Coronary heart disease

Coronary heart disease occurs when the coronary arteries, which deliver oxygen to the heart muscle, become narrowed or blocked because of the build-up of fat/cholesterol within the artery wall.

If the build-up is only mild, symptoms may include a feeling of pressure or tightness in the chest at times of increased activity or stress and/or shortness of breath or fatigue with physical exertion. When the blood supply to the heart muscle is severely reduced, chest pain (angina), heart attack (myocardial infarction), or heart rhythm disturbances (arrhythmia) may occur.

In New Zealand, 170,000 people (or one in 23 adults) are living with heart disease and every 90 minutes someone dies from the disease.

Causes and risk factors

The heart is a muscle that pumps blood to all parts of the body. When the heart chambers contract, blood is pumped out of the heart through the aorta (the main artery from the heart) carrying oxygen and nutrients to the rest of the body. The heart itself also needs oxygen to function. It is the job of the coronary arteries to deliver oxygen-filled blood to the heart muscle.

Coronary heart disease is also known as atherosclerotic heart disease, ischaemic heart disease, and coronary artery disease. It is the result of the narrowing or blockage of coronary arteries by plaque formed by fat/cholesterol on the artery walls (a process known as atherosclerosis).

There are many risk factors related to coronary heart disease. Some of these risk factors can be controlled through lifestyle changes and/or medications, while others cannot.

Controllable risk factors include:

• High blood cholesterol
• Smoking
• High blood pressure
• Type 2 diabetes
• Physical inactivity
• Obesity
• Poor diet
• Stress / anxiety.

Non-controllable risk factors include:

• Age
• Gender
• Ethnicity
• Family history
• Medical history.

Coronary heart disease affects men more commonly than pre-menopausal women. However, after menopause, the incidence in women increases to be virtually the same as men. Men older than 45 years and women older than 55 years are at increased risk.

Women who have endometriosis, gestational diabetes, polycystic ovary system, pre-eclampsia, or early menopause  (before 40 years of age) may have a higher than normal risk of developing coronary heart disease.

Overall, Māori and Pacific Island New Zealanders are more at risk of suffering from coronary heart disease.

Diagnosis

If coronary heart disease is suspected, a thorough physical assessment will be undertaken. This will include an assessment of risk factors and current symptoms. Additional tests to assist with making an accurate diagnosis may also be undertaken. Tests may include:

Blood tests

These tests check the levels of cholesterol, triglycerides, blood cells, clotting factors, and hormones in the blood. Blood tests may also be done to detect the presence of enzymes and proteins that can indicate problems with the heart.

Electrocardiogram (ECG)

A resting ECG records the electrical activity of the heart when at rest. This may show changes that indicate the heart muscle is not receiving enough oxygen. Electrical activity of the heart will be recorded using electrodes placed on the arms, legs, and chest.

Exercise ECG/ Exercise tolerance test (ETT)

This test is designed to assess the heart’s response to exercise and stress. It involves walking on an exercise treadmill or riding an exercise bike for up to 12 minutes at varying degrees of speed and incline. Continuous ECG and blood pressure recordings are taken and symptoms of coronary heart disease, such as shortness of breath, and pain in the chest, jaw or arm will be noted. A doctor and an ECG technician will be present at all times. 

Results based on the ECG, blood pressure recordings, and any symptoms experienced can indicate whether coronary heart disease is present.

Echocardiogram

An echocardiogram uses ultrasound waves to display the movements of the heart as it beats. The image produced allows doctors to precisely measure the dimensions of the heart, view the structures of the heart (such as the heart valves), and assess any damage to the heart muscle.

Stress echocardiography

This test, also referred to as a “stress echo”, involves the administering of certain medications into the blood stream through a drip in the hand or arm while the echocardiogram is being performed. These medications stimulate the heart and mimic the effect of exercise. This test is often used for people who are unable to exercise for medical reasons.

Coronary angiography (Angiogram)

A coronary angiogram (also known as cardiac catheterisation) is a diagnostic test that involves inserting a small, flexible tube (catheter) into an artery in the wrist or groin. 

The catheter is threaded up through the artery, into the aorta and is positioned at the entrance to the coronary arteries. A specialised x-ray dye containing iodine is injected through the catheter and into the coronary arteries. The x-ray dye is able to be seen on an x-ray screen and produces an outline of any narrowing or blockages in the arteries. Heart function and efficiency can also be assessed during this test.

Computerised tomography (CT) coronary angiography

This computerised x-ray technology uses multiple cross sectional x-ray images to create detailed three-dimensional pictures of the heart. 

A contrast dye is injected through a vein, usually in the arm, and x-rays are taken while the person is lying on a specialised x-ray table. The contrast dye briefly fills the arteries of the heart and the heart chambers, enabling them to be seen on the x-ray pictures. The three-dimensional pictures can indicate any narrowing, fat deposits, and calcium in the arteries. Information can also be gained about the heart muscle function and the heart valves. 

Nuclear heart scan (radionuclide scan)

A nuclear heart scan is an imaging test that involves the injection of a small amount of radioactive material, called a tracer, into the bloodstream. Computer generated pictures of the tracer are then taken as it moves through the heart. From these images it is possible to assess how the heart is functioning and detect any narrowed or blocked blood vessels. Nuclear heart scanning techniques include: positron emission tomography (PET) and single photon emission computed tomography (SPECT).

Treatment

Depending on the test results, various treatment options will be considered. Treatment may include medication, coronary angioplasty (with or without coronary artery stenting), or coronary artery bypass surgery (commonly known as coronary artery bypass grafting or CABG). 

Treatment is aimed at reducing or eliminating symptoms and reducing the risk of having a heart attack.

Medications

Classes of medications commonly used to treat coronary heart disease include:

• Beta blockers - These medications slow the heart rate and reduce the blood pressure, thus reducing the heart’s workload.
• Nitrates - These medications dilate (widen) the coronary arteries, making it easier for blood to be pumped through.
• Calcium channel blockers/calcium antagonists - These medications work by slowing the entry of calcium into the heart and blood vessel walls. This relaxes the arteries causing them to dilate, which lowers the blood pressure and reduces the heart’s workload.
• Angiotensin-converting enzyme (ACE) inhibitors and angiotensin II receptor blockers (ARBs) - These medications prevent the constriction of peripheral blood vessels, thereby reducing the pressure against which the heart must pump. They may also prevent the coronary heart disease getting worse.

An antiplatelet agent, such as aspirin or clopidogrel, may also be prescribed (unless there is a medical reason not to) as they help prevent the formation of blood clots, which reduces the risk of having a heart attack or stroke.
 
Some people will require medication called statins to lower their blood cholesterol levels, thereby reducing plaque build-up in the arteries and reducing the risk of having a heart attack. Common statins are simvastatin and atorvastatin.

Coronary Angioplasty and Stenting

Coronary angioplasty (percutaneous coronary revascularisation) is a non-surgical technique used to widen narrowed coronary arteries. The procedure is similar to an angiogram and involves inserting a balloon-tipped catheter into a narrowed coronary artery. 

As with an angiogram, the catheter will be inserted through an incision in the groin or wrist. The patient will be awake, but sometimes mildly sedated, for the duration of the procedure. The balloon is positioned at the site of the narrowing in the coronary artery. It is then inflated, compressing the plaque and slightly stretching the artery wall. This increases the diameter of the artery and therefore improves the flow of blood to the heart.
 
Most angioplasties also involve the placement of a stent. A stent is a small mesh tube that is placed in the narrowed coronary artery during the angioplasty procedure, acting as a scaffold to keep the artery open. The stent is mounted over the catheter’s balloon, so that when the balloon is inflated in the narrowed section, the stent opens. The balloon is then deflated and removed, leaving the expanded stent in place.
 
The use of stents has been shown to significantly reduce the rate at which coronary arteries re-narrow. The majority of stents are made of metal. However, some bio-absorbable stents made of a dissolvable polymer are also now in clinical use. Most stents are coated with a medication that further reduces the risk of re-narrowing of the artery. These are known as drug-eluting stents.
 
Coronary angioplasty and stenting has a high success rate, but it is not necessarily an appropriate treatment for all people with coronary heart disease. If the narrowing in the coronary arteries are numerous and severe, surgery may need to be considered.

Coronary Artery Bypass Grafting (CABG)

CABG involves using a blood vessel taken from elsewhere in the body to restore blood flow beyond the area of the narrowed artery. This is done by grafting one end of the blood vessel to the blocked coronary artery below the blockage or narrowing and the other end to the aorta, thus “bypassing” the blockage. Chest wall arteries, arteries from the forearm, and veins from the legs can be used as graft vessels. After the operation, joining a cardiac rehabilitation programme may be recommended to aid recovery.

CABG graphic courtesy of A. Bonsall MedicineNet.com

Prevention

There are a number of lifestyle changes or self-management steps that can be taken to prevent or reduce the risk of developing coronary heart disease. These include:

• Eating a healthy, balanced diet (see heart disease diet)
• Limiting alcohol intake
• Quit smoking
• Undertaking regular physical exercise – 30 minutes most days of the week (see heart disease exercise)
• Maintaining a healthy body weight
• Maintaining healthy blood cholesterol levels
• Effectively treating medical conditions such as type 2 diabetes and high blood pressure
• Being aware of risk factors.

Self-awareness and education to minimise risk factors is important in helping to prevent and control coronary heart disease.

Further information

Because coronary heart disease is the major cause of illness and death in New Zealand, refinements and new approaches to treatments are constantly being attempted and investigated. This research is recognised internationally. For further information on coronary heart disease, please contact a doctor or the National Heart Foundation of NZ.

The Heart Foundation of New Zealand (National Head Office)

Phone: (09) 571 9191
E-mail: [email protected]
Website: www.heartfoundation.org.nz

There are local branches in most New Zealand regions. 

References

Heart Foundation (Year not stated). General heart statistics in New Zealand (Web Page). Auckland: Heart Foundation of New Zealand. https://www.heartfoundation.org.nz/statistics/ [Accessed: 08/06/21]
Heart Foundation (Year not stated). Heart Treatments (Web Page). Auckland: National Heart Foundation of New Zealand. https://www.heartfoundation.org.nz/your-heart/heart-treatments [Accessed: 08/06/21]
Heart Foundation (Year not stated). Coronary artery disease (Web Page). Auckland: Heart Foundation of New Zealand. https://www.heartfoundation.org.nz/your-heart/heart-conditions/coronary-artery-disease [Accessed: 08/06/21]
National Heart, Lung, and Blood Institute (Year not stated). Coronary heart disease (Web Page). Bethesda, MD: National Institute of Health. https://www.nhlbi.nih.gov/health-topics/coronary-heart-disease [Accessed: 08/06/21]
NHS Choices (2020). Coronary heart disease (Web Page). Redditch: National Health Service (NHS) England. https://www.nhs.uk/conditions/Coronary-heart-disease/ [Accessed: 08/06/21]
O’Toole, M.T. (Ed.) (2017). Coronary artery disease. Mosby’s Dictionary of Medicine, Nursing & Health Professions (10th ed.). St Louis, MI: Elsevier.

Last Reviewed – June 2021

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