Part 1 – Introduction
“Diabetes is a major risk factor for heart disease…”
“Heart Disease is twice as common in people with diabetes…”
What exactly does this mean for you and me?
There is frequently much fear and uncertainty associated with a diagnosis of heart disease. The expression ‘heart disease’ itself can be used to describe any one of a variety of conditions. Adding to the potential confusion, is the fact that there are also several different phrases used to describe exactly the same condition.
This section of the web site (divided into 4 parts) aims to shed light on coronary heart disease and associated conditions, and to provide practical advice for prevention strategies, and up-to-date information on treatment approaches.
What’s covered on this page
Normal Heart Function – What the Heart Does
The heart pumps blood around the body, supplying oxygen and nutrients essential for life. It is largly muscle, which contracts and relaxes (‘beats’) continually, day and night.
Blood is carried away from the heart in arteries. Arterial blood is rich in oxygen. The blood arrives at various organs and tissues around the body, and the cells in these tissues use up the oxygen. Veins carry blood back to the heart. Venous blood is low in oxygen.
The oxygen that we need to survive comes from the air that we breathe. It is taken into the body through the lungs. The heart and lungs work together to take the oxygen to the body’s cells.
The heart has four ‘chambers’, two on each side. The right side of the heart collects ‘used’ blood from the body, and then pumps it to the lungs. The blood, now rich in oxygen, returns from the lungs to the left side of the heart. The left side of the heart then pumps the oxygen-rich blood to the rest of the body.
For more detailed information on the structure and function of the heart, see the section, “Normal Heart Functioning – How the Heart Should Work” in Part 2 of this Heart Disease section.
Just what exactly do all the terms mean?
There are a multitude of things that can go wrong with the heart and circulation system. Heart disease (‘cardiovascular disease‘) is an umbrella term, which covers a large number of different conditions. The ‘Quick Reference’ charts in this section (just below) aim to help you to understand what’s what.
Every organ system in the body is supplied with arterial blood, including the heart itself. The heart muscle is supplied with blood from the coronory arteries and their branches. Damage to the coronory arteries reduces the supply of blood to the heart muscle (‘myocardium‘); this is the basis of coronory heart disease (CHD), which is the most common type of heart disease, and is more common in people with diabetes.
CORONORY HEART DISEASE
[Quick Reference – Glossary of Terms]
|Coronary heart disease (CHD)||This term covers many aspects of heart disease, and may be associated with any of the following terms in this summary table.|
|Coronary artery disease (CAD)||Disease of the coronory arteries; these blood vessels supply blood to the heart muscle itself.|
|Ischaemic heart disease (IHD)||Disease of an area of heart muscle as a result of poor blood supply to that area – usually due to narrowed coronory arteries (i.e. CAD/CHD).|
|Hardening of the Arteries||As fat builds up in the wall of the blood vessel it attracts calcium and fibrous tissue, forming plaque.|
|Chest pain; frequently associated with exercise or exertion, and diminishes when at rest.
“Unstable” angina – pain is experienced at rest.
|Heart attack||A blockage in the blood supply results in death of an area of heart muscle; associated with severe chest pain, also nausea or vomiting.|
|Myocardial infarction (MI)|
|Arrhythmia||An irregular heartbeat; may cause palpitations and/or breathlessness.|
|Heart Failure||The heart fails to pump sufficient blood around the body.
“Congestive heart failure” may result in swollen lower legs or ankles (oedema), or breathlessness related to fluid build-up in the lungs (pulmonary oedema).
May be as a result of CHD, or other heart disease.
|Aneurysm||A swelling, ballooning or bulge in the blood vessel wall.|
|Embolism||A clot or dislodged piece of plaque (the ‘embolus‘) blocks the blood vessel.|
|OTHER HEART CONDITIONS|
|Congenital heart disease||Abnormalities of the heart that are present at birth – not related to having diabetes.|
|Cardiomyopathy||Disease of the heart muscle itself (as opposed to the blood vessels supplying the muscle) – not usually related to having diabetes.|
|Myocarditis||Inflammation of the heart muscle – not usually related to having diabetes.|
|Heart valve disease||Disease of the valves that control the flow of blood into and out of the four chambers of the heart – not generally associated with having diabetes.|
TREATMENTS AND TECHNOLOGIES
[Quick Reference – Glossary of Terms]
Coronory Artery Bypass Graft (CABG)
|Veins are taken from the leg and grafted on to the artery in order to restore adequate blood flow within the heart muscle.|
|Balloon angioplasty||Tiny balloons are used to stretch open narrowed or partially blocked arteries; fine wire stents can be used to keep arteries open.|
|See Appendix A for more detailed information on medications prescribed for heart disease and associated conditions|
|Blood thinners||ASPIRIN or WARFARIN – used to help prevent clots forming, which may otherwise precipitate a heart attack.|
|Clot busting drugs||ASPIRIN or STREPTOKINASE or tPA (tissue plasminogen activator) – used after a heart attack to help dissolve the clot and prevent further damage.|
|Cholesterol lowering drugs||STATINS lower blood cholesterol levels by slowing the production of cholesterol in the liver.
RESINS bind cholesterol in the intestines, reducing its absorption into the body.
|Triglyceride lowering drugs||FIBRATES speed up the breakdown of triglyceride-rich lipoproteins in the body.|
|GTN (glyceryl trinitrate spray or tablets)||Used in the tratment of angina pain. It is absorbed quickly through the lining of the mouth. GTN dilates the coronory arteries, improving blood flow through the heart muscle.|
The terms “risk” “relative risk” and “risk factor” are often used in medicine; they simply relate to your chances of getting a given disease.
I frequently use the analogy of crossing a road in relation to getting hit by a truck: the more times you cross the road, the greater are the chances that you will get hit by a truck. But of course that’s not the only factor involved – for example, a larger number of trucks using the road would also increase your risk. The speed at which you cross the road would affect the risk too. I am sure you could come up with more factors that would affect your chances of being hit by a truck. All of these factors are ‘risk factors’.
If we compare the chances of being hit by a truck under different circumstances then we are considering ‘relative risk’.
|A risk factor can be defined as follows:
“… a characteristic or feature relating to an individual – either a genetic or environmental factor – that can be used to predict that individual’s probability of developing heart disease”
|Risk factors that
cannot be changed
|Risk factors that
can be reduced or controlled
|* See section, “Where does diabetes fit in to the picture?”, below.|
There are a number of “Calculate your Risk” tools and software available that can be used to quantify risk; these are useful for patients and health professionals to use as a starting point, in order to determine the level of intervention that may be required.
In New Zealand, absolute cardiovascular risk is frequently calculated from the National Heart Foundation’s cardiovascular risk tables or electronic decision support tools, which have been developed based on the US Framingham Heart Study risk paper (1).
Although these risk equations have been validated in different populations, they may not be appropriate for Maori or Pacific Islanders, who have a higher risk than Europeans. Actually though, they may not be appropriate for people with diabetes irrespective of race or ethnic background (see below).
The New Zealand Guidelines Group (NZGG) published the Best Practice Evidence-based Guideline, “The Assessment and Management of Cardiovascular Risk” in 2003; this devoted a large section to the specific management of people with diabetes, highlighting the importance of the relationship between diabetes and heart disease.
Some risk factors we can do little about – we cannot (as yet) stop the aging process as such, neither can we change our sex, nor the genes that we inherit. Once we have diabetes, our risk of developing heart disease increases, irrespective of how well the diabetes is controlled. We cannot change the fact that we have diabetes.
Cardiovascular risk assessments are recommended on an annual basis for all people with diabetes. Usually, this would form part of the Annual Review. Using the National Heart Foundation’s cardiovascular risk tools may not be appropriate for some populations including Maori, Pacific Islanders, and ‘people with diabetes’ (see above). An alternative tool is that developed using UKPDS data. This is available from the Diabetes Trials Unit (refs) and may be more applicable for use in people with Type 2 diabetes. (What about Type 1’s?!)
Understanding the relationships between the various risk factors is difficult, and quantifying the effects in the presence of diabetes is also diffcult. But for certain we can take steps to reduce or minimise the risk; these are mainly healthy lifestyle options that we can undertake. Taking appropriate diabetes medications, making healthy food choices, exercising, and monitoring blood glucose levels will all help to reduce cardiovascular risk – i.e. your risk of developing heart disease or suffering from a heart attack or stroke.
Loss of “The Gender Advantage”
In the ‘normal’ or ‘non-diabetic’ population, men are known to have a greater risk of heart attack than women do, and they have attacks earlier in life. Even after menopause, although women’s death rate from heart disease increases, it is not as great as men’s. However, this advantage that women have over men is lost in people with diabetes. See the section on “Menopause” in “Women’s Pages” for more information.
Stevens R, Kothari V, Adler AI, Stratten IM, Holman RR. UKPDS 56: The UKPDS Risk Engine: a model for the risk of coronary heart disease in type 2 diabetes. Clinical Science (2001); 101: 671-679 [Corrections Clinical Science (2002); 102: 679 ]
Kothari V, Stevens RJ, Adler AI, Stratton IM, Manley SE, Neil HAW, Holman RR. UKPDS 60: Risk of stroke in type 2 diabetes estimated by the UKPDS Risk Engine. Stroke (2002); 33: 1776-1781 PMID: 12105351
Richard J. Stevens, Ruth L. Coleman, Amanda I. Adler, Irene M. Stratton, David R. Matthews, Rury R.Holman. UKPDS 66: Risk Factors for Myocardial Infarction Case Fatality and Stroke Case Fatality in Type 2 Diabetes Diabetes Care (2004); 27: 1: 201-207 PMID: 14693990
1: Diabet Med. 2005 Feb;22(2):228. Related Articles, Links Comment on: Diabet Med. 2004 Apr;21(4):318-23. Framingham risk equations underestimate coronary heart disease risk in diabetes. Stevens RJ, Coleman RL, Holman RR. PMID: 15660747
Diabet Med. 2004 Apr;21(4):318-23. Related Articles, Links Comment in: Diabet Med. 2005 Feb;22(2):228. Evaluating the performance of the Framingham risk equations in a population with diabetes. McEwan P, Williams JE, Griffiths JD, Bagust A, Peters JR, Hopkinson P, Currie CJ. PMID: 15049932
Diabetes Care. 2004 Jul;27(7):1843-4; author reply 1844-5. Related Articles, Links Comment on: Diabetes Care. 2004 Jan;27(1):277-8. Comparative study of prognostic value for coronary disease risk between the U.K. Prospective diabetes study and framingham models: response to Protopsaltis et al. Stevens RJ, Holman R. PMID: 15220283
Diabetes Care. 2004 Jan;27(1):277-8. Related Articles, Links Comment in: Diabetes Care. 2004 Jul;27(7):1843-4; author reply 1844-5. Comparative study of prognostic value for coronary disease risk between the U.K. prospective diabetes study and Framingham models. Protopsaltis ID, Konstantinopoulos PA, Kamaratos AV, Melidonis AI. PMID: 14694007
Diabet Med. 2004 Mar;21(3):238-45. Related Articles, Links Coronary heart disease risk assessment in diabetes mellitus: comparison of UKPDS risk engine with Framingham risk assessment function and its clinical implications. Song SH, Brown PM. PMID: 15008833