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

426.7, 426.81

Pre-excitation syndrome is a cardiac arrhythmia 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, and the ventricles are depolarized (excited) before (pre-) normal conduction system. This creates the ventricular pacemaker type of ectopic pacemaker.

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	no

References

↑ "General principles of asynchronous activation and preexcitation". Retrieved 2009-08-12.

Cardiovascular disease (heart) (I00–I52, 390–429)

Ischaemic

Coronary disease	Coronary artery disease (CAD) Coronary artery aneurysm Coronary artery dissection Coronary thrombosis Coronary vasospasm Myocardial bridge

Active ischemia	Angina pectoris Prinzmetal's angina Stable angina Acute coronary syndrome Myocardial infarction Unstable angina

Sequelae	hours Hibernating myocardium Myocardial stunning days Myocardial rupture weeks Aneurysm of heart / Ventricular aneurysm Dressler syndrome

Layers

Pericardium

Myocardium

Endocardium /
valves

Endocarditis	infective endocarditis Subacute bacterial endocarditis non-infective endocarditis Libman–Sacks endocarditis Nonbacterial thrombotic endocarditis

Valves	mitral regurgitation prolapse stenosis aortic stenosis insufficiency tricuspid stenosis insufficiency pulmonary stenosis insufficiency

Conduction /
arrhythmia

Bradycardia

Tachycardia
(paroxysmal and sinus)

Supraventricular	Atrial Multifocal Junctional AV nodal reentrant Junctional ectopic

Ventricular	Accelerated idioventricular rhythm Catecholaminergic polymorphic Torsades de pointes

Premature contraction

Pre-excitation syndrome

Flutter / fibrillation

Other / ungrouped

Other

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