Page 140 - Small Animal Internal Medicine, 6th Edition

112 PART I Cardiovascular System Disorders

Treatment and Prognosis Surgical valve reconstruction or replacement under cardio-
Large shunts can be treated with open-heart surgery and pulmonary bypass might be possible in some cases.
VetBooks.ir patch-grafting under cardiopulmonary bypass, similarly to TRICUSPID DYSPLASIA
VSDs. Ostium secundum defects can sometimes be treated
with transcatheter device occlusion depending on patient
mations of the tricuspid valve and related structures, similar
size, ASD size, and presence of an adequate rim of atrial Animals with tricuspid dysplasia (TD) have variable malfor-
septal tissue around the defect. Otherwise, animals are to those of MD. The tricuspid valve can be displaced ven-
managed medically if CHF develops. The prognosis is vari- trally into the ventricle (an Ebstein-like anomaly) in some
able and depends on shunt size, concurrent defects, and the cases. TD is identified most frequently in large-breed dogs,
level of pulmonary vascular resistance. particularly in Labrador Retrievers, and in males; cats are
also affected. Tricuspid valve dysplasia occurs concurrently
with PS in some dogs.
ATRIOVENTRICULAR VALVE The pathophysiologic features of TD are the same as those
MALFORMATION of acquired TR. Severe cases result in marked enlargement
of the right heart chambers. Progressive increase in RA and
MITRAL DYSPLASIA RV end-diastolic pressures eventually result in right-sided
Congenital malformations of the mitral valve apparatus can CHF. Tricuspid stenosis can occur but is rare.
be variable and include the following: shortened, fused, or The historical signs and clinical findings likewise are
overly elongated chordae tendineae; direct attachment of the similar to those of degenerative tricuspid disease. Initially,
valve cusp to a papillary muscle; thickened, cleft, or short- the animal may be asymptomatic. However, exercise intoler-
ened valve cusps; prolapse of valve leaflets; abnormally posi- ance, abdominal distention resulting from ascites, dyspnea
tioned or malformed papillary muscles; and excessive resulting from pleural effusion, anorexia, and cardiac
dilation of the valve annulus. Mitral valve dysplasia (MD) is cachexia often develop. The right-sided holosystolic murmur
most common in large-breed dogs and also occurs in cats; of TR is characteristic. However, not all cases have an audible
MD is the most common concurrent congenital malforma- murmur because the dysplastic leaflets may gap so widely in
tion among dogs with SAS. Valvular regurgitation is the systole that there is little resistance to backflow and therefore
predominant functional abnormality, and it may be severe; minimal turbulence. Jugular pulsations are common. Addi-
the pathophysiology and sequelae resemble those of acquired tional signs that accompany right-sided CHF include jugular
mitral regurgitation (see p. 119). Left-sided CHF is the most vein distention, muffled heart and lung sounds, and ballo-
common clinical manifestation. Mitral valve stenosis occurs table abdominal fluid.
uncommonly; when present, the ventricular inflow obstruc- Radiographs demonstrate RA and RV enlargement. The
tion increases LA pressure and can precipitate the develop- round appearance of the heart shadow in some cases is
ment of pulmonary edema. Mitral regurgitation usually similar to that seen in patients with pericardial effusion or
accompanies stenosis. dilated cardiomyopathy. A distended caudal vena cava,
Clinical signs associated with MD are similar to those pleural or peritoneal effusion, and hepatomegaly suggest
seen with degenerative mitral valve disease, except for the right-sided CHF.
younger patient age. Reduced exercise tolerance, respiratory RV and occasionally RA enlargement patterns are seen on
signs of left-sided CHF, inappetence, and atrial arrhythmias ECG. A splintered QRS complex configuration may be seen.
(especially atrial fibrillation) are common in affected animals. Atrial fibrillation or other atrial tachyarrhythmias occur
Mitral regurgitation typically causes a holosystolic murmur commonly. Evidence for ventricular preexcitation is seen in
heard best at the left apex. Animals with severe MD, espe- some cases, particularly in patients with the Ebstein-like
cially those with stenosis, can also develop syncope with anomaly.
exertion, postcapillary pulmonary hypertension, and, occa- Echocardiography reveals right heart dilation, which can
sionally, signs of right-sided (in addition to left-sided) be massive. Malformations of the valve apparatus can be
CHF. evident in several views (Fig. 5.9), although the left apical
Radiographic, ECG, echocardiographic, and catheteriza- four-chamber view is especially useful. Doppler flow pat-
tion findings are similar to those of patients with acquired terns are similar to those of MD. Intracardiac electrocardi-
mitral insufficiency. Echocardiography can depict the spe- ography is necessary to confirm an Ebstein anomaly, which
cific mitral apparatus malformations, as well as the degree of is suggested by ventral displacement of the tricuspid valve
chamber enlargement and functional changes. Animals with annulus; a ventricular electrogram recorded on the RA side
mitral stenosis have a typical mitral inflow pattern with pro- of the valve is diagnostic. CHF and arrhythmias are managed
longed high velocity, reflecting the diastolic pressure gradi- medically. Periodic abdomino- or thoracocentesis may be
ent between LA and LV. necessary in animals with cavitary effusions that cannot be
Therapy consists of medical management for CHF. controlled with medication and diet. The prognosis depends
Animals with mild to moderate mitral valve dysfunction on degree of valve dysfunction. Dogs with severe TR and
may do well clinically for years. However, for those with marked cardiomegaly have a guarded to poor prognosis, but
severe mitral regurgitation or stenosis, the prognosis is poor. some dogs survive for many years. Surgical replacement of