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Introduction
During a local high school football
game, the star quarterback, a 17-year-old male begins to experience
palpitations and periods of vertigo.
Concerned with this unusual feeling, he advises is coach, but is told it
is just nervousness and to get back on the field. As the star quarterback runs onto the field
for the next sequence of play, he collapses to the ground unconscious. Coaches, family, and paramedics rush to his
side to find that he is in cardiac arrest.
Paramedics are unable to revive him and 48 minutes later, he is pronounced
dead. What could possibly make a healthy
athletic 17-year-old male, with no known medical history, go into sudden
cardiac arrest and die? An autopsy will
reveal that the star quarterback died from a lethal arrhythmia, stimulated by a
rare medical condition known as Wolff-Parkinson-White syndrome (WPW).
What is
Wolff-Parkinson-White Syndrome?
Wolff-Parkinson-White
syndrome, also known as preexcitation syndrome and WPW,
“is a disorder in which an extra electrical connection between the atria and
the ventricles is present at birth.” (Beers,
2003, p. 153) This extra electrical
connection or accessory pathway, also known as the Bundle of Kent, causes
disruption in the hearts normal electrical pathway, which results in an
abnormally fast heart rate (tachycardia).
Wolff-Parkinson-White syndrome can result from random occurrence or
congenital. Random occurrences of
Wolff-Parkinson-White syndrome in the general population occur “in about
0.1 to 3.1 per 1,000 persons” (Cleveland
Clinic [CC], 2002). Parents with
Wolff-Parkinson-White syndrome, or accessory pathways, can pass the condition
to their children. Studies have shown
that the congenital occurrence of Wolff-Parkinson-White syndrome “could be as
high as 5.5 per 1,000 persons” (CC).
History
In
this current era of advanced medical technology, it is difficult to envision a
time when there was no way to determine what type of heart rhythm a patient was
experiencing. The invention of the
electrocardiograph (ECG) in the early 1920’s, changed the way physicians viewed
the heart and the way they treated cardiac related illnesses. In 1930, three cardiologists, Dr. Herold Wolff
and Paul Dudley White of the United States and Sir John Parkinson of Great
Britain, “described a distinct electrocardiograph (ECG) pattern in healthy
young people with short bursts of tachycardia” (CC, 2002). Physicians later discovered in 1933, that the
condition was a result of accelerated impulses traveling through the
ventricles. In 1944, after extensive
research, physicians established that the exact reason for this condition was
due to the presence of extra pathways
between the atria and ventricles.
Pathophysiology
To
understand the pathophysiology of Wolff-Parkinson-White syndrome, the
understanding of electrical conduction in a normal heart must first be
established. In a normal heart, the
electrical conduction begins in the sinoatrial node located in the right
atrium. The sinoatrial node is commonly
referred to as the heart’s pacemaker, due to the fact that is sets the pace for
the heart. As the sinoatrial node fires,
an action potential excites the atria into contracting. Next, the conduction travels to the
atrioventricular node, located in the interatrial septum. The conduction decreases in speed while in
the atrioventricular node, to allow time for the atria to empty blood into the
ventricles. The conduction then travels
from the atrioventricular node, to the atrioventricular bundle, or commonly
referred to as the bundle of His, located in the interventricular septum. Next, the conduction travels down both right
and left bundle branches. Lastly, the
conduction travels to the Purkinje fibers, where action potential excites the
ventricles into pumping blood into the systemic circulation system. In a heart that has Wolff-Parkinson-White
syndrome, the conduction starts in the sinoatrial node, but then may bypass the
atrioventricular node by a different bundle of nerves. The conduction then travels to the Purkinje
fibers, then back to the sinoatrial node, where the process repeats. The following statement explains additional
conduction abnormalities:
Although dozens of
locations for bypass tracts can exist in preexcitation, including
atriofascicular, fasciculoventricular, intranodal, or nodoventricular, the most
common bypass tract is an accessory atrioventricular (AV) pathway otherwise
known as a Kent bundle. This is the anomaly seen in WPW
syndrome. Conduction through a Kent
bundle can be anterograde, retrograde, or both. Another common preexcitation
syndrome, Lown-Ganong-Levine (LGL), also has an accessory pathway (the James
fibers), which connect the atria serially to the His bundle. The end result is
the same, preexcitation and a predisposition to the development of
tachydysrhythmias(Hemingway,
2006).
The significance of Wolff-Parkinson-White syndrome
is the tachydysrhythmias that it produces, such as atrial fibrillation, atrial
flutter, supraventricular tachycardia, ventricular tachycardia, and ventricular
fibrillation. Some tachydysrhythmias are
worse than others are. For example,
atrial fibrillation is a common rhythm found in geriatrics and can occur
without a patient experiencing physical signs and symptoms. In retrospect, ventricular fibrillation is a
lethal arrhythmia, in which the ventricles beat at a rate of 300 or more beats
per minute. In ventricular fibrillation,
there is not enough time for the ventricles to contract blood through the
systemic circulation system, and without immediate medical intervention, death
is imminent.
Signs
and Symptoms
Signs
and Symptoms of Wolff-Parkinson-White syndrome are synonymous with signs and
symptoms of tachydysrhythmias. Common signs include low blood pressure and a
heart rate greater than 150 beats per minute.
Common symptoms consist of heart palpitations, light-headedness, syncope
or fainting, vertigo or dizziness, respiratory distress, and chest pain or
chest tightness. In some cases, patients
live comfortably with Wolff-Parkinson-White syndrome, never having a
tachycardia episode. In the absence of a
tachycardia episode, the patient with Wolff-Parkinson-White syndrome will
present no signs and symptoms.
Unfortunately, most cases of Wolff-Parkinson-White syndrome do not
present itself until teenage years, especially while engaged in sports. The increased heart rate, associated with
sports, can exacerbate the condition, which can lead to lethal tachycardia
episodes.
Diagnosis
The
most common way to diagnose Wolff-Parkinson-White syndrome is by
electrocardiograph (ECG). It is
characterized by a short P-R interval, generally less than 0.12 seconds, and a
long QRS duration, generally more than 0.12 seconds. Additionally the upstroke of the QRS often
has a slur, called a delta wave(Bledsoe,
Porter, & Cherry, 2003, p. 1279).
Other medical tests such as the Holter monitor, exercise testing, and
electrophysiology testing can diagnose Wolff-Parkinson-White syndrome. In diagnosing a patient with potential
Wolff-Parkinson-White syndrome, it is imperative to obtain a complete medical
history. Key indicators such as family
history, history of atrial fibrillation, palpitations (especially when
exercising), and a history of syncope or fainting can assist the physician in
properly diagnosing Wolff-Parkinson-White syndrome.
Treatment
Most occurrences of
Wolff-Parkinson-White syndrome occur in the pre-hospital setting, therefore, it
is crucial for paramedics to have a vast knowledge of the condition and
associated signs and symptoms. The role
of a paramedic in the pre-hospital setting is not to treat
Wolff-Parkinson-White syndrome, but to treat the tachydysrhythmias that it
produces. For example, with a patient experiencing
asymptomatic supraventricular tachycardia, vagal or valsalva maneuvers are
attempted first. The most common vagal
or valsalva maneuver is instructing the patient to bear down as if they were
having a bowl movement. This stimulates
the parasympathetic nervous system and usually promotes bradycardia (slow heart
rate). If vagal or valsalva maneuvers
fail to decrease the heart rate, pharmacology intervention is attempted. The administration of Adenosine, which slows
conduction through the atrioventricular node, is the first line antiarrhythmic
agent. If supraventricular tachycardia continues,
refractory to Adenosine, Varapamil is administered. If pharmacology methods fail, electrical
synchronized cardioversion is the next step.
Synchronized cardioversion has a
success rate that ranges between 85 - 95%, depending on the location of the
extra pathway(Berger, 2006). Once the patient has arrived at the emergency
room, continued intervention is applied to ensure the heart is stabilized. An emergency room physician will then order
certain tests, listed in the diagnosis section, to confirm the presence of
Wolff-Parkinson-White syndrome. When the
diagnosis is confirmed, the definitive treatment of Wolff-Parkinson-White
syndrome is radiofrequency catheter ablation.
This is a surgical procedure, performed exclusively by cardiac
electrophysiologists, that destroys the abnormal electrical pathway.
RF ablation is currently the treatment of choice for
most adults and many children with symptomatic WPW syndrome (i.e., those who
have AV reentrant tachycardia or atrial flutter/fibrillation with conduction of
the accessory pathway). Success rates for
catheter ablation exceed 90%(Dr. Matthews, 2000-2007).
When radiofrequency catheter ablation is successfully
completed, the patient is generally considered cured of Wolff-Parkinson-White
syndrome. Reoccurrences of
Wolff-Parkinson-White syndrome after radiofrequency ablation is less than 5%.
Conclusion
In
conclusion, one can now see how a healthy athletic 17-year-old male, with no
known medical history, can go into sudden cardiac arrest and die. Wolff-Parkinson-White syndrome is a condition
that can produce lethal tachydysrhythmias, because of an extra electrical
connection or accessory pathway between the atria and ventricles. The immediate concerns, concerning treatments,
are to reduce the accelerated heart rate.
The definitive treatment is radiofrequency ablation, which destroys the
extra electrical connection. The ability
to identify signs and symptoms of Wolff-Parkinson-White syndrome, and seek
immediate medical attention, can give future high school star quarterbacks a
second chance at life.
References
Beers, M. H., MD (2003). The Merck Manual of Medical Information (2nd ed.). Rahway, NJ: Merck & Co., Inc..
Berger, A., MD (2006, May 30). Wolff-Parkinson-White syndrome.
Retrieved 19 January 2007, from
http://www.nlm.nih.gov/medlineplus/ency/article/000151.htm
Bledsoe, B. E., Porter, R. S.,
& Cherry, R. A. (2003). Essentials of
Paramedic Care. Upper Saddle River, New Jersey: Julie Levin Alexander.
Cleveland Clinic (2002, January). Wolff-Parkinson-White Syndrome (WPW). Retrieved
18 January 2006, from
http://www.clevelandclinic.org/heartcenter/pub/guide/disease/electric/wpw.htm
Dr. Matthews, R. (2000-2007). The Wolff-Parkinson-White syndrome. Retrieved
19 January 2007, from
http://www.rjmatthewsmd.com/Definitions/wolff_parkinson_white_syndrome.htm
Hemingway, T. J., MD (2006, June
14). Wolff-Parkinson-White Syndrome. Retrieved
18 January 2007, from
http://www.emedicine.com/emerg/topic644.htm#section~author_information
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