Unhusking

I got to provide anesthesia for a fairly fascinating disease the other day. The heart is encased in a thin veil of tissue called the pericardium. Normally, this is very compliant, meaning that if the heart wants to expand, its vestments permit it to. However, there is a family of disease states that involve the percardium or pericardial space (between the pericardium and the heart muscle). The most dramatic of these diseases is cardiac tamponade where fluid or blood accumulates in the space outside the heart and within the pericardium. The heart, not used to external pressures and confinement, struggles if this fluid accumulates quickly; even 50mL of fluid can be life threatening. As this fluid is trapped in the pericardial space and cannot go anywhere, all it can do is compress the heart.

On the other end of the spectrum is chronic constrictive pericarditis, which was the disease I saw a few days ago. In this case, the elastic sac around the heart becomes scarred and tight from radiation, infection, or old cardiac surgery. The heart's volume becomes fixed and the left and right sides have to share the space. Indeed, all the pressures within the pericardium equalize at parts of the cardiac cycle, a hallmark sign. The heart, unable to fill easily, fails.

It's remarkable to see this heart on the echocardiogram and then visually when the surgeons open the chest. It struggles, but when the surgeons release the fibrotic tissue, stripping the pericardium away from the heart, it jumps back to life (indeed, they do this surgery without stopping the heart, which is amazing). It's a delicate task as the pericardium is often scarred onto the heart, so the surgeons have to carefully dissect the outer layer from the rest of the muscle. It is akin to peeling a grape.