Medical research 

“The Survival Rate of Out-of-hospital Cardiac Arrest (OHCA)” (15 Jun 2022)

Press Release (For Immediate Release)

 Hong Kong's first 3-year case-based study on "The Survival Rate of Out-of-hospital Cardiac Arrest"

 - The survival rate of young patient is almost of 10 folds higher with timely in use of AED

-8 potential strategies to Increase Survival

(Hong Kong, 15th Jun 2022) Out-of-hospital cardiac arrest (OHCA) is the major cause of unexpected and sudden death. If patients with sudden OHCA are delayed in Cardiopulmonary Resuscitation (CPR) or public-access defibrillation (PAD)1, their survival rate will drop by 7-10% for every minute of delay. To investigate the prevalence and survival rate of OHCA in Hong Kong, SADS HK Foundation (SADS HK) commissioned a research team at the Department of Rehabilitation Sciences of The Hong Kong Polytechnic University (PolyU) to conduct the first large scale study using three-year medical cases’ data of “The Survival Rate of Out-of-hospital Cardiac Arrest (OHCA)” in Hong Kong. The main objective of this study is to investigate the prevalence and survival rate of young patients <=age 40 with OHCA in Hong Kong, and to find out the factors that could increase the survival rate of this targeted group. 

Low OHCA Survival in Hong Kong

The team gathered 22,014 OHCA cases between December 2017 and December 2020, of which 21,617 individuals didn’t survive to discharge. For the OHCA patients <=age 40, a total of 829 cases were identified, only 35 (4.2%) cases survived to discharge. From these 829 patients, only 34% and 6.8% had ever received CPR and AED respectively.

1.5 OHCA cases found every 2 days in Hong Kong’s young individuals

Dr Richard XU, Co-Principal Investigator of the study and Research Assistant Professor of the Department of Rehabilitation Sciences at PolyU, explained, “Previous studies on OHCA focus on the overall prevalence and survival rate, which offer limited insights about young patients. This finding is the first of its kind that focuses on Hong Kong OHCA young patients of ages 40 or below.” The study found that between December 2017 and December 2020, there were on average 1.5 OHCA incidents every 2 days that involved young patients in Hong Kong.

 10 folds improvement in survival rate with timely use of AED

Prof. Amy FU, the other Co-Principal Investigator who is also Peter Hung Professor in Pain Management and Associate Head of the Department of Rehabilitation Sciences at PolyU, said, “Our study shows survival to hospital was largely improved from around 15% to 24.8% and 44.6% when cardiopulmonary resuscitation (CPR) or Automated External Defibrillator (AED) were applied respectively; the survival to discharge from hospital was largely improved from about 2% to 9.2 % and 25% when CPR or AED were delivered at the incident site respectively. Such findings suggested that the survival rate for OHCA young patients is enhanced by nearly 10 times if they can receive AED on-time.”

She added that overall, only 17.7 % of the young people who were attacked by cardiac arrest could survive to arrive at hospital and 4.2% could leave hospital. Meanwhile, the male to female young patients ratio was 2 to 1.

8 potential strategies to Increase Survival Rate

Dr Siu Yuet-chung, Axel, Specialist in Emergency Medicine and Advisory Member of SADS HK, revealed that “When compared to other developed Asian countries/regions, the survival rate of Hong Kong OHCA individual is extremely low (1.8%). And there is an acute shortage of Automated External Defibrillator (AED) in Hong Kong and the number of AED in Hong Kong is about 120 times fewer than Japan (5,000 vs.610,000). The study proved that the CPR and AED absolutely increased 10 times of the rate of survival in young patients. Otherwise, the survival rate drops by 7-10% in every minute based on overseas experience.” Dr. Siu emphasizes “The public need to understand the importance of first aid, publicize the use of CPR or AED is needed.”

To increase the rate of survival, Dr. Siu urges to have 8 strategies. Firstly, public education that enables a better understanding on the cardiac warning signs to reduce OHCA. Secondly, CPR and AED must be added as mandatory curriculum in school in order to enhance the knowledge of first aid in our young generation. Thirdly, the government must consider the enactment of Samaritan’s Law to alleviate public concerns about administering first aid. Fourthly, all public places and private/public properties should be equipped with AEDs and our government should consider to offer subsidy to enhance the AED allocation ratio per capita. Fifthly, unified the logo of AED to facilitate the easier identification of the AED installment site. Sixthly, enhance the “AED Anywhere for Anyone” by Fire Services Department as a blueprint to further develop an AED location mobile apps to browse the AED location for quick response. Seventhly, the government should promote the AED registration of all AED in anywhere that can be accessible by public.

Finally, the government should also establish an OHCA database to centralize the integration of all OHCA data including the cases, demographic, locations, rate of survival, etc..

Patient sharing - Experienced the importance of First Aid

Tommy Fung, a patient of OHCA, shared his experience, “When it happened in the early morning, I suddenly lost consciousness. My wife told me that I was stiff and stopped breathing for a while. I was so fortunate that paramedics kept talking with my wife when they were on the way to my home and instructed her how to perform CPR even she had no experience at all. When they arrived, AED was applied immediately. I had been without spontaneous breathing for more than 20 minutes by the time I arrived at the hospital.” He hopes that the public will not underestimate the importance of first aid. Timely implementation of first aid could save the lives of people at home or around them.

SADS HK urges pay more attention to the warning signs of cardiac

OHCA could have many causes, it could lead to sudden death of an apparently healthy undiagnosed young person. Sudden Arrhythmia Death Syndromes (SADS) is one of the many causes. Prevention is better than cure. To prevent cardiac arrest due to SADS, SADS launched the subsidy scheme to support the SADS victim’s or family member for their first clinical consultation. SADS HK urges the public to pay more attention to the warning signs of cardiac and to understand family medical history. If anyone experience any warning signs, please seek the cardiologist’s medical advice as soon as possible to avoid OHCA accidents.

SADS HK medical research (2014-2015)

SADS HK medical research report was published in "Hong Kong Medical Journal" in January 2019
Please click the link to view the full medical report :
Sudden Arrhythmia Death Syndromes (SADS) in Young Victims of Sudden Cardiac Death in Hong Kong Identified by Clinical or Molecular Autopsy of Victims and Clinical Evaluation of Their First Degree Relatives

Brief Reult of SADS-HK Study (Oct 2017)

Under the two-year research project, young cardiac death victims with uncertain causes of death or inheritable cardiomyopathy examined at public mortuaries were chosen for molecular autopsies, while their first-degree relatives were referred for clinical assessment and/or genetic screening. Findings revealed that nearly 30% of the 21 sudden cardiac death victims carried SADS-related genetic variants. Approximately a quarter of sudden cardiac cases saw their victims died in sleep and three of them had a family history of sudden deaths. Around 30% of SADS victims experienced fainting for uncertain reasons when alive but failed to seek medical treatment or actively followed up on their conditions. Dr. Mok Ngai-shing, Specialist in Cardiology and Consultant of Princess Margaret Hospital, who oversees this project, said: “A family history of sudden deaths and fainting for uncertain reasons are vital clues to SADS and those with the conditions should seek early medical intervention to avoid missing the golden hour for diagnosis and treatment.”

According to the study, more than 50% of first-degree relatives subjected to genetic screening were found to carry SADS-related genetic variants , requiring follow-up medical care and preventive therapies. Dr. Chloe Mak, Specialist in Chemical Pathology and Consultant of Princess Margaret Hospital, who is responsible for the genetic screening administered in this project, said: “In this study, there are families with a strong family history of two to three sudden death victims with unknown causes. This causes the surviving family members great distress. This study not only partially confirms the causes of death among the sudden death victims but also facilitates their relatives with the dormant SADS disease to receive early preventive treatment based on their conditions, in order to reduce their risk exposure to sudden death.” Next-generation sequencing (NGS) was applied in the investigation into the victims’ causes of death, which yielded important genetic data and valuable experiences for the first time in local SADS research. The study is considered a major leap forward in genetic studies conducted in Hong Kong and also has established the foundation of a feasibility model on incorporating molecular autopsy in forensic investigation, next-generation sequencing analysis in hereditary cardiac disorders, genetic counseling, clinical assessment and referral.
Written by Dr. Ngai-Shing MOK,
Coordinating Principal Investigator,
Princess Margaret Hospital,Hong Kong


Sudden Cardiac Death (SCD) is one of the most common causes of death and a major and tragic complication of a number of cardiovascular diseases. The death is most often unexpected and has major implications for the surviving family and the community. SCD is defined as a death occurring usually within an hour of the onset of symptoms, due to an underlying cardiac disease. Whereas SCD in the older populations is most frequently due to underlying coronary artery disease and heart failure, SCD in young people (aged < 40 years) is commonly caused by genetic diseases such as inherited arrhythmogenic cardiomyopathies including hypertrophic cardiomyopathy (HCM) and arrhythmogenic right ventricular cardiomyopathy (ARVC), and cardiac ion channel diseases including Brugada syndrome (BrS), congenital long QT syndrome (LQTS), short QT syndrome (SQTS) and catecholaminergic polymorphic ventricular tachycardia (CPVT). They are collectively known as Sudden Arrhythmia Death Syndromes (SADS). While autopsy may reveal the underlying cardiac diseases in young SCD victims, up to 30% of the autopsy fails to identify a cause of death and those SCD victims are referred to as suffering from Sudden Unexplained Death (SUD). Recently we conducted a retrosepective 5-year review of autopsies done in local young SCD vicitms aged 5-40 years and found 25% of them suffered from SUD. It is believed that a significant proportion of SUD is caused by SADS.

As SADS are genetic diseases, two different approaches to identify SADS among young SUD victims have been used. The first approach involves detailed clinical and targeted genetic examination of the surviving relatives of SUD victims. Studies using this approach suggested that SADS may account for approximately 40% of autopsy-negative SUD in young people. However, this approach may not be able to identify subjects with concealed form of SADS due to incomplete penetrance and variable expressivity of the pathological mutations. The second approach is to perform molecular autopsy on SUD victims which involves post-mortem genetic testing for SADS. The landmark study on molecular autopsy by Mayo Clinic showed over one-third of SUD cases hosted a presumably pathogenic mutations of cardiac ion channel diseases. Thus a combined approach using both cardiac evaluation of surviving relatives and molecular autopsy on SUD victims should theoretically give a higher yield on elucidating the underlying causes of SUD. Identification of the underlying cause of SCD has at least two major clinical implications. First, the identification of a cause of death has a major influence in families in coming to terms as to why their child or spouse died suddenly. The diagnosis brings some level of closure in this respect. Second, the identification of a genetic cause of SCD provides the family with a diagnostic test for screening other at-risk family members, in conjunction with clinical screening approach and allows for an early initiation of therapeutic and preventive strategies in affected family members with the ultimate goal to reduce sudden death.

To date, there is scarce local data on the prevalence and types of SADS underlying SCD or SUD in young people. There is little local experience of performing molecular autopsy for SUD victims in Hong Kong. Molecular autopsy is not included as part of medico-legal investigation of underlying cause of SUD by forensic pathologists or within HA hospitals. We recently identified Brugada syndrome in a young SUD victim in Princess Margaret Hospital through molecular autopsy and clinical and genetic evaluation of his first-degree relatives. The present study is first of its kind in Hong Kong and it will provide important data on the prevalence and types of SADS among young SCD victims in local population.

Protocol Synopics

Protocol Title: Sudden Arrhythmia Death Syndromes in Young Victims of Sudden Cardiac Death in Hong Kong Identified by Clinical or Molecular Autopsy of Victims and Clinical Evaluation of Their First Degree Relatives

Study Location: Hong Kong

No. of Study Sites: 1

Study Design:
This is a prospective study. Young sudden cardiac death (SCD) victims (age 5-40 years old) will be identified and recruited into study by forensic pathologists after finding of either an inheritable arrhythmogenic cardiomyopathy or no structural heart disease on autopsy and a negative toxicology screening. Their first-degree relatives will be referred by forensic pathologists to study centre for genetic counseling and recruitment into the study

Primary Objective: To determine the prevalence and types of Sudden Arrhythmia Death Syndromes (SADS) as the underlying causes of SCD among local young victims through clinical and molecular autopsy of SCD victims and clinical and genetic evaluation of their first degree relatives

Secondary Objectives:
  1. To study the genetic basis of SADS among young SCD victims in Hong Kong
  2. To study the diagnostic yields of various approaches in identifying SADS in sudden unexplained death (SUD) families using (A) molecular autopsy in young SUD victims using the next generation sequencing techniques; (B) clinical evaluation of the first-degree relatives of young SUD victims, and (C) combining molecular autopsy in young SUD victims and clinical and targeted genetic evaluation of their first-degree relatives
No. of Subjects: 40 SCD victims and approximately 160 first degree relatives

Recruitment Period: 2 years

Follow-up Period: up to 6 months

Follow-up: Follow-up clinic visits at 3 months and if indicated at 6 months

Primary Endpoint:
Prevalence and types of SADS among the young SCD families in the study population identified by clinical and molecular autopsy of SCD victims and/ clinical and targeted genetic evaluation of their first-degree relatives

Secondary Endpoints:
  1. Genotypes of SADS victims in the study population
  2. Number of young SUD families identified with SADS by molecular autopsy
  3. Number of young SUD families identified with SADS by clinical evaluation of first-degree relatives
  4. Number of young SUD families identified with SADS by a combined approach
  5. Pattern of inheritance of SADS and their clinical and genetic characteristics among young SUD families

International Medical Research

Other International Medical Research and Articles on SADS/ Sudden Cardiac Death: