Atenolol Use in Cats with Subclinical Hypertrophic Cardiomyopathy

In the Literature

Coleman AE, DeFrancesco TC, Griffiths EH, et al. Atenolol in cats with subclinical hypertrophic cardiomyopathy: a double-blind, placebo-controlled, randomized clinical trial of effect on quality of life, activity, and cardiac biomarkers. J Vet Cardiol. 2020;30:77-91.

The Research …

Hypertrophic cardiomyopathy (HCM) is the most common cardiovascular disorder in cats, affecting up to 29.4% of feline patients.¹ Cats with clinical signs of HCM are often treated with diuretics, angiotensin-converting–enzyme inhibitors, β blockers, or antiplatelet and anticoagulant medications.² However, evidence-based data supporting specific and ideal therapies for subclinical feline HCM are lacking. Diagnostic findings for subclinical HCM include thickened left ventricular walls and left atrial dilation in the absence of other disease (eg, congenital heart disease, hyperthyroidism, systemic hypertension).  

This study* evaluated pet owner-perceived quality of life and activity levels in cats with subclinical HCM and lifestyle-matched healthy controls, as well as owner-perceived quality of life, quantitative activity measurements, cardiac biomarkers, and echocardiographic variables in cats with preclinical HCM, with and without atenolol therapy.  

A total of 27 healthy cats and 32 cats with subclinical HCM were included. As compared with healthy cats, cats with subclinical HCM had significantly more arrhythmias, higher cardiac troponin I concentrations, and higher N-terminal pro-B natriuretic peptide concentrations. There was no difference in overall activity scores or quality of life scores between healthy cats and cats with subclinical HCM. 

Of the 32 cats with subclinical HCM, 16 were randomized and given atenolol (6.25 mg PO every 12 hours; dosage was the same regardless of body weight, BCS, or echocardiographic findings) and 16 were given a placebo. All HCM patients were reassessed at baseline and again at 6 months. Cats receiving atenolol had significantly lower heart rate and murmur grades compared with cats receiving a placebo. In cats with subclinical HCM, atenolol treatment did not significantly affect systemic blood pressure, echocardiographic variables, quality of life, or activity levels.  

Atenolol has been prescribed by veterinary cardiologists to manage HCM, with the main goal of prolonging the subclinical phase of disease while maintaining a high quality of life. Atenolol use in humans with HCM remains a mainstay therapy, with evidence of improved clinical condition. In the present study, some benefits were noted in cats that had subclinical HCM and were receiving atenolol, but there was no significant improvement in all areas assessed. More significant results may occur in cats with severe subclinical HCM if an alternative survey is offered or if higher doses of atenolol are administered.

… The Takeaways

Key pearls to put into practice:

• Cats are often difficult to medicate. There are some benefits to atenolol therapy in cats that have subclinical HCM, but it is important to weigh the pros and cons of treatment and prescribe medications most likely to improve quality of life and longevity. Antiplatelet therapy can be prioritized in some cases.

• Atenolol therapy may be most useful when given based on the patient’s body size and BCS and on the severity of echocardiographic findings.

• Baseline diagnostics should be obtained prior to initiating medical therapy in cats with subclinical HCM. Recheck is needed after 6 months, and treatment should be adjusted to maximize positive effects.

*This study was funded by a grant from Morris Animal Foundation with additional support provided by IDEXX Laboratories.