How we can stop heart attack deaths

Just over 30pc of cardiac arrest deaths come without warning and without any prior history of, or recognisable symptoms of, coronary disease. Picture: iStock

Over the last month or so there have been a number of high profile, sudden and unexpected cardiac deaths in Australia. It is important for the community to understand that these deaths are common and largely preventable. There are many causes of sudden death but coronary heart disease is the commonest cause of death in Australia for both men and women. Around 60pc of these have a known diagnosis of coronary disease. However, just over 30pc of these deaths come without warning and without any prior history of, or recognisable symptoms of, coronary disease. Perfectly well one day, even running a marathon or high intensity cycling, then the next day they drop dead.

How do we prevent such a catastrophe when there is no warning, and are we doing enough to prevent these deaths in people with known disease?

Coronary disease occurs when cholesterol accumulates in the wall of a coronary artery and forms fatty collections called plaque. Mostly these plaques don’t block the artery enough to limit blood flow and therefore will not cause symptoms (generally symptoms such as angina only occur when the degree of obstruction has reached a 70pc or greater narrowing of the coronary lumen). However, even in plaques with minimal obstruction that cause no preceding symptoms the fatty collection can cause inflammation in the artery and in some cases the inflammation can lead to the plaque rupturing through to the inside of the artery. This itself doesn’t cause symptoms either but the fatty liquid in the plaque, when exposed to the circulating blood in the artery, can lead to a blood clot on the surface of the plaque which can then abruptly block the artery leading to a heart attack.

Fortunately most will survive such an event but in approximately 30pc of cases the heart will go into ventricular fibrillation or cardiac arrest and within seconds the patient will die unless CPR (cardiopulmonary resuscitation) can maintain cardiac output until someone can use a defibrillator to revert the heart rhythm to normal. Many lives are now being saved in the community due to the increasing knowledge about CPR and the availability of automatic defibrillators.

However, these community based saves are only a tiny percentage so how can we prevent the majority of cases that just die suddenly and without warning?

We now have the knowledge to prevent the vast majority of these tragedies. An understanding of risk factors can inform us as to who is at increased risk of developing coronary disease, and we have the technologies to diagnose those that have disease but are asymptomatic. Importantly we also have effective treatments so that once coronary disease is diagnosed we can prevent it from progressing thereby substantially reducing the risk of further heart attack and death.

Everyone should have regular risk assessments by their GP. Anyone with a family history of coronary disease or sudden death, anyone who is a smoker, or has high blood pressure or an elevated cholesterol is at risk. Males are at greater risk (at an equivalent age) and age is of course a major factor. Once the risk is considered significant, we can then do one of two tests to determine if the patient actually has coronary disease. The first is a special CT scan to measure the calcium in the coronary arteries (coronary calcium score). Normally this is zero and 30pc of people at low to moderate risk will have a score of zero. Someone with a CT calcium score of zero has a less than one in a thousand risk of cardiac death over the next 5 years. Any calcium is abnormal and is a result of previous scarring in the artery. The doctor may well decide to treat, depending on the overall risk assessment. The other test is a CT coronary angiogram (CTCA). This is more involved and involves injecting contrast into a vein in the arm and then a scan can outline the coronary arteries and we can then see plaque in the walls of the coronary arteries, even if the artery is not blocked. If there is no plaque, the risk of a cardiac death or a heart attack in the next 5 years is close to zero. Despite its potential lifesaving role coronary calcium score is not Medicare rebateable but only costs between $70 to $120. The CTCA is rebateable in certain circumstances but otherwise may cost between $600 and $1200. Most likely well over 90pc of patients with sudden cardiac death would have had an abnormal risk profile, and an abnormal coronary calcium score or CTCA and would have been prime candidates for preventive therapy.

How effective is treatment? The first thing to point out is that coronary stenting, although pivotal in the treatment of an acute heart attack, does not, in itself, reduce mortality or the incidence of heart attacks in asymptomatic high risk individuals or in patients with known stable coronary disease. This has been investigated in numerous clinical trials and the results are remarkably consistent. Stenting may reduce symptoms in people with angina but doesn’t save lives. Other treatments are necessary.

The treatment that does work is the use of lifestyle changes including smoking cessation, diet, exercise, weight loss, and most importantly the use of cholesterol lowering drugs which have revolutionised the management of this disease. It has been found that lowering the LDL cholesterol (LDLC) sufficiently combined with sensible lifestyle changes can, and does lead, to amelioration of the disease. Once this starts to happen the risk of adverse cardiac events diminishes dramatically. Levels of LDLC below 1.8 mml/L should be the minimum target as per Heart Foundation guidelines.

Those of us that see hundreds of high risk patients rarely see a patient die unexpectedly with coronary disease when they are appropriately treated, achieve LDLC levels of less than 1.8 mml/L and stick to sensible lifestyle changes. The great majority of the sudden deaths in the community can be prevented by identifying high risk individuals and following this advice. For the other 60pc of people who first present with angina or a heart attack that they survive, following these steps again results in extremely low risk of death or further heart attacks.

Currently however follow up studies of patients with known coronary disease show that over half of patients are not taking medications appropriately, and as such these patients remain at risk.

In summary we can dramatically reduce the incidence of coronary mortality and morbidity by the following:

1. Everyone should get a risk assessment by the age of 40.

2. The lack of any symptoms, or the ability to exercise to a high level does not mean you don’t have coronary plaque that may rupture and cause sudden death or a heart attack.

3. Tests such as exercise tests, stress echocardiography or nuclear studies tell us if there is a blockage greater than 70% that might cause symptoms. They do not tell us if we have coronary plaque. Many patients with sudden death could have a negative test the day before they drop dead.

4. The onset of any symptoms such as chest tightness or shortness of breath require immediate medical assessment.

5. If there is any concern about the risk then a coronary calcium or CT coronary angiogram should be considered. Those with abnormal results require specific preventative therapy as outlined above

6. Although effective treatment for those suffering an acute heart attack, in patients with no symptoms or with stable angina coronary stenting does not prevent death or heart attacks.

7. In those that have been diagnosed with coronary disease, the biggest problem is a failure to continue taking medications. We generally aim for an LDL cholesterol level of less than 1.8 mml/L, preferably down to 1.4. Ask your doctor for a copy of your results.

8. Finally the vast majority of unexpected cardiac deaths and the untold grief and waste of human lives can be prevented by understanding these principles.

Brett Forge is a cardiologist at West Gippsland Hospital, Victoria. Professor Richard Harper AM, is emeritus director Monash Heart, Monash Health; chair Cardiology Committee, MBS Review