Sudden Cardiac Death
Abstract & Commentary
By Harold L. Karpman, MD, Clinical Professor of Medicine, UCLA School of Medicine. Dr. Karpman reports no financial relationship to this field of study.
Synopsis: The authors attempt to redefine SCD by concluding that it uncommonly or even rarely occurs "suddenly out of the blue" without any premonitory symptoms.
Source: Zipes DP, et al. Neural modulation of cardiac arrhythmias and sudden death. Heart Rhythm. 2006;3:108-113.
Sudden cardiac death (SCD) is defined as unexpected death due to cardiovascular causes occurring in a person with or without pre-existing heart disease within one hour after onset of change in clinical status.1 The mechanism of death in most episodes of SCD is due to ventricular tachycardia which degenerates into ventricular fibrillation (VF). Sixty to 80% of episodes of SCD occur in patients afflicted with coronary artery disease and most of the other cases are due to nonischemic cardiomyopathy, infiltrative and/or inflammatory cardiac diseases or acquired valvular heart disease.2 Finally, a small number of episodes of SCD occur in individuals with genetic abnormalities such as hypertrophic cardiomyopathy, congenital heart defects such as anomalous coronary arteries, and rarely in patients with Brugada syndrome or catecholaminergic ventricular tachycardia.
Despite widespread advances in the diagnosis and treatment of ischemic heart disease, SCD remains the major cause of death in the industrialized nations. It accounts for more than 300,000 deaths per year in the U.S. alone, which is approximately 20% of all deaths.2 Classically, SCD occurs quite suddenly, is unexpected and seemingly is random in nature and, as a result, early detection efforts have always focused on the individuals at highest risk (especially the subset of SCD patients without overt signs or symptoms of cardiac disease) looking for evidence of cardiac disease.3
Searching for preventative measures for SCD, Muller and his colleagues4 collected information on cases of out-of-hospital SCD in the Berlin, Germany, emergency medical system via a questionnaire. In addition, bystander interviews were performed by an emergency physician who was staffed in a physician-manned mobile intensive care unit or a rescue helicopter both of which were connected with a single central hospital (Universitatsmedizin Berlin) which serviced approximately 10% of the 3.5 million inhabitants of Berlin. For the present study, SCD was defined as sudden unexpected arrest of presumed cardiac origin in adults over the age of 18, such arrest having occurred within 24 hours after onset of any symptoms which could retrospectively be interpreted as being of cardiac origin. Patients with symptoms of longer duration or which were clearly of non-cardiac origin were excluded from the analysis. Of 5831 rescue missions, 406 involved patients with presumed cardiac arrest and 274 of these were witnessed. Typical angina was present for a median of 120 minutes in 25% of the witnessed SCD episodes and 33% of episodes during which patients had a symptom duration of less than one hour. SCD was found to occur more often at home in the presence of relatives and after a significant period of typical symptoms.
Commentary
Muller's conclusion4 that 72% of SCD events occurred at home is consistent with previous data reported from United States.5 Although 25% of episodes occurred in totally asymptomatic patients, symptoms of angina followed by dyspnea, nausea/vomiting, and/or dizziness/syncope occurred for varying degrees of time in the remainder of the patients. Patients who suffered SCD at home tolerated the symptoms longer (75 minutes) than did those patients who were in public areas (20 minutes). Symptoms were tolerated for a median time of 60 minutes (range 10-380 minutes) before collapse occurred and the authors concluded that, in this particular study population, signs and symptoms which could herald the onset of SCD were present often for a significant period of time. As was noted in previous reports,6 patients were more likely to survive when SCD occurred in public places where emergency medical services had faster access and where patients were more likely to receive bystander CPR. It should be recognized that the statistical conclusions of this study may be somewhat flawed because, in 148 of the 554 cases of nontraumatic episodes of SCD, the emergency physician was called off by first-arriving emergency medical technicians equipped with a defibrillator because of apparent signs of irreversible death, and only the age and sex of these patients were registered—no additional information was obtained on this group of patients. In addition, although they redefined SCD by allowing a long symptom duration of 24 hours, when they applied stricter definitions than those used in their study, the results apparently did not change significantly.
The authors have attempted to redefine SCD by concluding that it uncommonly or even rarely occurs "suddenly out of the blue" without any premonitory symptoms. If they are correct, the majority of episodes of SCD are avoidable or more likely to be resuscitated if premonitory symptoms are recognized and earlier treatment is initiated. Finally, and most important, because the majority of episodes of SCD occurred in domestic settings and in the presence of relatives, the authors stress the importance of training patients and relatives to recognize warning signs and symptoms and to react accordingly.
Relatives who are more likely to be witnesses of SCD should at least learn to perform basic life support since most programs that aim to encourage the use of automatic defibrillators and early defibrillation focus mainly on public places. Of course, as the cost of automatic defibrillators decrease and efficiency/efficacy improve, it almost certainly would pay to consider installing AICD units in homes of patients who are at high risk of developing SCD. Appropriate training and recognition programs should be implemented in order to lead to earlier recognition of patients at risk of SCD, and thereby encourage more rapid contact of emergency medical services, all of which will result in a higher percentage of bystander CPR leading to a higher probability of survival in patients with SCD.
References
1. Zipes DP, et al. Neural modulation of cardiac arrhythmias and sudden death. Heart Rhythm. 2006;3:108-113.
2 Meyerburg RJ, et al. In: Zipes DP, Cardiac electrophysiology: from cell to bedside. Fourth edition, Philadelphia: WB Saunders;2004:720-731.
3. Huikuri HV, et al. Sudden death due to cardiac arrhythmias. N Engl J Med. 2001;345:1473-1482.
4. Muller D, et al. How sudden is sudden cardiac death? Circulation. 2006;114:1146-1150.
5. Van Doornum S, et al. Screening for atherosclerosis in patients with rheumatoid arthritis: comparison of two in vivo tests of vascular function. Arthritis Rheum. 2003;48:72-80.
6. de Vreede-Swagemakers JJ, et al. Circumstances and causes of out of hospital cardiac arrest in sudden death survivors. Heart. 1998;79:356-361.
The authors attempt to redefine SCD by concluding that it uncommonly or even rarely occurs "suddenly out of the blue" without any premonitory symptoms.You have reached your article limit for the month. Subscribe now to access this article plus other member-only content.
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