Page 251 - Feline Cardiology

258 Section G: Congestive Heart Failure

Right Heart Failure Left Heart Failure

Pulmonary Elevated LA
edema pressure Arterial
Parietal pleural veins Pulmonary veins hypotension

LA
Visceral
Elevated
CVP RA pleural
veins
RV LV Elevated
LVEDP
Pleural effusion
Hepatic venous
Liver
congestion
Ascites Portal circulation
Congestive Heart Failure Peripheral edema Kidney Activation

of RAAS

Systemic circulation
Figure 19.1. Pathophysiology of left and right heart failure. Left heart failure is the end result of severe left heart disease of many
etiologies. Pulmonary edema forms when the left ventricular end-diastolic pressure (LVEDP) exceeds 25 mm Hg, and ascites or pleural
effusion develops when right ventricular end-diastolic pressure exceeds 10–15 mm Hg. In cats, pleural effusion may develop second-
ary to left heart failure, likely because visceral pleural veins drain into the pulmonary veins, or secondary to right heart failure since
the thoracic duct and parietal pleural veins empty into the cranial vena cava. In addition to elevated diastolic pressure, cardiac output
decreases, which causes arterial hypotension and activation of the sympathetic nervous system and the renin angiotensin aldosterone
system (RAAS).

common in cats and include dilated cardiomyopathy
(DCM) or arrhythmogenic right ventricular cardiomy- consists of pleural effusion (91%), ascites (55%), and
opathy (ARVC) (see Figure 19.2). Ventricular volume pulmonary edema (36%).
overload caused by valvular insufficiency or left to right • Heart failure is present in slightly over half of cats
shunting congenital heart defects (e.g., ventricular septal with unclassified or restrictive cardiomyopathy. Pleural
defect) may also lead to elevated diastolic filling pressure effusion is more common than pulmonary edema in
these patients.
and development of CHF (see Figure 19.2).

Incidence/Prevalence of the Disorder
The vast majority of information about congestive heart
failure in cats has been derived from retrospective case
Key Points
series that have described CHF in hundreds of cats with
naturally occurring heart disease, although prevalence
• HCM is the most common cause of heart disease and in the overall feline population is unknown. HCM is the
heart failure in cats. CHF occurs in one-third to one- most common heart disease in cats, and CHF occurs in
half of cats with HCM. Pulmonary edema is the most
common cause of dyspnea in cats with HCM and CHF. one-third to one-half of these cats (Rush et al. 2002;
• Biventricular (left- and right-sided) heart failure is Ferasin et al. 2003). Conversely, approximately one-half
present in nearly all cats diagnosed with DCM and to two-thirds of affected cats will not develop congestive
heart failure. Half of cats diagnosed with CHF second-