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Atenolol and survival in cats with asymptomatic hypertrophic cardiomyopathy

Clinical Scenario

One of your colleagues asks you to scan Rupert, a 5 year old, male neutered, domestic long-haired cat, as she detected a heart murmur at his vaccination last week. On clinical examination you find no abnormalities except a grade 2-3/6 systolic heart murmur which you think is of greatest intensity on the left hand side. Rupert’s owners think he is fine and had no concerns prior to his vaccination. On echocardiography you find significant thickening of the left ventricular wall at the end of diastole and diagnose asymptomatic hypertrophic cardiomyopathy (HCM). Rupert’s owners want to know if they should treat him or not, as they are worried that he will develop heart failure and they will lose him. You wonder if beginning administration of beta blockers while Rupert is asymptomatic will help improve Rupert’s life expectancy......

3-Part Question (PICO)

In [cats with asymptomatic hypertrophic cardiomyopathy] does [atenolol versus no treatment] [improve life expectancy]?

Search Strategy and Summary of Evidence

Search Strategy

MEDLINE(R) In-Process & Other Non-Indexed Citations and MEDLINE(R) 1946 to Present using the OVID interface

(cat.mp. OR cats.mp. OR feline.mp. OR felines.mp. OR felis.mp. OR exp Cats/)

AND

(heart disease.mp. OR heart diseases.mp. OR cardiomyopathy.mp. OR cardiomyopathies.mp. OR cardio myopathy.mp. OR cardio myopathies.mp. OR cardiac disease.mp. OR cardiac diseases.mp. OR HCM.mp. OR exp Heart Diseases/ OR exp Cardiomyopathies/ OR exp Cardiomyopathy, Hypertrophic/)

AND

(atenolol.mp. OR betablocker$.mp. OR beta blocker$.mp. OR tenormin.mp. OR b1 blocker$.mp. OR b1 antagonist$.mp. OR exp Atenolol/ OR exp Adrenergic beta-Antagonists/)

CAB Abstracts 1910 to Present using the OVID interface

(cat.mp. OR cats.mp. OR feline.mp. OR felines.mp. OR felis.mp. OR exp cats/)

AND

(heart disease.mp. OR heart diseases.mp. OR cardiomyopathy.mp. OR cardiomyopathies.mp. OR HCM.mp. OR cardiac disease.mp. OR cardiac diseases.mp. OR cardio myopathy.mp. OR cardiomyopathies.mp. OR exp heart diseases/ OR exp cardiomyopathy/)

AND

(atenolol.mp. OR beta blocker.mp. OR beta blockers.mp. OR betablockers.mp. OR betablocker.mp. OR b1 blocker.mp. OR b1 blockers.mp. OR b1 antagonist.mp. OR b1 antagonists.mp. OR tenormin.mp. OR exp atenolol/ OR exp beta-adrenergic receptors/ OR exp beta-blockers/)

Search Outcome

MEDLINE

  • 250 papers found in MEDLINE search
  • 248 papers excluded as they don't meet the PICO question
  • 0 papers excluded as they are in a foreign language
  • 1 papers excluded as they are review articles/in vitro research/conference proceedings
  • 1 total relevant papers from MEDLINE

CAB Abstracts

  • 38 papers found in CAB search
  • 36 papers excluded as they don't meet the PICO question
  • 0 papers excluded as they are in a foreign language
  • 0 papers excluded as they are review articles/in vitro research/conference proceedings
  • 2 total relevant papers from CAB

Total relevant papers

2 relevant papers from both MEDLINE and CAB Abstracts

Comments

The 2 references found in CAB were the same study (one was a summary), so only one of the references is included in the evidence summary.

Summary of Evidence

Schober KE, 2013, USA

Title: Effect of treatment with atenolol on 5-year survival in cats with preclinical (asymptomatic) hypertrophic cardiomyopathy
Patient group: Cats with preclinical hypertrophic cardiomyopathy
N=63, 42 cats treated with atenolol, 21 not treated with atenolol
Study Type: Cohort study
Outcomes:
  • 5 year cardiac and all cause morbidity and mortality
  • Cause of death
  • Time to death
Key Results:
  • No significant difference in cardiac mortality between HCM cats treated with atenolol versus not treated with atenolol after 5 years (10/42 died (24%) vs 4/21 died (19%); p = 0.756).
  • No significant difference in all cause mortality between HCM cats treated with atenolol versus not treated with atenolol after 5 years (45% died vs 38% died, p = 0.727).
  • No significant difference in non-cardiac mortality between HCM cats treated with atenolol versus not treated with atenolol after 5 years (21% died vs 19% died, p = 1.000).
  • Time to death (all cause mortality) of cats that died within the study period was not significantly different between HCM cats treated with atenolol or not treated (1133+/-503 days vs 1043+/-659 days, p=0.061).
  • Survival at 5 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 for cats with DLVOTO.
  • No significant difference in all-cause mortality within 5 years between cats with HCM and control cats (p=0.445), although significantly higher cardiac death in HCM group compared to control group (22% cardiac death vs 0% cardiac death, p = 0.026).
Study Weaknesses:
  • 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 LVOT and a significantly larger left atrial size than the HCM cats not treated with atenolol (p<0.05)
  • Relatively small group sizes and no sample size justification; group sizes too small to compare survival with or without atenolol in cats with DLVOTO
  • No measure made of quality of life/clinical well being
  • Following the start of the study, additional treatments varied for the cats
  • Owner compliance assumed in medication administration
  • The control cats were younger than the cats with HCM and all had a systolic heart murmur
Attachment:
No attachments.

Comments

This is a relatively small, prospective observational cohort study and as such, no randomisation or blinding was used creating a greater potential for bias than with a randomised controlled trial. An appropriately powered randomised controlled trial would provide more reliable evidence, however, as highlighted in this study, the lack of a positive control drug and the potential unwillingness of owners to administer a placebo drug over a period of time would make this difficult. In particular, a trial focussing on the use of atenolol in HCM cats with DLVOTO (as the untreated group was too small in this study) would help to clarify any advantage of this drug in this subgroup of asymptomatic HCM cats.

The majority of cats in the study are reported as being DSH with a few other unnamed breeds potentially influencing the application of results to other populations of cats.


Bottom line

There is currently no evidence to suggest that long term administration of atenolol in cats with asymptomatic HCM will improve their 5 year survival time.

Disclaimer

The BETs on this website are a summary of the evidence found on a topic and are not clinical guidelines. It is the responsibility of the individual veterinary surgeon to ensure appropriate decisions are made based on the specific circumstances of patients under their care, taking into account other factors such as local licensing regulations. Read small print

References

Schober KE, Zientek J, Li X, Fuentes VL, Bonagura JD, (2013). Effect of treatment with atenolol on 5-year survival in cats with preclinical (asymptomatic) hypertrophic cardiomyopathy. Journal of Veterinary Cardiology 15: 93-104.

About this BET

First author:
Kathryn Wareham
Second author:
Rachel Dean
Institution:
CEVM, University of Nottingham
Search last performed:
2015-08-11 13:15:27
Original publication date:
2015-08-28 13:15:27
Last updated:
2015-08-28 13:15:27
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