EXPRESS: Efficacy of High-Dose Carvedilol Treatment for Cats with Stage B1 Obstructive Hypertrophic Cardiomyopathy.

High-dose carvedilol effectively reduces LVOT obstruction and myocardial injury in treatment-resistant feline oHCM.

This prospective interventional study evaluated high-dose carvedilol (HD) treatment in client-owned cats with Stage B1 obstructive hypertrophic cardiomyopathy (oHCM) that inadequately responded to standard-dose (SD) therapy. Eleven cats underwent echocardiographic assessment including speckle-tracking echocardiography for myocardial strain evaluation and cTnI assay for myocardial injury quantification. While SD treatment reduced left ventricular outflow tract velocity (LVOTV) from 4.9 m/s to 4.3 m/s, it remained above the 2.5 m/s threshold. HD treatment successfully reduced LVOTV below 2.5 m/s in 10/11 cats (1.6 m/s). Both SD and HD improved longitudinal strain in endocardial and epicardial layers compared to pre-treatment, with superior results in the HD group. Circumferential strain showed no changes. Most significantly, cTnI levels decreased progressively from pre-treatment (0.334 ng/mL) through SD (0.192 ng/mL) to HD (0.018 ng/mL), indicating reduced myocardial injury. No cats experienced adverse effects including bradycardia or hypotension. These findings suggest high-dose carvedilol effectively improves hemodynamics and myocardial function in treatment-resistant Stage B1 oHCM without safety concerns.

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