Cat heart disease in 2026 means feline hypertrophic cardiomyopathy (HCM), thickening of the heart's main pumping muscle. Penn Vet reports it affects about 1 in 7 apparently healthy cats, with risk rising with age, and 2026 care centers on staging and early action.
Penn Vet HCM update Cornell University College of Veterinary Medicine describes HCM as the most commonly diagnosed cardiac disease in cats. It can appear from 4 months to 16 years old and reduces pumping efficiency. Cornell cardiology overview.
Table of Contents
- Who develops HCM most often?
- What does HCM do inside the body?
- How do vets confirm HCM?
- What do HCM stages mean?
- What should owners do in 2026?
Who develops HCM most often?
HCM can affect any cat, but prevalence rises with age. Penn Vet links higher inherited risk to Maine Coon and Ragdoll breeds through cardiac sarcomere mutations. A 2026 Frontiers review puts prevalence at 14.7% in apparently healthy cats.
That age and breed pattern shapes screening decisions. Owners of older cats and those breeds gain the most from proactive heart checks. Risk never equals certainty, so individual testing still matters.
What does HCM do inside the body?
Most cats with HCM stay subclinical with no outward signs. NC State Veterinary Hospital notes a small proportion progress to congestive heart failure, left-atrial enlargement, fainting, or arterial thromboembolism.
Thromboembolism can block blood flow to the hind limbs. It causes sudden pain, paralysis, or death. Heart failure allows fluid to build in the lungs.
- Sudden trouble breathing or rapid breathing
- Fainting, collapse, or extreme lethargy
- Sudden hind-leg pain, weakness, or paralysis
- Cold hind limbs or crying out in pain
How do vets confirm HCM?
Echocardiography is the gold standard for diagnosis. The Schwarzman Animal Medical Center says it measures wall thickness plus chamber size and function. Clinicians must first rule out hypertension, hyperthyroidism, and dehydration that also thicken heart muscle.
That rule-out step prevents misdiagnosis and wrong treatment. Blood pressure measurement, thyroid testing, and hydration assessment come before a final HCM label. An echo then tracks change over time.
What do HCM stages mean?
The ACVIM consensus classifies feline cardiomyopathies by phenotype. The Journal of Veterinary Internal Medicine staging moves cats from Stage A at-risk with no disease through subclinical Stage B at low versus higher risk to clinical heart failure or thromboembolism.
Stage guides prognosis and treatment choices. Stage A calls for monitoring of at-risk breeds. Stage B separates low-risk cats from higher-risk cats that need closer echo follow-up and preventive planning.
What should owners do in 2026?
On March 14, 2025, the FDA gave conditional approval to Felycin-CA1 delayed-release sirolimus tablets for ventricular hypertrophy in cats with subclinical HCM. The agency listing marks it as the first FDA-approved drug for any feline HCM indication. FDA approval listing In the 36-cat RAPACAT study, TriviumVet prescribing materials report treated cats averaged a 0.17 mm reduction in left-ventricular maximal wall thickness versus a 0.94 mm increase with placebo.
Dosing is once weekly with liver and bloodwork screening. The 2026 Frontiers review reports 11.3% ten-year thromboembolic risk in preclinical cohorts and argues atrial dysfunction should center diagnosis and emerging sirolimus and echo-tracking therapy. Frontiers review abstract Bring breed, age, and any fainting or leg-pain episode to the visit to speed staging.
- Ask about echo screening for senior cats, Maine Coons, and Ragdolls
- Ask what rule-outs apply before an HCM diagnosis
- Ask about stage, recheck timing, and emergency signs
- For subclinical HCM, ask whether weekly sirolimus fits and what liver and blood monitoring it needs