Non-ST-segment elevation myocardial infarction (NSTEMI) is a form of acute coronary syndrome characterized by myocardial necrosis, documented by elevated cardiac biomarkers, but without persistent ST-segment elevation on the electrocardiogram. Coronary occlusion is usually partial or transient, resulting in less extensive ischemia than in STEMI. Nonetheless, NSTEMI carries a high risk of adverse events, making prompt management essential.
NSTEMI is mainly caused by a partial or intermittent occlusion of a coronary artery, often due to rupture of an atherosclerotic plaque with formation of a subocclusive thrombus. Unlike STEMI, in which ischemia is transmural, NSTEMI is associated with subendocardial ischemia which, if left untreated, may progress to a more extensive infarction.
The main pathophysiological mechanisms of NSTEMI include:
The extent of myocardial necrosis depends on the duration of ischemia and the presence of coronary collateral circulation.
Patients with NSTEMI generally present with prolonged chest pain, similar to that of STEMI but often less intense and less frequently associated with shock symptoms. The pain may be oppressive, retrosternal, and radiate to the left arm, jaw, or back, usually lasting more than 20 minutes.
Other associated symptoms may include:
The diagnosis of NSTEMI is based on three main elements:
In NSTEMI, the ECG may show changes such as ST-segment depression, T-wave inversion, or nonspecific abnormalities. However, the absence of ECG abnormalities does not rule out the diagnosis, making the assessment of cardiac biomarkers essential.
High-sensitivity troponins are crucial to confirm myocardial necrosis. A progressive rise differentiates NSTEMI from unstable angina, in which biomarkers remain within normal limits.
Echocardiography helps identify regional wall motion abnormalities indicative of ischemia and rule out other causes of chest pain, such as aortic dissection.
Risk assessment in patients with NSTEMI is essential for determining the therapeutic approach. Scores such as the GRACE score allow the identification of patients at high risk of adverse events, in whom an early invasive strategy is indicated.
The treatment of NSTEMI aims to reduce ischemic burden, prevent progression of coronary occlusion, and improve long-term prognosis.
NSTEMI patients should receive beta-blockers to reduce myocardial oxygen consumption and nitrates to relieve chest pain.
Antithrombotic therapy includes:
Coronary angiography is performed early in high-risk patients to assess the need for percutaneous coronary intervention (PCI) or coronary artery bypass grafting (CABG).
Complications of NSTEMI may include:
The prognosis of NSTEMI depends on the timeliness of treatment and the severity of underlying coronary artery disease. In-hospital mortality is lower than that of STEMI but remains significant, especially in patients with comorbidities or delayed diagnosis. Secondary prevention, based on the control of cardiovascular risk factors and adherence to pharmacological therapy, is essential to reduce the risk of recurrence.