Biochemical Markers Of Myocardial Necrosis Research Articles

The challenge of acute coronary syndromes

I n t roduc t ion Acute coronary syndromes (ACS) pose multiple challenges to physicians, cardiologists, internists, and emergency department physicians, as well as to general practitioners. General practitioners are responsible for early recognition of ACS among patients with chest discomfort and identification of patients who require hospital admission; cardiologists and other specialists prescribe initial and subsequent medical therapy and select patients for immediate, early, or elective revascularisation by percutaneous techniques (balloon angioplasty, stent) or bypass surgery. A systematic approach may guide the physicians to meet these challenges (table). The term ACS encompasses a spectrum of patients who present with chest discomfort or other symptoms caused by myocardial ischaemia. The unification of these manifestations of coronary artery disease under a single term reflects the understanding that these are caused by a similar pathophysiology, characterised by erosion, fissuring, or rupture of a pre-existing plaque, leading to intravascular thrombosis and impaired myocardial blood supply? The presence or absence of mechanical obstruction by the plaque and its contents, the amount and extent of associated thrombus formation, and the degree of collateral circulation determine the outcome of patients, particularly whether myocardial ischaemia recovers fully or results in minor or major myocardial necrosis. The common pathophysiology of different clinical presentations of ACS logically requires a similar therapeutic approach. In the 1970s, attention focused on management of lifethreatening arrhythmias. Coronary care units were introduced to detect and treat such arrhythmias by pacemakers (A-V block) or defibrillation (ventricular fibrillation). 2-~ Defibrillators were also introduced in ambulances. Antiarrhythmic drugs were also introduced to prevent ventricular fibrillation. Subsequently, attention shifted to measures to reduce myocardial oxygen consumption with [3-blockers, nitrates, and calcium antagonists. ' These agents prevented progression to myocardial infarction in patients with unstable angina, and improved outcome in selected patients with evolving infarction." In the past 10 years, reperfusion therapy has been introduced, supported by intensive antithrombotic and anticoagulant therapy. The value of reperfusion therapy with coronary occlusion (evolving infarction) by thrombolytic therapy or direct angioplasty has been well established. 9-n However, the indications for, and opt imum timing of, percutaneous or surgical coronary intervention in the spectrum of patients with unstable angina are still debated. H

Use of the combination of myoglobin and CK-MB mass for the rapid diagnosis of acute myocardial infarction

Early identification of patients presenting with myocardial infarction (MI) is necessary for rapid initiation of treatment. Currently, MI has been diagnosed using the combination of the history, electrocardiogram (ECG), and biochemical markers of myocardial necrosis. Unfortunately, all lack sufficient sensitivity and specificity to confidently identify most patients with MI in a timely enough fashion to influence early intervention. Development of newer immunochemical assays for CK-MB mass and myoglobin have allowed for earlier, more rapid diagnosis; however, each has important limitations. The diagnostic sensitivity of CK-MB mass, myoglobin, and the combination of both were analyzed at the time of presentation (0 hours) and again 4 hours later in 101 patients admitted from the emergency department (ED) with possible MI. Twenty patients were subsequently diagnosed as having MI. The sensitivity of the initial ECG was 60%, compared with the sensitivities of the initial myoglobin and CK-MB mass of 70% and 30%, respectively. By 4 hours the sensitivity of myoglobin had increased to 85% and CK-MB mass to 90%. The combination of the initial myoglobin and CK-MB mass had a sensitivity of 85%. Combining these two markers, using both the initial and 4-hour samples, raised the sensitivity to 100%, with a specificity of 100% and negative predictive value of 100%. When patients with diagnostic ECGs were excluded, the sensitivity of the combination at 0 hours was 80% with a specificity of 84%, while the use of the 0- and 4-hour markers had a sensitivity and specificity of 100% and 100%, respectively. We conclude that the combination of CK-MB mass and myoglobin can rapidly diagnose or exclude MI in as short as 4 hours after ED presentation, and accuracy is not different in patients without diagnostic ECGs. Application of this strategy could potentially lead to more rapid intervention in patients with MI, while also allowing early identification of lower risk patients.

Biochemical markers of myocardial necrosis in acute myocardial infarction and thrombolysis.

This paper summarizes the most important biochemical properties of several biochemical markers of myocardial injury and discusses the practical applications of these markers for the diagnosis of acute myocardial infarction, for the noninvasive detection of coronary artery recanalization after treatment with thrombolytic agents, and for the early identification of cardiovascular events in unstable angina.