Myocardial infarction (MI, heart attack) Causes, Symptoms, warning signs, Differential diagnosis, Emergency aid

Myocardial infarction (MI, heart attack)
Causes

• MI is essentially the death of myocardial tissue, caused by an insuffi  ciency of oxygen supply to the myocardium.
• It usually results from rupture of an atheromatous plaque in a coronary vessel,leading to thrombus formation, blocking the vessel and causing occlusion of the
• vessel and myocardial ischaemia.
• Heart muscle begins to die within 20–40 minutes if blood fl ow is not restored, and necrosis is irreversible if the coronary vessel remains occluded for more than 4–6 hours.
• Epidemiology
• Average UK incidence of MI is about 1 in 200 in the population per year.
• Relative incidence in men and women is about 2.2:1.
• Mortality is about 25%, and half of those who die never reach hospital.

Symptoms and warning signs

• Central chest pain or sensations of severe pressure, fullness, squeezing or discomfort:
• lasting for more than a few minutes
• of increasing intensity
• radiating to the shoulders, neck, arms or jaw
• not relieved by rest or cardiac medication
• with any or all of the following:
• sweating or cool, clammy skin
• skin pallor and/or bluish lips
• shortness of breath
• nausea or vomiting
• dizziness or fainting
• rapid or irregular pulse
• anxiety.

Differential diagnosis
Chest pain may be a symptom of indigestion, pleurisy, pneumonia or other disorders, but the duration, severity of pain, intensity of distress and accompanying symptoms of an MI leave little doubt that, whatever the cause, the situation is an emergency.
Emergency aid

• Put patient into a half-sitting position, with head and shoulders supported (e.g. with cushions or pillows) and knees bent.
• Dial 999 for an ambulance.
• Help patients to use any angina medication they are carrying.
• If patient is fully conscious, give a 300 mg aspirin tablet to chew.
• Monitor breathing and pulse rate and be prepared to give mouth-to-mouth
• ventilation and chest compressions if necessary.