Coronary Artery Disease (Artery Blockage)
Coronary artery disease (CAD) usually occurs when cholesterol and plaque accumulate inside the coronary arteries (blood vessels supplying oxygen-rich blood to heart muscles) blocking the flow of oxygen-rich blood to the heart muscles. The plaque can sometimes rupture and form a blood clot that can completely block the vessel, leading to a heart attack and possible permanent heart damage.
CAD is the most common of all heart diseases, and a leading cause of death. Despite this, it often goes unnoticed as the plaques develop over many years.
The main function of the heart is to deliver oxygen-rich blood to every cell in the body. The arteries are the passageways through which the blood is delivered and the veins are the passageways through which the blood is collected and returned to the heart. The coronary arteries supply blood to the heart muscle. When the coronary arteries become narrow or blocked, blood flow to the heart is reduced. This decrease in blood flow to the heart deprives the heart muscle of oxygen. Heart attack (also called myocardial infarction) is when part of the heart muscle is damaged or dies because it isn’t receiving oxygen.
Causes of Coronary Artery Disease
CAD occurs due to atherosclerosis, a condition where cholesterol accumulates in the wall of coronary arteries over time associated with inflammation forming plaques resulting in narrowing of the arteries and restricting the flow of blood to the heart muscle.
Symptoms may not manifest in the initial stages when there is a decrease in blood flow, but may show up as the plaque continues to build.
The most common symptom is angina, characterized by pain, discomfort, heaviness, tightness or numbness in the chest. It can also be felt in the neck, jaw, back, left shoulder or arms, and is often mistaken for heartburn or indigestion.
Other symptoms include shortness of breath, weakness, giddiness or fainting, sweating, and nausea. Up to 20% of the patients with heart attack have no chest pain. This is seen in diabetics, women and elderly patients. These people will mostly experience shortness of breath, nausea, sweating, fatigue or dizziness.
If you feel any of these symptoms, you should see your doctor or present to an emergency department immediately.
Some of the risk factors include:
- Cigarette smoking
- High blood pressure
- Diet rich in cholesterol and saturated fat
- Physical inactivity
- Advanced age
- Family history
- Heart attack (myocardial infarction):
- Heart failure: Over time, when the heart muscle is starved of oxygen and weakens, other conditions can occur such as heart failure (heart can’t pump sufficient blood for your entire body) and arrhythmias (irregular heartbeats).
Your doctor will examine and review your medical history, and order one or more of the following diagnostic tests:
- Electrocardiogram (ECG): to record the heart's electrical activity
- Echocardiogram: to view the heart's size, structure and motion using sound waves
- Stress test: to record the heart's electrical activity while you run on a treadmill
- Angiogram: to view the flow of blood in the heart arteries using a special dye and x-rays
- Computerized tomography (CT) scan: to screen your heart arteries for calcium and narrowing
Heart attack (myocardial infarction)
Heart attack is a medical emergency and if you suspect symptoms of heart attack, you should call for an ambulance or seek immediate medical help. The following tests may be conducted in the emergency department at the hospital:
- Blood Tests: Routine blood tests may be done for blood counts, electrolytes, cholesterol and cardiac enzymes. The cardiac enzymes in blood are markers of heart damage.
- Electrocardiogram (ECG): An ECG is a test to measure the electrical activity of the heart and provides your doctor with information about your heart rate, rhythm, size of the heart chambers and previous damage to the heart. It is non-invasive and painless and is performed by attaching electrodes to various parts of the body.
Complications of a heart attack
Complications depend upon the location and extent of the heart damage (due to blocked blood supply). Early intervention and treatment could prevent these complications.
- Cardiac arrhythmias - cardiac arrhythmias are disruptions in the natural rhythm of the heartbeat.
- Cardiac Failure - here the heart fails to pump blood to meet the metabolic demands of the body.
- Pericarditis - pericarditis is the inflammation of the pericardium, the outer covering of the heart which acts as a shock absorber for the heart.
- Recurrent heart attacks - increased risk of heart attacks and angina in the future.
Blood clots (Thromboembolism) - blood clots may be formed due to irregular rhythms and prolonged immobility. You may be prescribed blood thinning agents which needs to be monitored with regular blood tests.
If a heart attack is confirmed, then immediate treatment may include:
- Relieve anxiety and shock
- Pain relief
- Emergency coronary angiogram +/- angioplasty or stenting
- Medications to stabilize the heart rhythm
- Emergency coronary bypass surgery
General treatments include those listed below.
CAD treatment involves lifestyle changes, medication, interventional procedures and heart surgery.
It is essential to stop smoking in order to prevent worsening of blockages in the heart arteries. Adopting a healthy lifestyle that incorporates plenty of physical activity, nutritious low fat food, limited alcohol, and a good weight management regime will go a long way in preventing and controlling coronary artery disease. Diabetes must be controlled and managed very tightly; ideally your blood sugar levels should be 5-8 mmol/L on regular finger prick testing. The following lifestyle modifications can help to prevent or lower your risk for heart disease and heart attack and improve your heart health
- Healthy Diet Choices - eating a low fat, low salt, low cholesterol diet
- Don’t Smoke - if you do smoke, talk to your doctor about available options to help you quit. You will immediately lower your risk of heart disease as soon as you quit.
- Exercise - increasing your physical activity is a great way to reduce stress, improve sleep, lose weight, and improve your overall sense of wellbeing. Always discuss with your doctor before beginning any new exercise program.
- Weight Loss - being overweight puts extra strain on your heart. Discuss weight loss options with your doctor and follow their advice.
- Diabetes Control - take your diabetic medications, check with your doctor for exercises and physical activity as well as nutrition advice.
Along with life style modifications, medications may be needed to control symptoms and progression of coronary artery disease. More than one medication may be prescribed. Medications to control and limit the progression of CAD include cholesterol-lowering medication such as statins, beta blockers to reduce the work of the heart and blood thinners such as aspirin, clopidogrel and ticagrelor to prevent clots forming in the heart arteries. It is essential to continue these medications once started; any change in medication should be discussed with your GP or cardiologist first. Some common coronary artery disease medications are listed below.
- Anti-platelet agents: These include Aspirin, Clopidogrel and Ticagrelor; they reduce the tendency of small blood cells called platelets to stick together, which helps prevent the formation of a thrombosis. Often a combination of aspirin plus clopidogrel or ticagrelor is required rather than just aspirin alone.
- Nitroglycerin (GTN): These quick-acting sublingual tablets or spray relax the arteries of the heart and relieve angina attacks.
- ACE (angiotensin converting enzyme) inhibitors: stops the production of a chemical that makes blood vessels narrow and is used to help control high blood pressure, particularly in patients with diabetes and in cases of heart failure.
- Long-acting nitrates reduce the frequency of angina attacks. These can be in the form of tablets or patches and are very effective. Their main side effect is headache, but this often disappears once the nitrate has been taken for some weeks.
- Beta blockers work by slowing down the heart rate and decreasing the force of the heart muscle. This reduces the heart’s need for oxygen and improves the supply of blood to the heart muscle.
- Calcium channel blockers reduce the frequency and severity of chest pain and control blood pressure. They reduce the muscle tension in the coronary arteries and also slightly relax the heart muscle, reducing the heart’s need for oxygen and reducing blood pressure.
- Cholesterol lowering medication (statins). These medications reduce production of adverse types of cholesterol within the body. They limit build up of plaque in the heart arteries and prevent development of disease in bypass grafts in the long term. They should be considered lifelong treatment once started even if cholesterol levels are normal.
Certain procedures can be used to open up the blocked arteries:
- Balloon angioplasty: An inflated balloon is inserted into the blocked artery to compress the deposits against the arterial wall.
- Coronary artery stenting: Frequently a stent is placed the narrowed heart artery at the time of angioplasty to keep it open.
These interventional procedures are used in people presenting with heart attacks to open an acutely blocked artery and in people with angina to open some heart arteries. The blockages need to be discrete and suitable for the procedure. People with diabetes or disease in multiple heart arteries are sometimes better treated with surgery.
This is a major surgical procedure performed through an incision in the centre of the chest (sternum) using the heart-lung machine to support the heart during which arteries and veins harvested from other sites in the body are used to bypass blockages in the heart arteries. This procedure is used to treat people who have multiple narrowings in the heart arteries, who have diabetes in addition to CAD and people with impaired heart function due to CAD. Your heart surgeon Dr Orr can provide you with further in depth information about this procedure.