Pericardial Effusion in a Labrador Retriever Dog
The present study was aimed to report the diagnostic features of Pericardial
effusion (PE), observed in commonly employed cardiac diagnostic modalities viz.,
radiography, electrocardiography and echocardiography. A 9-year-old, female
Labrador Retriever dog (24 kg) was brought to the Referral Veterinary Polyclinic,
Indian Veterinary Research Institute-Izatnagar with the complaint of exercise
intolerance, listlessness, lethargy, generalized weakness and inappetence. Physical
examination revealed tachypnoea, distended abdomen and on auscultation muffled
heart sounds were observed. Based on physical examination findings, animal was
put on other cardiac diagnostic techniques to arrive at final diagnosis. Diagnostic
features characteristic to pericardial effusion, an abnormal accumulation of
fluid inside the pericardium, were observed. Globoid heart appearance and large
Vertebral Heart Score (VHS) was observed on lateral thoracic radiograph. Electrocardiography
(Lead II) revealed decreased R wave amplitude (decreased left ventricular contraction).
On echocardiographic examination an echo free space between epicardium and pericardium
was observed. All these findings were indicative of pericardial effusion, however,
without an exact aetiology. This article reports the successful diagnosis of
pericardial effusion in Labrador Retriever. However, to confirm the aetiology
other diagnostic tests like haematology, pericardial fluid analysis and histopathology
need to done.
Received: August 25, 2013;
Accepted: October 29, 2013;
Published: February 27, 2014
Pericardial effusion (PE) is an abnormal accumulation of fluid inside the pericardium,
a thin layer of tissue which encloses the heart like a sack. The pericardium
does not easily stretch and hence a sudden effusion causes high pressure inside
the pericardium, constricting the heart leading to cardiac tamponade, an impairment
of ventricular filling as a consequence of increased intrapericardial pressure
caused by the accumulation of fluid within the pericardial cavity. This impairment
in ventricular filling leads to reduction in the amount of blood pumped around
the body (Gugjoo et al., 2013b). Pericardial
effusion usually occurs without any underlying cause (idiopathic pericardial
effusion) in middle-aged, older large dog breeds. Tumours are also common causes
of pericardial effusions in dogs (Campbell, 2006).
Aetiology of PE in dogs cannot be detected solely on the basis of physical examination
(Miller and Sisson, 2000; Stepien
et al., 2000) but may be identified based on the results of different
diagnostic modalities viz., radiography (Tobias and McNiel,
2007), electrocardiography, haematological and pericardial fluid examination
(Sisson and Thomas, 1999; Tobias and
McNiel, 2007), histopathology (Stepien et al.,
2000) and echocardiography (Cobb and Brownlie, 1992;
Tobias and McNiel, 2007). The present study reports the
role of radiography, electrocardiography and echocardiography in the diagnosis
of PE in dogs and the insufficiency of such modalities to arrive at the aetiology.
HISTORY AND CLINICAL SIGNS
A 9-year-old, female Labrador Retriever dog (24 kg) was brought to the Referral
Veterinary Polyclinic, Indian Veterinary Research Institute-Izatnagar, with
the complaint of exercise intolerance, listlessness, lethargy, generalized weakness,
inappetence and assume a sternal or standing position, with its elbows abducted.
Physical examination revealed a distended abdomen, tachypnea (60 breaths min-1)
with both respiratory and abdominal breathing. Mucous membranes were pale, capillary
refill time was prolonged and rectal temperature was 101.2 F. Auscultation revealed
muffled heart sounds but with no murmurs or arrhythmias. Femoral Pulse was weak.
As cardiac involvement was suspected, patient was put to further cardiac diagnostic
modalities viz., thoracic radiography, electrocardiography (ECG) and echocardiography.
On radiography done in lateral recumbency, pleural effusion and a globoid heart
structure with cardiac silhouette slightly merged with the diaphragm was observed.
Vertebral Heart Score (VHS) calculated was 11.0 (Fig. 1).
On electrocardiography, a normal sinus rhythm was observed. However, the amplitude
of QRS complex, an indicator of ventricular depolarization was significantly
reduced. In particular, the mean amplitude of the R waves in lead II was 0.7
mV (Fig. 2). Variations in R wave amplitude could be detected
though non-specific to electrical alternans. Thoracic ultrasonography showed
the presence of pleural effusion and on echocardiography pericardial effusion
was evident in the form of an echo-free space between epicardium and pericardium
without any tumorous mass.
||Globoid heart on lateral thoracic radiograph (LA and SA shows
long axis and short axis of heart for VHS calculation)
|| Electrocardiogram showing small QRS complexes in Lead II
Animal was diagnosed to be suffering from pericardial effusion; however exact
aetiology could not be determined.
The present study was aimed to report the features of different cardiac diagnostic
modalities viz., radiography, electrocardiography and echocardiography in case
of pericardial effusion and also to show whether these modalities are sufficient
to arrive at aetiology of the case. The present case was diagnosed as pericardial
effusion although the exact aetiology was not confirmed. PE can result from
number of causes like haemorrhage or exudation from neoplasm, exudates from
infection, or can be idiopathic. In the present study, the tumour mass though
not visible on echocardiography or radiography but cannot be ruled out (Johnson
et al., 2004; Stepien et al., 2000).
The insensitivity of echocardiography to diagnose the pericardial effusion due
to tumour mass may be due to the diffuse nature of the masses like mesothelioma
(Stepien et al., 2000), inability to distinguish
between fibrinous pericardial thickening and pericardial mass lesions (Sanflippo
and Weyman, 1994) or to the timing of echocardiographic examination in the
course of disease process (Cobb and Brownlie, 1992).
However, fibrinous pericardial thickening was also not observed. The term idiopathic
pericardial effusion is given to the condition in which there is no evidence
of neoplasia and no confirmed infectious source in the accumulated fluid is
detected (Dunning, 2002). The infectious and neoplastic
causes can be detected by cytology or culturing of pericardial fluid and histopathological
Decreased cardiac output and stroke volume leads to pale mucus membranes and
prolonged capillary refill time as preload is decreased in cases of pericardial
effusion leading to decreased cardiac output. Muffled heart sounds result from
the dampening of sounds in the fluid between heart and thoracic wall. Globoid
cardiac silhouette and higher VHS on lateral radiograph signifies the cardiac
enlargement which may be due to the actual enlargement of heart or due to pericardial
effusion. VHS in the present study was found to be 11.0 which was quite higher
compared to the normal value (10.3) given for Labrador Retriever (Gugjoo
et al., 2013a). R wave amplitude in Lead II was significantly decreased
(Gugjoo et al., 2014). This decrease in R wave
amplitude can result due to number of reasons and in relation to the present
study, the likely cause might be an increase in the fluid within the pericardial
sac leading to, electrical current short circuiting (Badiger
et al., 2012), increase in distance of potential generator from recording
electrodes (Rokey et al., 1991) and decrease
in cardiac chamber size and volume (Karatay et al.,
1993). Variations in R wave amplitude not characteristic of electrical alternans
were observed as beat to beat changes were not found but changes were found
to occur after 3-4 beats (Fig. 2). The variations in this
study suggest that perhaps the motion of this dog's heart within the pericardial
fluid was not rhythmic or regular, unlike that of electrical alternans wherein
it is rhythmic (Campbell, 2006). Echocardography, a
non-invasive technique that can provide much more information than radiography
as it can distinguish the pericardium, pericardial fluid and heart structures
that are indistinguishable on a radiograph. Echocardiography is quite a sensitive
and specific method as it can detect even a small amount of pericardial effusion
(Miller and Sisson, 2000). Echocardiography is quite
a sensitive and specific method as it can detect even a small amount of pericardial
effusion (Smith and Rush, 1999). This clinical article
reports diagnosis of pericardial effusion in Labrador Retriever using cardiac
diagnostic modalities viz., radiography, electrocardiography and echocardiography,
however without an exact aetiology.
Authors are highly thankful to the Director of the Institute for providing
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