His bundle pacing by Dr. Vaibhav Yawalkar MD DM Cardiology, Consultant Interventional Cardiologist, Nagpur, MH, India

1. HIS bundle Pacing

2. • Basic Concepts of Pacing
• Current options for pacing & limitations
• HIS bundle anatomy
• HIS bundle pacing technique
• Technical Challenges

3. Basic concepts of Pacing
• Applied voltage produces electric field, interacts with
intrinsic cardiac electrical activity
• Low-voltage (1 to 5 V) pacing stimuli = Pulses
(Pacemaker/CRT)
• High-voltage (500 to 1400 V) = Shocks (ICD)

4. Basic concepts of Pacing
• Pacemaker leads :
– Unipolar : One intracardiac electrode (Cathode at Tip)
– Bipolar : Two intracardiac electrodes (Cathode at Tip & Anode as ring)
• Pacemaker generator:
– Titanium case with battery & electronics plus plastic header

5. Capture

21. Whether to increase “Voltage”
or “Pulse Width” ?

27. Strength-Duration Relationship
• The rheobase is the
minimum current(or
voltage) for a pulse of
infinite duration that
results in depolarization.
• The chronaxie is the
pulse duration on the
curve that corresponds to
twice the rheobase
current

29. Local Electrogram

36. Pacemaker Code

37. Current options for pacing
• Single chamber RV pacing
• Dual chamber (Atrium + Ventricular pacing) with atrial
tracking
• Cardiac resynchronization Biventricular pacing

38. Issues with current pacing options
• Single chamber RV pacing cause intraventricular &
interventricular dyssynchrony
• Apart from RV apex, alternative RV sites such as the
septum and outflow tract have not reduced dyssynchrony
• Dyssynchrony increases the incidence of heart failure
(HF) and persistent AF, more so in patients with LV
dysfunction
• AV dyssynchrony causes “Pacemaker Syndrome”, reduces
Cardiac Output by 20-25% & leads to LV dysfunction in
long run
*DAVID (Dual Chamber and VVI Implantable Defibrillator) trial
*MOST (Mode Selection Trial)

39. Issues with current pacing options
• Dual chamber pacing with atrial tracking & pacing RV only
when needed has shown some benefit
• But this can not be done in cases of complete AV block
• Though Dual chamber pacing solves issue of AV
dyssynchrony , issue of intra & interventricular
dyssynchrony remains

40. Issues with current pacing options
• CRT with biventricular pacing has improved HF outcomes
and reduced mortality in patients with LBBB and severe LV
systolic dysfunction
• But its role in patients with preserved LV systolic function
remains unresolved

41. Advantages of HIS bundle Pacing
• Direct biventricular pacing over the physiologic His-Purkinje
system
• No issue of intra & interventricular dyssynchrony
• Possibility to correct LBBB if site of block is proximal to
intended pacing point
• Compared to RV apical pacing, small RCTs have shown
that His Bundle pacing improves exercise capacity, LVEF,
reduces HF hospitalizations

42. Issues with His Bundle Pacing
• Technically challenging, only 80% success rate as of now
• LBBB, if site of block is too distal may not be corrected
• Intraventricular conduction defects due to large scars will
still cause dyssynchrony
• In Non-selective His bundle pacing, local septum activation
may lead to dyssynchrony
• Possibility of damage to His bundle during lead placement
• Long term data regarding efficacy awaited

43. His Bundle anatomy
• Wilhelm His Jr., a Swiss anatomist an cardiologist, first
described the His bundle structure
• His bundle and the proximal branches initially originate as
part of the primitive interventricular septum
• During the second trimester of gestation, the AV node
connects with the proximal portion of the developing His
bundle
• Failure of this junction to develop leads to congenital
complete heart block

44. His Bundle anatomy
• His bundle extends inferiorly and leftward from the AV
node
• Reaches past the posterior and inferior margins of the
membranous IVS, and remains undivided for a few
millimeters
• At the crest of the muscular IVS, the His bundle starts to
divide
• The trunk of the left bundle branch often splits into 3
fascicles after the proximal 2 cm

45. His Bundle anatomy
• Proximal part of the His bundle rests on the RA–LV
portion of the membranous septum
• More distal His travels along the RV-LV portion of the
membranous septum, immediately below the aortic root
• Both the atrial and ventricular portions of the His bundle
can be accessed for permanent ventricular pacing.

46. His Bundle anatomy

47. His Bundle anatomy
Type I Type II Type III

48. FUNCTIONAL LONGITUDINAL DISSOCIATION OF
THE HIS BUNDLE
• Conduction fibers arose from
the proximal portions of the
common His bundle and were
predestined to the individual
bundle branches
• Multiple insulated filaments
contained within a single
common cable

49. HBP LEAD IMPLANTATION TECHNIQUE
• Narula et al first showed that HB can be paced
• Deshmukh et al. first introduced permanent HBP in
humans in 2000
• Between 2006 and 2011 multiple case reports and case
series were published

50. HBP LEAD IMPLANTATION TECHNIQUE
• Positioning the lead was main issue
• Initially standard leads were used & deflectable stylus or
reshaped stylus was used for positioning
• The precise position was determined by electrophysiology
mapping catheter to localize largest His deflection
• Mapping technique was time consuming

51. His Bundle Electrocardiogram

52. Specialized pacing lead & Sheath
• Lead : SelectSecure 3830, Medtronic (UNIPOLAR)
• Sheath: C315 His (Fixed), C304 SelectSite (Deflectable)
Medtronic
• 95% success rate of lead placement without mapping catheter

54. HBP LEAD IMPLANTATION TECHNIQUE
Venous access : Cephalic,
Subclavian , Axillary veins
Fixed curved sheath C315 His
introduced over guide wire
Proximal curve directs sheath
towards tricuspid annulus
Distal curve directs towards
septal surface
Lead selectsecure 3830 inserted
such that just tip lies beyond
sheath
Simultaneous signal mapping
to compare with His deflection

56. HBP LEAD IMPLANTATION TECHNIQUE
• If more prominent atrial electrograms are noted, the sheath
is rotated gently clockwise to move lead more ventricularly.
• Atrial to ventricular electrogram ratio of 1:2 or greater is
achieved
• The sheath is pointed toward the superior-anterior septum
or mid-septum by minimal clockwise or counter-clockwise
rotation
• Once a near-field His electrogram is identified, pacing is
performed at 5 V at 1 ms to assess His capture

57. HBP LEAD IMPLANTATION TECHNIQUE
• Pacing lead is slowly rotated clockwise approximately 5
times for anchoring
• His bundle capture threshold of ≤ 2.0 V at 1 ms is
acceptable
• If the bundle block is evident lead is directed more distally
• Lead can be positioned on atrial side of tricuspid annulus
(Proximal HIS) or Ventricular side (Distal His)
• His bundle injury current can often be recorded & predicts
excellent outcome

58. Selective & Nonselective HB Pacing
• SELECTIVE HBP: Ventricular activation occurs directly and
completely over the HPS
• NONSELECTIVE HBP: Activation of both His bundle and
local ventricular tissue
• Depends on distance of pacing lead from His bundle & pacing
stimulus amplitude
• There is little hemodynamic and clinical difference between
the 2 forms
• Nonselective HBP has safety benefit, as if HB capture failure
occurs ,backup RV pacing (via local septal myocardium) is
available

59. Various Thresholds
• Selective His threshold: Stimulus only capturing His
bundle without local ventricular tissue
• Selective His + Bundle branch correction threshold: If
there is baseline BBB, stimulus needed to correct BBB
(after adjusting lead position)
• Non-Selective His threshold: Stimulus capturing both His
bundle & Local ventricular tissue

62. S- QRS SQRS
H- QRS
Pseudo
Delta
wave

64. Technical Challenges
• High capture thresholds due to central fibrous body 
battery depletion
• Capture threshold may increase during follow up
• There is risk of lead failure & many routinely implant
backup RV lead
• Tricuspid valve movement may unhinge lead
• Lead extraction if needed may be challenging
• Sensing issues as interference from both atrial &
ventricular signals

65. RV Pacing vs His Bundle Pacing

66. Conclusions
• HBP is an attractive mode of physiological pacing with
significant promise for future applications
• Many case reports have proved it’s benefits in AV block, AV
ablation & pacing in patients with chronic AF, CRT in HF.
• Improvement of tools and further validation of its efficacy in
large randomized clinical trials is awaited

67. THANK YOU