Cardiac Function

Background Increases in cardiac biomarkers of myocardial injury and particularly cardiac troponin (cTn), in the absence of analytical confounders, define the presence of myocardial injury which in the proper clinical situation can lead to the diagnosis of acute myocardial infarction (AMI). Other biomarkers such as natriuretic peptides (NPs) facilitate the diagnosis and/or exclusion of heart failure (HF). These and other important biomarkers improve patient management by leading to an earlier diagnosis, facilitating triage, helping to define treatments, and allowing for an expediated assessment of short- and long-term outcomes. Not only is patient care enhanced but with proper use, costs are constrained. Content Concepts and definitions of myocardial anatomy and physiology of the heart are briefly described, along with structural changes that occur during the onset and progression of heart disease. Analytical and biochemical characteristics of cardiac troponin I (TnI), cardiac troponin T (TnT), b type natriuretic peptide (BNP), and the NTproBNP fragment (NT-proBNP) and the assays used to measure them are discussed. The clinical use of cTn is discussed in helping to diagnose and rapidly exclude AMI. Modern-day high-sensitivity assays can also aid in both primary and secondary prevention. Outcome studies are reviewed to demonstrate the role of cTn in risk stratification and appropriate selection of treatments. The clinical role of BNP/NT-proBNP in diagnosing acute and chronic HF, their emerging role in predicting the development of HF, and their use in distinguishing dyspnea of a pulmonary origin from that due to myocardial dysfunction are highlighted. The use of NP assays in defining prognosis and identifying possible treatment options is addressed. Finally, novel biomarkers for detecting myocardial injury, hemodynamic stress, inflammation, plaque rupture, and ischemia are discussed.