and RWT are scant in dogs.

The aims of this retrospective study were: 1) to determine normal values for LVM/BSA e RWT (M-mode derived) in healthy dogs, 2) to evaluate the effect of sex, age, and breed on these echocardiographic parameters and 3) to compare LVM/BSA e RWT in healthy (>7 years) and hypertensive dogs.

The clinical archive (2015–2016) of the cardiology unit of DIMEVET (University of Milan, Italy) was searched for all dogs with a complete echocardiographic examination and systemic blood pressure determination. Dogs were grouped into healthy (based on no cardiac, metabolic, or renal disease) or hypertensive (according to ACVIM guidelines). From the digitally stored echocardiographic M-mode data, LVM/BSA and RWT were calculated. LVM was derived from geometric formula and indexed to BSA. RWT was calculated as the ratio between 2x posterior wall thickness and LV internal diameter at end diastole.

Eighty-three healthy dogs (48 female/35 male) and 26 hypertensive dogs were included in the study. The mean (SD) LVM/BSA and RWT were respectively 151g/m² (57) and 0.53 (0.10) in healthy dogs. No difference in sex and age (dogs >7 years vs. <7 years) was found. Sighthound dogs (n=20) showed a statistically larger LVM/BSA (221 g/m² vs. 129 g/m², p=0.00) with similar RWT than non-sighthound dogs (n=63) (0.54 vs. 0.53, p=0.74). Hypertensive dogs showed otherwise a statistically different RWT (0.69 vs. 0.55 p=0.011) from healthy dogs >7 years with similar LVM (153 vs. 132 g/m², p=0.098).

The results of our study suggest that these echocardiographic parameters may be of help in routinely classifying the hypertrophy pattern/LV geometry in dogs. In contrast with human findings, no sex difference was found in LVM/BSA. Sighthound dogs tended to show greater LVM/BSA values, likely to represent physiologic hypertrophy (normal RWT with increased LVM/BSA). Dogs with systemic hypertension had increased RWT with normal LVM and this could represent the first response of the LV to pressure overload.

Disclosures

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