Lifestyle measures

At a population level, interventions addressing traditional coronary disease risk factors have been implemented in the past decades. Smoking cessation, healthy diet, and physical exercise can reduce SCD burden.^47,48 Recently, the role of nontraditional risk factors, such as air pollution, has attracted considerable attention. In fact, uncontrolled urbanization and increased pressure of environmental stressors have been associated with elevated risk of cardiovascular diseases and VAs.⁴⁹ Community‑based programs aimed at reducing air pollution through improved public transportation and reduced CO₂ emissions have been proposed and further studies will be needed to measure how these initiatives may affect cardiovascular and SCD risk over time.

Early recognition and intervention: rationale for public‑access defibrillation programs

It is estimated that over 75%–80% of out‑of‑hospital CA (OHCA) cases occur at home, and less than one‑third in public places.⁵⁰ A recent report by the International Liaison Committee on Resuscitation (ILCOR) published in 2017 considered 9 national and 7 regional OHCA registries, reporting survival between 3% and 20% 30 days after resuscitation; with better survival (11%–47%) in the case of witnessed OHCA and with a shockable rhythm. In environments with public access to defibrillation, such as sports facilities, survival rises to 70%–90% thanks to early defibrillation.⁵¹ It is now clear that the time to defibrillation is of crucial importance in determining survival: the shockable rhythms, which can be effectively treated by early electrical defibrillation, in fact deteriorate within minutes into nonshockable rhythms characterized by a significantly worse prognosis.^52,53 Some case studies, in which the automated external defibrillator (AED) was applied and the rhythm was recorded on arrival, report the incidence of shockable rhythms between 36% and 79% in the case of witnessed OHCA, depending on whether the arrest occurred at home or in a public place and on the time of assistance arrival on site. In fact, the incidence of shockable rhythms, such as first‑detection rhythms, is significantly reduced in the same case series, to 25% and 38% when the intervention by the emergency medical system (EMS) takes place at home or in a public place, respectively, due to a longer time of the assistance arrival.⁵⁴

This is supported from a physiopathological point of view by a 3‑phase model of CA. The first phase is the electrical phase (within 3–4 min of syncope), the second phase is the circulatory phase (from 4 to 7 min), and the third phase is the so‑called metabolic phase (after 10 min; Figure 3).⁵⁵

During the electrical phase of CA, blood pressure drops but not to zero. The arterial pressure remains between 15 and 20 mm Hg, higher than the central venous pressure, which is approximately 5 mm Hg. In this phase, a gradient remains between the arterial compartment and the venous compartment, which maintains circulation, albeit at minimal speeds. Defibrillation is most effective in restoring the spontaneous cardiac rhythm, and it also re‑establishes the circulation and pressure independently of the basic life support maneuvers. A study conducted by Gilmore et al⁵⁵ demonstrated that if an action is taken in the very first minutes of CA, during the electrical phase, survival is independent of cardiopulmonary resuscitation (CPR), if defibrillation is performed promptly. In the subsequent phases, survival rate is progressively reduced, and CPR maneuvers combined with defibrillation are fundamental for effective resuscitation. In the circulatory phase of CA, blood pressure drops to zero. In this phase, survival is significantly reduced, and it is necessary to support circulation with cardiac massage and ventilation, as well as to interrupt the arrhythmia with defibrillation. Finally, in the third metabolic phase, the ischemia / reperfusion damage due to a lack of circulation becomes permanent and requires complex means of cardiac support with the lowest probability of survival.

The American Heart Association defines well what public access to defibrillation means: “making AEDs available in public or private places where large numbers of people gather or where people at high risk of cardiac arrest live.”⁵⁶

Early defibrillation, performed by witnesses or so‑called first responders, represents an organizational approach that may increase survival from OHCA. In fact, further reducing the EMS arrival time is impossible. A study funded by the United Kingdom Department of Health found that reducing ambulance times was not a cost‑effective policy.⁵⁷ Ong et al⁵⁸ showed that the average EMS response time in Singapore was 9.6 minutes, making public access to defibrillation an essential link in the chain of survival. Numerous studies have demonstrated that early defibrillation, regardless of who performed it, was associated with favorable neurological outcomes.⁵⁹ Ringh et al⁶⁰ demonstrated that defibrillation with public AEDs had higher survival rates than defibrillation by EMS due to a much shorter time to defibrillation.

Unfortunately, in Europe, there are still few communities organized according to the early defibrillation model, and the AEDs present in public places are often underused. According to the ILCOR data, AEDs available in the case of OHCAs are used only in 2% to 37% of cases, mainly due to missing integration with emergency services and a limited knowledge of defibrillation in the community.⁵¹

The programs of early defibrillation are based on establishing a widespread network of AEDs and training potential users, who can apply the AED in the shortest time possible (Figure 4).

In the 1980s, many projects were launched to involve communities in the use of AEDs in public places.^61-64 These devices have become increasingly simple to use, with guiding voices that assist in various phases of the rescue procedure and more precise algorithms for the recognition of arrhythmias, reducing the recognition time to less than 20 seconds.⁶³ In Rochester, Minnesota, United States, between 1990 and 1995, 31 patients with OHCA were treated with AEDs by the police, with a survival to hospital discharge of 58%.⁶⁵ Over the years, several projects have demonstrated effectiveness of early defibrillation in various contexts, including OHCA in public and private places.^60,66

In Europe, the city of Piacenza, Italy, has played a pioneering role in the implementation of an early defibrillation system since 1998, thanks to the Progetto Vita program.⁶⁷ The project involved law enforcement and volunteer rescuers and availability of AEDs in various public places. Timely interventions of lay rescuers with AED significantly increased survival as compared with traditional EMS (15.5% in the volunteer group vs 4.4% for the EMS; P = 0.002), already in the first published cases.⁶⁸ Similar success was achieved in Seattle in 2002, where survival from OHCA was 27%, 3 times the national average at that time.⁶⁸

In a randomized study, Hallstrom et al⁶⁹ demonstrated that survival to discharge from a hospital was higher when lay volunteers used the AED together with CPR than when CPR alone was used (30/128 survivors in the CPR+AED group vs 15/107 in the CPR only group; P = 0.03).

However, most of the available data are based on observational registries, which show an increase in AED use over time (from 21.4% in 2006 to 59.3% in 2012), and a reduction in the time between the onset of OHCA and connection of the AED carried out by lay people present on site (8 vs 9.9 min; P <⁠0.0001).^70-72 Berdowski et al⁷³ reported improved neurological outcome on discharge in patients rescued with AEDs present on site vs individuals who were rescued without the use of an AED and in whom defibrillation was carried out upon arrival of medical assistance.

Data relating to a Japanese national register published by Kitamura et al⁷⁴ highlighted an increase in the use of public AEDs from 1.1% in 2005 to 16.5% in 2013, which was associated with a greater probability of survival with favorable neurological outcome in the case of intervention by lay rescuers with public AEDs (38.5% vs 18.2% for EMS).

Recently, numerous studies have aimed at evaluating the economic effectiveness of AED distribution in public spaces. One of the most relevant works by Andersen et al⁷⁵ highlighted how, in the United States, installation of AEDs in public spaces is advantageous from an economic point of view, and suggested their wider distribution over the country’s territory.

The 2015 ILCOR guidelines⁷⁶ strongly recommend promoting public access to defibrillators. The most recent guidelines of the ESC, published in 2022,³² support early defibrillation as a class I intervention, with a high degree of scientific evidence, in the fight against sudden death.

The strategies of organizing early defibrillation assistance can be divided into 3 main categories:

1. Two‑tiered system, in which medical personnel of ambulances and police forces equipped with mobile AEDs are alerted simultaneously by a dispatcher of an emergency system;

2. Bystander system, in which AEDs are installed in public and private places accessible to passers‑by and are used by witnesses while waiting for the arrival of medical professionals;

3. Network of occasional rescuers (first‑responder network), that is, a network of non–health care volunteers, known as lay rescuers, available through a communication system coordinated via an EMS.

It is important to underline that these organizational approaches are not mutually exclusive. The choice depends on a specific situation and increasing availability of AEDs in the communities.

However, despite efforts to promote the distribution of AEDs and CPR education, the data available in the literature and our practical experience show that less than 12% of patients suffering from SCA are treated with an AED. This rate is particularly low in private places as compared with public ones (1.3% vs 15.3%).⁷⁷ This is because AEDs are not yet so widespread, and because approximately 50% of OHCAs are unwitnessed.

Educational interventions certainly increase the percentage of patients receiving bystander CPR and defibrillation. An example of this are the educational campaigns conducted in North Carolina, United States⁷⁸ and Japan,⁷⁹ which correspond to a greater probability of survival without neurological damage. However, it is necessary to simplify and concentrate public training on the use of AEDs, with or without CPR, to increase the number of interventions. Simplified training programs have been shown to reach a wider audience and are more likely to be successful.⁸⁰ The American Heart Association’s “Nation of Lifesavers” program, the British Heart Foundation’s “Call, Push, Rescue,” Osaka’s “PUSH” project, and Singapore’s “DARE” (Dispatcher‑Assisted first Responders) program are examples of streamlined training programs focused on teaching compression‑only CPR and AED.

The simplification should be supplemented by educational campaigns aimed at promoting CPR skills from a young age, in all schools of all levels. Annual training programs, lasting 1–2 hours, conducted by adequately trained teaching staff, are essential to develop in teachers the abilities to educate students on the use of the AED and CPR maneuvers, so that during their school career every student becomes capable of intervening in the event of OHCA. This organizational aspect is of considerable importance and must be addressed in parallel with the distribution of AEDs.