Acute Myocardial Infarction (AMI)
Features
- 330,000 people in this country have an AMI each year
- The affected coronary artery blocks completely and the heart muscle suffers death or severe damage
- This process occurs over a period of hours therefore early treatment or intervention can save a significant proportion of heart muscle.
- Symptoms are central chest pain, even at rest, lasting a longer period of time (usually hours), and of greater severity than angina, often accompanied by sweating, greyness, pallor, nausea and vomiting and a feeling of apprehension.
Main Complications
- Heart failure – where the heart fails to pump properly and the patient becomes very breathless.
- Disturbance of heart rhythm (arrhythmias) including heart block when the heart slows dramatically.
- Shock – where the blood pressure drops and vital organs such as the brain and kidneys no longer work properly.
- Blood clots (usually in legs) i.e. DVT’s (deep venous thromboses)
Investigations
- ECG – (Electrocardiogram-heart tracing) to detect tell tale changes.
- Blood tests (to show raised blood enzymes that reflect damage to the heart muscle).
NB. Both tests may take some time to become abnormal, and are usually repeated in patients with a suspected heart attack.
Treatment
- Transfer to CCU - (Coronary Care Unit), for intensive care, close monitoring and provision of resuscitation facilities.
- Oxygen and pain relief- usually with morphine, or diamorphine (heroin).
- Antiplatelet therapy– (Aspirin or clopidrogel).
- Thrombolysis– (to dissolve clot, ‘clot buster’) or anticoagulation (streptokinase and heparin medications are usually used). This is to dissolve the clot and help restore blood supply to the heart muscle.
- Beta blockers– reduces heart rate and blood pressure and thereforework of the heart.
1. Ace Inhibitors – are used after the first day or so and in the long-term management of people who have had a MI. They reduce the chance of death and prevent heart failure.
2. [Calcium channel blocker– “relax” the heart muscle and coronary arteries. - not normally used]
3. Angioplasty-following early coronary angiography may be advised in appropriate patients in specialist centres, particularly if treatment with a clot buster (thrombolytic) has not worked.
The annual death rate for smaller infarcts is between 5 and 10% and for large anterior infarcts with heart block is over 25%.
Prognosis
This depends on the size of the infarct, the type of infarct (where it occurs in the heart) and the presence or absence of complications.
Risk increases with : -
- Increasing age
- Female gender
- Complications affecting the heart muscle and pace making system of the heart (conduction system)
- Diabetes
- Previous angina or MI
With an uncomplicated course of recovery, with appropriate cardiac rehabilitation (which can reduce mortality), recovery should take place in around 8 weeks, when disability should then be minimal. Resumption of car driving should take place in 4-6 weeks. Psychological factors cannot be underestimated, many patients are profoundly affected, and rehabilitation programmes, which include graded exercise and counselling, are often invaluable to rehabilitation.
