Clinical meaning
Acute coronary syndrome encompasses a spectrum from unstable angina to NSTEMI and STEMI, differentiated by the degree of coronary occlusion and resultant myocardial injury. In STEMI, complete thrombotic occlusion requires emergent reperfusion through PCI or fibrinolysis, while NSTEMI management involves risk stratification using TIMI or GRACE scores to determine timing of invasive strategy. Atrial fibrillation results from multiple re-entrant wavelets or focal triggers in the pulmonary veins, leading to atrial electrical disorganization and loss of coordinated atrial contraction, which increases thromboembolic risk proportional to CHA2DS2-VASc score. Heart failure exacerbations involve neurohormonal activation with increased RAAS and sympathetic tone causing sodium and water retention, elevated filling pressures, and end-organ hypoperfusion that requires careful hemodynamic-guided management.