Page 1021 - Equine Clinical Medicine, Surgery and Reproduction, 2nd Edition

996 CHAPTER 8

VetBooks.ir cool on palpation with a prolonged CRT. Early in be beneficial for guiding drug selection. The pres-
ence of air indicates a possible anaerobic infection.
the disease the heart sounds may be easily auscul-
tated along with friction rubs. Once effusion has
developed, heart sounds are muffled. Splashing The presence of increased echogenicity or fibrin
tags is suggestive of active inflammation and infec-
sounds are unlikely to be heard unless gas- producing tion. Hypoechoic fluid may be due to idiopathic
bacteria are present. Pyrexia is not consistent. or benign effusion and antimicrobials may not be
Depression and colic signs have been reported but indicated. Idiopathic cases may benefit from the
are inconsistent. administration of corticosteroids (dexamethasone,
0.05–0.2 mg/kg i/v or i/m q24 h). NSAID therapy
Differential diagnosis (flunixin meglumine, 1.1 mg/kg i/v q12 h) is indi-
Pleuropneumonia, neoplasia, congestive heart fail- cated for both its anti-inflammatory and analgesic
ure and benign effusion secondary to hypoprotein- effects. Pericardiocentesis is the treatment of choice
aemia should be considered. for pericardial effusion-induced congestive heart
failure. Diuretics have been used in some cases, but
Diagnosis their efficacy has not been well documented.
An inflammatory leucogram and increased plasma
fibrinogen are common. An increased size and Prognosis
rounding of the cardiac silhouette are often evi- The prognosis is generally poor, but aggressive
dent on lateral thoracic radiographs. A gas cap may therapy has met with some success. Constrictive
be present in the occasional case. An ECG is use- pericarditis may be a sequela to effusive pericardi-
ful and decreased QRS amplitude is a hallmark of tis. With constrictive pericarditis, diastolic filling
pericardial effusion. Electrical alternans (variable is limited. Diagnosis is more complicated because
size of complexes with altering large and small com- of the absence of abnormal sounds or effusion. The
plexes) may also be present. Echocardiography is an clinical signs are similar. Echocardiography is of
invaluable tool both for initial evaluation and for value to evaluate the thickness of the pericardium as
monitoring progression and response to therapy. It well as cardiac function. Diastolic filling may appear
is also valuable in guiding pericardiocentesis. Fluid normal until the elastic capacity of the pericardium
within the pericardial space may be anechoic or of is reached. A sudden ending to diastolic filling is
variable echogenicity. Air may be present in anaero- observed. The prognosis is grave.
bic infections. The right heart may have a flattened
compressed appearance. Functional indices may be PERICARDIAL NEOPLASIA
reduced.
Pericardiocentesis may be used as a diagnostic aid Definition/overview
(Table 8.5). Samples should be submitted for cytolog- Pericardial neoplasia is extremely rare in the horse
ical examination and bacterial culture. and, if present, is often secondary to extension of
another intrathoracic neoplasm. Primary mesothe-
Management lioma has been reported, as has haemangiosarcoma.
Pericarditis with cardiac tamponade should be
considered a severe life-threatening condition that Aetiology/pathophysiology
requires immediate aggressive management. Mild Restriction of cardiac filling may develop as a result
effusion is not an emergency. Stall rest is indicated of extensive fluid accumulation in the pericardial sac.
in all cases.
Antimicrobial therapy is usually indicated. Clinical presentation
Bacterial culture and sensitivity testing should be The clinical presentation is similar to that for
performed. However, in advance of these results, pericarditis, consisting primarily of tachycardia,
broad-spectrum bactericidal antimicrobials (e.g. a weak rapid pulse, muffled heart sounds, venous
penicillin in combination with an aminoglyco- hypertension, jugular vein distension and ventral
side) are often necessary. Echocardiography may oedema. Decreased peripheral perfusion results in