Pre-Op Cardiovascular Testing for Kidney Transplant Recipients
Posted Jan 15 2010 12:00am
One of the challenges of taking care of your ESRD patients on the kidney transplant list is deciding on what kind of cardiovascular workup to perform. For obvious reasons, you don't want to be performing a major abdominal surgery on an individual with unstable coronary angina: cardiovascular disease is the most common cause of death with graft function at all times after transplant. Conversely, you also don't want to embark upon a costly, unnecessary, and potentially even harmful (e.g., contrast dye, possibility for atheroembolic disease) cardiac workup on a patient who doesn't have active cardiac issues.
The situation is even more confusing when you realize that patients with ESRD have an exceptionally high rate of coronary artery disease. This study by Ohtake et al performed screening cardiac caths on 30 patients with ESRD--and found that a full 53% of the sample had "angiographically significant CAD", including an even greater percentage (83%) in the subset of patients with ESRD and diabetes! Although it is controversial whether all of these patients would benefit from revascularization therapy, it makes the case that performing a "screening test" (such as ECHO or stress tests) is ESRD is not really worthwhile--you should just go ahead and cath everybody.
That being said, the more common approach to a cardiac workup in a patient being evaluated for kidney transplant is to use such a screening test. The two most popular are probably dobutamine stress echocardiography (which according to this recent AJKD review by Lentine et al has sensititives and specificities ranging from 37% - 95% and 71% - 95%, respectively) and myocardial perfusion studies (sensititives and specificities from 37% - 90% and 40% - 90%, respectively). As you can tell from the wide range of values reported above, the positive and negative predictive values of these tests are worse in the ESRD population than in the general population, making interpretation somewhat tricky. Electron beam CT scan, which determines a "calcium score" within coronary arteries to provide a risk assessment for CAD, has not been rigorously evaluated in the ESRD population.
The KDOQI Guidelines state that dialysis patients on the kidney transplant waiting list should undergo annual performance of non-invasive stress tests, such as those above, if they are considered "high risk"--which they define as having diabetes, known CAD, or having more than 2 traditional risk factors.