Pre-excitation syndrome

Pre-excitation syndrome
Classification and external resources

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
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.

Contents

Pathophysiology

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.

Types

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

References

  1. ^ "General principles of asynchronous activation and preexcitation". http://cmbi.bjmu.edu.cn/uptodate/cardiac%20arrhythmias/Preexcitation/General%20principles%20of%20asynchronous%20activation%20and%20preexcitation.htm. Retrieved 2009-08-12.