Acute Coronary Syndromes

The acute coronary syndromes represent a spectrum of the clinical presentations of a sudden reduction in blood supply to the heart muscle. This is usually caused by the development of a blood clot within a coronary artery at the site of rupture or "erosion" of a cholesterol rich plaque.  However occasionally tears in the blood vessel (a coronary dissection) not related to atherosclerosis, or a secondary problem such as obstruction of a vessel by clot that has come from the heart pumping chamber or the heart valves, cause an acute coronary syndrome.

The symptoms are those of an angina attack but they last more than 20 minutes, the pain keeps recurring, or is occurring with increasing frequency, with less provocation.

How do doctors diagnose a heart attack?

Patients with a suspected acute coronary syndrome need to be admitted to hospital.   In hospital the diagnosis is made by blood tests and ECG's.

What sort of heart attacks are there?

The ECG is the most important investigation to guide a doctor's management of a patient with an acute coronary syndrome. If there is total occlusion of a blood vessel by a clot this usually produces ST elevation on the ECG, suggesting the diagnosis of an ST elevation MI or "STEMI".

If the ECG does not show ST elevation then the patient has a non-ST elevation acute coronary syndrome (non-STEACS). Heart injury is then confirmed with a rise and fall in the troponin level and a non ST elevation MI or "NSTEMI" is then diagnosed. If the troponin does not rise, then "unstable angina" is diagnosed.

What are the treatment options?

There are several issues when treating a patient with an acute coronary syndrome. These include:

1.    Re-establishing adequate blood supply to prevent further damage to the heart muscle and trying to minimise the effect of the damage which has occurred

2.    Stabilising the “hot area” of unstable plaque

3.    Preventing complications of an MI

4.    Addressing the underlying risk factors that have resulted in the heart attack occurring

5.    Educating the patient about the above and the effect that this will have on their life in the future

Treating the primary problem

In a STEMI the aim is to re-establish blood flow either with drugs that are targeted at dissolving the occlusive blood clot or mechanically by placing an angioplasty balloon often with a stent through the clot and squashing it flat. This also helps to stabilise the underlying plaque rupture.  Primary PCI is only available at some hospitals, and "clot busting" drugs are therefore the preferred first option for most patients. The sooner these drugs are given the better the result, and ideally they should be given within 3 hours of the onset of symptoms to achieve the best results.

In a non-STEACS presentation, blood thinning agents are given to try and allow stabilisation of the clot, without further clot formation. These may include aspirin, clopidogrel and possibly a drug called a IIb/IIIa inhibitor that reduce the tendency for cells in the blood, called platelets, to clot.  In addition, a drug called Heparin (usually as an injection under the skin) is used and helps deactivate the bloods natural clotting factors and keep the blood thin. After a period of initial stabilisation the next step is usually to perform an angiogram with a view to identifying the vessel that has been the cause of recent problems and to treat the "culprit" lesion (narrowing) with an angioplasty and stent. On some occasions no narrowing is identified and no intervention needs to be performed, and on other occasions there are too many narrowings and a coronary artery bypass operation is recommended.

Preventing complications

In conjunction with treating the intra-arterial clot, other drugs are administered which are aimed at reducing the short and long-term complications of the acute coronary syndrome. These include:

Betablockers – these help to stabilise the heart rhythm, to reduce the heart's energy consumption by slowing the heart, to lower blood pressure and making the heart cells more energy efficient, and in the longer term to lessen the problems associated with heart failure.

Angiotensin Converting Enzyme inhibitors (ACE-Inhibitors) and Angiotensin Receptor Blockers (ARBs) – these help to reduce the change in shape of the heart that occurs in response to an area of the heart becoming scarred, thereby preserving heart function. In the longer term they have an effect at the blood vessel level of helping to reduce the inflammation that causes atherosclerosis and limit the risk of future problems.

Statins – these are administered to all patients to lower the cholesterol even if it is not raised, and lessen the inflammatory activity in the vessel wall. This has the overall effect of not only reducing the risk of further acute coronary syndromes, but also the risk of stroke and blockages in other arteries byapproximately 20-30% over 5 years.

Most patients will be on a combination of aspirin +/- clopidogrel, a statin, an ACE-Inhibitor or ARB and a beta blocker. Not everyone can take all of these medications because of side effects or other medical reasons not to take the drug;  however most patients can take at least some of these very useful agents.

Other risk factor issues

Diabetes Mellitus:
Diabetic patients are at higher risk of vascular disease. The risk is not an absolute one, but is a scale which is at the lowest in people with truly normal blood sugar, to higher with abnormal glucose handling, to the highest in diabetic people. Your doctor can assess this by both a fasting sugar (to diagnose diabetes), a glucose tolerance test or a test called a haemoglobin A1c which rises in conjunction with abnormal sugar handling of the body - essentially the lower the better in terms of vascular risk.

§  After a heart attack we know that the better the control of the serum glucose the better it is for your heart, and the less the risk of more problems. In hospital an infusion of insulin is often given to lower sugars in the short term, then insulin or oral agents may be started to be continued in the longer term.

§  If the HbA1c is high, but the sugar is not at the level to diagnose diabetes, then sugar control can be helped by a combination of diet and exercise, in conjunction with treatment of risk factors and other agents that may lessen the risk of developing diabetes, such as ARBs or metformin.

Smoking:
Smoking causes heart disease and lessens the beneficial effects of the agents that we give to try and thin the blood and prevent further complications. Smoking cessation is often the hardest change for a patient to make, yet the most beneficial in the longer term. It is an area in which there is no simple solution, and a variety of options may need to be explored. 

Hypertension:
Blood pressure should be well controlled after a heart attack. The medications mentioned above often have blood pressure lowering effects and will help with this.

Finally

Acute coronary syndromes often occur in previously healthy individuals. This places a psychological burden on the patient that should not be overlooked. Approximately 30% of people will experience a degree of depression after a heart attack. This is something that does not always need medication, but needs to be acknowledged, through the post infarct period where a period of recognition, education and acceptance of events occurs. The psychological effect may be more marked where one’s occupation or independence, including financial freedom, is threatened.  A clinical psychologist can be consulted if the psychological effects are pronounced.

Driving

There are certain legal guidelines to be considered before returning to driving and these can be found at www.ltsa.govt.nz under medical aspects of fitness to drive. If you have any questions about these they can be discussed with your doctor, who may have to seek guidance from the LTSA if there is an area of uncertainty.

The cardiac care of a patient with an acute coronary syndrome depends on team work. This is shared between the hospital medical team, the nurses along with a cardiologist, who deal with the initial acute management and longer term care led by primary care physicians (GPs) who oversee the community care of the patient and their risk factor control. An important bridge between the hospital and community is the cardiac rehabilitation service which is led by cardiac nurse specialists. This team helps to educate and rehabilitate the patient with an acute coronary syndrome back into life with the emphasis on prevention and empowering the patient to control their risk factors with the aim of living a normal life, free of limitation for as long as possible.

Remember!

Despite all of the efforts the cardiac team make we have not yet found a cure for atherosclerosis ('hardening of the arteries'), and whilst we have made huge steps forward in terms of prevention, the risk is still there. It is therefore very important that if symptoms recur medical attention be sought promptly.

§  If the symptoms are only with exertion and respond to rest then GP review should be sought within 24 hours.

§  If the symptoms are prolonged (>20minutes), do not settle with nitrolingual spray or are recurrent then urgent hospital attendance is necessary, by ambulance.

The reason for this careful approach is that if the symptoms are non cardiac then nothing is lost apart from a hospital review. But if a further acute coronary syndrome is in process then early treatment minimises the risk of damage to the heart.