QRS complex alternans

(Redirected from QRS alternans)
Jump to navigation Jump to search

WikiDoc Resources for QRS complex alternans

Articles

Most recent articles on QRS complex alternans

Most cited articles on QRS complex alternans

Review articles on QRS complex alternans

Articles on QRS complex alternans in N Eng J Med, Lancet, BMJ

Media

Powerpoint slides on QRS complex alternans

Images of QRS complex alternans

Photos of QRS complex alternans

Podcasts & MP3s on QRS complex alternans

Videos on QRS complex alternans

Evidence Based Medicine

Cochrane Collaboration on QRS complex alternans

Bandolier on QRS complex alternans

TRIP on QRS complex alternans

Clinical Trials

Ongoing Trials on QRS complex alternans at Clinical Trials.gov

Trial results on QRS complex alternans

Clinical Trials on QRS complex alternans at Google

Guidelines / Policies / Govt

US National Guidelines Clearinghouse on QRS complex alternans

NICE Guidance on QRS complex alternans

NHS PRODIGY Guidance

FDA on QRS complex alternans

CDC on QRS complex alternans

Books

Books on QRS complex alternans

News

QRS complex alternans in the news

Be alerted to news on QRS complex alternans

News trends on QRS complex alternans

Commentary

Blogs on QRS complex alternans

Definitions

Definitions of QRS complex alternans

Patient Resources / Community

Patient resources on QRS complex alternans

Discussion groups on QRS complex alternans

Patient Handouts on QRS complex alternans

Directions to Hospitals Treating QRS complex alternans

Risk calculators and risk factors for QRS complex alternans

Healthcare Provider Resources

Symptoms of QRS complex alternans

Causes & Risk Factors for QRS complex alternans

Diagnostic studies for QRS complex alternans

Treatment of QRS complex alternans

Continuing Medical Education (CME)

CME Programs on QRS complex alternans

International

QRS complex alternans en Espanol

QRS complex alternans en Francais

Business

QRS complex alternans in the Marketplace

Patents on QRS complex alternans

Experimental / Informatics

List of terms related to QRS complex alternans

Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]

Synonyms and keywords: QRS alternans

Related chapter: electrical alternans

Overview

Electrical alternans is an electrocardiographic phenomenon which describes the beat to beat alternation in the height (ie.e amplitude), duration (the length of the interval) or the direction (up or down) of any of the EKG complexes or intervals. While electrical alernans is usually thought of as alternation in the height or direction of the QRS complex, there can also be P wave, PR interval, QRS complex, R-R interval, ST segment, T wave, or U wave forms of alternans (see classification below).

Historical Perspective

  • 1909: First described by Hearing
  • 1910: Elaborated upon by Sir Thomas Lewis
  • 1948: First description of electrical alternans on the surfce EKG by Kalter and Schwartz [1]
  • 1978: The term ‘pseudoelectrical alternans’ was first described by Klein, Segni and Kaplinsky[2]

Pathophysiology

Electrical Alternans Due to Motion of the Heart

When the word alternans is used, the underlying pathophysiology that is most often thought of is alternans due to motion of the heart and its shifting position in relationship to the surface electrodes. The pathophysiologic mechanism underlying the alternation in the height or amplitude of the QRS complex is the swinging or shifting or the electrical axis of the heart. It should be noted that there can also be P wave and T wave alternans attributable to the motion of the heart.

While electrical alternans is frequently thought of in association with pericardial effusion, it should be noted that not all pericardial effusions cause electrical alternans, and that total electrical alternans (involving the p wave, QRS complex and the T wave) is present in just 5-10% of cases of cardiac tamponade.

It is underappreciated that the movement of the heart in hypertrophic cardiomyopathy can cause electrical altrical alternans as well.

Electrical Alternans Due to Changes in Electrical Conduction of the Heart

Electrical laternans can also be due to variation in the velocity of conduction through any of the anatomic structures of the heart. Usually this variation in the conductivity is caused by a change in heart rate, autonomic tone, vagal tone, or drugs. At a more fundamental level, the abnormality is thought to be due to changes in calcium handling in the sarcoplastic reticulum. The following complexes, either alone or in combination, may exhibit electrical alternans due to changes in electrical conduction: the P wave, the PR interval, the QRS complex, or the RR interval. The appearance of QRS alternans as part of a narrow complex tachycardia suggests the diagnosis of orthodromic atrioventricular (AV) reentrant tachycardia which conducts retrograde over an accessory pathway.

Causes

All Causes in Alphabetical Order

Due to Motion of the Heart

Due to Changes in Impulse Conduction

Differentiating Electrical Alternans form other Disorders

The electrical form of alternans should be differentiated from the mechanical form alternans in which case there is alternation of the strength of the pulse as is observed in pulsus alternans. Electrical and mechanical alternans may coexist.

Electrocardiographic Examples

An ECG showing electrical alternans in a person with pericardial effusion. Note the beat to beat change in the height and axis of the QRS complexes.


An ECG showing electrical alternans in a person with pericardial effusion. Note the beat to beat change in the height and axis of the QRS complexes.


An example of electrical alternans. Note the beat to beat change in the height and axis of the QRS complexes.


References

  1. Kalter HH, Schwartz ML. Electrical alternans. NY State J Med. 1948;1:1164-66.
  2. Klein HO, Di Segni E, Kaplinsky E (1978). "Procainamide-induced left anterior hemiblock of the 2:1 type (pseudoelectrical alternans)". Chest. 74 (2): 230–3. doi:10.1378/chest.74.2.230. PMID 679762.