BiV pacing

For biventricular paced rhythms, the narrowest complex is not always what is desired.

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Ideally, the complex should reflect good left ventricular activation, which is often represented by a small R wave in lead V1 (shown below)

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Too much positivity in lead V1 may be due to the following scenarios

-RV lead is very apically positioned

-there is too much offset between the LV and RV

-the AV delays may be too long --> this would be if a patient has intact AV conduction and a RBBB (less likely as most CRT pts will have a LBBB)

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No R wave in V1 may suggest that there is not enough offset between the LV and RV