ECG in Ventricular Preexicitation

8/20/2019 ECG in Ventricular Preexicitation

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ECG IN VENTRICULAR PRE-

EXCITATION

ECG in Other Conditions


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VENTRICULAR PRE-EXCITATION

SYNDROME

Definition = the activation of a ventricular territory(preexcited territory) before the arrival of the

impulse through the normal AV conduction system

due to the existence of an accessory pathway that

delivers the impulse beforetime in that aria.


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ACCESSORY PATHWAYS

Kent bundle (Kent fascicle) = connectsthe atria to the basis of the ventricle

(RA – RV or LA – LV).

James bundle = connects the atria tothe inferior part of AV node or to the

His bundle

Mahaim fibers = connect the inferiorpart of AV node/His bundle to a small

part of the septum


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TYPE A WPW SYNDROME

left Kent bundle (from LA to LV) = the pre-

excited territory is situated in LV.

rare.

ECG findings:

Positive ∆ wave and tall R in V1, V2,L3, aVF

Negative ∆ wave and predominant negative

complex in left leadsQRS axis isright deviated

Secondary ST-T changes.


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TYPE B WPW SYNDROME

right Kent bundle(from RA to RV) = the pre-excitedarea is situated in right ventricle.

the most frequent

form of WPW syndrome.

ECG findings:

Negative ∆ wave and predominant negative

complex in V1, V2,D3, aVF

Positive ∆ wave and tall R wave in left leadsQRS axis isleft deviated.

ST-T - secondary changes.


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LGL (LOWN- GANONG- LEVINE)

SYNDROME

The James fibers are shortcutting the

AV node=> the impulse arrives earlierin His system.

The impulse travels through the His

system so the QRS complex is

narrow(no delta waves).

On ECG:short PR interval (


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MAHAIM FIBERSNormal PR interval(the impulse from the atria

travels through the AV node).

Asmall delta wave at the beginning of the

ventricular complex (a portion of the septum is pre-

excited).

Usually there are no ST-T changes


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THE RISKS OF THE ACCESSORYPATHWAYS

The developing of a tachycardia by a reentry

mechanism.

In an atrial tachyarrhythmia (atrial fibrillation or

atrial flatter), if AV node is by-passed, the ventricles

will develop a ventricular tachyarrhythmia.


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ECG IN OTHER

CONDITIONS


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DIGITALIS EFFECTS ON ECG

digitalis acts by inhibiting Na-K pump and by

enhancing vagal tone

It is used in atrial fibrillation and cardiac failure

(NYHA III and IV)

Inhibits the SA node leading tosinus bradycardia

and the AV node leading to AV blocks

Increases the excitability of the idioventricular centers

leading to frequentmultifocal ventricular

premature beats which can lead toventricular

tachyarrhythmia

‚coved’ ST segment depression

flattened T wave


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ECG IN HYPERKALEMIA

Prolonged depolarizationLong PQ interval >0.20 seconds

Wide QRS complex > 0.12 seconds.

Shorter repolarizationShort QT interval

Tall T wave with shorter base


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ECG IN HYPOKALEMIA

Prolonged repolarizationLonger QT interval and a higher risk for development

of torsade de pointes

T wave has a longer duration, becomes bifid, with the

first part rather flat, and the second part taller (thesecond part of the T wave has been identified for a long

time as a abnormal ‚u’ wave).


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Hypercalcemia

Shorter QT interval due to a shorter ST segment

In very severe cases Osborn waves appear (also called

‚J’ waves) = waves situated at the junction of QRS

complex with ST segment. This determines a widerventricular complex.

Hypocalcemia

Prolonged QT interval due to a longer ST segment

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ECG in Ventricular Preexicitation