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Heart: hypertrophic cardiomyopathy (HCM)
Synonym(s): heart, cardiac, HOCM
Introduction
- Cause: unknown. Heritable in Maine Coon, Ragdolls, and probably Persians and Sphynx cats.
- Signs: sudden onset in apparently well cat, acute dyspnea, lethargy or signs of thromboembolism.
- Diagnosis: biomarkers, ultrasound, radiography, ECG.
- Treatment: diuresis, vasodilators, beta-blockers (in certain cases of HOCM and not when decompensated heart failure).
- Prognosis: variable.
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Presenting signs
- None, asymptomatic changes on ausculation (murmur not always present) Cardiac: sounds - overview.
- Lethargy.
- Dyspnea.
- Mouth breathing.
- Cyanosis.
- Syncope Syncope.
- Anorexia/inappetence.
- Signs of thromboembolism Thromboembolism: aorta.
- Collapse.
Acute presentation
- Sudden death.
- Hindleg paresis in cases of thromboembolism Thromboembolism: aorta.
- Death.
- Severe respiratory distress.
Age predisposition
- Young to middle-aged (mean age 6-5 years).
- Some breeds reported to present at a younger age than others, eg Ragdoll, Maine Coon and Sphynx.
Breed/Species predisposition
- Domestic short-hair British shorthair.
- Persians Persian longhair.
- Maine Coon Maine Coon.
- Ragdoll Ragdoll.
- Sphynx Sphynx.
Special risks
- Anesthesia Anesthesia: in cardiovascular insufficiency.
- Sedation Sedation or sedative protocol.
- Stress.
Pathogenesis
Etiology
- Two forms of HCM occur:
- Primary:
- Largely unknown in idiopathic form.
- Ragdoll (R820W) and Maine Coon (A31P) can have inheritable form associated with myosin binding protein C.
- Other inherited predispositions likely as in humans.
- Oversensitivity to circulating catecholamines may be involved.
- Secondary:
- Hyperthyroidism Hyperthyroidism.
- Outflow obstruction, eg congenital aortic stenosis Heart: aortic stenosis.
- Possibly related to hypertension Hypertension, eg in renal disease.
- Possibly related to growth hormone disorders Acromegaly.
- Primary:
Pathophysiology
- Characterized by hypertrophied non-dilated left ventricle.
- Left ventricular diastolic dysfunction → decreased distensibility of myocardium → increase in end-diastolic pressure with normal or reduced volume.
- Increased muscle mass, myocardial fibrosis, disordered arrangement of myofibrils → decreased distensibility.
- Abnormal myocardial relaxation → prolonged relaxation period and decreased rate of decline of left ventricular pressure.
- Decreased capillary density in myocardium, abnormally narrowed intramural coronary arteries, increased resistance in large coronary arteries due to systolic pressures → myocardial ischemia.
- Myocardial ischemia → abnormal relaxation, increased left ventricular filling pressures.
- May be mild hypertrophy with severe left heart failure - probably due to abnormal myocyte function.
- Systolic anterior motion of the mitral valve (SAM) might be present due to abnormal mitral valve apparatus/papillary muscle geometry resulting in hypertrophic obstructive cardiomyopathy (HOCM).
Systemic thromboembolism
- Turbulence → damages cardiac endothelium → endocardial collagen induces platelet adhesion and aggregation, extrinsic pathway activation Hemostatic disorders: acquired.
- Circulation of blood through heart is abnormal → areas of sluggish flow allow aggregation of platelets.
- Higher levels of serotonin in felines due to larger platelets than dogs and humans, felines more sensitive to effects of serotonin → higher susceptibility to aggregation.
Timecourse
- Onset can appear rapid.
- Survival can be months to years.
Diagnosis
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Treatment
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Prevention
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Outcomes
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Further Reading
Publications
Refereed papers
- Recent references from PubMed and VetMedResource.
- Luis Fuentes, V, Abbott, J, Chetboul, V et al (2020) ACVIM consensus statement guidelines for the classification, diagnosis, and management of cardiomyopathies in cats. J Vet Intern Med 34, 1062-1077 PubMed.
- Fox P R, Keene B W, Lamb K et al (2018) International collaborative study to assess cardiovascular risk and evaluate long-term health in cats with preclinical hypertrophic cardiomyopathy and apparently healthy cats: The REVEAL Study. J Vet Intern Med 32 (3), 930-943 PubMed.
- Cote E (2017) Feline congestive heart failure: Current diagnosis and management. Vet Clin North Am Small Anim Pract 47 (5), 1055-1064 PubMed.
- Luis Fuentes V, Wilkie L J (2017) Asymptomative hypertrophic cardiomyopathy: Diagnosis and therapy. Vet Clin North Am Small Anim Pract 47 (5), 1041-1054 PubMed.
- Hogan DF, Fox P R, Jacob K et al (2015) Secondary prevention of cardiogenic arterial thromboembolism in the cat: The double-blind, randomized, positive-controlled feline arterial thromboembolism; clopidogrel vs. aspirin trial (FAT CAT). J Vet Cardiol Supplement 1: S306-317 PubMed.
- Koffas H, Dukes-McEwan J, Corcoran B M et al (2006) Pulsed tissue Doppler imaging in normal cats and cats with hypertrophic cardiomyopathy. J Vet Intern Med 20 (1), 65-77 PubMed.
- Connolly D J, Cannata J, Boswood A et al (2003) Cardiac troponin I in cats with hypertrophic cardiomyopathy. J Feline Med Surg 5 (4), 209-216 PubMed.
- Kraus M S, Calvert C A & Jacobs G J (1999) Hypertrophic cardiomyopathy in a litter of five mixed breed cats. JAAHA 35 (4), 293-296 PubMed.
- Rush J E, Freeman L M, Brown D J et al (1998) The use of enalapril in the treatment of feline hypertrophic cardiomyopathy. JAAHA 34 (1), 38-41 PubMed.
Other sources of information
- Chetboul V (2017) Feline myocardial diseases. In: Textbook of Veterinary Internal Medicine. Ed. Ettinger & Feldman. pp 1278-1305.