LBBAP Flashcards
what’s the most used lead ?
3830 Select Secure pacing lead (Medtronic Inc, Minneapolis, MN)
where should the lead be positioned ?
Deep inside the interventricular septum 1-1.5 cm below the His bundle
How to confirm direct capture of LBB ?
A paced QRS of right bundle branch conduction delay pattern + at least one of the following criteria :
a. Demonstration of left bundle (LB) potential with LB- local ventricular electrogram interval of 20-35ms.
b. Demonstration of transition in QRS morphology from non-selective to selective left bundle capture or nonselective to LV septal capture with
decrementing output
c. Peak left ventricular activation time as measured in lead V5,6 <80ms
d. Programmed deep septal stimulation to demonstrate refractory period of LB
Peak Left Ventricular activation time ?
Peak Left Ventricular activation time is measured from the onset
of the pacing spike to the peak of the R wave in the lead V5-6. It indicates the rapidity of LV free wall activation. pLVAT measurements are used to decide the depth of the pacing lead and capture of the conduction system.
If pLVAT is short at high output (10 V) and prolonged at low output (2V), it indicates the lead is away from the LB region and has to be carefully advanced slightly further to reach the LB.
If LB is captured, pLVAT remains short and constant (<80ms) irrespective of the pacing
output. This may be prolonged in patients with intraventricular conduction defects and
ischemic cardiomyopathy with significant scar.
what’s Left bundle potential ?
Left bundle potential is a sharp high frequency signal preceding the local
ventricular electrogram by 20-35ms. LB potential should be recorded in patients with baseline narrow QRS or RBBB. In patients with LBBB, LB potential is not observed
DIAGNOSIS OF LBB CAPTURE BY DEMONSTRATION OF QRS MORPHOLOGY TRANSITION (using Threshold test)
For nsLBBP / LVSP transition, the V6RWPT should prolong >= 10 milliseconds
For nsLBBP / to s-LBBP there should be broadening of the V1 R/r wave with increase in V1RWPT and/or deepening of the Swave in leads I, V 5 , and V 6 ; alternatively, there should be a sudden appearance/prolongation of latency insurface ECG and discrete local potential on theendocardial channel
V6 -V1 interpeak interval ?
A value of V6 -V1 interpeak interval >44 milliseconds is highly specificfor diagnosis of LBB capture,
what’s the ideal target site ?
The ideal site to target is around 1-1.5cm below the His bundle along an imaginary line drawn from distal His signals to the RV apex in right anterior oblique (RAO) 30⁰ view
Pace mapping at this site will often show a “W” pattern in lead V1 with a notch at the
nadir of the QS complex, tall R in lead II and RS in lead III. Lead aVR and aVL will
show discordant QRS complexes
What are the important parameters to be monitored while advancing the lead
deep inside the septum ?
There are 3 important parameters to be monitored while advancing the lead
deep inside the septum :
(a) paced QRS morphology – the notch on the nadir of ‘W’ in lead V1 will gradually ascend up to form an R wave;
(b) unipolar pacing impedance increases gradually before it drops by 100-200 ohms as the lead reaches LV subendocardium;
(c) unipolar lead electrogram will display significant injury current
Fixation beats ?
These are premature ventricular depolarizations that are evoked by the mechanical trauma as the lead passes
through the interventricular septum and are observed in 59–96% of cases.
Morphology of these beats corresponds very well with the actual depth of the lead tip and paced QRS complex from
that location.
Premature beats with terminal r or R-wave in V1 can serve as a marker that the lead rotations should be interrupted
and ECG criteria tested since the lead is approaching or has reached
the left subendocardial area
