When Is Syncope Arrhythmic?

 When Is Syncope Arrhythmic?

Evan Martow, BMSc, MDCMd, Roopinder Sandhu, MI), MPHb'*

KEYWORDS

• Arrhythmia • Syncope • Bradyarrhythmia • Tachyarrhythmia • Cardiac monitoring

KEY POINTS

• Syncope is a symptom that presents with an abrupt, transient. and complete loss of con-

sciousness associated with inability to maintain postural tone, with rapid and spontaneous

recovery.

• Arrhythmic syncope (a subcategory Of cardiac syncope) can be a result Of bradyarrhyth-

mia (due to sinus node dysfunction and/or atrioventricular node or distal conduction sys-

tem disease) or tachyarrhythmia (due to ventricular tachycardia or supraventricular

tachycardia).

• Initial evaluation should include a history, physical examination, and 12-lead electrocar-

diogram (ECG). If the cause remains unclear, a high clinical suspicion for arrhythmic cause

will guide further testing and cardiac monitoring.

• The goal of cardiac monitoring is to obtain symptom-rhythm correlation. The choice of

cardiac monitoring device should be guided by the frequency Of Symptoms and the likeli-

hood that the patient may be incapacitated and, therefore, cannot voluntarily trigger the

ECG recording device.

• Referral to a heart rhythm specialist should be considered if high-risk features are present

On initial evaluation to expedite treatment, when the significance of findings is uncertain, or

when there is high suspicion Of an arrhythmic cause requiring further management.

DEFINITION

DEFINITION

Syncope is defined as an

• Abrupt, transient, complete loss of consciousness

• Associated with inability to maintain postural tone

• With rapid and spontaneous recovery

• With the absence of clinical features of alternative causes, such as seizure, head

trauma, psychogenic pseudosyncope.l

The authors have nothing to disclose.

a Division of Cardiology, university of Alberta, University of Alberta Hospital, Walter Mack-

enzie Health Sciences Centre, 8440 112 Street, Edmonton, Alberta T6G 2B7, Canada; b Division

of Cardiology, University of Alberta, Walter Mackenzie Health Sciences Centre, 8440 112 Street,

Edmonton, Alberta T6G 287, Canada

• Corresponding author.

E-mail address: rsandhu2@ualberta.ca

Med Clin N Am 103 (2019) 793-807

2019 Elsevier Inc. All rights reserved.

Martow & Sandhu

medical.theclinics.com

Presyncope symptoms, including extreme lightheadedness; visual sensations, such

as tunnel vision; and varying degrees of altered level of consciousness, may occur

before a syncopal event or resolve without syncope.

CAUSES OF SYNCOPE Syncope causes can be categorized as roncardiac or cardiac (Fig. 1). Arrhythmia is a cot-nrncY' caLse Of cardiac syncope and can subdivided into mias and tachyarrhythmias. are caused by • Sinus node dysfunction (historically dubbed sick sinus Which in- dudes inappropriate sinus bradycardia', sinus pause, atrial arrest,c sinoatrial exit block. and tachy-brady syndrome • Atrioventricular (AV' node or conduction system dysfunction Üolcnged PR inter- Val, secmd--d."ræ type I II AV block, AV bbck).2 result in due to inad«iuate cerebral perfusion frorn slow rates Or beats. Tachyarrhythmias can by tissl_æs above the level of the ventricle (stQ- raventricular) or within the ventricle itself. Supraventricular tachycardia (SVT) de- scribes tachycardia (atrial and/or ventricular rates > 100 beats per minute) driven by tissue from the His bundle or above. 3 Examples include AV reentrant tachycardia (AVRO. AV nodal ræntrant tachycardia (AVNRT). atrial tachycardia (AT), atrial flutter, and atrial fibrillation. Ventricular tachycardia (VT) can crcur in monomorphic and/or polymorphic forms. : Tachyarrhythmias result in syncope due to inadequate cardiac filling with poor cardiac output and cerebral Malfunctions in cardiac implanted devices can also result in If a pace- maker malfunction)ns, the underlying bradyarrhythmia may cause Addition- ally, cardiac devices can be implicated in pacemaker-mediated tachycardia, which can cauæ syncope. F' Arrhythmic Syncope Epidemiology and Diagnosis Syncope is a common presentation to emergency departments. accounting for an estimated I % to 6% Of all Visits annually. A high proportion Of these patients are hospitalized, ranging from 13% to 86%re The most common causes Of syncope are reflex syncope (—20%), followed by cardiac syncope 10%) and orthostatic syncope ( — 10%). Arrhythmic syncope represents a Significant proportion Of cardiac syncope cases. However, varying definitions, inclusion or exclusion criteria, and diagnostic approaches have led to wide variation in the reported proportions of syncope attributed to arrhythmia. 9- Arrhythmic syncope can be caused by either bradyarrhythmia tachyarrhythmia. The o*tive of monitoring for arrhythmic syncope is achieving symptom—rhythm correlation: if the patient reported symptoms with rhythm abnormalities