Death by heartbreak? TMT in cats

Although heartbreak is one of life’s worst experiences, “dying from a broken heart” isn’t just a dramatic song lyric. In people, Takotsubo cardiomyopathy (also known as “broken heart syndrome”) is triggered by severe physical or emotional stress. It causes transient heart muscle dysfunction that mimics a heart attack, including shortness of breath, chest pain, and ECG changes. Unlike a true myocardial infarction, there is usually no significant coronary obstruction, and many patients recover fully with supportive care.

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So, what about cats?

Emerging evidence suggests that some cats can also develop reversible cardiac changes following stress, including a traumatic event or anaesthesia. These cats often present exactly like hypertrophic cardiomyopathy (HCM) with congestive heart failure (CHF), myocardial thickening, arrhythmias, and tachycardia.

What do these cases look like?

• More commonly seen in younger cats
• Signs of congestive heart failure: tachypnoea or dyspnoea
• Examination findings: tachycardia, heart murmurs, gallop sounds, arrhythmias
• Diagnostics: myocardial hypertrophy, pulmonary oedema +/- pleural effusion, sometimes increased cardiac troponin or ST segment elevation on ECG
• Often preceded by a stressful or traumatic event, including anaesthesia for non-cardiac procedures

Despite presenting like HCM with CHF, follow-up often shows reverse remodelling, sometimes even after stopping treatment. In the absence of other causes of an HCM phenotype, this condition is termed Transient Myocardial Thickening (TMT).

These comparative images are taken from a paper on TMT associated with CHF in cats (Novo Matos J, Pereira N, Glaus T, et al. Transient Myocardial Thickening in Cats Associated with Heart Failure. J Vet Intern Med. 2018;32(1):48-56. doi:10.1111/jvim.14897) (https://pubmed.ncbi.nlm.nih.gov/29243322/ )

Unsure if the HCM phenotype fits the clinical picture? Discuss your case with HeartVets or refer to our cardiologists for further investigations.

Why the distinction matters

• Advanced HCM usually carries a guarded prognosis, requires long-term medication, and carries risk of acute events such as aortic thromboembolism or fatal arrhythmia.
• TMT by contrast, can have a much more favourable outlook with potential for full recovery.
• Differentiating the two requires echocardiography, careful history-taking, and ongoing monitoring.

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Other important considerations

• Myocarditis can mimic both HCM and TMT. Possible causes include Toxoplasma gondii, Bartonella species, viral infections, toxins, or drug hypersensitivity. Further testing may be required.
• Cats with TMT may experience recurrent CHF episodes if subjected to similar stressors in the future.
• Studies suggest cats with TMT generally have thinner left ventricular walls and less left atrial enlargement than those with HCM, but this distinction can be difficult in acute CHF.

Takeaway for practice

Remember that HCM is a diagnosis of exclusion – you need to actively search for and screen out other causes of left ventricular hypertrophy. In a cat over 8 this includes systemic hypertension and hyperthyroidism, in younger cats think of TMT and in cats of any age, acromegaly is a (rare) consideration. While TMT is far less common than HCM, recognising it can dramatically affect management, prognosis, and owner communication. Echocardiography, clinical monitoring, and attention to recent stressors are key to identifying these cases.

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