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Pre-excitation syndrome
Classification and external resources

Heart; conduction system. (Accessory pathways not shown.)
ICD-10 I45.6
ICD-9 426.7, 426.81
DiseasesDB 32903
MeSH D011226

Pre-excitation syndrome is a condition where the ventricles of the heart become depolarized too early, which leads to their partial premature contraction.



Normally, the atria (chambers taking venous blood) and the ventricles (chambers pumping blood towards organs) are electrically isolated, and electrical contact between them exists only at the "atrioventricular node". In all pre-excitation syndromes, at least one more conductive pathway is present. Physiologically, the normal electrical depolarization wave is delayed' at the atrioventricular node to allow the atria to contract before the ventricles. However, there is no such delay in the abnormal pathway, so the electrical stimulus passes to the ventricle by this tract faster than via normal atrioventricular/bundle of His system, so the ventricles are depolarized (excited) before (pre-) normal conduction system.


Several different types have been described. [1]

Type Conduction pathway PR interval QRS interval Delta wave?
Wolff-Parkinson-White syndrome Bundle of Kent (atria to ventricles) short long yes
Lown-Ganong-Levine syndrome "James bundle" (atria to bundle of His) short normal no
Mahaim-type Mahaim fibers normal long yes

See also




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