Only 10% of people with out-of-hospital cardiac arrest live for up to a year. By Michael Lim

MR A, an active male in his 40s, had completed a marathon the year before but he died suddenly while swimming. Jim Fixx, the celebrated running guru who triggered the American craze for running died suddenly while running at the age of 52. What both of them had in common were that they had underlying significant heart disease due to severe blockage of their heart arteries which were not known to them – and they both died of a heart attack during physical exertion.

Out-of-hospital cardiac arrest (OHCA)

The economic progress in the United States over the last several decades have not been matched by an increase in survival in those whose heart had “stopped” while outside a hospital environment (OHCA), with survival rates averaging less than 8 per 100. Over the last few years, an increase in public training on resuscitation techniques has increased the survival rates.

A recent 2014 publication of the data from the Cardiac Arrest Registry to Enhance Survival (CARES) in Circulation journal reported on the outcomes of more than 70,000 patients who experienced an OHCA over a seven-year period from 2005 to 2012.

The rates of OHCA survival increased from 5.7 per cent in the reference period of 2005 to 2006 to 7.2 per cent in 2008 and to 8.3 per cent in 2012. The improved final outcomes after discharge from hospital was a result of higher rates of patients reaching the hospital alive (pre-hospital survival) where the rates increased from 14.3 per cent in 2005 to 2006 to 20.8 per cent in 2012, and higher survival rates for those who have managed to reach the hospital alive (in-hospital survival).

The authors attributed the increase in pre-hospital survival to a modest increase in cardiopulmonary resuscitation and automated external defibrillator (AED) use during the study. Another recent Canadian study on OHCA published in Circulation journal looked at more than 34,000 OHCA patients who reached the hospital alive over a 10-year period from 2002 to 2012.

The annual incidence of OHCA patients was 36 per 100,000 persons in Ontario and remained about the same over the 10-year study period. The 30-day survival for OHCA patients improved from 9.4 per cent in 2002 to 13.6 per cent in 2011; one-year survival improved from 7.7 per cent to 11.8 per cent.

What was also very revealing in this study was that most patients who had OHCA had a “dying” heart rhythm when they were first attended to and these “dying” rhythms (non-shockable rhythms) are non-responsive to the automatic external defibrillator (AED).

In the study, 69 per cent had a non-shockable rhythm in 2006 and it did not change much in 2010 where 66.5 per cent had a non-shockable rhythm when they were first attended to.

Automatic External Defibrillator – medical, economic and legal considerations

Current studies demonstrate that despite the significant improvement in emergency services and the rapid advancement of techniques to open blocked heart arteries upon arrival at the hospital, the likelihood of death following an OHCA in well developed countries such as the United States and Canada is still extremely high at about 90 per cent.

While there is widespread consensus that AEDs can help to reduce OHCA deaths, the deployment of AEDs have to be balanced with the economic cost of doing so. This is especially so when most patients with OHCA have non-shockable rhythms and hence are not helped by AEDs. In addition, in a study in Denmark by Carolina, published recently in Circulation journal, the author noted that most AEDs were placed in areas with no or low incidence of cardiac arrests. Other than economic considerations, legal considerations may hamper the adoption of resuscitation devices in public places. The main concern is that there have been instances of legal action taken by families of deceased OHCA patients against the staff and owners of the public space, where staff of public spaces have resuscitated OHCA patients.

Potential negligence suit

Allegations of negligence include the staff member being slow in administering the AED, being not properly trained to administer an AED or failing to administer an AED optimally.

In addition, the AED documents the cardiopulmonary resuscitative efforts and those taking legal action have attempted to allege that the person administering the cardiopulmonary resuscitation did not perform it ideally, for example, the number of chest compressions per minute was inadequate or excessive.

Currently, the requirement for AEDs in public spaces is not mandated by law. Unless there is clarity, owners of public spaces and buildings may be hesitant to open themselves to potential negligence suits brought by members of the public who allege that their staff did not perform the resuscitation ideally in the event of an OHCA. Hence, while AEDs in public places are encouraged from a medical perspective, economic and legal considerations may deter its proliferation in public places. Given the dismal outcome where only 10 per cent live for up to a year for those with OHCA, it is better to prevent an OHCA than to treat an OHCA.

While most laypeople expect that they will have exertional chest pain if they have significant blockage of their heart arteries, the examples of Mr A and Jim Fixx illustrate that even if you can complete a marathon, it does not mean that it is impossible for you to have severe blockage of the heart arteries.

Getting medical attention

While exertional chest tightness is the most typical symptom of underlying blockage of the heart arteries, many elderly patients with severe heart artery disease may present with shortness of breath on exertion, feeling faint, upper abdominal discomfort or be completely asymptomatic.

Hence, if you suspect that you may have blocked heart arteries or are at a high risk for heart disease, you may want to consider getting yourself assessed for heart disease.

If you are young or are premenopausal:

• Opt for a simple ECG (electrocardiogram) exercise treadmill test as your first choice test.

• If your treadmill test is abnormal, you can opt for a more accurate test that does not require exposure to ionising radiation such as stress echo cardiogram (ultrasound of the heart); and stress magnetic resonance imaging (MRI) of the heart or MRI of the heart arteries.

• If these tests with non-ionising radiation are unavailable or unsuitable, a low radiation dose computed tomography (CT) scan of the heart arteries, also termed CT coronary angiogram, can be considered.

• Choose a centre which can do the scan with a low radiation exposure (limited to the heart and part of the lungs) of less than 3 millisieverts (unit of measurement of radiation absorbed) and has significant experience.

• You should generally be very careful with nuclear scans of the heart as the radioisotopes injected into your vein means that the entire body is exposed to radiation and some nuclear scans use isotopes and techniques which result in high-dose radiation exposure. While the CT allows visualisation of the site and severity of the heart artery narrowing, nuclear scans do not provide visualisation of the heart arteries.

If you are a 50-year-old post-menopausal woman or a 50-year-old male, the potential cancer risk from radiation exposure to a low dose CT coronary angiogram is negligible and hence if there is likelihood of heart artery blockage, CT coronary angiogram can be considered as it is the most accurate non-invasive test for heart arteries.

Finally, the procedure of inserting a piece of plastic tubing into the heart arteries to inject contrast media and take images of the heart arteries with X-rays (also called invasive coronary angiogram) is routinely used to confirm the presence of blockage of the heart arteries.

However, as it is costly and carries real risk of complications, it should only be considered if the non-invasive tests indicate a high likelihood of significant blockage of the heart arteries and there is intention to proceed with definitive treatment.