Page 213 - Small Animal Internal Medicine, 6th Edition

CHAPTER 9 Pericardial Disease and Cardiac Tumors 185

syncope, weakness, and weight loss are common complaints. Treatment and Prognosis
These signs may develop over weeks to months. Ascites and Pericardiectomy is necessary to improve ventricular filling.
VetBooks.ir jugular venous distention are the most consistent clinical pericardium is involved. Constrictive pericardial disease
This is more likely to be successful when only the parietal
findings, as in dogs with cardiac tamponade. Weakened
involving the visceral layer requires epicardial stripping. This
femoral pulses and muffled heart sounds are also typical. A
diastolic pericardial “knock” sound, resulting from abrupt procedure increases the surgical difficulty and associated
deceleration of ventricular filling in early diastole, has been complications. Pulmonary thrombosis reportedly is a
described but usually is not identified in dogs. A systolic common postoperative complication and can be life-
murmur or click, probably caused by valvular disease rather threatening. Tachyarrhythmias are another complication of
than the pericardial pathology, or a diastolic gallop sound surgery. In the postoperative period, modest diuretic doses,
may be heard. and possibly an angiotensin-converting enzyme inhibitor,
may be helpful. Positive inotropic and vasodilating drugs are
Diagnosis not indicated. Constrictive pericardial disease is progressive
The diagnosis of constrictive pericardial disease can be chal- and, without successful surgical intervention, ultimately
lenging. Typical radiographic findings include mild to mod- fatal. Serologic testing for Coccidioides (or other fungal
erate cardiomegaly, pleural effusion, and caudal vena cava agent) is advisable in endemic regions. Adjunctive antifungal
distention. Reduced cardiac motion may be evident on fluo- therapy has improved prognosis of affected dogs that survive
roscopy (as with cases of pericardial effusion). Echocardio- pericardiectomy.
graphic changes in dogs with constrictive pericardial disease
can be subtle. Suggestive findings on M-mode and 2-D
examination include diastolic flattening of the LV free wall CARDIAC TUMORS
and abnormal diastolic septal motion. During inspiration,
leftward deviation of the interventricular and atrial septa Etiology and Pathophysiology
reflects the relative increase in right heart filling at the Echocardiography has made the antemortem diagnosis of
expense of left heart filling during this phase of respiration. cardiac tumors more common, although the overall preva-
During exhalation, the septa shift rightward. The pericar- lence of such neoplasms is low. Some cardiac tumors cause
dium may appear thickened and intensely echogenic, but severe clinical signs, whereas others are diagnosed fortu-
differentiating this from normal pericardial echogenicity itously. By far, the most common cardiac tumor in dogs is
may be impossible. Mild pericardial effusion is seen in some HSA. The RA, especially the right auricle, most frequently is
cases. RA collapse is not expected with constrictive disease, the site of origin. Some HSAs also infiltrate the ventricular
in contrast to effusion with cardiac tamponade. Other obser- wall extensively. Occasionally, this tumor is found within the
vations include vena cava and hepatic vein dilation, as well LV, interventricular septum, or at the heart base. HSAs
as pleural and abdominal effusions. Doppler mitral and tri- usually are associated with hemorrhagic pericardial effusion
cuspid inflow velocities show increased variability with res- and cardiac tamponade (see p. 176). Primary cardiac HSA is
piration. The transtricuspid early filling (E-wave) peak likely to metastasize to other organs, including the lung and
velocity is greatest in early inspiration, whereas the maximum spleen. Primary splenic HSA only occasionally metastasizes
peak transmitral E-wave velocity occurs with the onset of to the heart. Golden Retrievers, German Shepherds, Afghan
expiration. ECG abnormalities described with constrictive Hounds, Cocker Spaniels, English Setters, and Labrador
pericardial disease include sinus tachycardia, P-wave prolon- Retrievers, among others, are at higher risk for this tumor.
gation, and reduced-voltage QRS complexes. Masses involving the heart base and ascending aortic
A CVP greater than 15 mm Hg is common. Intracardiac region usually are aortic body tumors (also known as che-
hemodynamic measurements are diagnostic. In addition to modectomas or nonchromaffin paragangliomas). This is the
high mean atrial and diastolic ventricular pressures, the second-most-common cardiac tumor type in dogs. These are
atrial pressure waveform shows a prominent y descent neoplasms of the chemoreceptor aortic bodies. However,
(during ventricular relaxation). In contrast, with cardiac ectopic thyroid or parathyroid or mixed-cell–type tumors
tamponade, the y descent is diminished because ventricular also can occur at the heart base. Heart base tumors mainly
diastolic expansion immediately raises intrapericardial pres- tend to be locally invasive around the root of the aorta and
sure and impairs caval flow into the RA (preventing the surrounding structures, although metastases to other organs
normal early diastolic decrease in CVP and y descent). With can occur and could be more common than previously
constrictive pericardial disease, filling pressure is low only in appreciated. Unless they cause symptomatic pericardial effu-
early diastole (during the time of y descent). Another classic sion or dysfunction of surrounding structures, heart base
finding with constrictive pericardial disease is an early dia- tumors can be an incidental finding. Chemodectomas are
stolic dip in ventricular pressure, followed by a mid-diastolic reported more frequently in brachycephalic dogs (specifi-
plateau as filling is curtailed; however, this is not seen con- cally Boxers, Boston Terriers, and Bulldogs) but affect indi-
sistently in dogs. Angiocardiography could be unremarkable viduals of other breeds as well. Clinical signs associated with
or might show vena caval and mild atrial enlargement with heart base tumors most often are related to pericardial effu-
increased endocardial-pericardial distance. sion and cardiac tamponade.