Pre-excitation syndrome

Pre-excitation syndrome
Electrical conduction system of the heart. (Accessory pathways not shown.) 1. Sinoatrial node 2. Atrioventricular node 3. Bundle of His 4. Left bundle branch 5. left posterior fascicle 6. left-anterior fascicle 7. Left ventricle 8. Ventricular septum 9. Right ventricle 10. Right bundle branch
Classification and external resources
Specialty
ICD-10	I45.6
ICD-9-CM	426.7, 426.81
DiseasesDB	32903
Patient UK	Pre-excitation syndrome
MeSH	D011226

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

Pathophysiology

Normally, the atria and the ventricles 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.

Types

Several different types have been described.

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	no

See also

• Electrical conduction system of the heart