NSTEMI (Non–ST-segment elevation myocardial infarction) and STEMI (ST-segment elevation myocardial infarction) are commonly known as heart attack. But they are different from each other in some extent. NSTEMI account for about 30% and STEMI about 70% of all heart attack (myocardial infarction).
Pathophysiology of NSTEMI vs STEMI:
Pathophysiologically, NSTEMI is somewhat different from STEMI. NSTEMI occurs by developing a complete occlusion of a minor coronary artery or a partial occlusion of a major coronary artery previously affected by atherosclerosis. This causes a partial thickness damage of heart muscle.
STEMI occurs by developing a complete occlusion of a major coronary artery previously affected by atherosclerosis. This causes a full thickness damage of heart muscle.
Symptoms of NSTEMI vs STEMI:
There is no difference between NSTEMI and STEMI in clinical presentation. In both cases, patients usually present with similar type of symptoms such as chest pain, nausea, vomiting, sweating, breathing difficulty.
ECG of NSTEMI vs STEMI:
NSTEMI does not show ST segment elevation in ECG (due to partial thickness damage of heart muscle) and later does not progress to a Q-wave. For this reason, it is also called a non–Q-wave myocardial infarction (NQMI). Usual ECG findings in NSTEMI are ST-segment depression or T-wave inversion.
On the other hand, STEMI shows ST segment elevation in ECG (due to full thickness damage of heart muscle) and later progress to a Q-wave. For this reason, it is also called a Q-wave myocardial infarction (QWMI).
Cardiac markers of NSTEMI vs STEMI:
Cardiac markers including CK-MB (creatine kinase myocardial band), troponin I and troponin T, all elevate both in cases. But the elevation of these markers is often mild in NSTEMI compared with STEMI.
Diagnosis of NSTEMI vs STEMI:
The diagnosis of a NSTEMI is based on a typical history of chest pain, no ST segment elevation in ECG plus elevation of cardiac markers in serum, and the diagnosis of a STEMI is based on a typical history of chest pain, ST segment elevation in ECG plus elevation of cardiac markers in serum.
Complications of NSTEMI vs STEMI:
Complications occur both in cases. But some complications like cardiogenic shock, left ventricular failure, severe mitral regurgitation due to papillary muscle rupture, cardiac tamponade due to ventricular wall rupture are more in STEMI (due to full thickness heart muscle damage) than NSTEMI.
Treatment of NSTEMI vs STEMI:
Antiplatelets (Aspirin, Clopidogrel, Ticagrelor), anticoagulants (Enoxaparin, Dalteparin, Fondaparinux), beta-blockers (atenolol, metoprolol, bisoprolol), nitrates (isosorbide dinitrate, glyceryl trinitrate), statins (atorvastatin, rosuvastatin, simvastatin, pitavastatin), ACE inhibitors (ramipril, enalapril, captopril, lisinopril) or ARBs (valsartan, candesartan, losartan, olmesartan) are given both in NSTEMI and STEMI.
In case of reperfusion therapy, primary PCI (percutaneous coronary intervention) is the treatment of choice for STEMI. Where primary PCI cannot be achieved within 120 minutes of diagnosis or PCI is not available, thrombolytic therapy such as streptokinase, tenecteplase, alteplase or reteplase should be given. On the other hand, early coronary angiography and revascularization, either by PCI or by CABG (coronary artery bypass grafting) is the treatment of choice for medium to high risk patients with NSTEMI. Drug treatment is appropriate in low risk patients with NSTEMI, and coronary angiography and revascularization reserved for those who fail to settle with drug treatment (low, medium and high risk patients are categorized in nstemi by GRACE score) . Thrombolytic therapy is harmful in NSTEMI. The aggregate data suggest that patients with NSTEMI may be put at risk of reinfarction if fibrinolytic therapy is used.
Prognosis of NSTEMI vs STEMI:
Short-term (in-hospital or one month) mortality is lower in NSTEMI (3-5%) compared to STEMI (10-15%). Re-infarction rate (further heart attack) is higher in NSTEMI (15-25%) after hospital discharge compared to STEMI (5-8%). Long-term mortality is similar or higher in NSTEMI compared to STEMI (two year mortality is approximately 30% in both cases).