In our discussion of cardiovascular infections, we now turn to pericarditis. Pericarditis is an inflammation
of the pericardium, the covering of the heart caused by any of a wide variety of infectious
and some noninfectious processes as well. The incidence in an autopsy series was found to be
somewhere between 2% and 6%. So, it’s not a particularly common problem. Among infectious causes,
there are essentially three main ones. These are viruses, in fact, viruses cause most pericarditis,
bacteria, and fungi. Among the non-infectious causes, we have cancer which unfortunately
is far too common especially carcinoma of the lung. Also, uremia which is vanishingly uncommon
because patients get chronic hemodialysis in most developed countries. It’s readily available.
So, we don’t see the pericarditis we used to see in uremia. But it’s still present in connective tissue
disorders such as systemic lupus erythematosus. There are other causes too. Some medications
can cause for example a lupus-like syndrome. They include isoniazid, hydralazine, and procainamide.
A pulmonary embolism in part of the lung that is adjacent to the heart could cause pericarditis.
It is very common in radiation therapy for cancer involving the mediastinum and involving the lungs.
Certainly, you can have it as a result of trauma. There is a condition called Dressler's syndrome
which may follow either an acute myocardial infarction or cardiac surgery where the pericardium
has to be opened and rarely, aortic aneurysm. Among the viruses that are known to fairly commonly
cause pericarditis, we consider coxsackievirus, one of the enteroviruses; another enterovirus,
the echovirus especially type 8; and cytomegalovirus may be among the common causes
in patients with AIDS. Most of them are lumped into what we call idiopathic pericarditis.
We assume that most of these are caused by viruses. Among bacteria that can cause pericarditis,
most of them get there from hematogenous seeding of the pericardium, or it can get there
from extension of a contiguous infection commonly pneumonia, a post-operative infection,
or as a result of surgery on the pericardium as I mentioned. Then post-traumatic is another cause
of a contiguous problem in the pericardium. Surprisingly, the microbiology of pericarditis
hasn’t changed that much. In the pre-antibiotic era, pneumonia was very common.
Well, pneumonia due to Streptococcus pneumoniae is still very common. Streptococcus pneumoniae
is still the number one cause of pneumonia. Since the pericardium is right near a potential
infected part of the lung, you can see why that would still be the case. Staph aureus still
is a very common problem. Mycobacterium tuberculosis unfortunately is a common problem
which remains. But in the modern era, gram-negative bacilli have crept in. This is a result
not only of the use of antibiotics but of surgical procedures, of hospitalization, and bacteremia
due to gram-negative bacilli and surgery on the lungs which can be associated with gram-negative
rod infections, et cetera. So, the modern era has gram-negative rods on the list. The early era did not.
Fungi can do it as well. Candida, here we’re showing you that classic look of candida with pseudohyphae
and budding yeast nearby. We’re also showing you Histoplasma capsulatum. What you’re seeing here
is a macrophage with a large nucleus that has engulfed these tiny yeasts. You have to look carefully
but they are there. They’re about 3 micron or so. They’re sort of pear-shaped. They look like they have
a capsule around them, that circle. These are tiny yeasts that you find as a cause of pericarditis
in endemic areas like Cincinnati, Ohio, St. Louis Missouri, places in the Ohio and Mississippi River Valley.