Cardiac Tamponade

Cardiac tamponade describes a situation in which fluid accumulates in the sac surrounding the heart—the pericardium—and begins to compress the heart itself. When enough fluid gathers, the heart chambers cannot fill properly between beats, which limits how much blood the heart can move forward with each contraction. This tends to develop over hours to days, though the speed varies. Owners often notice that their dog or cat becomes quieter, tires easily, breathes more rapidly even at rest, or has pale gums. Some animals collapse or seem suddenly weak. The signs reflect the body's struggle to maintain circulation when the heart is being squeezed from the outside. Tamponade can occur in any breed or age, though certain heart tumours and inflammatory conditions of the pericardium make it more common in middle-aged and older dogs. This page explores what signs may appear, what is happening inside the chest, how tamponade is investigated with imaging and other tools, and what approaches exist to relieve the pressure and address the underlying cause when one is identified.