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

Synonyms and Keywords: Ventricular escape; ventricular escape beats; ventricular escape beat, ventricular escape rhythm

Overview

A ventricular escape beat is a self-generated electrical discharge initiated by and causing contraction of the ventricles of the heart. It is a heart rhythm finding discovered on EKG, that indicates the normal electrical conduction system of the heart is disrupted or performing inadequately i.e failure of the SA node and AV node to generate an impulse. The ventricular escape beat follows a long pause in ventricular rhythm and acts to prevent cardiac arrest.

Pathophysiology

  • Ventricular escape beats occur when the rate of electrical discharge reaching the ventricles (normally initiated by the heart's sinoatrial node, transmitted to the atrioventricular node, and then further transmitted to the ventricles) falls below the base rate determined by the ventricular pacemaker cells.[1]
  • Normally, the pacemaker cells of the sinoatrial node discharge at the highest frequency (70 beats per minute) and are thus dominant over other cells with pacemaker activity. The AV node normally has the second fastest discharge rate (40-60 beats per minute). If the rate from both the SA and AV node fall below the discharge rate of ventricular pacemaker cells, a ventricular escape beat ensues (less than 40 beats per minute).
  • An escape beat usually occurs 2–3 seconds after an electrical impulse has failed to reach the ventricles. [2]

Causes

Life Threatening Causes

Life-threatening causes include conditions which may 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 Ventricular Escape Beat from other Diseases

  • Junctional escape beat : When the sinus rate falls below the discharge rate of the AV node, this becomes the dominant pacemaker, and the result is called a junctional escape beat. The AV node usually generates a rhythm at 40-60 BPM.
  • Idioventricular rhythm : An escape beat is a form of cardiac arrhythmia, in this case known as an ectopic beat. If there are only one or two ectopic beats, they are considered escape beats. If this causes a semi-normal rhythm to arise it is considered an idioventricular rhythm.
  • Premature ventricular contraction : An absence of P wave activity, associated with a widened QRS complex resembles a PVC, but occuring after a pause of variable duration differentiate ventricular escape beat from PVCs.
  • Complete heart block : In complete or third degree heart block there is sinus node activity but failure of conduction through the AV node. There are P waves dissociated from the ventricular complexes with a rate faster than the ventricular rate that differentiates complete heart block from ventricular escape beat where there is absence of P waves.

Diagnosis

History and Symptoms

The escape arrhythmia is a compensatory mechanism that indicates a serious underlying problem with the SA node or conduction system (commonly due to heart attack or medication side effect), and because of its low rate, it can cause a drop in blood pressure. Some of the symptoms related to hypotension are:

Physcial Examination

  • Bradycardia may be present. The rate is below 40 beats per minute.
  • Tachypnea may be present.
  • Elevated JVP may be seen if heart failure is present.
  • S3 gallop may be heard in the presence of heart failure.

Laboratory Findings

The following laboratory studies should be done, depending upon the cause, while investigating a case of ventricular escape beat.

Electrocardiogram

An electrocardiogram can be used to identify a ventricular escape beat. The QRS portion of the electrocardiogram represents the ventricular depolarization; in normal circumstances the QRS complex forms a sharp sudden peak. For a patient with a ventricular escape beat, the shape of the QRS complex is broader as the impulse can not travel quickly via the normal electrical conduction system.[3]

Factors Affecting Ventricular Escape Beat

  • Ouabain infusion decreases ventricular escape time and increases ventricular escape rhythm. However, a high dose of ouabain can lead to ventricular tachycardia.[2]

References

  1. C. Andreasen, et al. (2006) Mosby Elsevier, Mosby's Dictionary of Medicine, Nursing and Health Professions 7th edition, p1951
  2. 2.0 2.1 Banka VS, Scherlag BJ, Helfant RH (1975). "Contractile and electrophysiological responses to progressive digitalis toxicity". Cardiovasc. Res. 9 (1): 65–72. doi:10.1093/cvr/9.1.65. PMID 1122512. Unknown parameter |month= ignored (help)
  3. Adams MG, Pelter MM (2003). "Ventricular escape rhythms". Am. J. Crit. Care. 12 (5): 477–8. PMID 14503433. Unknown parameter |month= ignored (help)
  4. Kodama-Takahashi K, Kurata A, Ohshima K; et al. (2003). "Effect of cilostazol on the ventricular escape rate and neurohumoral factors in patients with third-degree atrioventricular block". Chest. 123 (4): 1161–9. doi:10.1378/chest.123.4.1161. PMID 12684307. Unknown parameter |month= ignored (help)




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