The challenge of acute coronary syndromes

Abstract

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