To the Editor:
In her review of cardiac assessment for renal transplantation, Pilmore (American Journal of Transplantation 2006; 6: 659–665) comprehensively assesses current methods for screening for coronary artery disease in patients with end-stage renal failure (ESRF) using myocardial perfusion studies with thallium scintography, dobutamine echocardiography and dipyridamole thallium scans (1). Recent developments in cardiac imaging with cardiac magnetic resonance imaging (CMR) suggest that this technique may also have much to offer in work-up of the renal transplant recipient. This is a promising method for noninvasive evaluation of myocardial perfusion as well as allowing detailed assessment of cardiac structure and function. Studies suggest that CMR is more accurate than radionuclide imaging at detecting small areas of myocardial infarction (2), which are likely to have therapeutic and prognostic implications for patients on the transplant list. Furthermore, while Pilmore rightly points out that data are lacking on the benefits of pre-emptive coronary revascularization of patients with ESRF, CMR can identify viable myocardium, therefore allowing appropriate selection of individual patients for revascularization procedures (3). This is particularly important given the high mortality of patients with ESRF undergoing coronary revascularization.
Our experience using CMR as research tool in patients being assessed for renal transplantation has confirmed a high incidence of myocardial ischemia (Figure 1) (4). Moreover with CMR we found that left ventricular dysfunction did not occur in the absence of myocardial ischemia, suggesting that left ventricular dysfunction in a patient with ESRF is highly suggestive of underlying coronary artery disease. This should be investigated aggressively with angiography in addition to medical therapy with beta-blockade, anti-platelet therapy and renin-angiotensin system inhibition as appropriate. Prospective study of patients studied with CMR is ongoing to assess the impact of its use and the relationship between CMR findings and long-term outcomes for both transplanted patients and those remaining on the wait list.
From a practical point of view CMR is noninvasive, does not use ionizing radiation (unlike radionuclide studies and CT angiography) and therefore is appropriate for performing repeated scans on transplant listed patients. Stress perfusion CMR, using pharmacological agents such as adenosine to induce coronary hyperaemia, has a high sensitivity and specificity for the presence of significant coronary artery stenoses (5).
Although nephrotoxicity has been reported with gadolinium-based contrast agents used for CMR, these are generally felt to be safe in renal insufficiency, and certainly safer than radiocontrast agents used for both conventional and CT coronary angiography. This allows CMR to facilitate comprehensive noninvasive cardiac assessment of the patient with advanced kidney disease, hoping to undergo pre-emptive renal transplantation, by detailing cardiac structure, function, assessing myocardial perfusion and viability, should revascularization be contemplated.
The argument could be made that CMR is expensive and not widely available. As its use is expanding and it integrates the results of multiple tests in a safe repeatable manner, potentially reducing the need for invasive investigations, these obstacles may be surmounted. The renal transplant community is ideally placed to embrace this technology that may progress from being a research tool to representing a ‘one stop’ screening investigation for potential transplant recipients.