Your Chances of Surviving Cardiac Arrest
Cardiac arrest can take a life in minutes. It’s an emergency where every second can make a difference in saving someone. So, what chance do you actually have to help someone when they go into cardiac arrest? We looked at some observational studies to determine the chances of surviving cardiac arrest and the difference that a defibrillator makes.
The Science Behind the Urgency
Cardiac arrest occurs when the heart suddenly stops beating, cutting off blood flow to vital organs, including the brain. Unlike a heart attack, where blood flow to part of the heart is blocked, cardiac arrest is an electrical malfunction that causes the heart to lose its normal rhythm. Without the heart pumping oxygenated blood, the body's cells begin to die within minutes. Brain cells are particularly vulnerable, and irreversible damage can occur after just 4-6 minutes without oxygen.
When cardiac arrest happens, the person will collapse, stop breathing, and have no pulse. The lack of oxygenated blood flowing to the brain and other organs means that every second counts. Without intervention, such as CPR (cardiopulmonary resuscitation) or defibrillation, the chances of survival decrease by 10% per minute.
CPR helps maintain some blood flow to the brain and organs by manually compressing the chest to pump the heart. However, it’s only a temporary measure until defibrillation, which shocks the heart back into a normal rhythm, can be performed. That’s why using an AED (Automated External Defibrillator) within the first few minutes is crucial to increasing survival chances. The window to save someone’s life is incredibly small, making immediate action essential.
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Survival Statistics: What Are the Odds?
A prospective observational study from the national OHCA registry analysed the outcomes of the 28,729 cases of EMS cardiac arrest reported in 2014 (53 per 100,000 residents of the UK population).
The findings:
- The mean age of cardiac arrest casualties was 68.6
- 41.3% of them were female
- 83% occurred in a place of residence
- 52.7% were witnessed by an EMS or bystander
- Of those witnessed by a bystander, 55.2% received CPR, and 2.3% received defibrillation with an AED
- In 20.6% of cases, the heart was in a shockable rhythm
- Survival to hospital discharge was 7.9%
Research consistently shows that using AEDs in out-of-hospital cardiac arrest cases significantly improves survival outcomes. We examined some studies from around the world to assess the impact of intervention with an AED.
A large community-based study in North America found that the survival rate to hospital discharge was doubled when AEDs were used by trained laypersons in public locations.
- 70% of cardiac arrests occurred in public locations.
- 72% of cardiac arrests were witnessed by bystanders.
- Survival to Hospital Discharge:
a: In places with volunteers trained in both CPR and AED use, 30 survivors out of 128 cardiac arrests (23.4% survival rate).
b: In places with volunteers trained only in CPR, 15 survivors out of 107 cardiac arrests (14% survival rate).
c: The relative risk of survival where CPR plus an AED was used was 2.0.
A study on improved survival after out-of-hospital cardiac arrest and the use of automated external defibrillators in The Netherlands reported that increased use of AEDs in public settings from 2006 to 2012 nearly tripled and was associated with a significant rise in survival with favourable neurological outcomes.
- AED use nearly tripled over the study period of 2006–2012, from 21.4% to 59.3%.
- Increased AED use reduced the median time from emergency call to AED connection from 9.9 minutes to 8.0 minutes.
- Overall survival with favourable neurological outcomes improved from 16.2% to 19.7% during the study period.
- This improvement was only significant in patients with an initial shockable rhythm, increasing from 29.1% to 41.4%.
A study on the impact of onsite or dispatched automated external defibrillator use on survival after out-of-hospital cardiac arrest found that onsite AED use significantly reduced the time to the first shock and increased the neurologically intact survival rate compared to when no AED was used before EMS arrival.
The study looked at 2,833 consecutive patients with nontraumatic out-of-hospital cardiac arrest before EMS arrival from 2006–2009 in The Netherlands.
- Onsite AEDs were used in 128 cases.
- Dispatched AEDs were used in 478 cases.
- No AED was used in 2,227 cases.
- Onsite AEDs reduced the time to first shock from 11 minutes to 4.1 minutes.
- Dispatched AEDs reduced the time from call to first shock to 8.5 minutes.
- Onsite AED: 49.6% neurologically intact survival for patients treated with an onsite AED.
- No AED: 14.3% neurologically intact survival without an AED.
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Factors That Affect Survival Rates
Statements like ‘the chances of survival decrease by 10% per minute’ and ‘survival to hospital discharge doubles’ help us understand the average chances in varied situations. But the truth is that each cardiac arrest situation is different. Many factors contribute to individual survival chances.
Understanding these factors helps us identify when cardiac arrest is a higher risk and when we need to adjust our approach to care. And all of this knowledge fortifies our emergency preparedness measures. Apart from the obvious (using a public access AED, and fast paramedic response time), here are some of the factors that affect survival rates.
Initial Cardiac Rhythm
Different cardiac rhythms affect shockability because only certain rhythms, like ventricular fibrillation (VF) and ventricular tachycardia (VT), are chaotic and electrically active in a way that can respond to a shock; defibrillation resets the heart’s electrical activity, allowing it to resume a normal rhythm.
A review of predictors of survival in out-of-hospital cardiac arrest reported that patients found in ventricular fibrillation (VF) or ventricular tachycardia (VT) had the highest survival rates to hospital discharge, with rates ranging from 14.8% to 23.0%.
When you use an AED, it analyses the casualty’s heart rate and determines whether it’s in a shockable rhythm. If it is, the AED delivers a shock (if it’s fully automatic) or tells the user to press a button to deliver a shock (if it’s semi-automatic).
Witnessed Cardiac Arrest
Survival rates increase when a cardiac arrest is witnessed by bystanders who can promptly call for help or assist. This is because you must act quickly, and waiting for an ambulance to arrive contributes to a significant loss of survival chances, minute by minute.
EMS-witnessed cardiac arrest has the highest chance of survival, followed by bystander-witnessed cardiac arrest, with no witnesses contributing to the lowest chance of survival.
Bystander CPR
Bystander CPR significantly raises the likelihood of survival by providing critical circulation until EMS arrives. CPR is essential immediately after cardiac arrest because it maintains blood flow to vital organs, especially the brain, buying critical time until advanced care or defibrillation can restore the heart's normal rhythm.
Starting CPR immediately can double or even quadruple survival from out-of-hospital cardiac arrest.
Location of Cardiac Arrest
Arrests occurring in public places have higher survival rates than those in private residences, partly due to a higher likelihood of bystander intervention and AED access. Defibrillation must occur, typically, in ten minutes or less following cardiac arrest. This means chances of survival are higher when it is witnessed and when there’s an AED nearby.
See average ambulance response times for your area.
Find your nearest AED.
An ambulance can’t always respond in under ten minutes, so installing more public access AEDs is important.
This is one of the reasons we’re urging more business owners and members of community-run groups to install defibrillators in public access areas of their premises. Always register your AED on The Circuit so it can be found by emergency call handlers when responding to a 999 call about a cardiac arrest. They will be able to tell the caller where it is and provide the key code if it’s in a locked cabinet.
Age
Younger patients generally have better outcomes, as age is often associated with fewer comorbidities and greater resilience during cardiac arrest events.
Here are the chances of surviving cardiac arrest by age, based on data from the Danish Cardiac Arrest Registry in 2011:
- Working-age patients (18-65 years): Return of spontaneous circulation on hospital arrival 34.6%.
- Early senior patients (66-80 years): Return of spontaneous circulation on hospital arrival 21.5%.
- Late senior patients (>80 years): Return of spontaneous circulation on hospital arrival 15.0%.
Pre-arrest Health Condition
Comorbidities like heart disease and diabetes can reduce the likelihood of survival following cardiac arrest.
Situations in which casualties have pre-existing conditions can actually increase survival rates, too. One study found that patients with coronary artery disease (CAD) had significantly higher survival rates (51%) compared to non-CAD patients (26%), likely due to the predictability and treatability of cardiac-related events.
How You Can Improve Survival Chances
Installing more AEDs in public places and raising awareness of where they are and how to use them is key to improving survival chances. Intervention with an AED can really make a difference in the outcome of a cardiac arrest. Let’s review what we learned in the studies earlier.
- Onsite AEDs reduced time to the first shock, from 11 minutes to 4.1 minutes, and led to a 49.6% neurologically intact survival rate—over three times higher than the 14.3% rate without an AED.
- Survival to hospital discharge doubled when AEDs were used by trained laypersons in public locations, showing a 23.4% survival rate with AEDs compared to 14% with CPR alone.
- Increased AED use in public settings nearly tripled over six years in one analysed area, raising survival with favourable neurological outcomes from 16.2% to 19.7%. Survival rates jumped from 29.1% to 41.4% for patients with a shockable rhythm.
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Make Sure You’re Ready to Help
If you own a business, run a community organisation, or have a duty of care to a group of people, consider installing a public-access AED to give bystanders the best chance of saving someone’s life.
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Take a look at our resource hub to learn more about defibrillators. Let’s strengthen our approach together and ensure we’re as prepared as possible.
