A    E    D
 
 AUTOMATIC EXTERNAL DEFIBRILLATION
 
 

CONTENTS:

1.  VENTRICULAR FIBRILLATION
2.  CHAIN OF SURVIVAL
3.  DEFIBRILLATION
4.  AUTOMATIC EXTERNAL DEFIBRILLATION
5.  CHARLESTON COUNTY EMS - AED PROGRAM
6.  CONCLUSION
7.  REFERENCE
 

LINKS:

 American Heart Association Ventricular Fibrillation

 American Heart Association - Automatic External Defibrillation
 

 

 
 

 
 
 
VENTRICULAR FIBRILLATION
 
 

Ventricular fibrillation is the result of chaotic electrical activity of the heart muscle fibers, thus making them unable to produce coordinated myocardial contraction. This results in immediate loss of the pump action of the heart which leads to cessation of essential oxygen carrying blood flow to the body. Loss of oxygen to the brain causes brain damage within a very short time, and irreversible brain death (4). Ventricular fibrillation can occur preoperatively, however, most frequently ( > 75 %) occurs outside of a hospital setting. In the US, of the more than 350,000 occurrences of sudden cardiac death, 75% are due to ventricular fibrillation (1). The incidence rates are equally high in the industrialized European counties, where 1 in 1000 habitants are victims of sudden cardiac death caused by ventricular fibrillation (5).

The major cause of ventricular fibrillation is ischemic heart disease. Thirty percent of victims of acute myocardial infarction die from ventricular fibrillation within the first 2 hours from the onset of symptoms. In contrast, 80% of those who survive sudden cardiac death are alive after one year (10). Ischaemia in the heart can cause areas of irritability, impede electrical impulses, resulting in life threatening arrhythmias. Other causes of sudden cardiac death by ventricular fibrillation include heart failure, drug toxicity , metabolic imbalances, electric shock and blunt injury to the chest (5).

Electrical defibrillation is the only effective treatment for terminating the deadly chaotic rhythms of ventricular fibrillation, and allowing the heart for restart a perfusing rhythm (5). The chances of a successful defibrillation and subsequent survivals diminish rapidly over time. Resuscitation success places emphasis on early defibrillation, with the chance of survival inversely related to the duration of time between onset of ventricular fibrillation and the application of defibrillation(3). Studies have shown that survival rates fall by 7-10% for every minute following the onset of ventricular fibrillation (4).
 
 

CHAIN OF SURVIVAL
 

The "chain of survival" is a universal as well as international concept used to describe the course of events that must occur and occur rapidly to offer the best chance of survival of sudden cardiac death due to ventricular fibrillation. The first link is "early assess". This is prompt notification of a medical emergency to request both trained personelle and necessary lifesaving equipment. This chain is strengthened by public education and availability of emergency communication systems. The second link is "early CPR", which can sustain a heart in ventricular fibrillation until personelle with medical equipment can arrive. The third link, "early defibrillation" is the most critical and has the greatest value as long as the preceding links do not fail. The fourth link, "early advanced Life support" is the emergency medical attention of specially trained personelle (6).


 
DEFIBRILLATION
 

The history of defibrillation is relatively short and has had a rapid growth in technological advances. The first human to be effectively treated with defibrillation was in 1947 performed by Dr. Claude S. Beck. The defibrillator he used was cumbersome, hardly portable and the thinking at that time was that defibrillation had to be performed directly on the heart, requiring a thoracotomy (1,2). By 1956, successful closed chest defibrillation occurred. This brought the emergence of defibrillators in emergency rooms and cardiac care units. The obstacle of portability was solved by 1960 when a defibrillator that would run on Direct Current (DC batteries) was developed. Once portable, a means of delivering them to the patient in need was the next step. This prompted the development of the modern day ambulance with advanced life support capabilities (1).

The rapid fifty year development and advancement in defibrillators and their application has not translated into a marked increase of lives saved. Despite the virtual hundreds of emergency medical programs with thousands of trained personelle, only a very small number of victims of sudden cardiac death from ventricular fibrillation are saved each year. The number one reason for this is that defibrillation occurs too late (1, 4).


 
A    E    Ds
 

Ventricular fibrillation is highly unpredictable and today unpreventable. With time being the critical element has come the emergence of automatic external defibrillators (AED). The term AED refers to an external, portable defibrillator that has an internal heart rhythm analysis system, a "brain". AED removes the need for training in rhythm recognition, allowing untrained persons to defibrillate a victim of sudden cardiac death form ventricular fibrillation. It is attached to the patient with two adhesive pads with connecting cables to analyze the rhythm and when appropriate deliver a shock. The instructions are given by computer voice and/or visual display (5).

The emergence of AEDs has stimulated much discussion of policies, legalities and controversy. The American Heart Association task force statement of AEDs for public assess defibrillation in 1997 recommended the logical extension of AEDs was to non-medical, minimally trained personnel. These "public assess" AEDs pose unique challenges.  Safety must be paramount both for the protection of the patient and the rescuer (7).

The International Liaison Committee on Resuscitation (ILCOR) endorses the policy that in many settings it is prudent and fortuitous for non-medical individuals to use AEDs. The ILCOR recognizes that early defibrillation is only effective when incorporated into a strong "chain of survival" (3).

The European Resuscitation Council guidelines for use of AEDs strongly endorses the use of AEDs by both EMS providers and first responders. The guidelines mandate that the programs operate with strict medical control to ensure safety and optimum opportunity for success (4).

Central to the discussions and controversy of AEDs is safety and efficacy. Research supports that survival rates with use of AEDs is comparable to those with manually operated defibrillators. In fact, one study showed that AEDs require and average of 1.1 seconds to analyze the rhythm and deliver a shock verses an average 2.0 seconds for manual defibrillation to occur. AED accuracy in interpreting rhythms has been shown to correlate strongly with experienced cardiologists. The AED was found to have a sensitivity of 78-100% and specificity of 92-100% in recognizing ventricular fibrillation and ventricular tachycardia (2). A study by Herlitz (8) reported the results of the first 6 years of use of the EADs. Ten out of 375 analyses showing ventricular fibrillation did not receive defibrillation. In three of these case the cause was identified as a low battery thus emphasizing the importance of careful supervision and maintenance of the devices. Four of the cases were caused by technical error. In all of the cases, a defibrillating shock was delivered less that 1 minute later (8).

Many studies have demonstrated the utility of AEDs in clinical, urban and suburban settings when used by EMTs. Isolated locations like cruise ships, airplanes and resort areas have also demonstrated survivor benefit of early defibrillation by AED (9). Companies across a broad range of industries have purchased AEDs as an adjunct to their emergency medical assistance programs. One such company, a metal foundry consisted of two separate buildings with 2,500 employees between them. The two facilities are 10 miles apart and 12 miles from the nearest town. The company purchased 2 AEDs at the cost of $3,000 each and incorporated training into an existing CPR and BLS program. The entire cost was $10,000 (6).

American Airlines have purchased 300 AEDs with a $.013 added cost per passenger per flight. An estimated 20 lives will be saved each year (10).  On the other side of the coin, United Airlines was sued because a passenger died on the runway from sudden cardiac death (6).  

Large entertainment facilities, like casinos, concert halls and stadiums are also investing in AEDs, training security guards in their use (6).  With blunt chest injury a cause of ventricular fibrillation, both players and fans have a potential to benefit from this technology.


 
CHARLESTON COUNTY PROGRAM
 
Major Bill Mastrianni, Assistant director, Chief of Field Operations of Charleston County EMS discussed the introduction of the automatic external defibrillators to their program.  Originally they were able to purchase 15 AEDs at the cost of $3,000.00 each.  The budget was from a combination of funds from county administration and the sheriff department.  Due to a limit of data to guide placement, the 15 EADs were divided as follows:  5 were to be placed by the sheriffs department and 10 by the county fire department.  This triggered the independent purchase of 50 AEDs by surrounding fire stations.  The EMS are tracking the data related to placement, training and use of the AEDs.  In the first quarter report it had been used 15 times. To date there have been no "saves".  Of  local interest, the Isle of Palms fire department has had an AED for 5 years and have had 3 declared saves.
 

 
CONCLUSION
 
Automatic external defibrillators are yet another example of modern health care technology.  Ventricular fibrillation warrants the development of such technology due the urgency of the situation, with time the crucial determinant of survival.  Some argue that AEDs should be placed next to every fire extinguisher.  At the cost of $3,000.00 each that is not feasible.  The laws of supply and demand will drive the cost down as more AEDs are produced and they become a consumer product.    However, even with the advent of defibrillators and their ready availability, there has not been the expected impact on mortality rates.   Ischemic heart disease (IHD) is the greatest contributing cause of ventricular fibrillation.  An AED on every wall may avail the technology, but does not address the underlying disease process.  IHD has both nonmodifyable and modifyable risk factors.  The modifyable, namely elevated cholesterol, hypertension, smoking, diabetes and obesity are often lifestyle choices.

Evidence does support placement of AEDS in "special" and "isolated" areas. Airplanes, cruise ships, resorts, casinos, even suburbia are investing in AEDs.  In these settings, the response rates have previously been delayed.  The jury is out on the cost benefit issue, but for liability reasons the jury is in and favorable.  Likewise, who wouldn't want one hanging on the wall if their heart were to start fibrillating?     

 
 

 
 
 
REFERENCES
 

 
1.Eisenberg, MS. Defibrillation: the spark of life. Scientific American.1998: 278 (6);86-91.

2.Truong, JH, Rosen, P. Current concepts in electrical defibrillation. Journal of Emergency Medicine. 1997: 15 (3);331-8.

3. Kloeck, W., et al. Early defibrillation: an advisory statement from the Advanced Life Support Working Group of the International Liaison Committee on Resusciation. Circulation. 1997: 95(8);2183-4

4.Bossaert, L.,et al. European Resuscitation Council guidelines for the use of automated external defibrillation's by EMS providers and first responders: A statement from the Early Defibrillation Task Force, with contributions form the Working Groups on Basic and Advanced Life Support, and approved by the Executive Committee. Resuscitation. 1998: 37 (2);91-4.

5. Bossaert, LL. Fibrillation and defibrillation of the heart. British Journal of Anesthesia. 1997: 79 (2); 203-13.

6. Shuble,M, Stross, W. Steeling ourselves against cardiac arrest. Occupational Health & Safety. 1998: 67(6);74-78.

7. Kerber, RE, et al. Automatic external defibrillators for public access defibrillation: Recommendations for specifying and reporting arrhythmia analysis algorithm performance, incorporating new wave forms, and enhancing safety. Biomedical Instrumentation & Technology. 1997: 31(3);238-44.

8.Herlitz, J, Bang, A, Axelsson, A, Graves, JR, Lindqvist, J. Experience with the use of automated external defibrillators in out of hospital cardiac arrest. Resuscitation. 1998:37(1);3-7.

9.  Mosesso VN, et al., Use of automated external defibrillators by police officers for treatment of out-of-hospital cardiac arrest. 1998 annals of Emergency Medicine. 32(2);200-7.

10.  Zimmermann, PG., Something Special in the Air:  automatic external defibrillators on American Airlines planes.  Journal of Emergency Nursing. 1997;23(4):340-2.

References reviewed  but not cited:

1.   Page, RL, et al.,  Defibrillation aboard a commercial aircraft.  Circulation. 1998; 97(15):1429-30.

2.  Mancini, ME, Kaye, W.  In-hospital first responder automated external defibrillation:  what critical care practicioners need to know.  American Journal of Critical Care. 1998; 7(4):314-9.

3. Martens, P, Calle, P, Vanhaute, O. Theoretical calculation of maximum attainable benefit of public access defibrillation in Belgium. Belgium Cardio Pulmonary Cerebral Resusciation Study Group. Resuscitation. 1998: 36(3);161-3.

4. Lezon,K. Code blue. Defibrillate. Nursing. 1998: 28(4);58-60

5. Ginsburg, W. Prepare to be shocked: the evolving standard of care in treating sudden cardiac arrest. Review. Am. Journal Emergency Medicine. 1998: 16(3);315-9.

6.Kapp, MB. Evolving clinical practices and legal standards of care: softening the shock. Comment editorial. Am. Journal of Emergency Medicine. 1998: 16(3);325-6.

7.Hallstrom, NG, et al. Potential cost-effectiveness of public access defibrillation in the US. Circulation. 1998: 97(13);1315-20.

8. Myerburg, RJ, et al. Managing ventricular fibrillation in patients with silent myocardial ischemia. N Engl J Med. 1992: 326; 1451-1455.

9.Guidelines for cardiopulmonary resuscitation and emergency cardiac care. Emergency Cardiac Care Committees, American Heart Association. JAMA. 1992: 268; 2171-2302.

10. Weisfeld, ML, et al. American Heart Association Report on the Public Access Defibrillation Conference, Dec. 8-10, 1994. Automatic External Defibrillation Task Force. Circulation. 1995: 92; 2740-2747.

11.Fromm, RE, Varon, J. Automated external versus blind manuel defibrillation by untrained lay rescuers. Resuscition. 1197: 33: 219-221.999

12. Paul Wood's Diseases of the Heart and Circulation. Third Edition. Ventricular Fibrillation. J.B. Lippincott Co.1968.284-286.