Basics of ICD - Dr Hafeesh Fazulu - Pushpagiri

1. BASICS OF ICD
Dr Hafeesh Fazulu
DM Resident in Cardiology,
Pushpagiri Medical College, Thiruvalla.

2. Topic Importance in exam

3. Outline
• Basics of ICD – Types, Leads, Coils, Indications, Trials on ICD
• Transvenous ICD, Subcutaneous ICD, Wearable Defibrillators
• Detecting Arrhythmias
• Discriminating Arrythmias
• Treating Arrythmias
• Anti-tachycardia pacing
• DC shock
• ICD troubleshooting
• Inappropriate ICD Shocks
• ICD implantation Procedure

4. What is an ICD ?

5. What is an ICD ?

6. What is an ICD ?
“External defibrillator that is minituarised
and implanted inside a persons chest wall”

8. Pacemaker vs ICD
Essential differences ?

9. Dual Coil
1. SVC
2. Ventricle
This of it as a “Pacemaker with addon
functionality of DC Shock”

10. Single and Dual-Chamber ICD

11. Single vs Dual Chamber

12. CRT-D
• Bi-ventricular pacing

13. Pacemaker vs ICD – SIZE ??
PACEMAKER ICD
Larger because of larger CAPACITOR

16. • Functions
• 1. Senses arrythmias
• 2. Therapy
• Anti-tachycardia pacing
• DC Shock

17. ICD Leads

18. ICD Leads
• Shocking coils on the leads
• High surface area
• Low resistance
Single Coil
Dual Coil

19. Single Coil Lead
• Coil in Ventricle

20. Dual Coil Lead
• 2nd coil in IVC

22. Single coil vs Dual coil

23. ICD = Pacemaker + ICD
• Shocking lead in ventricle
• Pacing Lead in Atrium

24. CRT-D

25. Subcutaneous ICD (S-ICD)
Mid axillary line
Shocking Coil

27. • Preferred in Pediatric age group
• Also if no vascular access
• Immunocompromised
• Life expectancy > 10 years
• Advantage
• No leads inside the heart
• Disadvantage
• No Pacemaker functionality

28. How does it work?
Sensing Shocking

29. ICD vs WCD

30. INDICATIONS

32. INDICATIONS FOR ICD

35. Quick review of trials on ICD

39. Detecting Arrythmias

40. • Same as pacemaker
• Heart Rate Criteria
• Shock only when rate is above

41. VT Zone Fast VT Zone VF Zone
Anti-tachy pacing DC Shock

42. Heart Rate Counters
Consecutive Probability Timed
Counter Counter Counter

43. Consecutive counter

46. Probable Counter
Or
ROLLING WINDOW Counter

47. Consecutive counter not working in VF

48. Rolling window (20/30)

49. Rolling window in VF

50. Timed Counter

51. • Combination of both consecutive and Rolling window (Probable)
counter

52. How fine VF is detected ??
• Small amplitudes / fine VF

53. Auto-adjusting sensitivity.

54. Discriminating each
arrythmias

55. • Not every fast rhythm needs a SHOCK

57. How does it discriminate ?
• Onset
• Regularity
• QRS Morphology
• AV association

58. At which zone do the discriminators become
active ? Need not
discriminate
in VF zone

59. Onset
ONSET DISCRIMINATOR

60. How to know the ONSET?

62. Average of R-R interval before tachydia and after tachycardia
ONSET DISCRIMINATOR THRESHOLD – 80%

65. Class - Day 2

66. Onset of VT in Exercise
• Onset discriminator is disarmed when exercise starts.

67. Then how to shock VT/VF in Exercise ?
• 3 minutes

68. Regular / Irregular
STABILITY DISCRIMINATOR

72. • We program a buffer
• Anything outside the
buffer is considered
irregular

73. R-R interval of 12 beats
Stability discriminator

74. Limitation
• More faster the AF/Afl , the more regular it becomes
• INEFFECTIVE
• Device will not withhold therapy – SHOCK !!!

75. But VF is also irregular ?
Discriminators NOT ACTIVE in VF Zone

76. QRS Morphology
Discriminator

78. Why QRS wide in VT ?

79. Baseline TEMPLATE

80. Similarity

81. Only morphology can help here in discriminating

82. Update your baseline template !

83. AV Association
DISCRIMINATOR

86. No therapy in 1:1 AV conduction

90. • Available only in Dual chamber ICDs

91. PR pattern analysis
In VT with retrograde conduction (1:1)

92. No shock in VT

93. Solution
PR pattern analysis
Looking at AV interval
and
Looking at VA interval

97. TREATING ARRYTHMIAS
With ICD

98. Anti-Tachycardia Pacing (ATP)

99. ATP is delivered at a particular percentage of cycle length.. Say 81%

100. Disadvantage
• ATP can convert VT to VF

101. Advantage
• Painless
• Better Battery life

102. How ATP terminates VT? (re-entry)
Normal
Myocardium
Scarred
Myocardium

103. How ATP terminates VT? (re-entry)

107. How ATP terminates VT ?
Scar tissue

108. How ATP terminates VT ?
ATP depolarises the
excitable tissue

109. How ATP terminates VT ?

110. How ATP terminates VT ?

111. How ATP terminates VT ?

112. How ATP terminates VT ?
Converting to VF ?

113. Large excitable gap is better – TO CATCH IT !!

114. Parameters in ATP

115. Two types
• Burst ATP
• Ramp ATP

118. Defibrillation

120. How defibrillation work ?
• Depolarised all tissues.
• Allows the Sinus node to take over.

122. How is VERY HIGH VOLT generated ?

124. It takes time to charge the capacitor

125. Implant Procedure

126. Day 3

127. HAPPY VISHU 2021

128. ICD TROUBLESHOOTING
Day 3

129. • Failure to sense
• Failure to defibrillate
• VF Induction
• Inappropritate Therapy / Inappropriate DC Shock
• AF
• SVT
• T wave over sensing
• Lead fracture

130. Failure to Sense
VF

131. Failure to sense during VF
Auto adjusting sensitivity

132. Sensing floor prevents oversensing EM interferences

133. TRUE VF Undersensing

134. Functional VF Undesensing

135. Torsades

136. Failure to Defibrillate

137. Shocked 6 times not reverted – but reverted on its own !!!
Interval PLOT
VF Line

138. Factors affecting success of defibrillation
• Single Coil vs Dual Coil – Single is as effective as dual
• Tissue being depolarised
• Change the vectors by changing single to dual and vice versa
• Amount of energy delivered

139. Shocking Vector in Single Coil vs Dual Coil
Can attempt to change vectors

140. How to test ?
• VF Induction

141. What is Electrical storm ?
VF/VT Refractory
to DC shock

142. Can you CPR/touch a patient getting ICD
shock?

143. Can we use External DC shock on a patient
with ICD ?
Yes
ICD program may get altered / erased

144. VF Induction
(defibrillation testing)

145. Defibrillation Testing

147. Method - 1
Replicates R on T phenomenon

148. Charing capacitor

149. Method - 2
Fast pacing at 50 Hz

150. Inappropriate Shocks
Inappropriate therapy

151. Causes

152. How AF causes inappropriate Shock ?

153. How SVT causes inappropriate shock ?

154. How lead fracture causes inappropriate shock?
Interface at the site of fracture generates NOISE which is sensed as VT/VF

155. How T wave oversensing causes inappropriate
shock?

156. How interference causes inappropriate
shock?

157. Management of inappropriate
Shock due to AF

158. Stability discriminator

159. 60

160. QRS Morphology discriminators – better
Diasable stability discriminator and ENABLE QRS Morphology
discriminator

161. Zone Discriminators
Disable the first 2 zones…

162. Lower the AF rate

163. THANK YOU

164. THANK YOU

165. Intravenous vs Subcutaneous

166. LEAD – Epicardial vs Endocardial

168. Defibrillation testing ??

169. Homework