Ventricular Fibrillation in Emergency Medicine 

  • Author: Keith A Marill, MD; Chief Editor: David FM Brown, MD   more...
 
Updated: Jun 23, 2011
 

Background

Ventricular fibrillation (VF) begins as a quasiperiodic reentrant pattern of excitation in the ventricles with resulting poorly synchronized and inadequate myocardial contractions. The heart consequently immediately loses its ability to function as a pump. As the initial reentrant pattern of excitation breaks up into multiple smaller wavelets, the level of disorganization increases. Sudden loss of cardiac output with subsequent tissue hypoperfusion creates global tissue ischemia; brain and myocardium are most susceptible. VF is the primary cause of sudden cardiac death (SCD).

Ventricular fibrillation is shown in the rhythm strip below.

Ventricular fibrillation. Rapidly recurrent despitVentricular fibrillation. Rapidly recurrent despite electrical biphasic defibrillation. Notice that recurrence begins after completion of the T wave and is not due to an R-on-T phenomenon in this case. This episode of ventricular fibrillation (VF) occurred in the emergency department and was present for less than 30 seconds prior to defibrillation, hence the course morphology. Also an undulating amplitude suggestive of torsades de pointes was present; however, the QT interval during sinus rhythm was normal, and the only known predisposing factors for tachydysrhythmia were newly diagnosed coronary artery disease with acute right coronary artery occlusion and a history of rheumatoid pericarditis.
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Pathophysiology

Sudden cardiac death can be viewed as a continuum of electromechanical states of the heart: ventricular tachycardia (VT), ventricular fibrillation (VF), pulseless electrical activity (PEA), and asystole. VF is the most common initial state, and, because of insufficient perfusion of vital cardiac tissues, it degenerates to asystole if left untreated.

The etiology of ventricular fibrillation (VF) remains incompletely understood. It often occurs in the setting of acute cardiac ischemia or infarction, and acute myocardial infarction (MI) is diagnosed in up to half of sudden-death survivors. The incidence of sudden death is also relatively high in the postinfarction period for months after an MI. Abnormal rapid stimulation of the ventricles can lead to fibrillation. This can occur during VT or in conditions, such as Wolff-Parkinson-White syndrome, when atrial fibrillation or flutter waves pass rapidly through a bypass tract to the ventricular musculature. Severe left ventricular dysfunction, a variety of cardiomyopathies, and acquired or idiopathic long QT syndrome also increase the risk of fibrillation.

Multiple events may lead to the initiation of VF. One etiology is mechanical or electrical stimulation of the myocardium during the early phase of repolarization (termed R-on-T phenomenon). When an impulse is delivered to the heart during the time period that corresponds to the upslope of the T wave, the ventricular myocardium is in a variable state of excitability because some of the muscle is still partly or completely refractory. The impulse may propagate electrically through the tissue but at a decreased rate through a tortuous pathway. Slowed abnormal conduction may allow the wave of depolarization to circle around and reexcite areas that have had sufficient time for repolarization.

Sustained VF may be due to a relatively small number of macroreentrant circuits or rotors, which are relatively stationary or drift through the 3-dimensional volume of the ventricular myocardium. These rotors may activate the cardiac muscle fibers at a high frequency, with secondary wavefronts emanating, traveling, and breaking up at variable distances from the source.

All fibrillation is not the same. VF begins as a coarse, irregular deflection on the ECG, then degenerates to a fine, irregular pattern, and eventually becomes asystole. This progression of electrocardiographic abnormalities reflects the electrical changes described above. The probability of successful defibrillation decreases as the VF waveform becomes smoother with time.[1]

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Epidemiology

Frequency

United States

The incidence of sudden cardiac death in the United States is approximately 300,000 cases per year. The distribution of rhythms found in patients with cardiac arrest depends largely on the average duration of the arrest state and, thus, the emergency medical system (EMS) response times. In monitored settings, such as casinos, where average response times are less than 5 minutes, the initial rhythm is ventricular fibrillation in approximately 70% of patients.[2] A circadian pattern of sudden cardiac death has also been reported.

International

Ventricular fibrillation also is prevalent worldwide, with a reported predominance in the northern hemisphere. Among some European populations, the annual incidence of cardiac arrests exceeds 6 cases per 10,000 people.

Mortality/Morbidity

The likelihood of survival of cardiac arrest victims also depends on the duration of arrest prior to treatment. Improved outcomes occur in patients who have a witnessed arrest, receive bystander cardiopulmonary resuscitation (CPR), obtain defibrillation and advanced cardiac life support from EMS personnel within 10 minutes of onset, and present with an initial rhythm of ventricular fibrillation (VF).

Cardiac arrests witnessed by bystanders have a better prognosis because the victim is more likely to receive early treatment. The rate of survival from VF in the community varies from 4-33%. The survival rate of all cardiac arrest victims regardless of presenting rhythm has been reported to be as high as 18% and as low as 2% in various EMS systems. Large urban centers tend to have lower rates of survival. These lower rates of survival have been attributed to lower rates of bystander CPR, longer response intervals, and fewer patients presenting with VF.[3]

Race

Black males have the highest incidence of sudden cardiac death.

Sex

Sudden cardiac death is more common among males than females, although the rates become similar for patients older than 70 years.

Age

Incidence initially peaks during the first 6 months of life, then rapidly declines until a second peak in those aged 45-75 years.

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Contributor Information and Disclosures
Author

Keith A Marill, MD  Faculty, Department of Emergency Medicine, Massachusetts General Hospital; Assistant Professor, Harvard Medical School

Keith A Marill, MD is a member of the following medical societies: American Academy of Emergency Medicine and Society for Academic Emergency Medicine

Disclosure: Medtronic Ownership interest None; Cambridge Heart, Inc. Ownership interest None; General Electric Ownership interest None

Coauthor(s)

A Antoine Kazzi  MD, Deputy Chief of Staff, American University of Beirut Medical Center; Associate Professor, Department of Emergency Medicine, American University of Beirut, Lebanon

A Antoine Kazzi is a member of the following medical societies: American Academy of Emergency Medicine

Disclosure: Nothing to disclose.

Mazen K Khalil, MD  Post Doctoral Research Fellow, Department of Cell Biology, Lerner Research Institute, Cleveland Clinic Foundation

Mazen K Khalil, MD is a member of the following medical societies: American College of Physicians

Disclosure: Nothing to disclose.

Aaron A Bright, MD  Assistant Professor of Clinical Emergency Medicine, Department of Emergency Medicine, LAC+USC Medical Center, Keck School of Medicine of the University of Southern California

Aaron A Bright, MD is a member of the following medical societies: American College of Emergency Physicians and Los Angeles County Medical Association

Disclosure: Nothing to disclose.

Specialty Editor Board

Steven A Conrad, MD, PhD  Chief, Department of Emergency Medicine; Chief, Multidisciplinary Critical Care Service, Professor, Department of Emergency and Internal Medicine, Louisiana State University Health Sciences Center

Steven A Conrad, MD, PhD is a member of the following medical societies: American College of Chest Physicians, American College of Critical Care Medicine, American College of Emergency Physicians, American College of Physicians, International Society for Heart and Lung Transplantation, Louisiana State Medical Society, Shock Society, Society for Academic Emergency Medicine, and Society of Critical Care Medicine

Disclosure: Nothing to disclose.

Francisco Talavera, PharmD, PhD  Adjunct Assistant Professor, University of Nebraska Medical Center College of Pharmacy; Editor-in-Chief, Medscape Drug Reference

Disclosure: Medscape Salary Employment

Gary Setnik, MD  Chair, Department of Emergency Medicine, Mount Auburn Hospital; Assistant Professor, Division of Emergency Medicine, Harvard Medical School

Gary Setnik, MD is a member of the following medical societies: American College of Emergency Physicians, National Association of EMS Physicians, and Society for Academic Emergency Medicine

Disclosure: SironaHealth Salary Management position; South Middlesex EMS Consortium Salary Management position; ProceduresConsult.com Royalty Other

John D Halamka, MD, MS  Associate Professor of Medicine, Harvard Medical School, Beth Israel Deaconess Medical Center; Chief Information Officer, CareGroup Healthcare System and Harvard Medical School; Attending Physician, Division of Emergency Medicine, Beth Israel Deaconess Medical Center

John D Halamka, MD, MS is a member of the following medical societies: American College of Emergency Physicians, American Medical Informatics Association, Phi Beta Kappa, and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

Chief Editor

David FM Brown, MD  Associate Professor, Division of Emergency Medicine, Harvard Medical School; Vice Chair, Department of Emergency Medicine, Massachusetts General Hospital

David FM Brown, MD is a member of the following medical societies: American College of Emergency Physicians and Society for Academic Emergency Medicine

Disclosure: Nothing to disclose.

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Ventricular fibrillation. Rapidly recurrent despite electrical biphasic defibrillation. Notice that recurrence begins after completion of the T wave and is not due to an R-on-T phenomenon in this case. This episode of ventricular fibrillation (VF) occurred in the emergency department and was present for less than 30 seconds prior to defibrillation, hence the course morphology. Also an undulating amplitude suggestive of torsades de pointes was present; however, the QT interval during sinus rhythm was normal, and the only known predisposing factors for tachydysrhythmia were newly diagnosed coronary artery disease with acute right coronary artery occlusion and a history of rheumatoid pericarditis.
 
 
 
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