Incomplete right bundle branch block

ECG Quiz 13

Incomplete right bundle branch block
Incomplete right bundle branch block

Prominent negative component of P waves in lead V1 resembles left atrial overload at one look. There is an rSr’ pattern in leads V1 and V2. This pattern can be seen in incomplete right bundle branch block and right ventricular volume overload situations like atrial septal defect. T waves are inverted in anterior leads. Incomplete right bundle branch block with left atrial overload can occur in ostium primum atrial septal defect with mitral regurgitation. But in that case we expect left axis deviation which are not seen here.

A closer look at the the negative P wave in V1 shows the sharp downward atrial intrinsicoid deflection. This pattern is known as pseudo left atrial overload pattern, often seen in atrial septal defect. Negative P wave in true left atrial overload is rounded and does not have a sharp atrial intrinsicoid deflection.