Case #3-- Pericardial Effusion
This electrocardiogram shows electrical alternans. Notice the alternating amplitude of the R-wave from one complex to the next.
Electrical alternans is caused by the heart swinging freely in the pericardial space which is filled with fluid. The mean electrical axis re-orients itself to the positive electrode located on the left rear leg and thus the amplitude changes from one cardiac cycle to the next.
The most likely abnormality in this 8-year old, German Shepherd is a hemangiosarcoma of the right atrium. This tumor is bleeding into the pericardial space and thus restricting venous return and ventricular filling.
The emergency treatment of pericardial effusion is pericardiocentesis. The right midthorax was surgically prepared and a local anesthetic (lidocaine) was injected into the skin, subcutaneous tissue, intercostal muscles, and pleura. A 6" Abbocath was inserted into the pericardial space while observing the electrocardiogram for ventricular premature contractions (a sign you are irritating the heart with your needle!). The first sample collected from the pericardial space was placed in a red-topped tube and was periodically examined for evidence of a clot. Had that sample clotted, you would know the fluid was taken from a cardiac chamber and not the pericardial space. Blood in the pericardial space will not clot due to the defibrination action of the beating heart. A total of 560 ml of blood was removed from the pericardial space.
Follow-Up: Due to the poor prognosis associated with hemangiosarcoma, the owner elected to take Vando home and allow him to enjoy the remaining weeks of his life.
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