Coronary thrombosis (heart attack)

Reviewed by Dr Neal Uren, consultant cardiologist and Dr Patrick Davey, cardiologist

What is a coronary thrombosis?

The heart is surrounded by three major coronary arteries that supply it with blood and oxygen. If a blood clot develops in one of these arteries, the blood supply to that area of the heart muscle will stop. This is known as a coronary thrombosis, a myocardial infarction or heart attack.

Most commonly a coronary thrombosis will cause severe chest pains behind the sternum (breast bone), often radiating towards the left arm. The area of muscle to which there is insufficient supply stops working properly if the blood clot is not dissolved quickly, eg with thrombosis dissolving (thrombolytic) medication.

Why does coronary thrombosis occur?

Coronary thrombosis, which usually takes place in the coronary arteries, frequently develops at the site of an atherosclerotic plaque rupture. Most people in the developed world have atherosclerosis (hardening of the arteries) in some parts of their body, without ever noticing it. Atherosclerosis may start around the age of 20 and develops gradually with increasing age.

Some people have symptoms of atherosclerosis in the coronary arteries which shows up as angina (pains in the chest). Conversely, plaque rupture leading to a coronary thrombosis often occurs in someone with no previous history of angina.

It is the lining of the artery supplying the heart muscle that forms an atherosclerotic plaque. This diseased area of the coronary artery can, if it ruptures, develop a blood clot on it, comprising blood clotting proteins, platelets and red blood cells. This formation has the potential to seal off the blood supply.

Risk factors

Numerous 'risk factors' are known to be associated with the development of coronary thrombosis. These include:

a family history of atherosclerosis

a high content of cholesterol in the blood

hypertension (high blood pressure)

smoking

male gender

if you suffer from diabetes Type 1 or Type 2

being overweight

stress

lack of exercise.

What are the symptoms of a coronary thrombosis?

The typical symptoms are:

spontaneous pain behind the sternum (breast bone) or the front of the left-hand side of the chest.

a possible radiation of the pain towards the left arm.

the pain can also radiate towards the hands, jaw, ear, stomach or the right arm.

a constricting sensation in or around the throat.

there can be severe and spontaneous breathing difficulties with or without pain.

sudden fainting or severe dizziness, often accompanied by pain.

What are the danger signals?

If severe chest pains, or any other of the symptoms mentioned above happen suddenly, then it could be a coronary thrombosis.

If you are already suffering from angina pectoris and the prescribed glyceryl trinitrate does not seem adequate, then it might be a danger signal. Usually angina pectoris happens only after some sort of effort, and the physical effort required to bring it on is generally the same from day-to-day. An important warning sign of worsening atherosclerotic coronary disease is that the amount of effort required to bring on the angina begins to lessen. It is of great concern when the angina comes on with no effort at all. If angina suddenly happens at rest, and lasts longer than 20 minutes, the patient should ring 999 for an ambulance.

At the hospital they can decide whether it is a myocardial infarction (coronary thrombosis), severe angina (chest pains) or possibly something completely different.

What should be done if coronary thrombosis is suspected?

When suffering from an acute thrombosis, the most important thing to do is get to a hospital as quickly as possible. Dial 999 and wait for the ambulance. It is important to wait and not drive there yourself, as the condition might worsen on the way. You should rest while waiting for the ambulance.

In the meantime, chew an aspirin of 300mg strength. If relatives or friends are close by, ring them and ask them to come and wait for the ambulance with you. Try not to get anxious, though this is difficult.

How does a doctor make the diagnosis?

When at the hospital, the doctor takes the patient's medical history, examines the patient and will record an electrocardiogram . In most cases this will reveal if there is an occlusion of a coronary artery. However, the examination is not 100 per cent certain and, in some cases, a small clot affecting a small area of heart muscle might be overlooked. If the pain is persistent, a second ECG may be taken 30 minutes later.

Once admitted, a series of blood samples will be taken over the first 24 hours that the patient is in hospital, which will reveal the presence of an injury to the heart muscle and the extent of that injury.

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