Heart Rhythm Disorders (cont.)
Wolfe-Parkinson-White Syndrome
Wolfe-Parkinson-White
syndrome is a specific type of PSVT, in which an inborn
error of wiring has occurred near the AV node, and an accessory electrical
pathway exists. The diagnosis is made by electrocardiogram
(EKG), and the treatment may include medications or catheter mediated ablation
of the involved pathway.
Atrial Fibrillation (A Fib)
Atrial fibrillation occurs when the atrium has lost the ability to beat in a
coordinated fashion. Instead of the SA node generating a single electrical
signal, numerous areas of the atrium become irritated and produce electrical
impulses. This causes the atrium to jiggle like a bowl of Jell-O instead of
beating. The AV node sees all the electrical signals, but because there are so
many, and because they are so erratic, only some of the hundreds of signals per
minute are passed through to the ventricle. The ventricles then fire irregularly
and often very quickly.
As in PSVT, the symptoms may be palpitations, lightheadedness, and shortness
of breath. The cause of atrial fibrillation, however, may be more significant,
since it may be due to aging of the conducting system of the heart and there may
be associated atherosclerotic heart disease. Therefore, atrial fibrillation with
rapid ventricular response associated with
chest pain or evidence of pulmonary
edema (pulmonary=lung +edema=fluid) may need emergent cardioversion (a procedure
that uses electricity to shock the heart back into a normal rhythm) or shock
therapy.
The long term significant complication of atrial fibrillation is the
formation of blood clots along the inside of the heart wall. These clots may
break off and travel to different organs in the body blocking blood vessels,
and causing the affected organs to malfunction because of the loss of blood
supply. A common complication is a clot traveling to the brain, resulting in a
stroke.
If the patient presents for medical care within less than 24 hours, then attempts
will be made to return the heart to normal sinus rhythm. If this window has
passed, there is great risk that during conversion back to a regular rhythm, a
blood clot will break loose. Therefore, the strategy to treat atrial
fibrillation is time-dependent. Within the first 24 hours, attempts will be made
to slow the heart and return it to normal rhythm using medications or electric
shock. After this window has passed, the treatment will be focused on rate
control only, and anti-coagulation therapy will be offered to prevent blood clot
formation.
Aside form the clot issue, atrial fibrillation is a safe rhythm and not life
threatening as long as the rate is controlled. Medications are used to slow the
electrical impulses through the AV node, so that the ventricles do not try to
capture each signal being produced. The reason to return people to a regular
rhythm has to do with cardiac output. In atrial fibrillation, the atrium does
not beat and pump blood to the ventricle. Instead blood flows into the ventricle
by gravity alone. This lack of atrial kick can decrease the heart's efficiency
and cardiac output by 10%-15 %.
Anticoagulation with warfarin (Coumadin) is almost always recommended for those patients
with atrial fibrillation.
If atrial fibrillation is poorly tolerated due to symptomatic palpitations or symptoms of reduced cardiac output, or if there are concerns with lifelong Coumadin therapy, more definitive therapy may include specific medications, electrical cardioversion, or catheter based ablation (sometimes with an adjunctive pacemaker inserted). Atrial fibrillation is a common condition, with many implications, and the best plan for each patient should be discussed at length with one's physician.
Next: Atrial Flutter »
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