1. Cardiac EP Lab :
Amplifiers, Filters, Digital Recording System
2. EP Procedure in Progress
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1. Patient
2. Catheter & Connectors
3. Junction Box
4. Fluro Display
5. EP Recording System
3. The Components
EP Equipment
◦ Recording System
◦ Amplifier
◦ Stimulator
◦ Catheters
Diagnostic
Ablation
◦ RF Ablator
Fluoroscopy & Radiographic table
Other Essential Equipment: Hemodynamic monitor, Pulse
Oximetry, Infusion pumps, External Defibrillator, Essential Drugs,
Temporary Pacemaker & Resuscitation equipment
The Patient
Handbook of Cardiac Electrophysiology: A Practical Guide to Invasive EP Studies and Catheter Ablation. F. D Murgatroyd, et al.
4. Diagnostic Catheters
◦ 4 – 7Fr, Hollow sealed tubes made of Polyurethane (steel braided core) or
Dacron fiber (woven core) material with platinum or steel electrodes at the
distal end.
◦ Conducting wires used are steel (polyurethane) or Silver (Dacron)
◦ Electrical signals are recorded from the endocardium by specialized
catheters with embedded platinum electrodes
◦ Commonly, there are either 4 (Quad), 8 (Octa), 10 (Deca: CS) or
20 (Duo Deca: RA, PV) electrodes
◦ These electrodes can also be configured to pace, that is, apply electrical
stimulation to the heart
Boston Scientific Image Library.
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Alden
Redel
Easy-Mate
Josephson
5. Ablation Catheter
7Fr Polyurethane hollow sealed tubes
Temperature sensor
◦ Thermistor
◦ Thermocouple
Tip Size
◦ 4 / 8 mm large dome - most commonly used tip dome
◦ 5 mm large dome
Irrigated (Thermocouple)
◦ 3.5 – 4 mm dome
◦ Also available 8 mm
◦ 6 – 12 perfusion holes
6. Diagnostic Catheter Placements
HRA High Right Atrium RA-SVC
junction
◦ Records Sinus node
HIS above TV
◦ Marker for the AV node
CS in CS and advanced in the
AV groove
◦ Records left atrial and ventricular
activity
RVA apex of right ventricle
◦ Records RV from bottom most area
Radiofrequency Ablation of Cardiac Arrhythmias; Lawrence S. Klein and William M. Miles; Scientific American Science and Medicine; May/June 1994.
Permission of authors.
7. Unipolar Signals
Derived from the potential
difference between a point
source using an exploring
electrode in direct contact
with the heart (positive input
- anode) and a zero reference
(negative input - cathode)
The Wilson CentralTerminal
or a remote electrode (e.g. in
the IVC) as the other
electrode
8. Bipolar Signal
Record signals using two
electrodes close to one another
Sharper local signals
Much smaller far field signals
Preferred recording method in
most EP labs
(Signal 1 + Noise) – (Signal 2 + Noise) = Signal 1 – Signal 2
Signal 1
Signal 2
9. Junction Box
JB or CIM receive IC signals
from the catheters and
provide an interface into the
physiologic recorded
◦ 20, 40, 54, 80, 102 upto 320
inputs
Multiple switches within
the JB are designated to
a recording and
stimulation channel
which is predefined by
the recording system.
Handbook of Cardiac Electrophysiology. Organization of the arrhythmia lab. Andrea Natale et al. 3:17-24. 2007.
10. Cardiac Amplifier
Consists of
◦ ECG Interface
◦ Hemodynamic Interface
◦ Intracardiac Interface (Jbox)
◦ Stimulation Interface
◦ Input Aux Ports
◦ Output Aux Ports
Functions
◦ Amplifies Input Analog Signals
◦ Apply filtering to input analog
signals
◦ Convert Analog data to digital
◦ Direct Stim impulse to
appropriate channel
Conducts POST (Power On SelfTest)
1. Board Integrity
2. Working Environment
12. Signal Amplification
Physiologic signals acquired from surface and IC electrodes are typically
◦ 25 μV (as measured in infracted regions during ventricular tachycardia mapping)
◦ 5mV (from a surface ECG lead)
◦ Upto 20 mV in healthy myocardium
Considerable amplification is required before the signals are digitized,
displayed and stored.
Amplifiers have different techniques of amplifying the input signals.
◦ Hardwired gain
◦ Gain value -> In mV,
percentage or factor
◦ Software gain
Venkatachalam K et al. Circ Arrhythm Electrophysiol 2011;4:965-973
13. Signal Amplification
Low gain - Surface ECG, Unipolar IC signals
Moderate gain - RV, RA,CS signals
High gain
◦ His signals (100-μV*)
◦ Mapping catheter signals
◦ Pulmonary vein catheter signals
Issues include gaining up noise, saturation of current causing amplifier
to blank out (typically flat line) and display no signals
Venkatachalam K et al. Circ Arrhythm Electrophysiol 2011;4:965-973
17. High Pass Filter
Allows frequencies higher than the cut off or
corner” frequency to pass
Anything lower than the corner frequency is
removed
Surface ECG and unipolar intracardiac signals
50Hz
Bipolar intracardiac signals 10-30Hz
Helps to remove baseline sway due to
breathing or movement
The selections available are Disable, 0.01Hz,
0.05Hz, 0.1Hz, 0.5Hz, 1.0Hz, 10Hz, 30Hz, and
100Hz.
System default is 30 Hz
21. Low Pass Filter
Allows frequencies lower than the cut off or
“corner” frequency to pass
Anything higher than the corner frequency is
removed
Surface ECG 100Hz
Intracardiac ECG 500Hz
Helps to remove high frequency electrical
noise from the lab surroundings
The selections available are 10 Hz, 25 Hz, 50
Hz, 100 Hz, 250 Hz, 500 Hz, 1000 Hz, and 2000
Hz. System default is 250 Hz
23. Amplitude change with different low-pass filter
settings (10 Hz vs 300 Hz).
10 Hz 300 Hz
24. Application of Filters
SignalType High Pass Filter Low Pass Filter
Surface ECG 0.5Hz 100Hz
Intracardiac Bipolar 30Hz 300Hz
Intracardiac Unipolar 1-2Hz 300Hz
Unfiltered Unipolar
0.1Hz
(or no high pass)
300Hz
Low Pass Filter
High Pass Filter0.05 Hz
300 Hz
25. Band Pass Filter
Is a combination of low and high pass filters
Allows a specific frequency range to pass
Diagnostic-quality ECG signals typically require a processing
bandwidth of 0.05–100 Hz, whereas monitor-quality ECGs may be
limited to 0.5–40 Hz
E.g. 10-500Hz is the band pass for intracardiac bipolar signals
E.g. 0.05-100Hz is the band pass for ECG
26. Notch Filter
Removes a specific frequency
In India mains frequency is 50Hz and cause electrical
interference in poorly grounded labs
A notch filter helps to remove this
It is better to remove the noisy piece of equipment as
clinically important signals occur at 50Hz
Notch Filter : OFF Notch Filter : ON
28. Issues of Notch Filtering
Notch Filtering causes
“Ringing” Effect when
applied to high
amplitude signals
29. Understanding A/D Conversion
16-bit A/D converter-
The analog to digital converter (A/D) is responsible for transforming the electrical
voltage detected by the amplifier into digital waveforms
Resolution
The ADC resolution is defined as the smallest incremental voltage that can be
recognized and hence it causes a change in the digital output. It is usually expressed as
the number of bits output by the ADC.
2 mV 16 bit = 216
= 65536 steps
Resolution16 0.0305 microVolt per step RTI
12 bit = 212
= 4096 steps
Resolution12 0.488 microVolt per step RTI
More bits means finer dots to accurately describe the waveform
2 mV
•16-bit resolution
produces finer dots
•With 1kHz
sampling, achieve
~1000 steps of
resolution for a 30
microvolt AF signal
Choosing the Right AmplifierTechnology requires High Speed and High Resolution
30. How many bits do we need
12/16/24/32- what do we need?
Calculating steps -> 2n
Displaying a 2 mV signal -> 2 / Steps
◦ 12 bit -> 4096 steps -> 0.488 microVolts
◦ 16 bit -> 65,536 steps -> 0.0305 microVolts
◦ 24 bit -> 16,777,216 steps -> 0.0001 microvolts
◦ 32 bit -> 4.3 million steps -> ????????
2 mV 16 bit = 216
= 65536 steps
Resolution16 0.0305 microVolt per step RTI*
* Resolution Relative To Input Signal
31. Sampling Rate
A/D converter is usually multiplexed (shared) by many
channels
Data sampling and data storage devices capable of dealing
with the aggregate rate of all channels
◦ Using a sampling rate of 1000 Hz (1 KHz) for 80 channel, the
sampling rate achieved is 80,000 Hz. *
Look for amplifiers which maintain the total IC channels
available at higher sampling rates.
◦ Some amps will give a #IC/Sampling rate
◦ i.e. at 2 KHz if total IC channels at 1 KHz is 180, you would get 90
IC recordable at 2 KHz and 45 IC channels at 4 KHz.
* R C Barr and M S Spach. Sampling rates required for digital recording of intracellular and extracellular
cardiac. Circulation. 1977;55:40-48
33. Noise Affecting Signals
EP laboratory is an extraordinarily noisy environment.
◦ ECG Machine, Pulse Oximeter, External Defib, EAM System,
Catheters.
◦ Patient acts are a huge antennae picking up environmental noise like
fluorescent lamps, wireless monitors etc
Leakage current of upto 10 μA acceptable per equipment
which most patients can tolerate without significant risk of
inducing ventricular fibrillation.
Leakage current can interfere substantially with our ability
to process extracardiac and intracardiac signals with
minimal artifact.
Venkatachalam K et al. Circ Arrhythm Electrophysiol 2011;4:965-973
35. Effect of Noise
The main sources of noise in ECG are
◦ Low Frequency noise (Baseline Wander)
Muscle Tremor
Respiration
◦ 50/60 Hz supply line noise
◦ High Frequency noise
Other interference (i.e., radio frequency noise from other equipment)
Fluorescent lamps / bulbs
Any A/C Motor based equipment (pumps, Air Conditioners etc)
36. ECG SIGNAL
Artifacts (disturbances) can have many causes.
Common causes are:
Movement
Environmental Noise
Sudden movement
From a nearby electrical appliance. A typical
example is a 100 Hz background distortion
from fluorescent lights. To be confused with
atrial fibrillation.
40. Grounding
Dedicated isolated ground
◦ Pipe
◦ Plate
◦ Water Pipe
◦ Steel encased in Concrete
◦ Ground Ring
Plate / Pole at a minimum depth of 8-10 ft
Must have a plate / ground resistance of < 5 ohms
Add second Plate / Pole if resistance > 5 ohms
The process of making a planned, continuous, connection between NON-
CURRENT CARRYING parts of the electrical wiring installation and the earth
and some other conducting body
Note : Grounding & Earthing are two different systems designed
for two entirely different purposes
42. EP Recording System
Consists of
◦ High End Intel based
workstation
◦ Special Interface cards
◦ 2, 3 or 4 HD monitors
◦ High End Graphics Card
◦ Dedicated Mirrored Storage
Space
◦ High Speed Laser Printer
43. EP Recording System
Function
◦ Interface to configure the
amplifier for signal acquisition
◦ Record and Display data
Real-time Monitor
Review Monitor
◦ Review historical data
◦ Provide for additional tools
Template matching
Auto measurements etc..
◦ Tools for archiving & backup
◦ Reporting tool
◦ Advance systems interface
with other imaging systems
48. Template Matching
Your review screen will update like this. Yellow is %
match Lead to Lead.
Overall match is displayed in two areas ( ).
49. T-Wave Subtraction
Subtract a T-Wave template from an overlapped PT
waveform to recover an obscured P wave
Saves time localizing atrial arrhythmias
Original
Revealed P-Wave
T-Wave Template
• Automated real-time waveform analysis for detection of P-wave morphology
using trigger detection
The T-Wave Subtraction feature automatically removes the T-wave
from an overlapped patient waveform to recover an obscured P-
wave.
51. Typical Workstation Specifications
Sr
#
Specification
1 Operating System Windows XP / 2000 Server
2 Computing Power
Intel® Core™2 DUO E8400 3.0 GHz - 6 MB L2 cache, with 1333 MHz
Front Side Bus
3 Memory (RAM) 4 GB DDDR RAM
4 Graphics nVIDIA GeFORCE GTS 450 PCIe (Dual Port). 1GB VRAM Dedicated
5 Monitors 24” or 27” EIZO monitors
6 Hard Disk HDD1 : 250 GB (7200 rpm) HDD2 : 300 GB (10K rpm)
7 Data Protection
OS drive & Data drive should be separate, hence if OS drive gets corrupt,
data drive still intact.
8 DVD/CD Archiving TEAC CD/DVD ±R±RW/DVD-RAM Speed : DVD+R 24x, DVD±RW 8x
9 Power Source Through dedicated isolation box
10 Printing Option to use own specs or HP
11 Work Table Anthro Cart
12 Image Capture Image Capture Kit for High Res Fluro Image Capture
