Every year thousands of people die from a fatal heart rhythm disturbance that appears to strike without warning. Although quick action with an automated external defibrillator helps revive some victims, most succumb to sudden cardiac death (SCD), also called cardiac arrest.

But the results of a study published recently in Circulation suggest that SCD might not be so sudden after all. The authors found that cardiac arrest is often preceded by warning signs that are misunderstood or ignored. Knowing these warning signs and what actions to take could save your life and those of countless others.

How the Study Was Done

The prospective study relied on data gathered by mobile emergency physicians in Berlin, Germany. During the course of one year, 554 people appeared to have a heart-related cardiac arrest. Fifteen were later reclassified, and the physicians were unable to obtain information on an additional 148. This left 406 to be included in the study. Of the 406, 72 percent died at home, 20 percent at work or in a public place and eight percent elsewhere.

Whether efforts to revive the patient were successful or not, the physicians immediately interviewed all bystanders and witnesses to the SCD on site. An attempt to resuscitate was made in 304 patients and was successful in 100. No resuscitation attempt was made in 102 patients for reasons not delineated in the study.

The cardiac arrest was witnessed in 274 of the 406 patients (67 percent), primarily by relatives. Cardiopulmonary resuscitation (CPR) was attempted on only 57 patients (14 percent). Of these, 23 percent (13) survived and were later discharged. Only four percent of the patients who were not given CPR survived. The authors noted that strangers were three times more likely than relatives and twice as likely as acquaintances to perform CPR.

Key Findings

More than 100 of the patients had a documented history of coronary artery disease, and 16 had been resuscitated previously following cardiac arrest. Thirty additional patients had hypertension, 18 had diabetes, 14 had chronic obstructive pulmonary disease (COPD) and 19 were smokers.

Symptoms immediately preceding the arrest were documented in 352 patients (80 percent). The most frequently noted symptom was angina lasting a mean of 120 minutes (22 percent). Other symptoms included breathlessness for a mean of 30 minutes (15 percent), nausea or vomiting for a mean of 120 minutes (seven percent) and dizziness or fainting (five percent).

Six percent of patients had other symptoms, and 25 percent apparently had no symptoms, or symptoms were unknown. Analysis revealed that 90 percent of patients had symptoms lasting more than five minutes, and 7.5 percent had symptoms lasting between two and five minutes.

The Implications

Of the 406 patients, the source of cardiac death in 149 (37 percent) was ventricular fibrillation (VF). In most people, VF is triggered by an acute cardiac event, such as a heart attack. While the condition requires a defibrillator to restore natural rhythm, CPR can often be successfully used until a defibrillator arrives on the scene.

Although the vast majority of patients in this study had heart disease or its
risk factors, neither the patients nor their relatives were aware of the risk of SCD. Eighty percent of the patients had symptoms that appeared to be cardiac in origin, which they tolerated for a median of 60 minutes (but as long as 380 minutes) before collapsing.

The authors concluded that SCD rarely occurs without warning. Instead, most patients have warning symptoms that are “misinterpreted, suppressed, or denied despite the presence of a preexisting cardiac disease or cardiac risk factors.”

According to Gary Francis, MD, professor of medicine and head of clinical cardiology, Cleveland Clinic Lerner College of Medicine, Cleveland, OH, “Sudden cardiac death continues to be a major problem, and we haven’t done too good a job at identifying just who is at risk. It has been assumed that many cases occur without any warning or with no known history of heart disease. These investigators brought to our attention that many SCD victims probably do have symptoms prior to their demise.

"Their findings are consistent with autopsy studies indicating most victims of SCD have severe underlying coronary artery disease (CAD). Therefore, patients with no previous history of CAD who experience symptoms should be investigated thoroughly and promptly. Patients with CAD whose symptoms worsen, or pattern of symptoms changes, should seek emergency care. The key word is ‘change’: Any change in symptoms or their severity requires medical attention.

The View from Duke

"Although the investigators aimed to understand the circumstances surrounding sudden cardiac death events, they in reality examined all cardiopulmonary arrests," says Sana Al-Khatib, MD, co-director of the Duke Center for the Prevention of Sudden Cardiac Death.

"What is the difference? By definition, sudden cardiac death is death that occurs within 60 minutes from the onset of symptoms. But this definition was not met by the majority of the events examined by the researchers.

In patients who had chest pain before collapsing, the duration of chest pain ranged from 20 minutes to 630 minutes. In patients who had shortness of breath before the arrest, the duration of shortness of breath ranged from 10 to 375 minutes.

Notwithstanding this major limitation, their study highlights the importance of educating the public about the symptoms that may precede cardiopulmonary arrest and encouraging more individuals to learn how to perform cardiopulmonary resuscitation (CPR) and how to use an external defribulator (AED)."