|
|
Answer to CPC #4 (Tuesday, December 17, 2002) This
patient presented with shock less than six months after orthotopic heart
transplantation. The causes of shock include cardiogenic shock, hypovolemic
shock, septic/anaphylactic shock and obstructive shock resulting from
pulmonary embolism. This patient clearly has cardiogenic shock,
as he presents with tachypnea, hypotension, increased jugular venous pressure,
cyanosis and lactic acidosis resulting from hypoprofusion. Echocardiogram
is confirmatory in that it excludes tamponade and demonstrates left ventricular
hypokinesis. |
In
a patient who has undergone heart transplantation, the main differential
diagnosis for cardiogenic shock centers on infection and on rejection.
The patient had no evidence of bacterial or fungal infection on blood
cultures, and no evidence of cytomegalovirus infection. Rejection can
be divided into that caused by cellular and humoral immune responses.
Cardiac biopsies are an excellent means to evaluate cellular rejection.
Cellular rejection is diagnosed by identifying lymphocytic infiltration
of the myocardium accompanying evidence of myocyte damage. The International
Society of Heart Lung Transplantation (ISHLT) Working Formulation of 1990
establishes a grading system ranging from grade 0 (no acute rejection)
to grade 4 (severe acute rejection), which is used in most centers (Figure
1). In contrast, the ISHLT Working Formulation does not define criteria
to diagnose humoral rejection. Humoral rejection is associated
with complement deposition and antibody deposition directed against donor
antigens located on the endothelial surface of the graft. Risk factors
for humoral rejection include a positive donor-specific cross match or
preformed anti-HLA antibodies. Pathologically, humoral rejection may be
associated with obliteration of the cardiac vasculature, a process known
as Coronary Allograft Vasculopathy or Accelerated Graft Arteriosclerosis.
However, cardiac biopsies taken to monitor for rejection do not sample
these larger arteries, and hence the biopsies may be normal or show the
resulting ischemic changes in the myocardium. We therefore should think
of humoral rejection when the clinical picture is consistent with rejection,
but the biopsies show little evidence of cellular rejection, as was seen
in this case. Hence, the most likely pathologic process is that of humoral
rejection.
Figure 1
The autopsy confirmed this clinical suspicion. The left
anterior descending coronary artery was 90% occluded by intimal proliferation,
without a dense atherosclerotic plaque (Figure 2). There was severe vascular
rejection of the coronary arteries with an exudative component. Examination
of the intracardiac capillaries revealed an endothelialitis characterized
by a proteinaceous exudate consistent with severe rejection, although
the inflammatory cell infiltrate around the capillaries was only moderate
(Figure 3). Other findings of note in the autopsy related to the effects
of cardiogenic shock; namely, chronic passive congestion of the liver
and acute pancreatitis (Figure 4). The latter findings likely account
for the patients' abdominal pain at presentation.
Figure 2
Figure 3
Figure 4
In summary, this patient expired from Coronary Allograft
Vasculopathy (Accelerated Graft Arteriosclerosis), which resulted in cardiogenic
shock. This is a lesion that is difficult to treat, as it does not seem
to be responsive to standard immunosuppressive therapies used to treat
the more common cellular rejection. Possible treatments include plasmapheresis,
but these are unlikely to be of help in advanced cases such as the one
presented.
Return
to Top |