Idioventricular rhythm

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Editor-In-Chief: C. Michael Gibson, M.S., M.D. [1]; Associate Editor(s)-in-Chief: Mahmoud Sakr, M.D. [2]

Synonyms and keywords: IVR

Overview

Normally, the SA node is responsible for triggering each heart beat that results in ventricular contraction. However, if the ventricle does not receive triggering signals at a rate high enough, the ventricular myocardium itself becomes the pacemaker or produces escape beats. This is called idioventricular rhythm.

Pathophysiology

Idioventricular rhythm originates in the ventricular area and the depolarization wave spreads either partially through the electrical conduction system or completely via direct cell-to-cell transmission.
Idioventricular rhythm can occur as any of the following mechanisms :
- an escape rhythm
- an increased automaticity of a single ventricular ectopic pacemaker. This increased automaticity may lead to rates that are faster than the intrinsic rate of the upper pacemakers.
The intrinsic rate in idioventricular rhythm is most commonly between 30 and 50 BPM, but the rhythm can be anywhere from 20 to 50 BPM.
The idioventricular complexes will have the morphological characteristics of the ventricular escape complex, two ventricular escape complexes, two ventricular escape complexes with associated AV dissociation or ectopic ventricular complexes.^[1]

Causes

Life Threatening Causes

Idioventricular rhythm is a life-threatening condition and must be treated as such irrespective of the causes. Life-threatening conditions can result in death or permanent disability within 24 hours if left untreated.

Common Causes

Causes by Organ System

Cardiovascular	Acute coronary syndrome, acute rheumatic fever, Andersen cardiodysrhythmic periodic paralysis, Brugada syndrome, cardiac tumor, complete heart block, congenital heart disease, congestive heart failure, dilated cardiomyopathy, hypertensive heart disease, hypertrophic cardiomyopathy, ischemic heart disease, Jervell and Lange-Nielsen syndrome, Lev’s disease, long QT syndrome, myocardial bridging, myocardial infarction, myocarditis, NSTEMI, pericarditis, Romano-Ward syndrome, STEMI, Timothy syndrome, valvular heart disease
Chemical/Poisoning	Carbamate poisoning, organophosphate poisoning, parathion poisoning
Dental	No underlying causes
Dermatologic	No underlying causes
Drug Side Effect	Acetylcholine, amiodarone, anthracyclines, beta-blockers, calcium channel blockers, cholinesterase inhibitors, daunorubicin, digitalis, doxorubicin, edrophonium, epirubicin, idarubicin, neostigmine, procainamide, propafenone, propofol, pyridostigmine, quinidine, tramadol
Ear Nose Throat	No underlying causes
Endocrine	Diabetic ketoacidosis, hyperthyroidism, profound hypothyroidism
Environmental	Hypothermia
Gastroenterologic	No underlying causes
Genetic	Andersen cardiodysrhythmic periodic paralysis, Brugada syndrome, congenital heart block, congenital heart disease, Emery-Dreifuss muscular dystrophy, Jervell and Lange-Nielsen syndrome, Kearns-Sayre syndrome, limb-girdle muscular dystrophy type 1B (LGMD1B), muscular dystrophy, myotonic dystrophy, Romano-Ward syndrome, Timothy syndrome
Hematologic	No underlying causes
Iatrogenic	Cardiac catheterization, cardiac resynchronization therapy, cardiac transplantation, coronary artery bypass grafting, heart surgery, hypertrophic cardiomyopathy alcohol septal ablation, infraclavicular brachial plexus block
Infectious Disease	Acute rheumatic fever, myocarditis, pericarditis, septic shock
Musculoskeletal/Orthopedic	Muscular dystrophy, myotonic dystrophy, Timothy syndrome
Neurologic	No underlying causes
Nutritional/Metabolic	Hypermagnesemia, hypocalcemia, metabolic acidosis
Obstetric/Gynecologic	No underlying causes
Oncologic	Cardiac tumor
Ophthalmologic	No underlying causes
Overdose/Toxicity	Acetylcholine, amiodarone, anthracyclines, cholinesterase inhibitors, propofol, quinidine, tramadol
Psychiatric	Takotsubo cardiomyopathy, severe anorexia nervosa
Pulmonary	Hypoxia
Renal/Electrolyte	Hyperkalemia, renal failure
Rheumatology/Immunology/Allergy	Acute rheumatic fever, neonatal lupus erythematosus
Sexual	No underlying causes
Trauma	Myocardial contusion, severe brain injury
Urologic	No underlying causes
Miscellaneous	No underlying causes

Causes in Alphabetical Order

Differentiating Idioventricular Rhythm from other Diseases

Below is a table to illustrate some of the similarities and disparities between different ventricular arrhythmias.

**An overview of ventricular arrhythmias**
	example	regularity	ventricular frequency	origin	AV-dissociation
Wide complex (QRS>0.12)
Ventricular escape beat(s)	^[2]	Irregular	1-2 bpm	Ventricle	Usually associated with AV-dissociation
Idioventricular rhythm	^[3]	Regular (mostly)	Usually 20-50 bpm	Ventricle	Usually associated with AV-dissociation
Accelerated Idioventricular Rhythm		Regular (mostly)	50-110 bpm	Ventricle	Usually associated with AV-dissociation
Ventricular Tachycardia		Regular (mostly) if monomorphic	110-250 bpm	Ventricle	AV-dissociation
Ventricular Fibrillation		Irregular	400-600 bpm	Ventricle	AV-dissociation
Ventricular Flutter		Regular	150-300 bpm	Ventricle	AV-dissociation
Torsade de Pointes		Irregular	150-300 bpm	Ventricle	AV-dissociation

References

↑ Miller, Geoffrey P.; Garcia, Tomas B. (2004). Arrhythmia recognition: the art of interpretation. Boston: Jones and Bartlett Publishers. ISBN 0-7637-2246-4.
↑ “ECG ¡V A Pictorial Primer”.
↑ “www.learnekgs.com”.

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[isbn0-7637-2246-4-1] Miller, Geoffrey P.; Garcia, Tomas B. (2004). Arrhythmia recognition: the art of interpretation. Boston: Jones and Bartlett Publishers. ISBN 0-7637-2246-4.

[urlECG_¡V_A_Pictorial_Primer-2] “ECG ¡V A Pictorial Primer”.

[urlwww.learnekgs.com-3] “www.learnekgs.com”.

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