Atenolol and survival in cats with asymptomatic hypertrophic cardiomyopathy.

and time to death were recorded. Key results: There was no significant difference in cardiac mortality between HCM cats treated with atenolol (10 of the 42 cats died [24 per cent]) and those not treated with atenolol (four of the 21 cats died [19 per cent]) after five years; P=0.756. There was no significant difference in all cause mortality between HCM cats treated with atenolol (45 per cent died) and those not treated with atenolol (38 per cent died) after five years; P=0.727. There was no significant difference in non-cardiac mortality between HCM cats treated with atenolol (21 per cent died) and those not treated with atenolol (19 per cent died) after five years; P=1.000. The time to death (all cause mortality) of cats that died within the study period was not significantly different between HCM cats treated with atenolol (mean [sd] 1133 days [503 days]) and those not treated (mean 1043 days [659 days]); P=0.061. Survival after five years in cats without dynamic left ventricular outflow tract obstruction (DLVOTO) was not significantly different whether treated with atenolol or not (P>0.33). Group sizes were not large enough to assess this for cats with DLVOTO. There was no significant difference in all cause mortality within five years between cats with HCM and control cats (P=0.445), although significantly higher cardiac death in the HCM group (22 per cent) compared to the control group (0 per cent) was seen; P=0.026. Study weaknesses: There were some differences in baseline characteristics between the treated with atenolol and not treated with atenolol groups which could affect the results. At the beginning of the study, the atenolol-treated group of cats with HCM had a significantly higher incidence of DLVOTO, significantly more left ventricular hypertrophy, a significantly higher grade of heart murmur, significantly higher peak velocity of left ventricular outflow, and a significantly larger left atrial size than the HCM cats not treated with atenolol (P<0.05). The group sizes were relatively small and there was no justification of the sample size; group sizes were too small to compare survival with or without atenolol in cats with DLVOTO. No measure was made of quality of life or clinical wellbeing. Following the start of the study, additional treatments varied for the cats. Owner compliance was assumed in medication administration. The control cats were younger than the cats with HCM and all had a systolic heart murmur.