Study to improve survival chances of sudden cardiac arrest patients
Posted on July 23, 2012, Monday
SGH EMBARKS on world’s first study to improve survival chances of sudden cardiac arrest patients.
For every patient who walks away from a sudden cardiac arrest, 49 others do not make it.
Ms Samantha Yong was one of those who pulled through despite the bleak odds.
When she first felt heart palpitations one day, the 22-yearold brushed it off.
After all, she had always been healthy save for a harmless allergy and, at her age, she did not think she needed to worry about heart problems.
A few days later, she collapsed in her bathroom while getting ready for work.
Ms Yong’s heart had simply stopped, without warning.
Fortunately, her husband, who was then her boyfriend, administered cardiopulmonary resuscitation (CPR) until the paramedics arrived.
“The CPR definitely saved my life. I was beginning to turn blue, so whatever he did kept me going until the paramedics arrived and restarted my heart with a defibrillator,” said Ms Yong.
But many others will not be as lucky as Ms Yong.
Only two per cent of those who suffer sudden cardiac arrests outside of a hospital survive, according to a 2003 study, which also found that the quality of CPR is an important but often overlooked factor in determining survival rates.
A desire to change the grim outcome faced by patients whose hearts suddenly stop prompted doctors at Singapore General Hospital (SGH) to embark on a clinical trial that relooks resuscitation techniques.
For the first time, a study will compare the success rates of administering an electric shock at two different points in the CPR cycle in people.
During CPR, both hands are used to compress the chest, then are pulled away to mimic the pumping action of the heart.
“The standard practice is to deliver the shock during the pause between CPR compressions.
But we think a shock delivered during the upstroke of the chest compressions (when pressure is released and the heart expands to fill with blood) may yield better results.
“Early CPR is important at that point to get some blood flowing and, with the residual oxygen in the blood, the heart is prepared, giving it a greater chance of restarting when a defibrillator is used,” said Assoc Prof Ong.
A defibrillator is a device that delivers an electric shock to stop the abnormal rhythm and get the heart to beat at a normal rhythm again.
Sudden cardiac arrest affects more than 1,000 people in Singapore annually.
Most cases are caused by an abnormal heart rhythm.
This makes the pumping action of the heart ineffective, resulting in a reduced supply of blood and oxygen to the brain, which causes the person to lose consciousness.
In the past, when paramedics performed manual CPR on patients, it was possible to deliver the dose of electrical energy only during a pause in the CPR cycle to avoid shocking the rescuer as well.
But since 2005, SGH has been using a CPR machine, which applies consistent pressure to the chest at a consistent pace.
As it is no longer necessary for the rescuer to be in direct contact with the victim, it has become possible to synchronise the shock delivery at any point of the cycle.
The trial team, led by Assoc Prof Ong, believes the best time to deliver the shock is during the upstroke of the CPR cycle when the heart is most filled with blood.
So, tweaking the timing of the shock delivery to coincide with this point of the CPR cycle is expected to have a positive impact on the outcome.
The multi-centre trial, which will involve almost 300 patients in Singapore and Holland, hopes to achieve similar success rates as those of a recent animal study, in which resuscitation was 20 per cent more successful when the shock was applied at the upstroke.
Cardiac arrest patients brought to SGH’s Emergency Department with severely abnormal heart rhythm are eligible and may be enrolled in the study, which started in April.
Public awareness is just as critical when it comes to improving survival rates, said Assoc Prof Ong.
Recognising the symptoms of sudden cardiac arrest and starting CPR immediately can mean either life or death for these patients.
“For every minute that nothing is done, whether it is CPR or defibrillation, the chances of the patient surviving decrease by 10 per cent,” he said.
Assoc Prof Ong noted that not only the old, the sick or those with a history of heart disease find their hearts suddenly stopping.
More than 65 per cent of the time in Singapore, sudden cardiac arrests occurred in healthy, active patients between the ages of 30 and 70 – as it did with Ms Yong 18 months ago.
The heart can stop for many reasons.
In Ms Yong’s case, doctors think her condition may be hereditary.
Her maternal grandfather died at 46 and her uncle died when he was 21.
No cause of death was established then but, as with Ms Yong, the collapse was sudden and occurred when both men were very healthy.
Ms Yong, who has returned to work as an editor at a publishing firm, now walks around with an implantable cardiac defibrillator.
It monitors her heart, helps keep its pace and administers an electric shock whenever it senses a cardiac arrest coming on.
“Since I got the implant, I’ve had four more episodes and, each time, the device has saved my life,” said Ms Yong, who urges people to learn CPR skills and use them on someone who has collapsed.
“Not many people realise how much of a difference they can make in someone else’s life just by knowing a simple skill,” said Ms Yong.
What to do when someone suddenly collapses
• If the victim is unconscious and not breathing, call for an ambulance.
• Start CPR early to get the blood flowing.
• If there is an automated external defibrillator (AED), use it to deliver an electric shock to the heart
• The AED, a simple device that can be used by anyone, is able to analyse the heart rhythm and prompt the first-aid provider to deliver the electric shock if necessary.
• A registry that lists venues with AEDs can be found at www.myheart.org.sg.
• This story was first published in Singapore Health, July/Aug 2012.