Page 272 - Feline Cardiology

Chapter 19: Congestive Heart Failure 279

diocentesis is common in cats with congestive heart aortic cusps is obtained, and the first diastolic frame in
failure. Moderate or severe pericardial effusion can cause which closure of the aortic valve is evident is selected.
cardiac tamponade and right heart failure. Careful dis- The aortic diameter (Ao) is measured by a line parallel
tinction of pleural and pericardial effusion is necessary. to the commissures of the right coronary and noncoro-
The pericardium should be identified at its attachment nary cusps, using the inner edge method (the internal
to the heart base and is helpful to distinguish pleural diameter of the structure is measured not including the
from pericardial effusion. Cardiac tamponade is subjec- wall thickness) (see Chapter 7). The left atrial diameter
tively assessed by visualization of diastolic collapse of (LA) is measured by a line parallel to the commissure of
the right atrium and/or right ventricle. The left ventricle the left coronary and noncoronary cusp, with care to
often appears underloaded when there is cardiac tam- avoid the pulmonary vein insertion into the left atrium.
ponade. This appears as a small ventricular internal An LA : Ao >1.5 indicates left atrial dilation. Although
diameter during diastolic and systole, and possibly the degree of left atrial dilation is subjective, suggested
mildly thickened left ventricular wall and septum (pseu- criteria for mild, moderate, and severe left atrial dilation
dohypertrophy). Accurate left ventricular measurements are LA : Ao 1.51–1.79, 1.79–1.99, and ≥2.0, respectively.
are only possible once the cardiac tamponade has been Left atrial dilation is usually moderate to severe in cats
relieved. If there is life-threatening cardiac tamponade, with heart failure. Sometimes the left atrial size decreases
immediate pericardiocentesis should be done prior to a to be only mildly dilated after acute aggressive diuretic
comprehensive echocardiogram. However, if the patient therapy. If left atrial size is normal, it is highly unlikely
is reasonably stable, a detailed echocardiogram should that congestive heart failure is the cause of pulmonary
be done to evaluate for cardiac or pericardial masses, infiltrates, and the cat should be evaluated for primary
which are better visualized in the presence of pericardial respiratory diseases. One exception is the cat that has Congestive Heart Failure
effusion. undergone an acute exacerbating event, such as intrave-
Identification of significant left and/or right atrial nous fluids, acute tachycardia, anesthesia in the preced-
dilation is essential to establish the diagnosis of conges- ing 48 hours, or Depo-Medrol® or other long-acting
tive heart failure versus primary respiratory disease, glucocorticoid injection in the preceding 7 days, where
which has immediate treatment implications. Left atrial the left atrial size may not be markedly dilated in the
dilation suggests that the left atrial pressure is elevated, face of congestive heart failure. Extremely rare causes of
which occurs secondary to systolic myocardial failure, cardiogenic pleural effusion in the face of normal atrial
diastolic dysfunction, valvular insufficiency, or left to size are constrictive pericarditis or a mass or an intralu-
right shunting congenital heart diseases. Presence of sig- minal cranial vena caval thrombus or mass. Pulmonary
nificant left atrial enlargement indicates severe cardiac edema and/or pleural effusion may be seen in cats with
disease and implies a poorer long-term prognosis, significant left atrial dilation and left heart failure,
although there is tremendous individual variation whereas right atrial dilation and right heart failure lead
regarding disease progression, response to therapy, and to pleural effusion and/or ascites and pericardial effu-
survival. Left atrial enlargement is an independent pre- sion. Right atrial size is subjectively evaluated from the
dictor for serious adverse cardiac events in people with right parasternal long-axis 4-chamber view and the right
HCM and was associated with more severe diastolic dys- parasternal cross-sectional view at the heart base. The
function and higher filling pressures (Yang et al. 2005). right atrium is normally smaller than the left atrium and
Likewise, increased left atrial size is negatively correlated is dilated when it is subjectively larger than the left
with survival time in cats with HCM (Rush et al. 2002). atrium. In cats with atrial dilation, it is essential to care-
The left atrial size is measured from a right parasternal fully evaluate for spontaneous echocardiographic con-
cross-sectional view at the level of the aortic valve (see trast or a thrombus within the dilated atrium (see
Chapter 7). The left atrium and aortic diameters are Chapter 20).
measured either from a two-dimensional image or by Myocardial structure and function are assessed from
using M-mode with the cursor placed through the body the right parasternal cross-sectional view at the level
of the left atrium and the aorta. The ratio of left atrial of the left ventricular papillary muscles. The fundamen-
diameter to aortic diameter (LA : Ao) is used to eliminate tal objectives for the triage echocardiogram are to
the influence of body size on left atrial size, and provides (briefly) assess myocardial structure and function and
a dimensionless index of atrial size. Two-dimensional identify whether there is markedly reduced myocardial
echocardiography is recommended for measurement of systolic function (e.g., dilated cardiomyopathy), overt
left atrial size, since it is not limited by the location and concentric hypertrophy of the left ventricular wall and
alignment of the cursor when using M-mode. The right septum, or the ventricle appears relatively normal in
parasternal short-axis basilar view at the level of the structure and function. Cats with an overtly thickened