Page 202 - Small Animal Internal Medicine, 6th Edition

174 PART I Cardiovascular System Disorders

CHAPTER 9
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Pericardial Disease and

Cardiac Tumors

Diseases of the pericardium and intrapericardial space can pericardial space to a variable degree and cause associated
disrupt cardiac function. Although these comprise a fairly clinical signs. Although the peritoneal-pericardial commu-
small proportion of cases presented for clinical signs of nication is not trauma induced in dogs and cats, trauma
cardiac disease, it is important to recognize them because the can facilitate movement of abdominal contents through a
approach to their management differs from other cardiac preexisting defect.
disorders. The normal pericardium forms a closed, double-
layered sac around the heart and is attached to the great Clinical Features
vessels at the heart base. Directly adhered to the heart is the The initial onset of clinical signs associated with PPDH can
visceral pericardium, or epicardium, which is composed of occur at any age (ages between 4 weeks and 15 years have
a thin layer of mesothelial cells. This layer reflects back over been reported). The majority of cases are diagnosed during
itself at the base of the heart to line the outer, fibrous layer the first 4 years of life, usually within the first year. In some
(parietal pericardium). A small volume (~0.25 mL/kg) of animals, clinical signs never develop. Males appear to be
serous fluid between these layers serves as a lubricant. The affected more frequently than females, and Weimaraners
pericardium anchors the heart in place, provides a barrier to may be predisposed. The malformation is common in cats as
infection or inflammation from adjacent tissues, helps well; Persians, Himalayans, and domestic longhair cats may
balance the output of the right and left ventricles, and limits be predisposed.
acute distention of the heart. Despite these functions, there Clinical signs usually relate to the gastrointestinal (GI) or
usually are no overt clinical consequences to its removal. respiratory system. Vomiting, diarrhea, anorexia, weight
Excess or abnormal fluid accumulation in the pericardial sac loss, abdominal pain, cough, dyspnea, and wheezing are
is the most common pericardial disorder. It occurs most most often reported; shock and collapse can occur also.
often in dogs, and causes clinical signs from development of Physical examination findings may include muffled heart
cardiac tamponade (see later in this chapter). Other acquired sounds on one or both sides of the chest; displacement or
and congenital pericardial diseases are seen sporadically. attenuation of the apical precordial impulse; an “empty” feel
Acquired pericardial disease that causes clinical signs is on abdominal palpation (with herniation of many organs);
uncommon in cats. and, rarely, signs of cardiac tamponade (see later in this
chapter).

CONGENITAL PERICARDIAL DISORDERS Diagnosis
Thoracic radiographs can be diagnostic or highly suggestive
PERITONEOPERICARDIAL for PPDH. Enlargement of the cardiac silhouette, dorsal tra-
DIAPHRAGMATIC HERNIA cheal displacement, overlap of the diaphragmatic and caudal
Peritoneopericardial diaphragmatic hernia (PPDH) is the heart borders, and abnormal fat and/or gas densities within
most common congenital malformation of the pericar- the cardiac silhouette are characteristic findings (Fig. 9.1, A
dium in dogs and cats. It occurs when abnormal embryonic and B). Especially in cats, a pleural fold (dorsal peritoneo-
development (probably of the septum transversum) allows pericardial mesothelial remnant) extending between the
persistent communication between the pericardial and peri- caudal heart shadow and the diaphragm ventral to the caudal
toneal cavities at the ventral midline. The pleural space is vena cava on lateral view might be evident. Gas-filled loops
not involved. Other congenital defects such as umbilical of bowel crossing the diaphragm into the pericardial sac, a
hernia, sternal malformations, and cardiac anomalies may small liver, and few organs within the abdominal cavity also
coexist with PPDH. Abdominal contents herniate into the may be seen. Pectus excavatum or other thoracic skeletal

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