CHAPTER 7: Ventricular Preexcitation
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CLINICAL PERSPECTIVE
AV connective
tissue
Atrial
AVN: AV node
HB: His bundle
RBB: right bundle
brunch
KB: Kent bundle
LBB: left bundle
branch
muscle
Ventricular
muscle
AVN
HB
LBB
RBB
KB
F I G U R E 7 . 1 .
Normal and accessory AV conduction system.
Solid bar,
nonconducting struc-
tures. AV, atrioventricular.
Ventricular preexcitation
refers to a congenital cardiac abnormality where part of the
ventricular myocardium receives electrical activation from the atria before the impulse
arrives via the normal AV conduction system. A schematic illustration of the anatomic
relationship between the normal AV conduction system and the accessory AV conduction
pathway provided by the bundle of Kent is displayed in Figure 7.1. Nonconducting struc-
tures, which include the coronary arteries and veins, valves, and fibrous and fatty connec-
tive tissues, prevent conduction of electrical impulses from the atrial myocardium to the
ventricular myocardium. AV myocardial bundles commonly exist during fetal life but then
disappear by the time of birth.
3
When even a single myocardial connection persists, there
is the potential for ventricular preexcitation. In some individuals, evidence of preexcitation
may not appear until late in life; whereas in others with lifelong evidence of ventricular
preexcitation on the electrocardiogram (ECG), the WPW syndrome may not occur until
late in life. Conversely, infants with the WPW syndrome may outgrow any or all evidence
of this abnormality within a few years.
4
