Page 95 - Feline Cardiology

Chapter 10: Congenital Heart Malformations 93

Pathophysiology Systolic anterior motion of the mitral valve may be
The stenosis results in increased left ventricular pressure observed.
and may lead to the development of left ventricular con-
centric hypertrophy, left atrial dilation, and the develop- Treatment
ment of left-sided heart failure. Interventional therapy for aortic stenosis might be con-
sidered depending on the location of the stenosis and
History and Chief Complaint other aspects of the individual case. For the many cases
The most common clinical presentations are associated that are not candidates for interventional therapy,
with the development of congestive heart failure and medical therapy is recommended with atenolol (6.25–
include tachypnea, dyspnea, and crackles (Stepien and 12.5 mg orally q 12 hours); such treatment should be Congenital Heart Disease
Bonagura 1991). Syncope has also been described initiated only if the cat is not in acute congestive heart
(Margiocco and Zini 2005). failure (which beta-blockade can worsen).

Physical Examination Prognosis
The heart murmur of aortic stenosis might be expected Cats with mild disease can live a normal life span. Cats
to be loudest at the left base over the aortic valve, but in with a more severe defect determined by Doppler echo-
some cases the murmur may be loudest at the sternum. cardiography are at increased risk of sudden cardiac
A gallop rhythm may be ausculted. death, or possibly the development of heart failure. Cats
that have subvalvular aortic stenosis (SAS) could pos-
Differential Diagnosis sibly be at increased risk of developing endocarditis as
in the dog, so prophylactic antibiotics might be war-
Systemic hypertension, hypertrophic cardiomyopathy, ranted prior to surgical procedures. In the dog, SAS is
and hyperthyroidism can all cause concentric hypertro- familial, so it should be considered that it also might be
phy of the left ventricle similar to that observed with in the cat, particularly if a breed or genetic line appears
aortic stenosis.
to have several affected individuals.

Diagnostic Testing
ATRIAL SEPTAL DEFECT
Electrocardiography
A sinus rhythm and normal axis may be observed, but Atrial septal defects are openings between the right and
left atrial enlargement (wide P wave) or left ventricular left atrium that result from abnormal atrial septation
chamber enlargement patterns (tall R waves) may be during development. During this process, the septum
observed. R waves of 2.1 mV were observed in 1 cat forms by growing apically (downward) from the base of
(Margiocco and Zini 2005). the heart and dorsally (upward) from the endocardial
cushion region where the atrioventricular valves develop.
Radiography There are three types of atrial septal defects: sinus
venosus (uncommon; in the dorsal septal region),
Radiographs may appear to be normal or may show septum primum (at the lower/basal septal region), and
evidence of left atrial or ventricular enlargement. A septum secundum, which are defects at the level of the
poststenosis dilation bulge may be observed within the foramen ovale.
aorta. Evidence of left heart failure with pulmonary
venous congestion and patchy pulmonary edema may Etiology, Pathophysiology,
be observed.
and Gross Pathology
Echocardiography Etiology
Echocardiography from the right parasternal long-axis A specific etiology is not known. The defect may be a
view may reveal an echogenic band below the aortic spontaneous developmental abnormality. A familial
valve (subvalvular), thickened aortic valve (valvular), or nature has not been observed in the cat.
supravalvular stenosis. Secondary findings could include
hypertrophy of the left ventricular walls and papillary Pathophysiology
muscles. The left atrium may appear dilated. Continuous- Because the pressure in the right and left atria are very
wave Doppler echocardiography should be used for similar, shunting from the left atrium to the right atrium
assessing the severity of the stenosis from a position that occurs mainly due to the greater compliance of the right
is parallel to flow of the aortic outflow (see Chapter 7). ventricle and sucking of blood from the right atrium