Page 1334 - Clinical Small Animal Internal Medicine

1272 Section 11 Oncologic Disease

Most of the information available is derived from small Many HBTs are discovered incidentally with no appar­
VetBooks.ir case series and retrospective data. ent clinical signs. Patients that are symptomatic typically
have signs referable to pericardial effusion or outflow
obstruction to the right side of the heart, either of which
Signalment may result in ascites.
Patients with LSA may have weight loss or signs
associated with pericardial effusion. Occasionally, the
Golden retrievers and German shepherds are predisposed patient may present with symptoms referable to conges­
to cardiac HSA. Afghan hounds, English setters, American tive heart failure. These include difficult or labored
cocker spaniels, Doberman pinschers, Labrador retriev­ breathing, exercise intolerance, coughing, inappetence
ers and miniature poodles have been reported to be at or lethargy.
increased risk as well. Most patients with mesothelioma have symptoms
English bulldogs, Boxers, and Boston terriers are the
most common breeds diagnosed with HBTs. Brach­ associated with pericardial and/or pleural effusion. As a
result, many present with dyspnea or increased respira­
ycephalic breeds are predisposed, but HBTs may develop tory rate and effort. An abdominal component to the
in other breeds. respiratory effort may be noted.
Cats of all breeds may develop cardiac lymphoma.
Cardiac lymphoma is quite rare in the dog. Rhabdomyosarcoma has been reported to be associ­
ated with right‐sided congestive heart failure (CHF)
but not pericardial effusion, and some patients may be
completely asymptomatic. Patients with intrapericardial
History and Clinical Signs lipomas are typically asymptomatic.

Dogs that have acute cardiac tamponade from sudden
hemorrhage by RA/RAu HSA into the pericardial space Diagnosis
typically pant, may collapse or experience hemodynamic
shock. Cardiac tamponade occurs when the intraperi­ Diagnosis of pericardial effusion can be made une­
cardial pressure exceeds the diastolic right atrial and quivocally with cardiac ultrasound (echocardiography).
ventricular pressures. This leads to collapse of the right Hemangiosarcoma is usually diagnosed via echocardiog­
ventricular outflow tract, right atrium and right ventricle raphy, revealing the presence of a mass lesion on the
(RV). Typically, the left atrial (LA) and left ventricular RA/RAu or RV junction of mixed echogenicity with
(LV) pressure exceeds the intrapericardial pressure, pre­ irregular anechoic regions. Patients may be hypotensive.
venting collapse. Collapse of the right‐sided chambers Radiographs typically reveal a globoid cardiac silhouette
leads to impaired filling, decreased pulmonary blood with pulmonary vascular underperfusion, but may be
flow and decreased filling of the left atrium and ventricle. deceivingly normal or only show mild cardiomegaly.
Even a small amount of fluid, if it suddenly develops can Electrocardiography (ECG) commonly reveals sinus
result in serious hemodynamic compromise, whereas tachycardia. The QRS complex may be of lower ampli­
slow accumulation can lead to signs that are insidious in tude (low‐voltage QRS). These comprise the most com­
onset. Chronic pericardial effusion leads to hepatic mon electrocardiographic abnormalities associated with
venous congestion and functional right heart failure, and pericardial effusion. The R‐waves may vary in amplitude
may result in a large, pendulous abdomen from ascites as from beat to beat, a phenomenon known as electrical
well as dependent subcutaneous edema. alternans. This occurs as a consequence of the heart
On physical examination, dogs classically have swinging back and forth in the fluid‐filled pericardium.
decreased or muffled heart and ventral lung sounds as The angle of the vector of LV depolarization is varied due
well as weak pulses. Other potential findings include a to the positional changes, subsequently altering the
fluid wave on palpation of the abdomen, hepatomegaly amplitude of the QRS complex. This generally happens
and pitting edema of the rear limbs. Beck’s triad of clini­ when the heart rate is between 90 and 140 bpm.
cal signs associated with cardiac tamponade is hypoten­ Ventricular premature complexes, accelerated idioven­
sion, distended jugular veins, and muffled heart sounds. tricular rhythm, ventricular tachycardia, paroxysmal
Attention should be paid to the quality of femoral pulses atrial flutter or atrial fibrillation, atrioventricular block,
as the pulses may noticeably get weaker with inspiration bundle branch blocks and other conduction system dis­
and stronger with expiration. This phenomenon, due to turbances may occasionally be encountered on ECG in
intrathoracic pressure changes and the subsequent patients with cardiac neoplasia. The ECG may also be
effects on the pulse pressure, is termed pulsus paradoxus completely normal. Often, physical examination is more
and is highly suggestive of pericardial effusion. reliable than radiographs and ECG. Cardiac magnetic