Diabetes and Heart Disease
Part 4 – Heart Attack
People with diabetes are two to four times more likely to have a heart attack or stroke, than people without diabetes. This puts people with diabetes into a high risk category before even having had chance to take up the challenge…
What’s covered on this page
What is a ‘Heart Attack’?
The heart is a powerful muscular pump that drives blood around your body. To keep the heart healthy, the heart muscle needs a constant supply of oxygen-containing blood from the coronary arteries. A heart attack, or myocardial infarction (MI), usually occurs when a coronary artery is completely blocked by a blood clot (coronary thrombosis) (see figure).
Heart attacks may occur out of the blue, without an immediately evident ’cause’; however, cold weather, exercise, stress and strong emotion can all precipitate a heart attack.
If a blood vessel supplyng essential oxygen to the heart muscle becomes totally blocked – by a clot, for example – the area of heart muscle that is normally supplied by that artery is suddenly starved of its blood supply and, therfore, its oxygen supply. Pain results, and, unless the blood flow is restored to that area within 10-20 minutes, that area of heart muscle dies, or becomes permanently damaged.
|<<< FIGURE >>>|
If the clot is displaced or dispersed within a very short period of time, the severity of the damage may be reduced. (This is why aspirin is given immediately in the case of a suspected heart attack.)
The position of the blocked vessel may also affect the outcome, and in general, the bigger the vessel the bigger the area of heart muscle that it supplies – and ultimately therefore, the bigger the area of damage.
Another factor affecting the ‘size’ of the heart attack is the extent of existing damage to other coronary arteries in the area that’s affected. And if a network of collateral blood vessels has developed previously, in order to ‘help out’ blood supply in an area threatened by atheroma, then the resulting damage is often much less.
|Collateral blood supply
The human body has designed its own backup in reserve for blocked coronary arteries; the ‘collateral circulation‘ is a system of small blood vessels that offer an alternative route between two segments of the same artery, or sometimes between two arteries. The blockage can therefore sometimes be by-passed, if the appropriate alternative route for blood flow is available via the collateral circulation. However, this alternative circulation is not well developed in everyone, and compensation may not be sufficient to sustain normal heart function.
As a result of a heart attack, the strength of the heart muscle as a whole is greatly reduced – this means that the ability of the heart to pump blood around the body is greatly reduced. A sudden drop in blood pressure may then occur, which can cause nausea or vomiting, dizziness, or sweating.
Immediately following a heart attack, the heart rhythm is sometimes disturbed. This is called a ‘cardiac arrhythmia‘ and means that the heart is not beating in its usual regular way. There is the risk of the heart stopping altogether (‘cardiac arrest‘) so it’s important that the heart is monitored closely during the following 24 – 48 hours after a heart attack.
Heart attack symptoms are not specific to a heart attack, and can be misinterpreted (or otherwise) as being related to indigestion or other gastric disorders, chest problems, neurological problems or other musculoskeletal problems.
On the other side of the coin, a heart attack may occur with atypical (unusual) symptoms, or with no symptoms at all.
People with diabetes (and elderly people) may only experience mild symptoms, even in the case of a serious ‘full blown’ heart attack (this is possibly because nerve fibres in the heart are less sensitive to the pain or pressing discomfort).
THE WARNING SIGNS
tightness of the chest similar to that of angina;
usually in the middle of the chest but may spread;
may be felt in any or all of several parts of the body, including: the lower jaw, neck, back, stomach, shoulders or down one or both arms;
may be felt as a growing, nagging discomfort;
may feel like a very heavy weight pressing down on chest
may be ‘burning‘ feeling, similar to heartburn or indigestion;
often, the pain or discomfort is not localised or positional, and is not affected by movement of the area, or by breathing movements;
Nausea or vomiting;
Dizziness or fainting;
Sometimes loss of consciousness – collapse.
Angina pain usually lasts for a matter of minutes, however the pain experienced in a heart attack may last for anything up to half an hour. Angina is often predictably brought on by exercising or stress, and is usually relieved by resting. In comparison, with a heart attack the pain is the same as that suffered with angina, but it tends to last longer, and doesn’t ease off on resting.
|‘Stable angina’ is brought on predictably by exercise or stress, and is well controlled with drugs.
The term ‘unstable angina’ covers the first episode of angina experienced, and episodes of angina that have become worse or changed in pattern.
Unstable angina is less predictable, may come on suddenly, and the pain may be brought on by only mild exertion. In people with known existing coronary heart disease this often indicates a deterioration in the condition, and can point to an impending heart attack. A change in the pattern of pain is important, and should be reported to your doctor straight away.
|ACUTE CORONARY SYNDROME is a general medical term covering unstable angina and heart attack.|
Clinically, the main difference between a heart attack and an episode of unstable angina is the damage to the muscle cells that occurs; this can be determined by measuring substances that are released into the bloodstream when heart muscle cells are damaged (see, ‘Tests used to diagnose a heart attack‘ below. The extent of damage to heart muscle cells caused by a heart attack is roughly indicated by a rise in cardiac enzymes in the following hours / days.The shortage of oxygen in unstable angina may cause considerable pain, but results in no lasting damage to the heart muscle cells, and levels of cardiac enzymes in the blood remain normal.
… Don’t wait to see if the pain goes away. Chew an aspirin, and call for help. If you have a nitroglycerine (GTN) spray then use it.
… Dial 111 for an ambulance …
… stay resting …
… be sure that you tell the telephone operator that you are suffering from chest pain, and that it may be a heart attack.
Before arriving at the hospital you are may be given:
oxygen through a face mask
aspirin (at least 300 mg in tablets)
pain relief (for example, diamorphine or morphine by injection)
You may also need resuscitation and defibrillation if you have had a cardiac arrest. (A cardiac arrest is when the heart stops pumping properly. See, “Immediate consequences of a heart attack“, above. Defibrillation means giving an electric shock to the heart to restore its normal rhythm.)
In the event of a suspected heart attack you will likely end up in hospital. When you are arrive at the hospital you will probably first be taken to ‘Accident and Emergency’ (A&E). When your condition is reasonably stable you will be moved to the coronary care unit (CCU) for close monitoring over the next 2-3 days, then you may be moved again to a ‘step-down’ ward before going home.
Immediate treatment of a suspected heart attack can be critical, so the doctor or paramedics initially attending may have already initiated the schedule of treatment, before a heart attack is confirmed.
At the hospital you will be asked about questions about your symptoms, and your medical history and diabetes management. At the same time the staff will be taking steps to stabilise you and make sure that you are as comfortable as possible.
Your heart rhythm will be monitored by ECG (see below) and your blood pressure will be monitored as well. Blood samples will be taken for various tests to confirm that you have had a heart attack (see below), and to assess your current or immediate state of health.
You may be given pain relief to ease the discomfort. You may be put on an insulin-glucose drip.
Sometimes a clot busting drug (often streptokinase or tenecteplase) is given intravenously, which may help to disperse the blood clot, if this is the underlying cause of the heart attack. Another drug called a glycoprotein IIb/IIIa inhibitor that has been shown to be particularly useful in people with diabetes may also be given.
An electrocardiogram (ECG, or EKG) is a special test that monitors electrical activity in the heart.
An ECG is used to measure the rate and rhythm of heart beats.
An ECG also provides information on the size and position of the heart chambers and the health of the valves that control blood flow within the heart.
Heart rate should be between 50 and 100 beats per minute.
Rhythm should be consistent and even.
ECG changes (see above) may be absent or non-specific, especially if an episode of chest pain is due to unstable angina.
An ECG can show whether an artery is partially or completely blocked and this may determine the immediate course of treatment necessary.
Specific deviations from the normal trace on an ECG can give indications as to where the problem in the heart lies.
In a clinical setting, heart attacks can be broadly classified as being either:
ST-elevation MI (STEMI) or,
non ST-elevation MI (NSTEMI)
The second category (NSTEMI) is often classified alongside unstable angina. NSTEMI differs from unstable angina in that levels of cardiac ‘biomarkers’ (special blood tests, see below) are raised in a heart attack or ‘MI’.
At the hospital, blood tests will be performed for a range of things to assess your immediate state of health, and to clarify whether you have had a heart attack or not.
Usually, the first choice markers for a recent heart attack are the troponins (TnT and TnI); these are proteins that are released into the blood stream when heart muscle cells are damaged. The level of Troponin T or I in the blood after a heart attack gives an indication of the extent of damage.
Creatine kinase (CK or CK-MB) is another enzyme that is released when heart muscle cells are damaged.
Imaging studies give a realistic insight into how the heart and it’s artieries are looking. Different types of imaging use different technologies and give different types of picture.
Examples of cardiac imaging include a chest x-ray and an echocardiogram or ultrasound.
Follow-up procedures and tests may occur in the hours or days after admission to hospital and might include any of the following.
an exercise ECG
a radionuclide scan
an MRI scan
If the tests collectively indicate that one or more of your coronary arteries are severely narrowed and that drug treatment is not likely to be successful, your doctors may advise you to have:
coronary angioplasty with stent, or
coronary bypass surgery
Once the heart attack is over, there is often enough good muscle left for the heart to carry on functioning near-normally.
Usually after a heart attack, your body will replace the area of the heart muscle that was damaged with ‘scar’ tissue. This may take anything from days to months. Often, within 2 – 3 months, the heart is working just as it was before the attack.
Sometimes a heart attack can causes severe damage to the heart muscle, and the heart doesn’t recover so well. When the power behind the pumping action of the heart is reduced, breathlessness, tiredness and swollen ankles may result. These are the signs of heart failure (see Part 5).
Comprehensive multifactorial cardiac rehabilitation following a heart attack has been shown to reduce mortality and morbidity, and to improve quality of life. But research has also shown that referral and uptake of rehabilitation programmes in New Zealand (and in other countries) is not optimal – this means that there aren’t as many people benefiting from cardiac rehabilitation programs as there could be, and should be.
For more detailed information, you can download a copy of the Cardiac Rehabilitation guidelines produced by the New Zealand Guidelines Group (NZGG) from here: Cardiac Rehabilitation Summary and Resource Kit.
An additional resource for Health Professionals:
After an unexpected heart attack, or episode of unstable angina, you may be prescribed a number of drugs to continue taking after you have been discharged from hospital. It really is important that you take these medications as prescribed.
Why do you need these medications?
to prevent a(nother) heart attack (aspirin, beta-blockers or anti-arrhythmic drugs);
to control risk factors such as high cholesterol levels or high blood pressure (cholesterol-lowering drugs and blood pressure lowering drugs);
to treat angina (nitrates, calcium antagonists or beta-blockers);
to relieve symptoms of heart failure such as breathlessness (diuretics or ACE inhibitors).
See Appendix A – Drugs for more details.
Diabetes management is an important factor for your short- and long-term health. When facing additional complications, such as recovering from a heart attack your diabetes managment is perhaps not at the top of your list of priorities. Do remember to consider your diabetes, however, as better control may lead to a more speedy recovery and should also aid your phsychological health and ability to maintain a positive attitude. Seek the support of your friends and family, and talk to other people in a similar situation.
|Your Heart –
an owners manual
by Victor Marks, Dr Monica Lewis & Dr Geral Lewis
Published in NZ by Tandem Press 2002
ISBN 1 877178 92 6
|Understanding Angina & Heart Attacks
by Dr Chris Davidson
Published in association with the British Medical Association 2007
ISBN 1 903474 22 1
|The Heart Recovery Book
A rehabilitation guide
by Irene Tubbs
Published by Sheldon Press 2006