CRM14: Conduction tissue pacing

Question 1

Indications for pacemaker implant

Answer 1

-CHB
-High grade AV block
-Chronotropic incompetence
-Sick sinus syndrome

Question 2

Problems with RV pacing

Answer 2

-Slow cell-cell conduction can cause electric and mechanical dyssynchrony
-RV apical pacing exacerbates risk of AF, HF, and death
-RV apical pacing associated with up to 20% risk of HF

Question 3

What can RV pacing lead to?

Answer 3

-RV pacing and LBBB cause similar intra-ventricular dyssynchrony
-RV pacing can be associated with pacing-induced cardiomyopathy

Question 4

Pacemaker advantages

Answer 4

-Low complication rate (1-2%)
-Battery 5-10 years
-Heart rate response
-AV synchrony maintained (DDD)

Question 5

Pacemaker disadvantages

Answer 5

-Venous obstructions
-Lead complications
-Interaction with cardiac valves
-Infection
-Pocket device erosion
-Pacing induced cardiomyopathy

Question 6

Alternatives to RV pacing

Answer 6

RV septal pacing
-Closer to conduction system than apex
-Long term outcomes not consistently superior to RV apical pacing
-Long term outcomes

CRT
-High non-response rate (30-40%)
-BiVp is a non-physiological approach
-Not cost or time effective for patients requiring brady pacing only

Conduction system pacing
-His bundle pacing
-LBB area pacing

Question 7

What 2 levels of conduction system are used in conduction system pacing

Answer 7

-His bundle
-LBB level

Question 8

Explain His bundle pacing

Answer 8

-Pacing lead positioned in His bundle region
-Maintains physiological pattern of ventricular activation via the native His-Purkinje system
-Pace His bundle -> Simultaneous conduction of R + L bundles -> Synchronous contraction of RV + LV

Question 9

RV pacing vs CRT vs His-bundle pacing

Answer 9

Question 10

Types of capture in His bundle pacing

Answer 10

Selective capture
-Only capturing His bundle
-Narrow QRS

Non-selective capture
-Capturing His and some of septum
-Medium length QRS

Septal capture
-Only septum is captured
-Long QRS

Question 11

Problems with His bundle pacing

Answer 11

-Technically challenging
-Long learning curve
-Long procedures (long fluoroscopy time)
-Small target site
-High thresholds (battery drain)
-Small R waves

Question 12

Explain Left Bundle Branch Area Pacing (LBBAP)

Answer 12

-Direct capture of left bundle or the fascicle branches along with LV septal myocardium

Question 13

Why is LBBAP the most effective method of physiological pacing?

Answer 13

-No major sensing problems (better R wave)
-Low and stable threshold
-Larger target site/easier implant

Question 14

Implanting the lead

Answer 14

-Venous access
-Selection of pre-shaped catheters across different manufacturers
-Manufacturer specific leads

Question 15

How do you know that LBBAP is in the right position?

Answer 15

-Angiography
-ECG
-PSA

Question 16

How is LBBAP lead positioned?

Answer 16

-LBBA is a wide target compared to narrow His bundle
-Catheter used to position the lead on septum 1-2cm below His region
-Contrast may be used to confirm positioning on the right septal border

Question 17

LBBAP pacing morphology

Answer 17

-LBBAP will show pattern of incomplete RBBB in V1
-Because LBBAP induces delayed RV activation
-LBBAP induced RV activation is benign
-The narrower the QRS duration the better

Question 18

What is LV activation time (LVAT)?

Answer 18

-Measurement performed on 12 lead ECG, on V5/V6
-Distance between pacing spike and peak R wave

Question 19

LVAT in LBBAP?

Answer 19

-True LBBAP should have short LVAT < 80ms
-Because you are capturing LBB and there is rapid LV free wall activation
-So short time for pacemaker to depolarise LV

Question 20

What is V6->V1 interpeak interval?

Answer 20

-R wave peak time measured between R wave in V1 and V5/V6 during LBB pacing
-During LBB capture, the LV is activating earlier than the RV
-Measure Stim at peak V6 and peak V1
> 40ms difference indicates true LBB capture

Question 21

What 3 factors can indicate LBBAP capture?

Answer 21

-Paced QRS morphology (V1 RBBB morphology and narrow complex)
-LVAT < 80ms
-V6 -> V1 interpeak interval >40ms

Question 22

His and Left Bundle Pacing follow up

Answer 22

-HBP: Looks for selective/non-selective capture during thresholds
-LBBAP: To confirm true LB pacing
-Similar programming, but more likely to use unipolar pacing polarity for LBBAP
-Not much programming flexibility if lead isn’t in optimal position

Question 23

His bundle pacing vs Left bundle branch area pacing

Answer 23