Cardiac Tamponade

The Heart in a Tightening Fist

Imagine your heart is a sponge sitting inside a thick rubber glove. Normally the glove is loose, so the sponge can squeeze and relax freely, soaking up water (blood) when it opens and wringing it out when it squeezes. Now imagine someone slowly pumps air into the space between the sponge and the glove—the glove gets tighter and tighter. The sponge still tries to open and close, but the outside pressure fights back harder each time. Soon the sponge cannot suck in any water because the glove is too tight. The sponge keeps trying to squeeze, but there is nothing inside it to squeeze out. That is cardiac tamponade (the heart squeezed by fluid around it): the pericardial sac is the glove, the fluid filling it is the pumped air, and the heart is the strangled sponge. The body panics (tachycardia, vessel squeezing, salt-holding) trying to save the sponge by forcing more water into it from the outside, but it does not work—only deflating the glove (draining the fluid) fixes it.