ST-Elevation Myocardial Infarction (STEMI)
STEMI is diagnosed when there is:
ST elevation of ≥1 mm in 2 contiguous leads or
New onset LBBB in the resting ECG
Ischaemic type chest pains of > 30 minutes and
Rise and fall in cardiac biomarkers
Echocardiography is recommended to evaluate regional and global LV function and to rule out differential diagnoses.
Management of STEMI
Oxygen
Oxygen is administered in patients with hypoxaemia (SpO2 < 95% or PaO2 < 60 mmHg). Routine oxygen is not recommended in patients with SpO2 ≥ 95%.
Nitrates
Patients with ongoing chest pain should receive S/L GTN 0.5 mg every 5 minutes for a total of 3 doses. If symptoms still persist, intravenous GTN should be considered. During acute ACS, intravenous nitrates may be administered in the following situations:
No symptom relief after 3 doses of sublingual GTN
Presence of dynamic ECG changes
Presence of left ventricular failure
Concomitant high blood pressure.
Contraindications to nitrate therapy:
hypotension (SBP< 90 mmHg), RV infarction, history of PDE-5 inhibitors ingestion (within 24 hours of sildenafil or vardenafil, or within 48 hours of tadalafil-aha). After the first 48 hours, oral or topical nitrates may be continued in patients with persisting ischaemia and/or HF.
Analgesics & tranquilizer
Pain is associated with sympathetic activation, which causes vasoconstriction and increases the workload of the heart. IV opioids like morphine can be used when necessary. Watch for adverse events such as hypotension and respiratory depression. Antiemetic such as IV metoclopramide or IV promethazine can be given concurrently.NSAIDs (except aspirin) should not be initiated and should be discontinued during hospitalization for NSTE-ACS because of the associated risk of MACE A mild tranquillizer (usually a benzodiazepine) can be considered inanxious patients.
Reperfusion therapy
In STEMI patients, reperfusion therapy is indicated in all patients with symptoms of ischaemia of ≤12 h duration and persistent ST-segment elevation. A primary PCI strategy is recommended over fibrinolysis within indicated timeframes. The DNT if fibrinolytic is to be administered should be within 30 minutes. Primary PCI is the preferred strategy in patients who have contraindications to fibrinolytic therapy and the high-risk patients.
High-risk patients
Large infarcts
Anterior infarcts
Hypotension and cardiogenic shock.
Significant arrhythmias
Elderly patients
Post-revascularization (post-CABG and post-PCI)