Abstract and Introduction
Abstract
Cardiovascular disease (CVD) remains the most common cause of death after kidney transplantation worldwide, with the highest event rate in the early postoperative period. In an attempt to address this issue, screening for CVD prior to transplant is common, but the clinical utility of screening asymptomatic transplant candidates remains unclear. A large degree of variation exists among both transplant center practice patterns and clinical practice guidelines regarding who should be screened, and opinions are based on mixed observational data with great potential for bias. In this review, we discuss the potential risks, benefits, and evidence for screening for CVD in kidney transplant candidates, and also the next steps to better evaluate and treat asymptomatic kidney transplant candidates.
Introduction
Cardiovascular disease (CVD) is a significant cause of morbidity and mortality for wait-listed kidney transplant candidates, and it is the most common cause of death in transplant recipients. The risk of a major adverse cardiac event (MACE) is relatively constant while on the waiting list, then rises markedly in the early posttransplant period and declines to a lower rate thereafter (Figure 1). Understandably, clinicians are highly motivated to screen for CVD before transplant, hoping to prevent events early after transplant and to improve long-term outcomes.
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Figure 1.
Waiting list and posttransplant acute myocardial infarction (used with permission from Kasiske et al.).
Asymptomatic chronic kidney disease (CKD) patients often have significant coronary artery disease (CAD), with prevalence estimates of 37–53% for at least one coronary artery with 50% or greater stenosis. This high prevalence of asymptomatic CAD presents a compelling argument to screen transplant candidates with prior CAD, older age, or those with diabetes to identify asymptomatic patients who may benefit from preemptive coronary revascularization, both to improve perioperative MACE and also to improve the long-term outcomes after transplantation. It has also been argued that screening can be used to exclude high-risk individuals from transplantation and thereby protect a scarce resource. Finally, screening low-risk patients may identify those who would benefit most from risk-factor intervention.
Although the potential benefits of screening are compelling, they must be cost-effective and outweigh the potential for harm. This is particularly challenging in the CKD population where a high proportion of patients have noncoronary CVD, and the sensitivity and specificity of testing for CAD may be less than that in the general population. Testing for CAD may include noninvasive measures such as myocardial perfusion studies (MPS), dobutamine stress echocardiograms (DSE), biomarkers, or cardiac computed tomography (CT) followed by evaluation with coronary angiography.
Any screening test should be cost-effective, with benefits outweighing harms. Specifically, testing must improve outcomes of importance to patients, not consume resources that would be better spent in other ways, and not produce harms that outweigh the benefits. In the absence of randomized controlled trials (RCTs), the optimal method, or even the benefit, of pretransplant screening and intervention remains unclear. The evidence in favor of CAD screening before kidney transplantation, including the accuracy of noninvasive tests, the prognostic value for future clinical outcomes, and the evidence for both screening and intervention on CAD before transplantation is weak at best. We first review the evidence for screening and revascularization in asymptomatic high-risk patients unselected for CKD, followed by the evidence in patients with CKD unselected for transplant candidacy. Finally, we review the evidence for screening and revascularization in kidney transplant candidates who are likely healthier than those unselected for candidacy but also undergo the additional risk of surgery, and discuss the next steps to ensure the best management and outcomes in these high-risk patients.