How do I manage and monitor a cat diagnosed with hypertrophic cardiomyopathy long-term?

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Feline hypertrophic cardiomyopathy (HCM) management is stratified by disease stage: preclinical cats with left atrial enlargement (LAE) receive clopidogrel for arterial thromboembolism (ATE) prevention, while cats in congestive heart failure (CHF) require loop diuretics as the cornerstone of treatment. --- Prognosis and risk stratification should anchor every monitoring conversation with owners. In preclinical HCM cats, CHF or ATE occurred in 30.5% and cardiovascular death in 27.9% over the study period. Risk of CHF at 1, 5, and 10 years was 7.0%, 19.9%, and 23.9%, respectively; risk of ATE at those same intervals was 3.5%, 9.7%, and 11.3%. Cardiovascular death risk at 1, 5, and 10 years was 6.7%, 22.8%, and 28.3%, respectively. Once cardiovascular morbidity develops, mean survival is 1.3 ± 1.7 years. Only 10% of preclinical HCM cats reach 9–15 years. 1 All-cause mortality is significantly greater in preclinical HCM cats than apparently healthy cats (65% vs. 40%) due to the cardiovascular death burden superimposed on noncardiovascular causes. 4 Cats with HCM and a concurrent arrhythmia at diagnosis carry approximately 3 times the risk of death compared to HCM cats without an arrhythmia. 2 Echocardiography is the definitive diagnostic and monitoring tool. Mild to moderate left ventricular (LV) wall thickening is a diagnosis of exclusion — hyperthyroidism, systemic hypertension, acromegaly, and dehydration must be ruled out before attributing LV hypertrophy to HCM. 3 LAE on echocardiography identifies high-risk cats who may have no murmur on physical examination. 6 Dynamic left ventricular outflow tract obstruction (DLVOTO) from systolic anterior motion (SAM) of the mitral valve is the most common cause of a murmur in HCM cats; severe DLVOTO warrants treatment, while lesser degrees do not. 3 Advanced echocardiographic techniques including speckle tracking echocardiography (STE) and tissue motion annular displacement (TMAD) can detect longitudinal systolic dysfunction