Current markers of myocardial ischemia and their validity in end-stage renal disease

Coronary artery disease is highly prevalent in patients with end-stage renal disease, and accounts for much of their observed morbidity and mortality. Despite this, diagnosing myocardial disease in this population remains problematic, because many patients present with abnormal baseline electrocardiograms, frequently compounded by silent or atypical symptoms. Conventionally used enzymatic markers of cardiac injury have not resolved this dilemma because of their poor specificity in end-stage renal disease. In particular, nonspecific elevations in creatinine kinase-muscle brain enzyme, a widely accepted marker of cardiac injury, have been consistently observed in the absence of other demonstrable evidence for cardiac injury. Recently, the cardiac troponins (troponin I and troponin T) have emerged as more sensitive markers for cardiac ischemia, facilitating rapid bedside diagnosis and early risk stratification. Unfortunately, cardiac troponin T shows poor specificity in end-stage renal disease, possibly because of variable expression in extracardiac tissues. On the other hand, troponin I consistently maintains a high sensitivity and specificity, and is the most sensitive marker for ischemic heart disease in this patient population.