Posts Tagged ‘lbbb hv interval’

These simple questions were asked once upon a time  when cardiologists were not known as interventionists.Now many of them  have neither time  nor interest  to ask such questions .! An article   which came in Circulation 1974 addresses this question lucidly.

It is known, HV interval represents infra hisian conduction . And LBBB is  just that ! Then , why it is not prolonging it ?

The answer is ,  it does prolong  the HV interval  by 20 -40 ms , but , it is not manifested in surface ECG .  A 20 ms increment in PR interval (Say 160 to 180 ms ) is not a big issue generally.

* Then the concept of incomplete and complete LBBB is always there to confront us !

Many believe , the intraventricular conduction delay in LBBB may simply represent  the  “unmaking effect”  of   LBBB   which  re-routes  the conduction  in the slightly delayed  , circuitous   right bundle  highway   . But it is only a   assumption.Many things can happen in a  ischemic , degenerative, dysfunctional heart.

When does the HV interval prolong pathologically in LBBB ?

Acute LBBB (Note Left bundle  has two fascicles , technically  equivalent to bifasicular  block )  A 40ms  increment in HV interval (Hence in  PR interval also)   can be a dangerous delay in LBBB .

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