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