Page 168 - Feline Cardiology

Chapter 11: Hypertrophic Cardiomyopathy 167

warrant the initiation or intensification of anticoagulant pleural fibrosis or loculated small pockets of pleural
therapy. Periodic measurement of blood pressure, renal effusion, which are less amenable to removal and pallia-
values, and thyroxine level should be done in middle age tion by thoracocentesis.
to older cats. Hypertension and hyperthyroidism may Recheck echocardiograms in cats with severe HCM
develop over time independently from HCM and exert and heart failure are targeted to specifically evaluate
deleterious cardiac effects. whether there is spontaneous contrast or an intracardiac
thrombus and confirm that there is still adequate myo-
Monitoring the Symptomatic Cat with HCM cardial function. It is rare but possible that cats with
and Heart Failure severe HCM may develop myocardial failure in the end-
Follow-up thoracic radiographs are essential to monitor stage of disease (i.e., “burnt-out” HCM), and these cats
efficacy of diuretic therapy and identify reaccumulation may benefit from addition of pimobendan and possibly
of pulmonary edema or pleural effusion. Pulmonary reducing or tapering of atenolol.
venous distension and subtle perihilar interstitial infil- Cardiomyopathies
trates are early signs of heart failure, which would dictate OUTCOME AND PROGNOSIS
mildly increasing the furosemide dose. Although serial
BNP blood tests are helpful to monitor people with Survival time is highly variable in cats diagnosed with
heart failure, serial monitoring in cats with heart failure HCM. Young, male, purebred cats (especially Ragdoll
is not established and no clinical data is available on its cats) tend to have more severe disease that is rapidly
utility for aiding dose titration of diuretics in feline heart progressive. In a study of homozygous affected Maine
failure. Radiographs may be taken after a week of initiat- coon cats with familial HCM, severe concentric hyper-
ing diuretic therapy, and then intermittently (every 3–4 trophy was usually present by 12 months of age, heart
months) in compensated cats on heart failure therapy. failure by 20 months of age, and most cats died by 4
In cats that have persistent heart failure despite medical years of age (Kittleson et al 1999). In a study of 260 cats
therapy, repeat radiographs are done a week after diagnosed with HCM, median survival time of cats sur-
increasing the diuretic dose. Renal panels are also fol- viving more than 24 hours from time of diagnosis was
lowed at the same rechecks as radiographs. In cats that 709 days (range 2–4418 days) (Rush et al. 2002). Median
develop pleural effusion as the main cause of dyspnea, survival time was 1129 days (range 2–3778 days) in
ultrasound may be useful to quickly assess the severity asymptomatic cats, 563 days (range 2–4418 days) in cats
of pleural effusion and whether thoracocentesis is neces- with heart failure, and only 184 days (range 2–2278
sary. If there is not significant pleural effusion, thoracic days) in cats suffering from ATE. Each cat is an indi-
radiographs are recommended to evaluate whether pul- vidual, and the bell curve is wide with marked range in
monary edema is present. Review of the resting respira- survival times, so diagnosis does not equal imminent
tory rate and effort log may be very informative in cats death. As in people, increased left atrial size and age were
that are unable to have routine recheck radiographs, negative predictors of survival (Rush et al. 2002).
with high suspicion of recurrent heart failure if the Another study of 74 cats with HCM reported median
resting respiratory rate is persistently >40 breaths/ survival time of >1830 days in asymptomatic cats, but
minute or the respiratory effort is persistently increased. only 92 days for cats in heart failure, and 61 days for cats
Although unusual, some cats have more than mild con- with ATE (Atkins et al. 1992). Half of cats with heart
gestive heart failure demonstrated on radiographs failure and all cats with ATE were not alive after 6
despite normal resting respiratory rate. months. Based on clinical experience, the prognosis is
Periodic thoracocentesis is often needed to remove good for cats with mild static HCM that have normal
pleural effusion in cats with heart failure. The rapidity left atrial size and minimal progression in ventricular
of pleural effusion accumulation serves as a prognostic hypertrophy over 12–16 months, and these cats often
indicator for early cardiac death. The furosemide dose have normal life spans. Once significant left atrial dila-
usually should be significantly (and aggressively) tion occurs, there is a high likelihood of development of
increased in cats with rapidly progressive pleural effu- heart failure within months to 2 years. Once heart failure
sion requiring thoracocentesis more than twice a month. develops, it is the authors’ experience that cats tend to
Most cats tend to tolerate thoracocentesis for palliative live for between several weeks and 18 months, and most
treatment of pleural effusion on a monthly or longer fewer than 8 months depending on presence of revers-
basis (ideally the longer the better), and tractability of ible trigger for heart failure (better prognosis), rapid
the cat, and the owner’s ability to return for the proce- progression of structural cardiac changes (worse prog-
dure, may play a pivotal role in centesis frequency. nosis), and owner participation, abilities, and insight
Chronic deleterious effects of pleural effusion include (better prognosis).