Most patients have symptoms prior to an actual heart attack – generally a “tightness” behind the breastbone, which generally is caused by an increase in heart rate. The coronary arteries fill in between heart beats therefore anything which increases your heart rate will reduce the time your coronary arteries have to provide blood flow to the heart muscle- the myocardium. Once the heart muscle is deprived of oxygen it becomes irritable leading to palpitations and, if not relieved, death of the muscle.
Surrounding the dead muscle is a variable sized area of heart muscle at risk of dying because of inadequate oxygen supply – this condition is known as myocardial ischaemia.
The heart rate is under the control of the autonomic nervous systems, which, in the case of the heart, is driven by adrenaline the so-called “flight or fight” hormone.
Adrenaline acts at various sites of the body
- On the sinus node in the heart which controls rate to increase heart rate - On the bronchial tubes in the lung to cause them to dilate allowing greater flow of air into the lungs - On the small arteries in the skin and gut to constrict (narrow) reducing blood flow to these areas and making more blood available to the muscles- to fight or fly - Increases the blood sugar by increasing breakdown of glycogen to glucose, important food for the muscles to contract better.
Whilst increased adrenaline production is common with exercise it also occurs in states of shock, fear, or anger producing gooseflesh and sweating (remember the first time you saw the shower scene in the Hitchcock Movie Psycho).
As well as increasing the heart rate adrenaline may cause cardiac irregularity, increased blood pressure, or palpitations. It is this irregularity which may lead the heart to chaotic beats and finally fibrillation and death.
This is the first symptom of a heart attack in about 20% of people – sudden death – the victim just collapses to the ground. Whilst he may gasp a few breaths he has no cardiac output- no blood is leaving his heart- he is pulseless.
This terminal condition (ventricular fibrillation) is very easily treated by first aid measures and cardiac shock- termed defibrillation. Nowadays many areas which have high populations (or as in aeroplanes, confined areas) have people friendly defibrillators available which only shock patients who have rhythms which are treatable by shock. These machines have easy instructions and any bystander who can read can apply the electrodes and save the patient’s life.
Often people wrongly refer to this cause of death as a massive heart attack- it takes some time (often up to an hour) to die from a massive heart attack. In this case the heart attack causes such significant damage to the main ventricle of the heart as to reduce blood pressure to critically low levels and death results.
http://www.articlebiz.com/article/17958-1-how-do-i-know-if-i-am-having-a-heart-attack/
