Araz Rawshani, Sahlgrenska Academy at the University of Gothenburg CREDIT Photo by Charlotta Sjöstedt

The probability of surviving sudden cardiac arrest outside hospital has more than doubled in 30 years. This is shown by a national Swedish register study covering more than 130,000 cases.

Sudden cardiac arrest affects some 10,000 people in Sweden annually. Saving them is a race against the clock, and the actions of bystanders who can perform cardiopulmonary resuscitation (CPR) and use a defibrillator are entirely crucial. Three in four events occur as people go about their everyday lives, while only one in four takes place in hospital.

The outcome of sudden cardiac arrest is usually fatal, regardless of where it happens. The condition is also the most common cause of death for people with diabetes, heart failure, or coronary artery disease, making it a widespread form of ill-health.

The current study, published in the European Heart Journal, includes data from the Swedish Cardiopulmonary Resuscitation Registry on 106,296 cases of out-of-hospital cardiac arrest (OHCA) in the years 1990–2020. The study also includes data on 30,032 in-hospital cardiac arrest (IHCA) cases in the period 2004–2020.

Three decades of development

Araz Rawshani, a researcher at Sahlgrenska Academy at the University of Gothenburg and a specialist doctor at Sahlgrenska University Hospital, is the corresponding author of the study.

“This is a comprehensive study that describes care and survival following sudden cardiac arrest. It’s a detailed report that clarifies three decades’ resuscitation in Sweden as a whole, and it shows that the situation has been changing rapidly for patients and the care providers alike,” he notes.

The findings show that for OHCA, survival more than doubled in 1990–2020 to approximately 11 percent. This whole improvement occurred in the late 1990s and early 2000s, and that no further rise in survival has taken place over the past decade.

For IHCA, survival rose by a factor of 1.2 in the period from 2004 to 2020, reaching about 35 percent. This improvement occurred largely from 2010 on and, according to the researchers, was due to better skills and resources in healthcare.

“In out-of-hospital cardiac arrest,” Rawshani says, “the rise in the number of people trained to perform CPR is probably the driver of that positive trend. Millions of Swedes have been trained in this vital skill, which can come in useful at any time, and these people intervene ever more often. Today, nonprofessionals (bystanders) start the CPR in the majority of all cases of cardiac arrest outside a hospital.”

Ambulance delays, more difficult cases

“The upward trend of out-of-hospital survival came to an end for several reasons,” Rawshani continues. “First, the ambulances aren’t managing to arrive in time for the patients; the delays in getting to them have constantly increased. Second, the proportion of patients who are relatively easy to resuscitate ­­­­— that is, those whose heart stops because of acute or chronic coronary artery disease ­­­­— has fallen dramatically in the past few decades.”

The fact that hard-to-treat cases ­­­­— with cardiac arrests caused by lung disease or heart failure, for example — are a growing category means that successful resuscitation will become harder to achieve in the future. What is more, women are overrepresented in this category, which explains the survival gap between the sexes. In 2020 almost 14 percent of the men, against some 8 percent of the women, survived OHCA.

“The study indicates that health care, from the emergency measures taken by paramedics to post-resuscitation nursing, is set to face new and daunting challenges in the years ahead, with a patient population who will get increasingly difficult to resuscitate.

“Further improvements in survival call for new ways of training considerably more people in cardiopulmonary resuscitation; maintenance of expertise; and the requisite technical advances to deliver defibrillators earlier,” Rawshani concludes.

Smokers have weaker hearts than non-smokers,according to research presented at ESC Congress 2022.¹ The study found that the more people smoked, the worse their heart function became. Some function was restored when people kicked the habit.

“It is well known that smoking causes blocked arteries, leading to coronary heart disease and stroke,” said study author Dr. Eva Holt of Herlev and Gentofte Hospital, Copenhagen, Denmark. “Our study shows that smoking also leads to thicker, weaker hearts. It means that smokers have a smaller volume of blood in the left heart chamber and less power to pump it out to the rest of the body. The more you smoke, the worse your heart function becomes. The heart can recuperate to some degree with smoking cessation, so it is never too late to quit.”

According to the World Health Organization, tobacco kills more than eight million people each year.² Cigarette smoking is responsible for 50% of all avoidable deaths in smokers, with half of these due to atherosclerotic cardiovascular diseases such as heart attack and stroke.³ The detrimental effects of smoking on the arteries and arterial diseases such as heart attack and stroke are well established.⁴

Studies have also shown that smoking is associated with a higher risk of heart failure, where the heart muscle does not pump blood around the body as well as it should, usually because it is too weak or stiff. This means that the body does not receive the oxygen and nutrients it needs to work normally. The link between smoking and heart structure and function has not been fully examined. This study therefore explored whether smoking was related to changes in the structure and function of the heart in people without cardiovascular disease, and the effect of changing smoking habits.

The study used data from the 5^th Copenhagen City Heart Study which investigated cardiovascular risk factors and diseases in the general population. A total of 3,874 participants aged 20 to 99 years without heart disease were enrolled. A self-administered questionnaire was used to obtain information on smoking history and to estimate pack-years, which is the number of cigarettes smoked through life. One pack-year is defined as 20 cigarettes smoked every day for one year.

Participants had an ultrasound of the heart, called echocardiography, which provides information about its structure and how well it is working. The researchers compared the echocardiography measures of current smokers versus never smokers after adjusting for age, sex, body mass index, hypertension, high cholesterol, diabetes and lung function.

The average age of participants was 56 years and 43% were women. Nearly one in five participants were current smokers (18.6%), while 40.9% were former smokers and 40.5% had never smoked. Compared to never smokers, current smokers had thicker, weaker and heavier hearts. Increasing pack-years were associated with pumping less blood. Dr. Holt explained: “We found that current smoking and accumulated pack-years were associated with worsening of the structure and function of the left heart chamber – the most important part of the heart. Furthermore, we found that over a 10-year period, those who continued smoking developed thicker, heavier and weaker hearts that were less able to pump blood compared to never smokers and those who quit during that time.”

She concluded: “Our study indicates that smoking not only damages the blood vessels but also directly harms the heart. The good news is that some of the damage is reversible by giving up.”