Intraventricular conduction delay EKG examples

A narrow QRS complex requires highly synchronous electrical activation of the ventricular myocardium through the rapidly conducting His-Purkinje system (HPS). and intraventricular conduction delays (IVCDs) affects the morphology or duration, or both, of the QRS complex. These changes can be fixed and present at all heart rates, or they can be transient aberration either tachycardia or bradycardia dependent.

Shown below is an EKG with an RsR’ pattern (M pattern) in leads III, aVL, aVF, and notching of the QRS complex in V5 depicting a left bundle branch block. Wide QRS complexes are seen throughout the EKG.

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Shown below is an EKG with an rSR’ pattern in leads III, aVR, aVF, V1, V2, and V3 depicting a right bundle branch block.

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In LAFB the anterior part (fascicle) of the left bundle is slow. This results in delayed depolarization of the upper anterior part of the left ventricle. On the ECG this results in left axis deviation. The QRS width is <0.12 seconds in isolated LAFB.

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Shown below is an EKG showing sinus rhythm, with a wide QRS and a right axis deviation. The S1 Q3 pattern suggests an isolated left posterior fasicular block. One should also consider right ventricular hypertrophy, but in this case there is no sign of right atrial abnormality, and his echocardiogram was normal.

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Shown below is an EKG depicting atrial fibrillation with a controlled ventricular rate. The QRS is wide (>120ms) and has a tall R’ inV1 and an S wave in V6. There is a left axis deviation. The cardiogram suggests a right bundle branch block and a left anterior hemiblock. The patient has a cardiomyopathy with an ejection fraction of 20%.

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Shown below is phase 3 aberration and phase 4 aberration mechanism of IVCD. RBBB is more common than LBBB.

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