Understanding who’s at risk for sudden cardiac death

Editor’s note: This is the final column in a series from Penn Medicine physicians this month on heart health.

Let’s start with a hypothetical scenario. Two adults who live in the same neighborhood and lead similar lifestyles have the same underlying heart condition: coronary artery disease.

One patient experiences intense chest pain, caused by restricted blood flow to the heart. He goes to the emergency department, where physicians diagnose his condition and treat him, in part, by placing a stent inside the artery to prop it open.

The other patient never experiences any symptoms. Instead, he suffers sudden cardiac arrest and dies.

Unfortunately, that scenario is common. Each year in the United States, more than 350,000 people succumb to sudden cardiac death (SCD), the immediate cessation of the heart’s ability to function properly. Coronary artery disease is the most common risk factor linked to sudden cardiac death. Yet, questions exist about why some people are more likely to die suddenly than others who have the same medical condition.

Unlike heart attacks, which occur when blood flow is slowed or prevented by a blockage in one or more of the coronary arteries, sudden cardiac arrest results from a catastrophic failure of the heart’s rhythm or underlying electrical circuitry. The heart beats dangerously fast. The disorganized electrical rhythm, in which the heart quivers or flutters rather than pumps – known as ventricular fibrillation – prevents the delivery of blood to the rest of the body. Within a minute, the lack of blood flow to the brain causes a person to lose consciousness. Death follows shortly after, unless the victim receives emergency treatment, such as cardiopulmonary resuscitation (CPR) or defibrillation, immediately.

Some people experience symptoms of heart disease, such as a racing heartbeat or dizziness. However, many patients never experience any symptoms. Cardiac arrest can be the first sign.

At Penn Medicine, one of our research programs focuses on understanding why some people have a heightened risk of SCD. In studying this question across the United States population, we have identified a number of variables that are predictive of SCD, including male gender, African American race, smoking, high blood pressure, diabetes, low levels of HDL (good cholesterol), poor kidney function, and abnormal measures on an EKG. These factors, when combined, help us to calculate an overall score, and identify individuals or subgroups with a higher risk of SCD. Still, no magic bullet exists to prevent SCD in the majority of the population. As a result, we are more likely to make headway by focusing on the following areas:

1. Awareness and education. Increase access to programs – particularly in schools and community centers – that not only educate people on how to recognize the signs and symptoms of heart disease, but also inform them how to respond in an emergency situation. CPR training is a critical component. If performed immediately, CPR can double or triple a cardiac arrest victim’s chance of survival. Unfortunately, Philadelphia lags behind other cities when it comes to the percentage of victims who received bystander CPR, as well as the survival rate for witnessed cardiac arrests. Increased education and training will help drive change.

2. Technology. In the last decade, we have seen the increased availability and use of automatic external defibrillators in public areas, such as the Philadelphia International Airport, schools, malls, and gyms. AEDs – portable devices that deliver an electric shock through the chest to the heart – can potentially stop an irregular heartbeat and allow a normal rhythm to resume following sudden cardiac arrest. Similarly, the emergence of health-focused wearable devices enable people to track and record their heart rhythm. Philadelphia remains a major area of business and international investment, and we should encourage partnerships that can lead to innovative ways to improve defibrillator access and technology.

3. Research and collaboration. Philadelphia is home to several major medical centers, and boasts some of the most innovative researchers and leaders in health care. We believe it’s important to foster collaboration among institutions to develop common registries of SCD cases. By formally collecting and tracking information related to cardiac arrest events in our city, we will be able to develop insights on how best to organize our primary and emergent care to prevent SCD.

In this era of technological advancement, there will be many opportunities to prevent and improve the outcomes of catastrophic heart rhythm abnormalities. We must commit ourselves to addressing the health-care priorities that are a matter of life and death.

Rajat Deo, MD, MTR, is an associate professor of medicine and a cardiac electrophysiologist in the Perelman School of Medicine at the University of Pennsylvania. Kenneth B. Margulies, MD, is director of heart failure and transplantation research and a professor of medicine in the Perelman School of Medicine at the University of Pennsylvania.