ECG Predictors of Arrhythmia in Syncope

Written by Nicole McCoin

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In the evaluation of older patients with syncope, certain ECG abnormalities increase the risk of 30-day serious cardiac arrhythmias. These ECG abnormalities include non-sinus rhythm; multiple premature ventricular conductions; short PR interval; first degree atrioventricular block; complete left bundle branch block; and ST, T, and Q-wave abnormalities consistent with acute or chronic ischemia.

Why does this matter?
Syncope in older patients is a challenging presenting complaint, as differentiating between life-threatening and benign causes can be quite difficult. Any further aid we can get to help us decide which patients are at higher risk for a life-threatening cause is helpful.

“Thank you so much for admitting this 66 year-old male with a negative syncope workup thus far in the ED,” said no admitting physician ever.
This was a prospective, observational study at 11 EDs of adults aged 60 years or older who presented with syncope or near syncope. Patients who had serious cardiac arrhythmias discovered during the ED workup were excluded. Of the remaining study cohort of 3,416 patients, 104 patients (3%) had a serious cardiac arrhythmia within 30 days of the initial ED workup. The median time to diagnosis of that serious cardiac arrhythmia was 2 days. The following ECG abnormalities increased the risk of 30-day serious cardiac arrhythmia: non-sinus rhythm (OR 2.8); multiple premature ventricular conductions (OR 2.4); short PR interval (OR 2.7); first degree atrioventricular blocks (OR 1.9); complete left bundle branch block (OR 2.4); and ST, T and Q-wave abnormalities consistent with acute or chronic ischemia (OR 1.8).

So, how can this help you? Certainly one or more of these ECG abnormalities during the initial workup of an older patient with syncope should heighten your concern regarding the potential presence of a more serious underlying cause of the syncope. This study could be highlighted in your discussion with the admitting physician regarding your concerns and indications for admission. However, we must all keep in mind another key point in this study: 22% (approximately 1 in 5) of the patients with a 30-day serious cardiac arrhythmia had a normal initial ECG or an initial ECG with nonspecific ST- segment abnormalities. So, we cannot rely on the ECG in isolation to make workup and disposition decisions about these older syncope patients. We must look at the big picture (e.g. clinical symptoms and signs, comorbidities, social situation, etc.) when determining the best plan for these patients. The ECG abnormalities listed above may help support your reasoning for further admission and workup, but the lack thereof should not necessarily be an argument to support the patient’s discharge or belief that a benign cause of syncope is present.

Source
ECG Predictors of Cardiac Arrhythmias in Older Adults With Syncope.  Ann Emerg Med. 2018 Apr;71(4):452-461.e3. doi: 10.1016/j.annemergmed.2017.11.014. Epub 2017 Dec 21.

Another Spoonful
Dr. Smith, of Dr. Smith's ECG blog, has a great post on the ECG and syncope.

Peer reviewed by Thomas Davis

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