Transeint myocardial thickening

Question 1

What is the pathomechanism for transient myocardial thickening

Answer 1

Some diseases can mimic HCM by causing an increase in left ventricular wall thickness but:
- it is not due to myocyte hypertrophy or hyperplasia
- not due to intracellular accumulation of metabolic products (storage diseases)
- not due to interstitial infiltration of proteins, cells or fluid such as in amyloidosis or myocarditis

The exact pathomechanism is not known but in view of the fast reverse remodelling seen, myocardial edema and/or transient cellular infiltration might be responsible

Question 2

Give some examples of diseases than can give a HCM phenotype

Answer 2

In cats, an HCM phenotype has been described with:
- endocrine disorders (e.g., hyperthyroidism, acromegaly)
- dehydration (pseudohypertrophy)
- infiltrative disease (e.g., cardiac lymphoma)

Question 3

What is the typical cat suffering from TMT

Answer 3

TMT occurs in younger cats (1.7 years versus 8 years) which have a history of an antecedent event (e.g., general anesthesia for neutering within days of presentation with CHF or corticosteroid administration)

Question 4

What are the potential causes of myocarditis leading to increased LVWT

Answer 4

Increased LVWT can occur with:
- toxoplasma myocarditis
- FIV myocarditis
- eosinophilic myocarditis

Question 5

How are cardiac troponin I in case of TMT

Answer 5

Cardiac troponin I is markedly elevated in most cats with TMT but some cats with TMT may have normal to mildly increased cTnI

Question 6

What is a specific echocardiographic difference between TMT and HCM

Answer 6

Cats with TMT have mild increases in left atrial size and decreased atrial fractional shortening
- these findings suggest an acute myocardial insult without time for the left atrium to adapt to the increased filling pressures (i.e., to dilate) which causes acute increase in left atrial and pulmonary capillary pressure resulting in acute pulmonary edema