Number 2: Should You Worry About That Syncopal Episode?
Distinguishing Cardiac Syncope From Vasovagal Syncope in a Referral Population
Tretter JT, Kavey RW
J Pediatr. 2013;163:1618-1623
Methodology. Syncopal events, in which an individual has sudden loss of consciousness as a result of reduced cranial blood flow, followed by prompt recovery, are common in children. However, very few episodes of syncope have cardiac causes.
To improve care for children with syncope, specifically with an eye toward reducing testing for those with probable vasovagal syncope, Tretter and Kavey studied 89 children who were referred to a pediatric cardiology clinic for evaluation of vasovagal syncope and compared them with 17 children with cardiac causes of syncope. They reviewed potential precursors to syncopal episodes and whether there was a family history of cardiac events (all types). The review also included outpatient and emergency department records and labs for syncope symptoms before referral to the cardiology clinic.
Results. Of the 17 patients with a cardiac cause of syncope, 10 presented to the emergency department in arrest without a pulse. These children were thought to represent aborted sudden cardiac arrests. Significant differences between children with cardiac and vasovagal syncope are shown in the table.
Table. Differences Between Cardiac and Vasovagal Syncope
| Variable | Type of Syncope | |
|---|---|---|
| Cardiac | Vasovagal | |
| Mean age (yrs) | 10.5 | 12.7 |
| Previous syncope event | 29% | 64% |
| Syncope surrounding activity | 65% | 18% |
| Syncope at peak exercise | 53% | 6% |
| Presyncopal events | 12% | 69% |
| Any trigger (anxiety, noxious) | 0% | 24% |
| Prolonged standing | 0% | 24% |
| Cardiopulmonary resuscitation before evaluation | 65% | 0% |
Family history was not helpful in differentiating the cause of syncope, although a positive family history was slightly more common among children with a cardiac cause (41%) than a vasovagal cause (25%). This difference did not reach statistical significance. There were no significant differences in the numbers of children who reported either chest pain or palpitations before their syncopal event.
Among children with a cardiac cause of their syncope, 47% had long QT syndrome and 18% had cardiomyopathy. Among the two thirds of children with vasovagal syncope in whom an ECG was obtained, all were eventually read as normal by the investigator group, whereas 76% of the children with cardiac syncope had abnormal ECGs. When physical and laboratory evaluations were examined, 29% of the children with a cardiac cause of syncope had an abnormal physical examination, compared with none of the patients who had vasovagal syncope.
In analyzing four particular risk factors that the literature has previously suggested to be pertinent for syncope—syncope with exertion, a concerning cardiac family history, abnormal physical examination, or abnormal ECG—the investigators found that the patients in the cardiac syncope group had a mean of 2.1 risk factors compared with 0.4 among the vasovagal cohort. Limiting cardiac referrals to children with at least one of those risk factors would have resulted in cardiology referrals for all of the children later found to have cardiac syncope and would have eliminated 60% of the referrals for children who were evaluated and found to have vasovagal syncope.
Viewpoint. This article illustrates the challenges of trying to tease out the clinical epidemiology of a relatively "rare" event, true cardiac syncope. I think that the article was popular because of the combination of the frequency of noncardiac syncope and anxiety on the part of providers about missing a true cardiac case. In that vein, the study truly excelled by taking an analytic approach that suggests a clinical threshold, above which a generalist pediatric provider should refer for specialty care. The risk factors identified in this study could easily be adapted to daily use. These findings certainly suggest that we could do more in primary care practice and in emergency department settings to rule out cardiac causes of syncope, but it would be important to have any screening ECGs that are obtained read by a cardiologist (as was done in this study) and make sure that we review our cardiac examination capabilities
And the most-read article by pediatric readers in 2014 is...