Effect of treatment with atenolol on 5-year survival in cats with preclinical (asymptomatic) hypertrophic cardiomyopathy
Introduction
Hypertrophic cardiomyopathy (HCM) is the most common cardiac disease in cats, leading to clinical signs and considerable mortality.1, 2, 3, 4, 5 While recommendations for medical therapy of HCM with congestive heart failure are generally consistent,6 treatment of cats with preclinical (asymptomatic) HCM remains controversial, largely owing to the absence of evidence from prospective controlled outcome studies.6, 7 Most treatments have been extrapolated from theoretical benefits, mechanistic studies, and observations made in other species. Disease characteristics that might be favorably modified by the institution of medical therapy in cats with preclinical HCM include left ventricular (LV) hypertrophy, myocardial fibrosis, dynamic LV outflow tract obstruction (DLVOTO), LV diastolic dysfunction, myocardial ischemia, ventricular arrhythmias, predisposition to thrombosis, left atrial (LA) dysfunction, “unwanted” or stress-induced tachycardia,8 and abnormal neurohormonal activation. However, the pathophysiologic importance of these therapeutic targets in feline HCM is still poorly understood, so that “watchful waiting”, rather than pharmacological intervention, has been advocated by some cardiologists in cats with preclinical HCM.6, 7 Others favor the use of negative inotropic and chronotropic agents in HCM, as such treatments seem highly successful in alleviating outflow gradients and controlling heart rate.6,d
Selective and non-selective beta-adrenergic blocking agents such as atenolol or propranolol are empirically used in the treatment of cats with HCM4, 6, 9 before the onset of clinical signs despite a lack of supportive data on their long-term benefits. However, in the authors' experience, the administration of beta adrenergic blockers to cats with HCM and DLVOTO may lead to clinical improvement with regard to activity and exercise level. Nevertheless, in another study, addition of atenolol to furosemide in the treatment of cats with cardiomyopathy and compensated heart failure did not reveal any advantage in clinical outcome.e In addition, administration of atenolol at therapeutic doses to healthy cats10,f and cats with HCMd resulted in reduced LA mechanical function, increased LA size, and decreased flow velocity in the left auricle, raising concern with regards to the safety of beta blocker use in cats with HCM. To the authors' knowledge, no studies have investigated the clinical outcomes of treating preclinical HCM with atenolol in cats.
The objective of this study was to prospectively evaluate the effect of treatment with atenolol on 5-year survival in cats with preclinical HCM. We hypothesized that administration of atenolol would improve 5-year outcome.
Section snippets
Animals, materials and methods
The study protocol was reviewed and approved by the Animal Care and Use Committee and the Institutional Review Board of the Department of Veterinary Clinical Sciences, College of Veterinary Medicine, The Ohio State University, Columbus, Ohio.
Results
A total of 94 cats entered the study: 63 cats with HCM and 31 healthy control cats. Group characteristics are presented in Table 1, Table 2, Table 3. There was no difference between control cats and cats with HCM with regards to BW, gender, and breed. Cats with HCM were slightly older than control cats (P = 0.045; Table 1). All cats (control and HCM) had systolic heart murmurs, although murmur intensity was different between groups (P < 0.001). Cats with HCM had a higher frequency of gallop
Discussion
To the authors' knowledge, the long-term effect of atenolol on outcome in cats with preclinical HCM has not been reported. The major findings of this prospective study revealed that (1) twice daily treatment with atenolol at recommended doses did not influence 5-year outcome in cats with preclinical HCM and (2) that 5-year survival was predicted by age at diagnosis and LA size, whereas severity of LV hypertrophy, class of diastolic function, and presence of DLVOTO were not independent predictor
Conclusions
Our study failed to demonstrate an effect of atenolol on 5-year survival in cats with preclinical HCM. Further randomized, controlled, long-term, variable dose, multicenter trials on the use of atenolol in cats with preclinical HCM are needed to better understand the therapeutic potential of beta adrenergic blockade in feline HCM.
Conflict of interest
None.
Acknowledgements
This study was supported by grants from The IAMS Company and IDEXX Laboratories, Inc. We would like to thank Becky Connors, Laura Spayd, and Patti Mueller for their contributions.
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2022, Journal of Veterinary CardiologyCitation Excerpt :There were more SAEs reported in the CG, which reflects mainly the ineffectiveness of the study drug since many of these SAEs were related to emergency treatment and hospitalization due to repeated CHF episodes. Beta blockers, and less frequently calcium channel antagonists, have been used in the management of cats with preclinical CMP [1,35,36,41–46]. However, concerns have been raised regarding potential adverse effects of these drugs in cats, including lethargy, inappetence, hypersalivation, weight loss, and reduced LA function [36,41–47].
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