Coronary artery disease CAD

What happens inside the coronary arteries

The coronary arteries branch off the aorta, the large blood vessel that carries blood away from the left ventricle to the rest of the body. Their job is to deliver oxygenated blood to the heart muscle itself. They are small vessels, only 3 to 4 millimetres wide.

Over many years those arteries can narrow through a process called atherosclerosis, in which increased cholesterol levels allow fatty plaque to build up on the artery walls. This happens gradually, which is why coronary artery disease usually develops quietly over decades rather than appearing suddenly.

At rest, a narrowed artery can often still deliver enough blood to keep things ticking along. Once a coronary artery is narrowed enough, the heart muscle can still get the blood it needs at rest but not when demand rises, which is why symptoms so often show up on exertion. That is why symptoms so often appear during exertion and then settle again with rest.

How a narrowed artery can become a blocked one

As atherosclerosis progresses, it can damage the wall of the vessel, and that wall may rupture. Damage of this kind can trigger a blood clot, known as a thrombus, forming at the site.

A thrombus can restrict blood flow to a portion of the heart muscle. When that happens, the muscle is deprived of oxygen and begins to die, and the result is a myocardial infarction, better known as a heart attack. Heart attacks can be treated if detected early and usually require an immediate percutaneous coronary intervention to the affected vessel, but a prolonged heart attack can lead to haemodynamic compromise and even death if the heart muscle is irreparable.

A clot can also break away from the original vessel and travel in the blood, at which point it is called an embolus. An embolus may block another area of the heart, lodge in the lungs as a pulmonary embolism, or reach the brain and cause a stroke.

Ischaemic stroke, where the blood supply to part of the brain is stopped or reduced by a blood clot, accounts for around 85% of strokes in the UK. Those clots form through the same process of atherosclerosis that narrows the coronary arteries, although clots can also form in the heart for other reasons, such as atrial fibrillation. Coronary artery disease is therefore not only a problem for the heart, because the same disease process affects the wider circulation.

The symptoms you may notice

In its early stages, coronary artery disease often causes no symptoms at all. When symptoms do appear, the most common is chest pain, and the pattern of that pain matters as much as where you feel it.

Anginal chest pain can feel like a tight squeeze on the chest or a dull ache that does not go away. The feeling may spread to the arms, jaw and back, and it can resemble some of the symptoms of a heart attack. It is usually triggered by physical activity or stress and normally stops after a few minutes of rest.

Heart attack symptoms vary from person to person and are usually different in males and females. Most people experience chest pain, shortness of breath, sweating, pain radiating into the jaw, back or left arm, and sometimes nausea. On rare occasions a heart attack can be silent, with no preceding symptoms at all. If you think you or someone with you is having a heart attack, call 999 straight away.

• Chest pain, tightness or a dull ache, often brought on by exertion or stress
• Shortness of breath
• Pain spreading to the arms, jaw, back or left arm
• Sweating
• Nausea
• Fatigue
• Dizziness

What raises your risk

Most people who have a heart attack have associated risk factors that put them at higher risk of developing coronary artery disease in the first place. Those risk factors are usually split into two groups, the ones you can change and the ones you cannot.

The ones you cannot change include age and gender, congenital heart issues present from birth, a genetic predisposition to heart disease, and a higher risk determined by ethnic background. Men tend to develop coronary artery disease earlier than women, although women remain at significant risk later in life, and their symptoms are sometimes less typical.

Understanding those factors does not make them any less real, but it does help guide screening and preventative care. Someone with a strong family history, for example, may benefit from earlier cholesterol testing and closer monitoring. It is also worth knowing that some people with no visible risk factors still have a heart attack. These silent risk factors may only present themselves when an attack occurs, which is why symptoms should be properly assessed rather than explained away.

The modifiable risk factors can, in the most part, be reversed, and they are where prevention usually starts.

• Obesity or a high BMI
• A poor diet
• High cholesterol levels, known as hypercholesterolaemia
• High blood pressure, known as hypertension
• Diabetes
• Smoking

How coronary artery disease is diagnosed

Diagnosis usually begins with a careful history. What brings the discomfort on, how long it lasts, what relieves it and what other symptoms come with it often tells Dr Jogiya more than any single test.

A 12 lead ECG is almost always the first investigation. It can be completely normal between episodes, so it is usually combined with blood tests and an echocardiogram, which shows the structure and function of the heart at rest. Raised inflammatory and cardiac markers on a blood test reliably indicate an acute heart attack, and the ST segment on the ECG is a good indicator of the health of the heart muscle. A heart attack diagnosed by ST elevation on an ECG is known as a STEMI, and heart attacks without that elevation are known as NSTEMIs.

An exercise tolerance test or a stress echocardiogram shows what happens when the heart is asked to work harder, while a CT coronary angiogram gives direct anatomical information about the arteries themselves without an invasive procedure. If those results raise enough concern, an invasive coronary angiogram gives the most accurate map of the arteries.

A coronary angiogram is an invasive procedure that looks at the condition of the coronary arteries. A small tube called a catheter is inserted through the wrist or the leg and advanced to the aorta, where the coronary arteries branch off, so that the inside of those arteries can be seen and assessed. A contrast dye is used so that the arteries show up clearly on a special type of X ray known as fluoroscopy.

How coronary artery disease is treated

Treatment varies depending on the severity of the blockage in the artery. For many people it starts with controlling cholesterol, which usually requires medication such as a statin alongside dietary changes, cutting down on processed food and unhealthy fats. Medication to reduce the risk of clots, such as aspirin, is also commonly prescribed.

Lifestyle changes make a real difference to symptoms and to the underlying disease. A balanced diet, cutting down on alcohol, quitting smoking, losing weight and regular exercise all support cardiac health.

Where an artery is narrowed, a balloon angioplasty can be performed. This pushes the artery walls open and allows more blood to flow through the vessel. Because there is sometimes a risk of the vessel closing up again or re-narrowing, a stent may be inserted to keep it open, in a procedure known as percutaneous coronary intervention or PCI. These can be carried out at the same time as a coronary angiogram, using the same catheter and the same approach.

If an artery is completely blocked, a procedure can be performed to bypass the affected artery. This is known as a coronary artery bypass graft, or CABG. You may be required to stay in hospital for a few days after a CABG, whereas the other procedures are usually performed as day case operations.

Following a heart attack, regular medication may be needed on a long term prescription. This can include blood thinners, anti-inflammatory medicines such as aspirin, and cholesterol controlling medication such as statins. Some people also need rehabilitation sessions to regain strength and cardiac function. It may take a few weeks to return to your normal level of activity, and regular rehabilitation can improve your prognosis and help you return to normality.

When to seek help

Call 999 if chest pain is severe, lasts more than 15 minutes, does not ease with rest, or comes with sweating, sickness, breathlessness or a feeling of impending doom. This may be a heart attack, and minutes matter.

If your usual pattern of chest pain has changed, coming on with less effort than before, at rest, or more frequently, that is unstable angina until proven otherwise and needs same day medical assessment.

Symptoms that are easy to explain away still deserve a proper cardiac assessment. Chest pressure put down to indigestion, breathlessness climbing the stairs, unusual fatigue or a sudden drop in your exercise tolerance are all worth investigating. A consultation typically begins with a thorough history, a 12 lead ECG, an echocardiogram and blood tests, with further imaging arranged only if the clinical picture warrants it. The earlier symptoms are properly investigated, the more options there usually are.