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Intracardiac Electrograms
The document discusses intracardiac electrograms (IEGMs) and catheter positions used in electrophysiology studies. It provides information on unipolar and bipolar recordings, including how bipolar signals are constructed and how they approximate the rate of change of the cardiac wavefront. The document also discusses how the direction of cardiac activation influences the electrocardiogram and how unipolar and bipolar recordings compare. Key factors that influence electrogram morphology such as conduction speed, myocardial mass, and tissue characteristics are also reviewed.
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Intracardiac Electrograms
- 1. Intracardiac Electrograms (IEGM) and Catheter Positions 1
- 2. Unipolar Recording V1 lead used for the negative (reference) pole - + Catheter with the positive electrode placed in the heart 2
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- 5. Bipolar Electrogram Construction Unipolar Bipolar Uni 1 - - - = Uni 2 + + Uni1 (+) – Uni2 (-) = Bipolar Bipole Uni-distal Uni-proximal 5
- 6. Bipolar signal construction + Differential amplifier t1 t2 t3 t4 t5 t6 t7 t8 t9 t10 t11 - t1 t2 t3 t4 t5 t6 t7 t8 t9 (Signal 1 + Noise) – (Signal 2 + Noise) = Signal 1 – Signal 2 6
- 7. Bipolar EGMs Bi E1 E2 7
- 8. Electrophysiology of thecardiac muscle cell 8
- 9. Affect of theDirection of Activation on the Electrogram 9 http://www.vetgo.com/cardio/concepts/concsect.php?sectionkey=5§ion=Electrocardiology
- 10. Direction of Activationand its Influence on the Bipolar ECG +– – – – – – – – – – – – – – – – – – – – – – – – +– – – – – – – – – – – – – – – – – – – – – – – – +– – – – – – – – – – – – – – – – – – – – – – – – +– – – – – – – – – – + – – – – – – – – – – – – – – - +– – – – – – – – – – – – – – – – – – – – – – – – +– – – – – – – – – – – – – – – – – – – – – – – – +– – – – – – – – – – – – – – – – – – – – – – – – +– – – – – – – – – – – – – – – – – – – – – – – – +– – – – – – – – – – – – – – – – – – – – – – – – +– – – – – – – – – – – – – – – – – – – – – – – – 10
- 11. Direction of Activationand its Influence on the Bipolar ECG –––––––––––––––––––––––+ – –––––––––––––––––––––––+ – –––––––––––––––––––––––+ – – – – – – – – – – –+ – – – – – – – – – – – – + – - – –––––––––––––––––––––––+ – –––––––––––––––––––––––+ – – – – – – – – – – – – – – – – – – – – – – – –+ – – – – – – – – – – – – – – – – – – – – – – – –+ – – – – – – – – – – – – – – – – – – – – – – – –+ – – – – – – – – – – – – – – – – – – – – – – – –+ 11 –
- 12. Direction of Activationand its Influence on the Bipolar ECG ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– – – – – – – – – – – – – – – + – – – – – – – –- – – – – – – – – – – – – – ––––––––––––––––––––––––––––––––––– A B C ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– ––––––––––––––––––––––––––––––––––– 12 – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – – –
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- 14. Influence of individualcells on the Unipolar Electrogram The influence of any active cell upon the unipolar recording is inversely proportional to the distance between the cell and the electrode Because activation propagates from cell-to-cell, active cells are organized along a wave “front” Consequently, the unipolar electrogram AP is a summation of membrane currents unipolar 14
- 15. Unipolar versus ActionPotential 15
- 16. Comparison of Bipolarversus Unipolar Recording 16
- 17. Comparison of Unipolarversus Bipolar Recording E1 E2 Unipolar recordings measure an amplified version of voltage at a single electrode (E1) and retain both near and far field signal components Bipolar recordings measure the amplified difference between two unipolar electrodes (E1 - E2), which reduces common-mode noise and far-field signal components 17
- 18. Unipolar versus Bipolar E1 E2 Bipolar recordings approximate a measure of the rate-of-change of the wavefront This measure is approximate because cardiac wavefronts do not propagate uniformly and the medium is not ideal 18
- 19. Propagating Activation Wavefront 19
- 20. Propagating Activation Wavefront Depol. toward positive electrode Repol. toward positive electrode Positive Signal Negative Signal Depol. away from positive electrode Repol. Away from positive electrode Negative Signal Positive Signal 20
- 21. Comparison of theFiltered and unfiltered Unipolar and Bipolar Recordings • Note the peak negative slope indicated by the arrow in the unfiltered unipolar recording corresponds to the indicated negative peak in the 21 highpass-filtered unipole, confirming the approximation to rate-of-change.
- 22. Comparison of theFiltered and unfiltered Unipolar and Bipolar Recordings • Note the brief occurrence of the zero slope (arrow) in the unfiltered unipole which corresponds with the zero-crossing and phase-reversal of the highpass-filtered unipole. It also corresponds to the zero crossing of the 22 unfiltered bipole and the most positive peak of the filtered (32Hz) bipole.
- 23. Unipolar versus BipolarRecording Physical basis of electrograms - Summary – The unipole records the perspective-view of the wavefront Wavefront = summation of the action potentials over space and time Action potential = generated by membrane ion currents – The bipole records the derivative (slope) of the unipole – Bipolar recording (spatial) and the highpass filter (temporal) are correlated, and have a lower sensitivity to low frequencies (slow conduction) and higher sensitivity to high frequencies (fast conduction) 23
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- 27. Signal Filtering Noise Problems influencing the signal fidelity: – Signal to noise ratio – Distortion of the signal To limit these a properly designed amplification system with 27 filters is required
- 28. Filtering The leads record the raw electrical potential data and send it to the amplifier. The Amplifier increases the amplitude of the signals Amplifier (often up to a factor of 10000). The high-pass filter removes any base line drift or High Pass Filter physiologic noise by cutting off anything below a set value. An isolation amplifier isolates the circuit from the Isolation Amplifier patient (this can be done by transmitting the signals optically). The low-pass filter removes any environmental noise Low Pass Filter by cutting off anything above a certain value. The resultant signal is either the surface EKG or intracardiac signals of interest. 28
- 29. Filtering Surface ECG signals are concentrated in the bandwidth between 1Hz - 80Hz. Intracardiac ECG signals are concentrated in the bandwidth between 15 - 60Hz High Resolution ECG signals are concentrated between a bandwidth of 0.05Hz - 300Hz 29
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- 31. Filtering ECG data filtered with 60Hz Notch Filter 0.35 0.3 0.25 0.2 Magnitude unfiltered ECG 0.15 filtered ECG 0.1 0.05 0 0 0.2 0.4 0.6 0.8 1 1.2 1.4 -0.05 Frequency (f) 31
- 32. Filtering – LowpassFilter Lowpass Filter V Corner Frequency (Passes LF) Pass-band Stop-band f cutoff frequency (250 - 500 Hz) A lowpass filter allows lower frequencies to pass through while reducing higher frequencies, relative to an upper cutoff frequency. In conventional electrophysiology, this cutoff (corner) frequency is typically in the range of 250 to 500 Hz. 32
- 33. Filtering Highpass Filter Highpass Lowpass Filter V Corner Frequency repol (Passes LF) (Passes HF) depol Stop-band Pass-band cutoff freq cutoff freq f cutoff frequency (30 - 32 Hz) (250 - 500 Hz) (30 - 32 Hz) The highpass filter is the exact opposite of the lowpass filter in which higher frequencies are now allowed to pass through while reducing lower frequencies, relative to a lower cutoff (corner) frequency, which is typically 33 Hz. 30
- 34. Bandpass Filtering Combined = Bandpass Filter (passes depolarization) physiologic environmental V repol depol Highpass Lowpass cutoff freq cutoff freq f (30 - 32 Hz) (250 - 500 Hz) •The highpass reduces signal components related to physiologic noise, i.e., repolarization. Thus the intent of these filter settings is to allow signal components related to depolarization to pass. •The lowpass section of the bandpass filter is intended to reduce environmental noise. 34
- 35. Filtering Subtle point about highpass section: V 32 Hz f ~16 Hz ~64 Hz • The bandpass filters actually exhibit a gradual response to frequency, as shown in the figure, rather than an idealized, straight-line response • Frequencies below 16Hz (green), are reduced enough by the filter that they are essentially insignificant. • At frequencies approximately twice the cutoff frequency (in this case 64 Hz) there is a range of frequencies above this point in which the response of the filter is fairly flat and the signal components are passed 35 through essentially unchanged.
- 36. Filtering Subtle point about highpass section: approximates the derivative V Depolarization f ~16 Hz ~64 Hz • The red line shows a special filter response which computes the time-derivative of the signal. • The gradual response of the highpass filter between 16 to 64 Hz is a reasonable approximation of the rate-of-change for signal components that fall into that range of frequencies. • The majority of the signal energy related to depolarization falls between 15-60 Hz. Thus unipolar recordings made with a highpass filter set at 32 Hz are correlated with wavefront change. Note both the highpass filtered unipole and the unfiltered bipole are both correlated with wavefront 36 change.
- 37. Clinical use ofUnipolar Recording 37
- 38. Expected Electrogram Progression wavefront A “QS” receding Schematic Representation of RA Stimulation of HRA portrays endocardial breakthrough from the SA node network with typical waveform morphologies: 50% – 50% approaching & B • early “QS” “RS” receding • mid “RS” • late “R” wavefront C approaching “R” 38
- 39. Actual Electrogram Progression SinusRhythm “QS SA Node ” A B C 39
- 40. Actual Electrogram Progression SinusRhythm “QS ” A B Mid Lateral “RS” C 40
- 41. Actual Electrogram Progression SinusRhythm “QS ” A B “RS” C IVC Junction “R” 41
- 42. R Wave Amplitudeis Dependent on the Amount of Myocardium Involved Large mass Small mass myocardial myocardial recruitment recruitment Large mass or Large mass or distance = Large distance = Large amplitude amplitude 42
- 43. Amplitude of theECG is effected by the size of the Myocardium 43
- 44. Myocardial Characteristics andthe Bipolar ECG 1. If the tissue is diseased it will exhibit low- frequency low amplitude Healthy electrograms, but if healthy it will have high frequency high- amplitude electrograms Disease d 2. With a set distance between the two electrodes of the bipolar Dead ECG, you can see the activation time and thus it tells you conduction speed 44
- 45. R Wave Widthis Dependent on the Conduction Speed Wide R Wave Narrow R Wave Slow conduction Rapid conduction such as across diseased or with myocardial recruitment deep tissue results in post-exit results in a narrow a wide duration duration 45
- 46. Unipolar Recording: CircusMovement CL 1 1 CL Start 2 2 4 3 3 4 The red loop represents one cycle 1 length (CL) of the tachycardia CL End 46
- 47. Unipolar Recording: CircusMovement • The electrogram is a result of the 1 activation from “A” and “B” • “A” = activation moving toward the electrode • “B” = activation moving away from the electrode B A CL CL End A The red loop represents one cycle length (CL) of the tachycardia B CL Start 1 1 1 47
- 48. Q wave (qs-RS)pattern • QS Pattern at the arrhythmia focus site • A qs-RS pattern can occur when: • There is a preferential pathway from the arrhythmia focus • Activation proceeds from a low to high current generating region • There is myocardium exhibiting anisotropic conduction Normally an arrhythmia focus has a negative deflection resulting in a QS Pattern, but that is not always true 48
- 49. Unipolar Recording: WithinSmall Conducting Channel Preferential pathway from the arrhythmia focus – Two components of Breakout site activation occur: Slow confined conduction * with large and rapid activation Rapid myocardial breakout conduction 49
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- 51. Double Potentials Barriersto Turn around conduction point 3 2 1 * Bipolar ECG Unipolar ECG Turn around point = end of a fixed or functional barrier such as scar 51 tissue (fixed) or the crista terminalis (functional)
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- 53. Double Potentials Barriersto conduction Bipolar ECG Unipolar ECG 3 2 1 * Area of slow conduction 53
- 54. Flatline Between DoublePotentials Slow conduction zone (SCZ) * SCZ ＋ ＋ * ＋ ＋ ＋ SCZ ＋ 54 *
- 55. Double Potentials Double potentials are indicative of a line of block Crista terminalis is an important anatomical and functional barrier in atrial flutter Lines of block are either fixed or functional (anisotropy) Atriotomy sites and the Eustachian ridge are examples of fixed lines of block Evidence exists that block in the region of the crista terminalis during atrial flutter is a form of functional conduction block 55
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- 57. Anisotropic Myocardial Activation Results in a qs-RS Pattern 57
- 58. Utility of UnipolarRecording Allows the recording of detailed electrogram information from the distal electrode of the ablation catheter – Confirmation of the earliest activation site (QS pattern) – Analysis of the ST segment reveals the degree of tissue contact – Presence of ST elevation after ablation confirms the tissue has been ablated ST elevation: reflects myocardial tissue damage 58
- 59. Utility of UnipolarRecording Confirmation of the earliest activation site (QS pattern) QS Pattern 1 1-2 2 3 3-4 4 rS Pattern 59
- 60. Unipolar versus Bipolar + Endocardium * Epicardium 60
- 61. Utility of UnipolarRecording Analysis of the ST segment reveals the degree of Pre-ablation: strong tissue contact tissue contact ST elevation: reflects myocardial tissue damage 61 61 ST elevation
- 62. Utility of UnipolarRecording ST segment elevation post-ablation confirms the tissue has been damaged, thus the tissue has been ablated Pre-ablation Post-ablation 62 ST segment changes (elevation): Post-ablation
- 63. Unipolar Catheters SVC HEART HRA Ablation catheter Record unipolar recording between the distal IVC electrode of the ablation catheter (or the electrodes on the CS catheter) and one of the Reference electrodes reference electrodes in the IVC 63
- 64. Utility of UnipolarElectrogram Recording Utility for determining the best ablation site in WPW PQS Pattern; Recording multiple HIS simultaneous unipolar recordings CS catheter with electrodes all positive (Uni 1-10) 64 Reference electrode is 64 negative
- 65. Waveform during pacing& sinus rhythm Bi Uni 65 65
- 66. Peculiarities of UnipolarRecording A B 66 Soejima, et al., J Cardiovasc Electrophysiol, Vol. 16, pp. 1017-1022, September 2005
- 67. Catheter Positions andTheir Recordings 67
- 68. Relationship of theSurface 12 lead Electrogram to the Activation Sequence P-Wave P-R Interval QRS Complex ) 68
- 69. Relationship of theIntracardiac Electrogram to the Activation Sequence A-Wave = HRA His potential = His V Wave = CS (LBB) & RVa (RBB) 69
- 70. Intracardiac Electrogram Recordings– Catheter Placement HRA CS His HRA CS His RVA RVA 70
- 71. Catheter Types Fixed Curve Steerable 71
- 72. Intracardiac Electrograms –HRACatheter ATRIAL DEPOLARIZATION 72
- 73. Intracardiac Electrograms –HisCatheter A HV A HV A HV A HV ATRIAL DEPOLARIZATION HIS BUNDLE DEPOLARIZATION VENTRICULAR DEPOLARIZATION 73
- 74. Intracardiac Electrograms –CSCatheter A V A V A V A V ATRIAL DEPOLARIZATION VENTRICULAR DEPOLARIZATION 74
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- 76. Special Uses ofthe CS: Catheter: Bracketing Left-Sided Pathways 1 Wider Narrow Wider The general location of a left sided AP can be located by bracketing the AP using the CS electrograms. • Intervals between the “A” and “V” waves, or vice versa, is wide-narrow-wide • Determines the general location of the AP 76 • In the case above that is CS2-3
- 77. Intracardiac Electrograms –RVACatheter VENTRICULAR DEPOLARIZATION V V RVA catheter recording 77
- 78. Normal Activation Sequenceas Seen from the Intracardiac Recordings 78
- 79. Electrogram Recordings -correlation with surface ECG Between dashed lines = A wave Between solid lines = V wave Between dashed & solid lines = H potential if from the His catheter 79
- 80. Normal Activation Sequence Earliest A wave Earliest v wave 80
- 81. Intracardiac EGM recordings– Catheter Placement 81
- 82. Baseline Electrogram RecordingMeasurements PR segment NORMAL RANGE P wave ST segment PA (IACT) - 20-60 msec AH - 50-130 msec His - 10-25 msec HV - 35-55 msec P-A H-V A-H 82
- 83. Display Sweep Speed 50mm/sec 200mm/sec The EP doctor uses different paper speeds to analyze the data. The faster the speed (100-200mm/sec), the more details he can see. The slower the speed (25-50mm/sec), the easier to see the overall picture or induction of an arrhythmia. The doctor will switch back and for between the various speeds. The 12 lead uses 25 mm/second. 83
- 84. Intracardiac recordings canreveal more than the Surface ECG 84
- 85. Intracardiac recordings canreveal more than the Surface ECG 85
- 86. Intracardiac recordings canreveal more than the Surface ECG 86
- 87. Intracardiac recordings canreveal more than the Surface ECG 87