1
Q
What is voltage?
A
The potential difference between two points that drives current flow.
2
Q
What is current?
A
The flow of electric charge measured in amperes (A).
3
Q
What is resistance?
A
The opposition to current flow, measured in ohms (Ω).
4
Q
What is Ohm’s Law?
A
V = I × R (Voltage = Current × Resistance).
5
Q
What does impedance represent?
A
The total opposition to alternating current, including resistance and reactance.
6
Q
What is capacitance?
A
The ability of a structure to store electrical charge, measured in farads (F).
7
Q
In electrophysiology, what does a capacitor represent physiologically?
A
The cell membrane.
8
Q
What is the main function of a filter in signal processing?
A
To remove unwanted frequencies or noise from the recorded signal.
9
Q
What does a low-pass filter do?
A
Allows low-frequency signals to pass, attenuates high frequencies.
10
Q
What does a high-pass filter do?
A
Allows high-frequency signals to pass, attenuates low frequencies.
11
Q
What is the usual frequency range for intracardiac signals?
A
30–500 Hz.
12
Q
What is the usual frequency range for surface ECG signals?
A
0.05–150 Hz.
13
Q
What is gain?
A
The ratio of output amplitude to input amplitude.
14
Q
What is the typical amplitude of an atrial electrogram?
A
0.1–5 mV.
15
Q
What is the typical amplitude of a ventricular electrogram?
A
1–20 mV.
16
Q
What does signal amplification do?
A
Increases small voltages for easier visualization and analysis.
17
Q
What is aliasing?
A
A distortion that occurs when sampling frequency is too low relative to signal frequency.
18
Q
What principle prevents aliasing?
A
Nyquist theorem (sampling rate must be >2× signal frequency).
19
Q
What unit is used to measure frequency?
A
Hertz (Hz).
20
Q
What is the frequency of a signal with a 5 ms cycle length?
A
200 Hz.
21
Q
What is baseline drift?
A
Slow variations in signal baseline due to respiration or electrode movement.
22
Q
How is baseline drift corrected?
A
High-pass filtering or baseline stabilization algorithms.
23
Q
What causes 60 Hz interference?
A
Power line noise coupling into recording circuits.
24
Q
How can 60 Hz noise be minimized?
A
Proper grounding and shielding of cables and equipment.
25
What does “bipolar recording” mean?
Voltage measured between two closely spaced electrodes.
26
What does “unipolar recording” mean?
Voltage measured between one exploring electrode and a distant reference.
27
Which recording type has higher spatial resolution?
Bipolar recording.
28
Which recording type detects far-field signals better?
Unipolar recording.
29
What determines the amplitude of an intracardiac signal?
Proximity, tissue mass, and electrode orientation to the wavefront.
30
What is a differential amplifier?
An amplifier that outputs the difference between two input signals.
31
What is common-mode rejection?
The ability of an amplifier to eliminate signals common to both inputs (like noise).
32
What is CMRR?
Common-Mode Rejection Ratio — a measure of amplifier’s ability to reject noise.
33
What causes signal saturation?
Input voltage exceeds amplifier range, clipping waveform peaks.
34
What can cause signal clipping?
Excessive gain or high-amplitude artifact.
35
What are artifact sources in EP recordings?
Patient movement, respiration, electrode motion, EMI.
36
What is an isolated amplifier?
A device that electrically separates patient circuit from recording system for safety.
37
What is the typical input impedance of an EP amplifier?
Very high (10⁶–10⁹ Ω) to minimize signal loss.
38
What is the sweep speed for EP recordings?
Typically 100–200 mm/s.
39
What does faster sweep speed do?
Spreads waveforms for finer temporal resolution.
40
What does slower sweep speed do?
Compresses waveforms to display longer time intervals.
41
What determines time resolution?
Sampling rate and sweep speed.
42
What is sampling rate?
The number of data points recorded per second (Hz).
43
What sampling rate is typical for intracardiac recordings?
≥1000 samples per second.
44
Why is high sampling rate important?
To accurately represent rapid deflections in intracardiac signals.
45
What is signal-to-noise ratio (SNR)?
Ratio of true signal amplitude to noise amplitude.
46
How can SNR be improved?
Proper grounding, filtering, and shielding.
47
What causes phase distortion?
Improper filter settings altering timing relationships in the waveform.
48
What is the purpose of a notch filter?
To selectively remove 50/60 Hz interference.
49
What can excessive filtering cause?
Loss of important signal details or morphology distortion.
50
What does the term “isoelectric line” mean?
The baseline level with no net voltage difference.
51
What determines the polarity of a recorded signal?
The direction of depolarization relative to the recording electrode.
52
What does a positive deflection indicate on a bipolar electrogram?
Depolarization moving toward the active electrode.
53
What does a negative deflection indicate on a bipolar electrogram?
Depolarization moving away from the active electrode.
54
What happens when a wavefront travels perpendicular to bipolar electrodes?
Biphasic or low-amplitude signal.
55
Why are catheter electrodes made of platinum or iridium?
They are biocompatible and provide stable, low-impedance contact.
56
What is electrode impedance?
The resistance to alternating current at the electrode–tissue interface.
57
What factors affect electrode impedance?
Electrode surface area, material, contact pressure, and frequency.
58
What is typical electrode impedance in EP catheters?
50–1000 Ω.
59
How does electrode size affect signal amplitude?
Smaller electrodes produce higher-resolution but lower-amplitude signals.
60
What is the impact of poor electrode contact?
Decreased signal amplitude and increased noise.
61
What causes overshoot in filtered signals?
Improper high-pass filter or phase shift.
62
What is decoupling in EP systems?
Electrical isolation to prevent leakage current to the patient.
63
What is the safe leakage current limit for medical equipment?
≤100 microamperes (μA).
64
Why is patient isolation important in EP labs?
To prevent electrical shock and equipment interference.
65
What is the purpose of a grounding pad?
To provide a safe pathway for stray electrical current.
66
What can occur if multiple grounds exist in the system?
Ground loops causing noise or artifacts.
67
What is the term for current flow caused by potential differences between grounds?
Ground loop current.
68
What does an “isolation transformer” do?
Electrically separates circuits to enhance patient safety.
69
What is radiofrequency (RF) energy used for in EP?
To deliver controlled heating for cardiac tissue ablation.
70
What frequency range is used for RF ablation?
Approximately 350–750 kHz.
71
What is the primary mechanism of RF lesion formation?
Resistive heating followed by conductive heat spread.
72
What is the critical tissue temperature for irreversible injury?
Around 50–55°C.
73
What happens if temperature exceeds 100°C during RF ablation?
Steam pops or char formation may occur.
74
What is impedance drop during RF ablation indicative of?
Tissue heating and improved contact.
75
What does a sudden impedance rise during ablation indicate?
Coagulum or thrombus formation.
76
What type of current is used in RF ablation?
Alternating current (AC).
77
Why is RF current chosen over direct current for ablation?
AC avoids polarization and excessive tissue damage.
78
What is cryoablation?
A method using extreme cold to create tissue injury and conduction block.
79
What temperature range is typical for cryoablation?
−70°C to −80°C.
80
What is cryoadhesion?
The freezing of tissue to the catheter tip, stabilizing contact.
81
What is lesion formation during cryoablation dependent on?
Temperature, contact, and duration of application.
82
What is power in electrical terms?
The rate of energy transfer, measured in watts (W).
83
How is power calculated?
P = V × I (Power = Voltage × Current).
84
What is the typical power range for RF ablation?
20–50 W.
85
What determines lesion depth during RF ablation?
Power, duration, contact force, and catheter tip size.
86
What is the effect of irrigation during ablation?
Cools electrode surface, allowing higher power without coagulum.
87
What is typical saline flow rate for irrigated ablation?
17–30 mL/min.
88
What happens if irrigation flow stops mid-ablation?
Rapid temperature rise and potential thrombus formation.
89
What is the significance of contact force measurement?
Ensures optimal pressure for effective and safe lesion creation.
90
What is the optimal contact force range for RF ablation?
10–40 grams depending on location.
91
What does the “force–time integral” represent?
Total force applied over ablation duration — correlates with lesion size.
92
What is impedance monitoring used for during ablation?
To assess tissue contact and lesion progression.
93
What does excessive impedance (>200 Ω) indicate?
Poor contact or catheter not in blood pool.
94
What does a low impedance (<80 Ω) indicate?
Catheter tip possibly in blood or thrombus.
95
What is the typical baseline impedance of cardiac tissue?
100–150 Ω.
96
What type of heating predominates within 1–2 mm of the electrode–tissue interface?
Resistive heating.
97
What type of heating occurs deeper in tissue?
Conductive heating.
98
What is the cooling effect of blood flow called?
Convective cooling.
99
How does convective cooling influence lesion formation?
It limits lesion depth by dissipating heat.
100
What does thermocouple in an ablation catheter measure?
Temperature at or near the electrode tip.
101
Why can temperature readings underestimate tissue temperature?
Cooling by irrigation or blood flow lowers sensor reading.
102
What physical principle explains why current density is greatest at the catheter tip?
Smaller surface area concentrates current flow.
103
How does electrode size affect lesion size in RF ablation?
Larger electrodes create broader, shallower lesions; smaller ones create deeper, narrower lesions.
104
What is current density?
The amount of current per unit area (A/cm²).
105
What determines resistive heating intensity?
Current density and tissue resistivity.
106
How does tissue dehydration affect impedance?
It increases impedance.
107
What is the typical tissue resistivity in myocardium?
Approximately 500 Ω·cm.
108
What role does electrode orientation play in signal morphology?
Orientation relative to wavefront determines polarity and amplitude.
109
What is the difference between near-field and far-field signals?
Near-field = local activation; far-field = distant electrical activity.
110
How can you reduce far-field signal contamination?
Use closely spaced bipolar electrodes.
111
What is the purpose of mapping filters?
To enhance near-field signal visualization.
112
What happens to recorded signal amplitude as electrode spacing increases?
It decreases for near-field and increases for far-field signals.
113
What is the spatial resolution of a mapping catheter determined by?
Electrode size and interelectrode spacing.
114
What does signal phase mapping display?
Timing of activation as phase angles (useful for rotors).
115
What is the unit of electric field strength?
Volts per meter (V/m).
116
What causes energy loss in cables and connectors?
Resistance and capacitance effects.
117
What does RF generator measure continuously during ablation?
Power, impedance, and temperature.
118
What is automatic power control?
Adjusting power to maintain target temperature.
119
What is temperature-controlled ablation mode?
Power output varies to maintain set temperature.
120
What is power-controlled ablation mode?
Constant power output regardless of temperature.
121
What advantage does power control provide?
Predictable energy delivery and lesion reproducibility.
122
What disadvantage does temperature control have?
Tip cooling can mask true tissue temperature.
123
What are saline irrigation holes for?
To deliver fluid cooling evenly across electrode surface.
124
What is the “Joule effect”?
Heat produced when current passes through resistance.
125
How is total energy delivered calculated?
Energy (J) = Power (W) × Time (s).
126
How much energy is delivered in a 30 W ablation lasting 60 s?
1800 joules.
127
What is tissue conductance?
The inverse of resistance (ease of current flow).
128
How does tissue conductance change with temperature?
It decreases as tissue heats and desiccates.
129
What is desiccation?
Drying of tissue from excessive heating, increasing impedance.
130
What is carbonization?
Burned tissue creating nonconductive char on electrode surface.
131
What is the danger of char formation?
Thrombus formation or embolization.
132
What is “steam pop”?
Explosion of steam bubbles within tissue from overheating.
133
What power and temperature conditions increase risk of steam pops?
High power, >80°C, prolonged delivery, poor cooling.
134
What does impedance rise >20 Ω during ablation suggest?
Coagulum or overheating.
135
What does impedance drop >10 Ω typically indicate?
Effective lesion formation.
136
What is saline conductivity relative to blood?
Slightly higher; saline is a better conductor.
137
What is blood conductivity relative to tissue?
Blood conducts better than tissue due to ion content.
138
How does blood flow rate affect lesion depth?
Higher flow = smaller lesions (more cooling).
139
What effect does epicardial fat have on lesion formation?
Acts as an insulator, reducing heating efficiency.
140
What physical law describes heat conduction?
Fourier’s law.
141
What does Fourier’s law state?
Heat flows from regions of higher to lower temperature at a rate proportional to the gradient.
142
What law relates current to electric field strength and conductivity?
Ohm’s law in differential form (J = σE).
143
What is dielectric constant?
The measure of a material’s ability to store electrical energy in an electric field.
144
Why is the myocardium anisotropic?
Electrical conductivity varies by fiber orientation.
145
What is anisotropy?
Direction-dependent conduction properties of tissue.
146
What is the approximate conduction velocity in atrial myocardium?
0.5–1.0 m/s.
147
What is the conduction velocity in Purkinje fibers?
2–4 m/s.
148
What is the conduction velocity in AV nodal tissue?
0.05 m/s.
149
What influences conduction velocity?
Cell coupling, ion channel density, and tissue geometry.
150
What is the relationship between voltage gradient and conduction speed?
Larger voltage gradient = faster depolarization spread.
151
What is depolarization threshold?
Minimum voltage needed to trigger an action potential.
152
What determines depolarization threshold?
Membrane potential, ion channel state, and extracellular ions.
RCES/RCIS - CCI
flashcards
Decks in class (7)
# Cards
