The myocardium may infart when a branch of a coronary artery is blocked. The commonest cause is an atheromatous plague complicated by thrombosis. The extent of myocardial damage depends on the size of the blood vessel and site of the infart. The damage is permanent because cardiac muscle cannot regenerate,and the dead muscle is replaced with non-functional fibrous tissue. Speedy restoration of blood flow through the blocked artery using clot dissolving drugs can greatly reduce the extent of the permanent damage and improve prognosis,but treatment must be started within few hours of the infarction occurring. The effects and complications are greatest when the left ventricle is involved.
Myocardial infarction is usually accompanied by vey severe crushing chest pain behind the sternum which,unlike angina pectoris,continues even when the individual is at rest. It is a significant cause of death.
COMPLICATIONS.
These may be fatal and include:
- Severe arrhythmias,especially ventricular fibrillation,due to disruption of the cardiac conducting system.
- Acute heart failure,caused by impaired contraction of the damaged myocardium and,in severe cases,cardiogenic shock.
- Rupture of a ventricle wall.
- Pulmonary or cerebral embolism originating from a mural clot within a ventricle,i.e a clot that forms inside the heart over the infart.
- Pericarditis.
- Angina pectoris.
- Recurrence.
