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Many individuals can be managed for 6 months to several years.In a retrospective study of 74 cats with HCM (Atkins et al. JAVMA, 1992):

  • Median survival time (MST) overall was 732 days.
  • Cats free of clinical signs lived much longer (MST 1830 days) than cats with heart failure (MST 92 days). Cats with heart failure lived longer than cats with thromboembolism (MST 61 days).
  • Cats with an initial heart rate > 200 did worse than if heart rate < 200.

In a more recent retrospective study of 260 cats with HCM (Rush et al. JAVMA, 2002):

  • Median survival time overall was similarly 709 days.
  • MST for cats free of clinical signs was 1129 days, while MST for cats with clinical signs was as follows: 654 days for cats with syncope, 563 days for cats with CHF, and 184 days for cats with ATE. The longer survival times for cats with clinical signs in this more recent study may be due to changes over time in the natural history of disease, differences in disease severity, or improvements in medical therapy.
  • Increasing left atrial size and age were associated with shorter survival times

There is no data to suggest whether the obstructive form has a different outcome from the non-obstructive form.It is unknown whether asymptomatic or symptomatic patients live longer with long term therapy than with placebo. Interim analysis of the only prospective, placebo-controlled, randomized clinical trial in cats with HCM and CHF has failed to show that any therapy (ACE-inhibitor, calcium channel blocker, or beta-blocker) with furosemide is superior to furosemide alone.Even though anti-thrombotic therapy is utilized, thromboemboli may still cause limb paralysis which may result in the owners requesting euthanasia.For cases due to systemic hypertension, we believe antihypertensive therapy (especially amlodipine) can potentially reverse the underlying disorder.There is also no experience attempting to relate the degree of concentric hypertrophy with outcome. In people there is no relation between the degree of concentric hypertrophy and outcome.