Washington D.C: Chances of death for women who suffer cardiac arrest outside a hospital are more compared to men as they are less likely to be resuscitated by bystanders, a new study claims.

A study published in the journal, ‘European Heart Journal’, found that people did not recognise women who collapsed were having a cardiac arrest, leading to delays in calling the emergency services and delays in providing resuscitation treatment.

Cardiac arrest occurs when the heart goes into an irregular rhythm and then stops beating completely. It is different from a heart attack (or myocardial infarction).

Dr Hanno Tan, the lead researcher said, “We found that the worse outcome in women is largely attributable to the fact that women had about half the chance of having a shockable initial rhythm compared to men.”

The term shockable initial rhythm is the heart rhythm recorded when someone with cardiac arrest is connected to an electrocardiogram machine; it is very fast (often more than 300 beats a minute) and chaotic. This fast and irregular rhythm prevents the heart from beating in a coordinated way so that there is no effective pump function, and blood can no longer circulate around the body and to the heart, leading to cardiac arrest.

Death occurs within minutes unless the heart can be shocked back to a normal rhythm by means of electrical current from a defibrillator. If this does not happen, then the shockable initial rhythm dissolves into a “flat line”, which indicates the absence of any electrical activity from the heart.

At this point, it is too late for defibrillation to work properly and the only remaining option left is chest compression to try to restore circulation sufficiently for the heart to regain its electrical and mechanical activity. The ability to recognise and treat a cardiac arrest within minutes is, therefore, crucial to being able to treat patients while they still have a shockable initial rhythm and before their heart stops.

Dr Tan and his team analysed data from all revival attempts made by emergency services between 2006 to 2012 in the Netherlands. They identified 5717 out-of-hospital cardiac arrests treated during this period, 28% of which occurred in women.

The researchers also found that women were less likely than men to receive a resuscitation attempt by a bystander (68% versus 73%) even when there was someone there to witness the collapse (69% versus 74% ). Survival from the time of the cardiac arrest to admission to hospital was lower in women (34% versus 37%), and women were less likely to survive from admission to discharge (37% versus 55%).

Overall, the chances of women surviving to be discharged from the hospital were about half that of men (12.5% versus 20%). The researchers believe this is largely explained by the lower rate of shockable initial rhythm in women – 33% versus 52% – and found several reasons that might explain this difference.

Researchers say that a possible reason why fewer women have shockable initial rhythm by the time the emergency services reach them may be because women tended to have a cardiac arrest when there were other people around to see it happen (for demographic reasons, there are more elderly women living on their own than men), and because the symptoms of a heart attack (one of the most common causes of cardiac arrest) may not be recognised so quickly in women.

The researchers call for a range of measures to tackle the problem of survival differences between men and women, ranging from public awareness campaigns about heart attack and cardiac arrest in women to reorganisation of health care systems in order to provide faster resuscitation to women, particularly those living on their own, for instance, by wearable devices that monitor heart rate and circulation and that can send alerts to monitoring systems.

Limitations to the study include the fact that 181 surviving patients were not included because they did not consent, and data on pre-existing diseases in 27.5% of heart attack patients were missing, although in both cases the missing data were distributed evenly between the sexes.

The researchers had no information on symptoms patients may have reported before their heart attacks, which may have influenced how quickly witnesses might make an emergency call.