It would be best to be able to identify patients prior to their sudden arrhythmic death, but so far no study of an unselected population has been able to characterize variables. A nationwide study among young adults in Denmark attempted to clarify symptoms that young individuals experienced prior to a sudden arrhythmic death. Many causes of cardiac death are secondary to coronary artery disease, as discussed in last month's column, but now more causes have been identified with sophisticated DNA analysis.
Symptoms before Sudden Arrhythmic Death Syndrome
Glinge C, Jabbari R, et al.
J Cardiovasc Electrophysiol
Sudden cardiac death often remains unexplained after a comprehensive post-mortem evaluation and toxicology testing, and negative investigative results range up to 40 percent of all sudden cardiac death in young people. It is difficult to prevent sudden death because there is no sure way to identify individuals at risk. There are some symptoms, albeit with low predictive values and low sensitivities, that characterize subsequent cardiac arrest.
The aim of this study was to identify and describe the symptoms and medical history preceding sudden cardiac death in a nationwide cohort of unselected young patients ages 1-35. The researchers identified 314 cases of sudden cardiac death. The most common cause of death was structural heart disease, most commonly coronary artery disease but also myocarditis, hypertrophic heart disease, and arrhythmogenic right ventricular heart disease. These authors evaluated 136 non-toxicology-related deaths in patients experiencing cardiac arrest, and compared them with a control group of individuals who died in vehicle crashes.
All individuals in Denmark are given a civil registration number that enables an individual's medical history to be available to multiple sources. A forensic autopsy is conducted by law on all those for whom the cause of death cannot be ascertained from an external examination or other sources. The investigators studied hospital and physician records, and conducted interviews with relatives on all autopsy cases that were described as sudden, unexpected death. The authors also attempted to define the premortem incidence of chest pain, dyspnea, presyncope, syncope, palpitations, and other cardiac events.
Toxicology testing was occasionally positive, but the authors did not believe that any of the cases had a toxicological profile that would explain the cause of death. No previous medical history was described in the medical records of 45 percent of cases.
Overall, 35 percent of individuals with sudden arrhythmic death had at least one presumed cardiac symptom prior to death. Most never contacted a physician or ED with seemingly benign symptoms. Prodromal symptoms occurred more than 24 hours before death in 22 percent and in less than 24 hours in 17 percent. Most of the sudden deaths (89%) occurred while the patient was sleeping or awake and relaxed. Only nine percent died during high-intensity activity. The most common prior cardiac symptom was presyncope or syncope, occurring in 17 percent of young people. A small number of patients also had dyspnea and chest pain. Interestingly, 18 percent of sudden death patients had a prior documented seizure at some time in their life, and about half had been diagnosed with epilepsy (not further discussed). It's unclear whether some seizures occurred at the time of death from an arrhythmia.
Only 35 percent of sudden death patients had a cardiac symptom before death. Of these, only 22 percent of patients contacted a health care provider. Presumed cardiac symptoms also included chest pain (12%), dyspnea (13%), palpitations (2%), presyncope/syncope (17%), and seizures (18%). The most common symptom prompting a medical evaluation was presyncope/syncope, and 61 percent of those had consulted a general practitioner or an ED. Apparently, cardiac disease was not suspected in these cases. No previous medical history was elicited in almost half of the cases.
Comment: Prior studies report a much lower incidence of symptoms prior to cardiac arrest in otherwise healthy young people than this research, but this investigation was quite extensive. These investigators found that statistically more patients with sudden arrhythmic death syndrome had cardiac symptoms prior to death than controls. The actual cause of syncope could not be determined. It is interesting that 18 percent of patients had a seizure and were diagnosed with epilepsy. Of course, a sudden cardiac arrhythmia that terminates spontaneously could cause a seizure and be mistaken for epilepsy. That being said, I believe it is axiomatic that young patients who suffer a seizure should have electrocardiogram taken upon initial evaluation. Unfortunately, if they are not currently seizing, the cardiogram likely would not indicate cardiac pathology, but carefully looking for Wolff-Parkinson-White syndrome, Brugada characteristics, or a prolonged QT syndrome would be paramount.
Despite the availability of comprehensive medical records, it is interesting that only 22 percent of patients had a health care system contact due to a cardiac symptom. Of course, these symptoms were all retrospectively related to the heart, but the sensitivity of presyncope/syncope as being caused by a cardiac event is low. Most cases of presyncope/syncope in young individuals are not due to an arrhythmia. Likewise most seizures are not due to arrhythmia, but some of them are. For example, a patient in the throes of an acute MI in the ED who has a seizure should first be thought to have ventricular fibrillation, not epilepsy.
Most individuals would not readily describe heart disease as a cause of presyncope/syncope, and many other reasons could account for these symptoms, particularly in young patients. Seventeen percent of patients who suffered a subsequent cardiac arrest had presyncope/syncope or a seizure that is often difficult to differentiate from syncope. Most importantly, only one of five patients who had these symptoms contacted a health care system. It is another issue whether the clinician who had been handling this patient should have suspected cardiac disease; they apparently did not. It appears that these young people with syncope did not have an ECG at the time of the initial medical evaluation.
How then does the emergency physician interpret these data? Seeing a young patient with presyncope/syncope or a seizure is not uncommon. It is difficult to differentiate an arrhythmia from a neurogenic seizure, and often these patients are evaluated with a head CT scan, put on an anticonvulsant, and referred to a neurologist for EEG evaluation or other workup. Whether a neurologist would perform further cardiac evaluation is unclear.
Most likely presyncope/syncope was due to a malignant arrhythmia that terminated spontaneously. Finding new onset atrial fibrillation, bradycardia/tachycardia, or heart block or hearing a murmur of aortic stenosis leads the clinician to diagnose a cardiac condition in need of further workup. If one does not find an ECG cause for an arrhythmia, such as WPW, a prolonged QT syndrome, Brugada syndrome, or a hypokalemia, it is a stretch to attribute the symptoms to a potentially life-threatening event. I am always reluctant to discharge patients who have true syncope and no cause is found, but it's getting more and more difficult to have these patients admitted to the hospital. I think cardiac monitoring while in the ED is necessary; you just might catch a short run of asymptomatic ventricular tachycardia. I also believe an ECG is mandatory in all patients with syncope, but the literature is not in agreement. Sun, et al., reported nearly 500 young patients with presyncope/syncope and found no yield from an ECG. (Ann Emerg Med 2008:51:240.) These authors advised that an ECG was not necessary as part of the ED evaulation. Go figure.
I don't believe a head CT is necessary — though they are often ordered — in a young syncope patient with no headache, altered mental status, or neurologic findings. I suppose some think that unwitnessed syncope could actually have been a seizure. Of course, near-syncope could just be a prolonged period of lightheadedness that would not always mandate an ECG in otherwise healthy 30-year-olds. Most health insurance companies will deny payment for a formal hospital admission in a patient who is otherwise asymptomatic but had a history of syncope and has normal labs and a normal ECG. The differential diagnosis of presyncope/syncope is gargantuan, and does not always cause a clinician to think of a malignant cardiac event that precedes sudden death, particularly in a young person.
Next month: Seizures can be caused by a cardiac event, and ED patients with a seizure should be considered for a cardiac cause.
Young Individuals with Sudden Arrhythmic Death
* The most frequent causes of sudden cardiac death in young people are coronary heart disease (13%), myocarditis (7%), hypertrophic heart disease (6%), and arrhythmogenic right ventricular cardiomyopathy (5%).
* Autopsy and toxicology-negative cases of sudden arrhythmic death of young people range from 14 to 43 percent.
* Concerning or premonitory symptoms can occur days to weeks before sudden death, but symptoms before sudden death have low predictive value and low sensitivities.
* Antecedent symptoms more than 24 hours before cardiac arrest were present in 25 percent of patients and symptoms less than 24 hours before arrest were present in 17 percent.
* Presyncope/syncope was the most common cardiac symptom (17%) prior to sudden death.
* Other symptoms prior to death included seizures (18%), chest pain (12%), dyspnea (13%), and palpitations (1%).
* No previous medical history was recorded in 45 percent of cases.
* The majority of sudden death patients did not have a premortem ECG.
* Overall, about 35 percent of cases of sudden arrhythmic deaths had one cardiac symptom prior to death, but only 22 percent had consulted a health care provider.
Source: J Cardiovasc Electrophysiol 2015;26(7):761.
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