Management of asymptomatic (occult) feline cardiomyopathy: Challenges and realities.

Background: Cardiomyopathy distinguishes a heterogeneous group of myocardial disorders that represent the most prevalent cause of feline heart disease. Etiology is uncertain and the natural history is presently unresolved. Hypertrophic cardiomyopathy is the most common of these conditions, and while the majority of affected cats are asymptomatic, a proportion is at risk to develop serious morbidities--the most devastating of which include congestive heart failure, arterial thromboembolism, and cardiac death. Predicting when or whether an asymptomatic cat might develop morbidity is hindered by lack of evidence-based clinical trials. Superimposed, these issues create an irresolvable predicament that presently confounds medical decision-making.

Methods: Review of current perspectives for managing asymptomatic (occult) feline cardiomyopathy.

Results: Complex pathophysiology and (likely) sarcomeric mutations give rise to heterogeneous cardiac phenotypes and variable clinical findings. Echocardiography remains the gold standard to clarify cardiac morphology. Frequently, however, detection of echocardiographic alterations--though often of unproven clinical significance--extrapolates by inference or implication a specter of disease, and with this, leads to a path of long-term treatment and testing. Presently, there is no proof that any particular therapy reduces morbidity or prolongs survival of cats affected with occult cardiomyopathy. Recently, however, evidence has accumulated to support the belief that certain prognostic indicators suggest risk for poor outcome. Accordingly, and in absence of evidence-based clinical trials, current practice has shifted to view therapy with the intent to target pathophysiology underlying documented or perceived clinical markers, whose presence portends high risk in certain patients. Affected animals and potentially siblings should be monitored using clinical testing that also takes into account age-related comorbidities.

Conclusions: Asymptomatic (occult) feline cardiomyopathy includes complex and heterogeneous diseases whose outcomes are challenging to predict. Review of available evidence-based treatment data leaves no uncertainties regarding drugs with established efficacy. There presently are none. Current management focuses upon identification of documented risk factors, individualized and tailored therapy, and cogent monitoring. Drugs most commonly considered in this paradigm include those that might reduce thromboembolic risk in cases with substantial left atrial enlargement or dysfunction, agents to counteract left ventricular remodeling, or medications that ameliorate systolic or diastolic dysfunction. Discovering reliable prognostic indicators may further improve stratification to identify patients at highest risk, or detect subsets that respond favorably. These issues shape the challenge to identify sensible preventative management and cost-effective, long-term monitoring strategies.