An Interesting Case: An 'Evanescent' ECG Pattern

Richard Musialowski Jr., MD, FACC, FASE
Rick Musialowski Jr.

by Rick Musialowski Jr., MD, FACC, FASE

This is an interesting case that presented to one of Atrium Health’s emergency departments. A 28-year-old woman presents with complaints of chest pain with atypical features. She has a history of tobacco use but no other traditional cardiac risk factors. Her paternal family history is unknown and there is no family history of premature sudden cardiac death. She works in the construction industry and was at work with an abrupt onset of pain. She denies illicit drug use. She endorsed chills, but no documented fever or symptoms of infection. She denies prescription or over-the-counter (OTC) medications and no medications were given in the emergency department (ED). She had not consumed a meal nor had any recent food intake. No history of palpitations or syncope. She was pain-free on presentation with a normal initial troponin. The first electrocardiogram (ECG) was obtained. 

Brugada ECG 

Per our usual chest-pain protocol, a second ECG was obtained in the department. She continued to remain asymptomatic.

Baseline ECG 

There was no change in troponin values and she was discharged from the ED with the diagnosis of noncardiac chest pain. A 2-week event recorder was placed to assess for ventricular arrhythmias. The interpretation of the event recorder was completely normal without any ventricular excitability, including during sleep. She is scheduled to follow-up with our electrophysiology service for future surveillance and consideration of antiarrhythmic provocation of her type 2 pattern in an effort of risk stratification.

‘Evanescent’ ECG Pattern

As seen in our case, the ECG pattern of Brugada syndrome can be “evanescent.” The prevalence of Brugada syndrome is believed to be 1 in 2,000 to 1 in 5,000, with higher prevalence in Far East countries. There is a male predominance (8:1). The average age of sudden death among those with Brugada syndrome is 40 years.

The patient in this case did not have the usual demographics and risk factors. Genetic transmission is autosomal dominant, but there is often incomplete penetrance. Brugada syndrome has a complex genetic background. At least 17 genes are implicated. A limited portion of patients with Brugada syndrome (estimated ≤ 30%) can be identified with extensive genetic screening. Due to the variety of genes, routine genetic testing is not indicated. 

The arrhythmic events associated with Brugada syndrome can occur at any age. Initial presentation is often later in life. The most recent data from international registries of unselected Brugada patients suggest a cardiac arrest/sudden death rate of 1% to 3% per year with a cardiac event rate, which is modulated by age. Cardiac events may be triggered by fever, drugs like tricyclic antidepressants and abundant meals.

Hypotheses

The exact mechanism of arrhythmia is not completely understood, but appears to be reentrant. One hypothesis suggests the ST-elevation is due to the epicardial action potential that becomes shortened because of a combination of loss of repolarizing currents (INa or ICa) paired with the physiologic high levels of transient outward potassium current (Ito) in the right ventricular outflow tract (RVOT). This generates the substrate for reentrant arrhythmias during phase 2 of the action potential. Another hypothesis suggests impaired (Ina) in the RVOT causes slow conduction and asynchronous activation with voltage gradients, causing ST-elevation and promoting reentrant arrhythmias. Recent data obtained show that both mechanisms are likely to coexist.

Treatment, Management Options

All patients with a clinical diagnosis of Brugada syndrome should avoid drugs that can unmask or worsen the ECG pattern. For example, quinidine blocks outflow potassium (Ito) channels and prevents reentry. A resource to learn more about drugs that can affect the ECG pattern is the website www.brugadadrugs.org.

Also, it may be useful to prevent recurrence of cardiac arrest in patients who already received an implantable cardioverter defibrillator (ICD) or when ICD is contraindicated.

Epicardial catheter ablation of fragmented potentials in the RVOT has been proposed in patients with Brugada syndrome. No robust genotype-phenotype correlation has been established.

Patients considered at highest risk are those resuscitated from a prior cardiac arrest and those with a spontaneous type 1 ECG plus syncope. Patients with type 2 or 3 pattern can be provoked by class Ic antiarrhythmic challenge, usually procainamide, to determine whether the high-risk type 1 pattern is present.

References:

American College of Cardiology. Adult Clinical Cardiology Self-Assessment Program (ACCSAP), version 9. Available at: https://www.acc.org/education-and-meetings/products-and-resources/accsap9-adult-clinical-cardiology-self-assessment-program.

Nademanee K, et al. Circulation. 2011;doi:10.1161/CIRCULATIONAHA.110.972612.

Priori SG, et al. J Am Coll Cardiol. 2012;doi:10.1016/j.jacc.2011.08.064.

For more information:

Rick Musialowski Jr., MD, FACC, FASE, is director of cardiovascular education at Sanger Heart & Vascular Institute-Atrium Health Care System.

Disclosure: Musialowski reports no relevant financial disclosures.