Plus-Hex CLINICAL
Introduction
Cardiac tamponade is a condition that develops secondary to pericardial effusion. It occurs when fluid accumulates in the pericardial sac, compressing the heart, thus interfering with its ability to move blood around the body( Figure 1) [ 1 ]. Due to the constant pressure from the effusion, the heart cannot function adequately, meaning the cells and tissues within the body are not receiving sufficient oxygen( O 2
), increasing the risk of multi-organ dysfunction or failure. In short, the pericardial effusion is the fluid that surrounds the heart, and cardiac tamponade is the pressure caused by it. If left untreated it can be life-threatening [ 2 ].
Clinical signs
There are several clinical signs indicative of pericardial effusion / cardiac tamponade. However, some of the signs are vague and they can often be overlooked or mistaken for a variety of other conditions.
Signs of cardiopulmonary deficits may be seen, such as pale or cyanotic gums, weak peripheral pulses and hypotension. The pressure around the heart limits venous return, impairing the filling of the right side of the heart, which often results in tachycardia as a compensatory mechanism [ 3 ]. However, as there are numerous causes of tachycardia, further diagnostic investigations are recommended to pinpoint the cause and allow appropriate treatment to begin.
Blood pressure( BP) and blood flow are under strict neuroendocrine control, and when there are alterations in these bodily systems, the renin – angiotensin – aldosterone system( RAAS) is activated. As a result of attempting to maintain systemic BP despite the reduction in stroke volume, peripheral vasoconstriction occurs, which is often noted as cold extremities during physical examination of the patient [ 4 ].
The insufficient filling and emptying of the heart leads to increased pressure of the vessels in and around the lungs, making it more difficult for the animal to take deep breaths, posing the risk of respiratory arrest and, ultimately, cardiopulmonary arrest [ 5 ]. A cough may be present, caused by the surplus fluid accumulated around the heart and lungs [ 6 ]. This may be apparent during a hands-off examination, alongside laboured or shallow breathing and / or increased respiratory rate.
Muffled heart sounds are often heard on auscultation of the thorax. The fluid within the pericardial sac acts as a barrier between the heart and the stethoscope, dulling the typical‘ lub-dub’ sound of each beat [ 7 ]. Heart sounds should be checked bilaterally, as one side may be more affected than the other.
When the heart is not working effectively, poor perfusion of the kidneys and the activation of the RAAS cause the retention of sodium and water in the body. With this considered, patients may present with a distended abdomen or pulmonary oedema due to the build-up of fluid and impaired circulation.
A Normal heart B Pericardial fluid C Pericardial effusion D Pericardium
E Pericardial sac( pericardium) surrounding the heart
F Fluid accumulation inside the pericardial sac affects the heart ' s ability to pump efficiently
Figure 1. Pericardial effusion in dogs [ 1 ].
Volume 41( 2) • April 2026
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