Upload
others
View
0
Download
0
Embed Size (px)
Citation preview
Medical Education
4 71 Ohm’s Law EnergyDisclaimer
5 82 Device Function SensingObjectives
StimulationThreshold
6 93 Overview Questions
Fundamentals of Pacing Therapy
Electrical Terms and Concepts
2 ©2007 Boston Scientific Corporation
Medical Education
Disclaimer
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
This presentation is provided with the understanding that the slide content must not be altered in any manner as the content is subject to FDA regulations.
This presentation is to be used in conjunction with other resource material including the applicable Boston Scientific device physician’s manual and any implant accessories instructions for use.
This presentation is not intended to replace implant training.
Proper surgical procedures and techniques are the responsibilities of the medical professional.
If this presentation is not used in its entirety, the following information must be included:
• Appropriate Indications
• Contraindications
• Warnings
• Precautions and Adverse Events
3 ©2007 Boston Scientific Corporation
Medical Education
Objectives
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Define basic electrical terms
Explain how these terms relate to device function
Discuss the relationship between voltage, current, and resistance
Define stimulation threshold and factors affecting it
Explain pacemaker sensing and factors affecting it
When we complete this program you will be able to:
4 ©2007 Boston Scientific Corporation
Medical Education
Overview
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Ohm’s Law• Voltage
• Current
• Impedance
Energy
Stimulation Threshold
Sensing• Slew Rate
Electrical Terms and Concepts:
5 ©2007 Boston Scientific Corporation
Medical Education
Ohm’s Law
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Ohm’s Law: V = I x R
Describes the relationship between voltage, current, resistance: V = I x R; I = V/R; R = V/I
Voltage The electrical force that makes current move through a conductor – measured in volts (V)
Impedance The total opposition presented to the flow of current by an electrical circuit or device –measured in ohms (R)
Current The transfer of electrical charge (electrons) through a cross-section of a conductor –measured in amperes (I)
6 ©2007 Boston Scientific Corporation
Medical Education
Ohm’s Law
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
The force or “push” that causes electrons to move through a circuit
Measured in volts
Represented by the letter “V”
Often referred to as amplitude
Voltage:
7 ©2007 Boston Scientific Corporation
Medical Education
Ohm’s Law
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Current:
The flow of electrons in a completed circuit
Measured in mA (milliamps)
Represented by the letter “I”
8 ©2007 Boston Scientific Corporation
Medical Education
Ohm’s Law
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Impedance:
The opposition to current flow
Measured in ohms
Represented by the letter “R” (W for numerical values)
Often referred to as resistance
9 ©2007 Boston Scientific Corporation
Medical Education
Ohm’s LawCan Be Used to Find Current
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Example 1:
Voltage = 5 V
Impedance = 500 Ω
What will the current be?
I = V/R 5 V ÷ 500 Ω = 0.010 Amperes x 1000 = 10 mA
10 ©2007 Boston Scientific Corporation
Medical Education
Ohm’s LawCan Be Used to Find Current
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Example 2:
Voltage = 2.5 V
Impedance = 500 Ω
What will the current be?
I = V/R 2.5 V ÷ 500 Ω = 0.005 Amperes 0.005 x 1000 = 5 mA
11 ©2007 Boston Scientific Corporation
Medical Education
Ohm’s LawCan Be Used to Find Current
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Example 3:
Voltage = 5 V
Impedance = 250 Ω
What will the current be?
I = V/R 5 V ÷ 250 Ω = 0.020 Amperes 0.020 x 1000 = 20 mA
12 ©2007 Boston Scientific Corporation
Medical Education
Ohm’s LawElectrical Analogy
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Voltage = Current x Resistance
“Normal” Resistance
“Low” Resistance
“High” Resistance
“Normal”Current
“High”Current
“Low”Current
Current is similar to the flow of water
Voltage is analogous to water pressure
Resistance can be compared to resistance to flow
13 ©2007 Boston Scientific Corporation
Medical Education
Device FunctionInsulation Break
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Current is Escaping:
Decreased Resistance
Increased Current Drain
Increased Energy Usage
14 ©2007 Boston Scientific Corporation
Medical Education
Device FunctionLead Fracture
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Current Cannot Reach Heart:
Increased Resistance
Decreased Current Drain
Decreased Energy Usage
15 ©2007 Boston Scientific Corporation
Medical Education
Device FunctionHigh Impedance Leads
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Reducing Electrode Size:
Increases impedance
Decreases current drain
Increases longevity
Smaller current drainLarger current drain
16 ©2007 Boston Scientific Corporation
Medical Education
Device FunctionImpedance
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
High Impedance
Decreases battery current drain, increases longevity
Low Impedance
Increases battery current drain, decreases longevity
17 ©2007 Boston Scientific Corporation
Medical Education
Device FunctionConstant Voltage Pacemakers
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
V = IR
V = IR
18 ©2007 Boston Scientific Corporation
Medical Education
Stimulation Threshold
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Definition:
The minimum electrical stimulus needed to consistently capture the heart outside of the heart’s refractory period
19 ©2007 Boston Scientific Corporation
Medical Education
Stimulation ThresholdPulse Amplitude
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
The voltage delivered by the electrical pacingstimulus (volts)
Amplitude
Pacing Pulse
20 ©2007 Boston Scientific Corporation
Medical Education
Stimulation ThresholdPulse Width
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Pacing Pulse
Pulse Width
Duration of the electrical pacing pulse (milliseconds)
21 ©2007 Boston Scientific Corporation
Medical Education
Stimulation Threshold
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Amplitude (V) + Pulse Width (ms) = Output
Lowest Output that Captures Outside of Refractory = Threshold
22 ©2007 Boston Scientific Corporation
Medical Education
Stimulation Threshold
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Why Measure?
Assure proper lead placement
Determine safety margin
23 ©2007 Boston Scientific Corporation
Medical Education
Stimulation Threshold
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Affected by:
Lead Maturation
Lead Technology
Medications
Lead Location
24 ©2007 Boston Scientific Corporation
Medical Education
Stimulation ThresholdLead Maturation
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Chronic Electrode:
Excitable Tissue
Non-Excitable Fibrotic Tissue
Virtual Electrode
Electrode
25 ©2007 Boston Scientific Corporation
Medical Education
Stimulation ThresholdsEffect of Steroid
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Pulse Width = 0.5 msec
0
3 6
Implant Time (Weeks)
Non-steroid
1
2
3
4
5
Steroid/IROX Electrode
0 1 2 4 5 7 8 9 10 11 12
Pu
lse W
idth
(m
s)
S. Furman, D. Hayes, D Holmes; “A Practice of Cardiac Pacing” 2nd Revision, 1989; p.36
26 ©2007 Boston Scientific Corporation
Medical Education
Stimulation ThresholdStrength Duration Curve
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Capture
Noncapture
1.0Pulse Width (ms)
Pulse Amplitude
27 ©2007 Boston Scientific Corporation
Medical Education
Stimulation ThresholdStrength Duration Curve
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions Pulse Width (ms)
Voltage StimulationThreshold (Volts)
2.0
1.5
1.0
.50
.40
.25
0.5 1.0 1.5 2.0 2.5 3.0
28 ©2007 Boston Scientific Corporation
Medical Education
Energy
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
V2 TE =
R
E = Energy
V = Voltage
T = Time
R = Resistance
29 ©2007 Boston Scientific Corporation
Medical Education
Energy
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
2x Voltage = 4x Energy
2x Pulse Width = 2x Energy
30 ©2007 Boston Scientific Corporation
Medical Education
Energy
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
5.02 (.50ms)25 µJ
500
31 ©2007 Boston Scientific Corporation
Medical Education
Energy
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
2.52 (.50ms)6.25 µJ
500
32 ©2007 Boston Scientific Corporation
Medical Education
Energy
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
5.02 (.25ms)12.5 µJ
500
33 ©2007 Boston Scientific Corporation
Medical Education
Sensing
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Definition:
Sensing is the ability of the pacemaker to “see” when an intrinsic depolarization is occurring
34 ©2007 Boston Scientific Corporation
Medical Education
Sensing
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Accurate sensing requires filtering out extraneous signals
Unwanted signals include:
T-waves
Far-field events
Myopotentials
35 ©2007 Boston Scientific Corporation
Medical Education
Sensing
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Electrophysiological properties of the myocardium
Characteristics of the electrode
Lead placement
Sensing amplifiers of the pacemaker
Lead polarity
Lead integrity
EMI
Sensing may be affected by:
36 ©2007 Boston Scientific Corporation
Medical Education
Sensing
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Review of Sensitivity:
1.0mV
4.0mV
2.0mV
*programmed sensitivity
*
37 ©2007 Boston Scientific Corporation
Medical Education
Sensing
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Review of Sensitivity:
1.0mV
4.0mV
2.0mV
Programming a higher setting decreases the sensitivity of the device – fewer signals are sensed
38 ©2007 Boston Scientific Corporation
Medical Education
Sensing
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Review of Sensitivity:
1.0mV
4.0mV
2.0mV
Programming a lower setting increases the sensitivity of the device – more signals are sensed
39 ©2007 Boston Scientific Corporation
Medical Education
Sensing
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions
Slew Rate:
∆ V / Time = Slew Rate
40 ©2007 Boston Scientific Corporation
Medical Education
Questions
Electrical Terms and Concepts
Disclaimer
Objectives
Overview
Ohm’s Law
Device Function
Stimulation Threshold
Energy
Sensing
Questions