Myocardial Infarction and Nsteacs

NSTEACS = non-ST elevated acute coronary syndrome.

Clinical guidelines

• Variable pain; may be mistaken for indigestion

• Similar to angina but more oppressive

• So severe, patient may fear imminent death—‘angor animi’

• Approx. 20% have no pain

• ‘Silent infarcts’ in diabetics, hypertensives and elderly

• 60% of those who die do so before reaching hospital, within 2 h of the onset of symptoms

• Hospital mortality is 8–10%

Physical signs

These may be:

• no abnormal signs

• pale/grey, clammy, dyspnoeic

• restless and apprehensive

• variable BP: ↑ with pain; ↓ heart pump failure

• variable pulse: watch for bradyarrhythmias

• mild cardiac failure: 3rd or 4th heart sound, basal crackles

Investigations

1. ECG: This is valuable with characteristic changes in a full thickness induction. The features are shown in Figure M2.

2. Cardiac enzymes: The typical enzyme patterns are presented in Figure M3. Troponin 1 or T, which peaks at about 10 h, is now the preferred test. The elevated enzymes can help time the infarct.

3. Technetium pyrophosphate scanning: Scans for ‘hot spots’.

4. Echocardiography: Used to assist diagnosis when other tests are not diagnostic and to assess cardiac function, e.g. ejection fraction and cardiac wall motion.

Management of myocardial infarction and NSTEACS

General principles:

• Aim for immediate attendance if suspected

• Pre-hospital: make diagnosis, assess risk, ensure stability

• Call a mobile coronary care unit, esp. if severe

• Optimal treatment is in a modern coronary care unit with coronary catheter laboratory (if possible) with continuous ECG monitoring (first 48 h), a peripheral IV line and intranasal oxygen

• Pay careful attention to relief of pain and apprehension; establish a caring empathy with the patient

• Give aspirin as early as possible (if no contraindications)

• Prescribe a β-blocker drug and an ACE inhibitor early (if no contraindications and appropriate)

• Prevent possible sudden death in early stages from ventricular fibrillation by monitoring and availability of a defibrillator

First-line management (e.g. outside hospital) Perform ECG (assistant) and classify ACS into STEMI or NSTEACS and notify the medical facility that will be receiving the patient.

• Oxygen 4–6 L/min only if hypoxemic (aim to keep PaO₂ >90%), then wean off

• Secure an IV line (withdraw blood for tests, esp. troponin)

• Glyceryl trinitrate spray or 300 mcg (½) SL or spray 400 mcg (every 5 mins if nec.—max. 3 doses)

• Aspirin 150–300 mg: chewed or dissolved before swallowing

Add if necessary:

• morphine ...