Preventing Sudden Cardiac Death Is Possible

For patients with certain cardiovascular conditions and risk factors, sudden cardiac arrest is more than a theoretical concern.

But over the past 25 years, the development of various types of defibrillators — at-home, implantable, wearable — can give the immediate shock needed if a patient at high risk goes into ventricular arrythmia.

The approach is saving lives, but not enough; implantable devices have complications and most wearable devices can’t be worn all the time. Stories of “if only” tragedies abound, like that of patients who suffered sudden cardiac death while in the shower, their wearable device hanging inches away on the hook of the bathroom door.

Cardiologists who study sudden cardiac death say closing the gap is possible, with attention to several critical shortcomings.

Determining Risk 

The first, and most important, area for improvement is understanding of who is likely to experience a sudden cardiac event.

About 80% of sudden cardiac arrests globally are related to coronary artery disease, said Eloi Marijon, MD, a cardiovascular and cardiac electrophysiology specialist at the European Georges Pompidou Hospital in Paris, France, who coauthored a 2023 report of a Lancet Commission calling for multidisciplinary action to reduce the global burden of sudden cardiac death. But the number of patients with the condition who eventually have an arrest is low, said Kumar Narayanan, MD, a cardiologist and electrophysiologist at Medicover Hospitals in Hyderabad, India, and a coauthor of the Lancet Commission document.

“As of now, we do not have good tools to screen and identify those people,” said Narayanan. “We need much better prediction, which will translate to better prevention.” (A related story on Medscape Medical News looks at sudden cardiac arrest in people with no history of heart problems.)

Patients with “advanced markers of damage” — such as heart failure with reduced ejection fraction or a high fibrotic burden and certain characteristics of fibrosis — are at highest risk, he said. Acute myocardial infarction and coronary artery bypass grafting also can raise risk temporarily. In fact, risk is “dynamic,” varying over time, he said, making predicting arrest particularly challenging.

Although Narayanan calls current prediction methods “imperfect,” known risk factors are helping cardiologists provide appropriate patients with a growing selection of devices to deliver shocks when and where an arrest occurs.

Home Is Where the Heart Stops

Having an automated external defibrillator (AED) at home, where most arrests happen, has been an option for patients at risk since the 1980s. But studies of home AEDs have shown mixed results. A 2013 study found the use of AEDs at home by laypeople to be safe and effective, leading to the survival of two thirds of patients who received defibrillation. But a 2008 randomized controlled study found no benefit from home AEDs over cardiopulmonary resuscitation performed by emergency medical services in high-risk patients.

The value of implantable cardioverter-defibrillators (ICDs) for patients who have heart failure with reduced ejection fraction has been shown in studies since the late 1990s. Current guidelines from American and European groups recommend ICDs for the primary prevention of sudden cardiac arrest and death in these patients. In both guidelines, recommendations are class 1A, indicating strong support by high-quality evidence of a clear benefit.

ICDs are usually a permanent solution, but not a perfect one, said Marijon, a cardiovascular and cardiac electrophysiology specialist at the European Georges Pompidou Hospital in Paris, France, and a coauthor of the Lancet Commission report.

“An ICD for life has a 100% chance of complications,” Marijon said. Studies show ICDs may incorrectly administer shocks when there is no arrest, and intravascular leads may fail or become infected, requiring surgical intervention. Efforts are underway to improve these devices, but industry and researchers should collaborate to develop models that protect patients yet have fewer complications, he added.

Newer options for patients at high risk include cardiac resynchronization therapy, which involves the implantation of a biventricular pacemaker, and catheter ablation, which can correct certain arrythmias associated with risk for sudden cardiac arrest, although its ability to prevent arrest is unclear.

Wear That Defibrillator 

For patients who have a transiently high risk for arrest after acute myocardial infarction or coronary artery bypass grafting or who are waiting for ICD implantation, wearable cardioverter-defibrillators are an option.

LifeVest, a wearable device for sudden cardiac arrest that detects ventricular tachyarrhythmias and administers a shock to correct them, was first tested in the WEARIT and BIROAD studies, as reported in 2004. Those studies showed a beneficial effect in treating arrests. But when LifeVest was assessed in patients who had experienced a recent myocardial infarction in a 2018 major randomized controlled trial, the difference between it and regular care was not significantly different. However, a later analysis of the 2018 trial data showed that LifeVest was effective, both statistically and clinically, in patients who used it as intended.

Questions of effectiveness aside, using the vest as intended has proven difficult for patients. Compliance issues have dogged the ability of wearable devices to prevent sudden cardiac arrest. “It’s the Achilles heel for all of them,” said Emile Daoud, MD, an electrophysiologist at the TriHealth Heart and Vascular Institute in Cincinnati. “The question is not whether they work; the science of defibrillation we have figured out pretty well. Acceptance is really the problem.”

False alarms, inappropriate shocks, and discomfort are frequent complaints with LifeVest, which is the only commercially available wearable cardioverter-defibrillator.

New devices have been designed to improve compliance. The ASSURE wearable device has been shown to have a low rate of false alarms. Jewel, a lightweight wearable cardioverter-defibrillator, uses a patch placed over the heart and a box worn on the side of the torso to monitor cardiac activity and restore normal function. Unlike other wearable products, it can be worn in the shower and during exercise or sleep, which can improve compliance and avoid tragedies like the sudden cardiac arrest in the shower, said John Hummel, MD, an electrophysiologist at the Ohio State University Wexner Medical Center in Columbus, Ohio, who was the principal investigator for a 2024 study of the device.

Next Generation 

Technology will help improve these devices, according to Narayanan and Marijon, and the quality of life and survival of patients at high risk. Recent advances in drug therapy for heart failure and ischemia should also help prevent sudden cardiac arrest, according to the Lancet Commission report.

With aging populations and higher rates of coronary artery disease, all medical measures — better screening and diagnosis of cardiac diseases, improved treatments, more AEDs in homes and public places, and widespread use of implantable and wearable cardioverter-defibrillators — must be brought to bear, the report stated.

“We need some disruptive innovations in prediction and prevention,” said Narayanan, who points to artificial intelligence and machine learning as showing particular promise to better diagnose the underlying conditions and better predict the risk of arrest.

But medical advances are not enough. The Lancet Commission report urges international research and collaboration, as well as awareness among the public and policymakers.

“Governments could do more,” said Simone Savastano, MD, a cardiologist at Fondazione IRCCS Policlinico San Matteo in Pavia, Italy. “If you work with children or young men and women, you can raise a generation that is aware and is more keen to help a cardiac arrest patient.”

Daoud reported receiving consulting fees or honoraria from Biosense-Webster, AltaThera, and OSU EP Section Educational conferences; he is the chief medical officer of S4 Medical and he has received fees from the American Board of Internal Medicine and the Journal of the American College of Cardiology. Hummelreported receiving consulting fees from Medtronic, Volta Medical, S4 Medical, Abbott Medical, and Element Science. Marijon disclosed receiving grants from Abbott, Biotronik, Boston Scientific, Medtronic, MicroPort, and Zoll; consulting fees from Medtronic, Boston Scientific, Zoll, and Abbott; and payment or honoraria for lectures, presentations, speakers’ bureaus, manuscript writing, or educational events from Medtronic, Boston Scientific, Zoll, and Abbott.

Narayanan and Savastano reported no relevant financial conflicts of interest.

Carolyn Brown is a freelance scientific and biomedical reporter in Ottawa, Canada.