Basic Concepts—Electricity and Pacemakers Module 3 Student Notes An introduction to the fundamental electrical concepts used in pacing and defibrillation. This module will teach you the baseline information necessary for working toward more advanced knowledge in pacemaker operation. It is possible that you may want additional supplemental materials to enhance your knowledge or provide more practice. If you feel this is necessary for you, ask your instructor for suggestions on books or other tools. Instructor Notes This module should take approximately 2 hours to cover. To deliver this module, the following materials are recommended: Printed participant guides for each participant Overhead projector and screen Optional: Whiteboard or flip chart While delivering the module, engage the learners by asking questions and getting them to talk about the subject based on their previous knowledge. Evaluate the learners by delivering the knowledge check at the end of this module. An acceptable score is 100% (there are only two questions, and both must be answered appropriately). World Headquarters Medtronic, Inc. 710 Medtronic Parkway Minneapolis, MN 55432-5604 USA Internet: www.medtronic.com Tel: (763) 514-4000 Europe Medtronic International Trading Sàrl Route du Molliau Ch- 1131 Tolochenaz Switzerland Tel: (41 21) 802 7900 Asia-Pacific Medtronic International, Ltd. 16/F Manulife Plaza The Lee Gardens, 33 Hysan Avenue Causeway Bay Hong Kong Tel: (852) 2891 4456 Canada Medtronic of Canada Ltd. 6733 Kitimat Road Mississauga, Ontario L5N 1W3 Tel: (905) 826-6020 Toll-free: 1 (800) 268-5346 Medtronic USA, Inc. Toll-free: 1 (800) 328-2518 (24-hour technical support for physicians and medical professionals) Latin America Medtronic USA, Inc. Doral Corporate Center II 3750 NW 87th Avenue Suite 700 Miami, FL 33178 USA Tel: (305) 500-9328 UC199701790d EN Medtronic, Inc. Minneapolis, MN December 2007

Objectives Upon completion you will be able to: Describe the relationship between voltage, current, and resistance Describe the clinical significance of alterations in voltage, current, and resistance Student Notes Instructor Notes Read and discuss the objectives. Why is understanding these relationships significant to the audience? This is the foundational information required to evaluate pacemaker performance and make some of the most basic and significant programming decisions.

Voltage Current Impedance Characteristics of an electrical circuit: Including a pacemaker circuit Voltage Current Impedance Student Notes Instructor Notes

Voltage Voltage is the force, or “push,” that causes electrons to move through a circuit In a pacing system, voltage is: Measured in volts (V) Represented by the letter “V” Provided by the pacemaker battery Often referred to as amplitude or pulse amplitude Student Notes The terms “amplitude” and “voltage” are often used interchangeably in pacing, undoubtedly to express “Voltage Amplitude,” which refers to the voltage output. Instructor Notes

Current The flow of electrons in a completed circuit In a pacing system, current is: Measured in milliamps (mA) Represented by the letter “I” Determined by the amount of electrons that move through a circuit Student Notes Current: The movement of electricity, or free electrons, through a circuit. Current is measured in amperes and represented by the symbol I (capital I). One ampere is a unit of electrical current produced by 1 volt acting through a resistance of 1 ohm. In pacing we express current as milliamps: 1 Ampere = 1000 milliamps Instructor Notes

Impedance The opposition to current flow In a pacing system, impedance is: Measured in ohms (W) Represented by the letter “R” The measurement of the sum of all resistance to the flow of current Student Notes Impedance is the sum of all resistance to the flow of current. The resistive factors to a pacing system include: Lead conductor resistance The resistance to current flow from the electrode to the myocardium Polarization impedance, which is the accumulation of charges of opposite polarity in the myocardium at the electrode-tissue interface Instructor Notes Resistance is a term used to refer to simple electric circuits without capacitors, and with constant voltage and current. Impedance is a term used to describe more complex circuits with capacitors and with varying voltage and current. Therefore, the use of the term impedance is more appropriate than resistance when discussing pacing circuits, although both are used.

Voltage, Current, and Impedance are Interdependent The interrelationship of the three components is analogous to the flow of water through a hose Voltage represents the force with which . . . Current (water) is delivered through . . . A hose, where each component represents the total impedance: The nozzle, representing the electrode The tubing, representing the lead wire Student Notes In this analogy, voltage can be thought of as water pressure delivered by the system. Current is analogous to the amount of water delivered at the end of the hose, and resistance is the sum of all the forces opposing this flow of water. For example, the restriction at the nozzle, the friction along the hose and pipes, even the atmospheric pressure the water must flow through once it exits the hose. Increasing the force of the water (opening the valve more, or somehow increasing the water pressure) will deliver more water to the hose, but it will also increase some of the resistance (for example, the friction within the hose and pipes). Instructor Notes Each of these three components in an electrical circuit are interdependent – this analogy may help you understand the relationship.

Voltage, Current, and Impedance Recap Voltage: The force moving the current (V) In pacemakers it is a function of the battery chemistry Current: The actual continuing volume of flow of electricity (I) This flow of electrons causes the myocardial cells to depolarize (to “beat”) Impedance: The sum of all resistance to current flow (R or W or sometimes Z) Impedance is a function of the characteristics of the conductor (wire), the electrode (tip), and the myocardium Student Notes On this slide we have a review of the main terminology used to this point, and the symbols used to represent this concept in calculations, or perhaps in a medical record. Instructor Notes

Voltage and Current Flow Electrical Analogies Spigot (voltage) turned up, lots of water flows (high current drain) Water pressure in system is analogous to voltage – providing the force to move the current Student Notes Using the garden hose as an analogy, the higher the voltage, the greater the push, or “flow” of electrons (and the greater the current drain). Instructor Notes This slide provides more information about the analogy on a mouse click. First ask the following question: Ask: When the spigot is turned up, is there more or less water flow? More—which is analogous to high current drain Click your mouse to provide more information about the analogy. Spigot (voltage) turned low, little flow (low current drain)

Resistance and Current Flow Electrical Analogies Normal resistance – friction caused by the hose and nozzle Low resistance – leaks in the hose reduce the resistance More water discharges, but is all of it going to the nozzle? Student Notes Resistance affects current flow. Leads with an insulation breach, such as the garden hose pictured in the middle, will measure a low resistance reading with a resultant high current drain, and possible premature battery depletion. Conversely, if there is a high resistance, such as a lead conductor break (represented by the knot), the current flow will be low or non-existent. Instructor Notes An analogy for the effect of resistance on current flow. High resistance – a knot results in low total current flow

V I R Ohm’s Law V = I X R I = V / R R = V / I V = I X R V R = I V I = Describes the relationship between voltage, current, and resistance V = I X R I = V / R R = V / I V = I X R V I R V R I = Student Notes If any two values are known, the third may be calculated (cover the value you are seeking and the others appear in the appropriate format to calculate the unknown value). Instructor Notes V I = R

So What? Ohm’s law tells us: If the impedance remains constant, and the voltage decreases, the current decreases If the voltage is constant, and the impedance decreases, the current increases So What? Student Notes Ohm’s Law provides the rationale for many of the decisions we will make when evaluating pacing systems and making programming decisions. Instructor Notes Ask: So, what is the CLINICAL significance to all this information? Proper management of electrical characteristics is important for patient safety and device longevity

Status Check Start with: Solve for Current (I): What happens to current if the voltage is reduced but the impedance is unchanged? Start with: Voltage = 5 V Impedance = 500 W Current = 10 mA Solve for Current (I): I = V/R I = 5 V ÷ 500 W = 0.010 Amps Current is 10 mA Reduce the voltage to 2.5 V Voltage = 5 V Impedance = 500 W Current = ? Is the current increased/ decreased or unchanged? I = V/R V = 2.5 V ÷ 500 W = 0.005 Amps or 5 mA The current is reduced Student Notes If: Voltage = 2.5 V Impedance = 500 ohms 1 Ampere = 1000 milliamps Then use the formula I = V ÷ R to find I (the current). The amount of current that flows through a pacemaker system is very small: Use milliamps as a unit of measurement rather than amps. Convert amps to milliamps by multiplying amps by 1000 (or move the decimal three places to the right). Instructor Notes The clinical significance of reducing the current: Ask: What affect will this have on the longevity of the pacemaker battery? It will increase device longevity by reducing the drain on the battery Ask: Will the pacing output still reliably capture the myocardium? The less current the less likely you are to reliably capture the myocardium

Status Check What happens to current if the impedance is reduced but the voltage is unchanged? Start with: Voltage = 5 V Impedance = 500 W Current = 10 mA Solve for Current (I): I = V/R I = 5 V ÷ 500 W = 0.010 Amps Current is 10 mA Reduce impedance to 250 W Voltage = 5 V Impedance = 250 W Current = ? Is the current increased/ decreased or unchanged? I = V/R V = 2.5 V ÷ 250 W = 0.02 Amps or 20 mA The current is increased Student Notes If: Voltage = 5 V Impedance = 250 ohms 1 Ampere = 1000 milliamps Then use the formula I = V ÷ R to find I (the current). The amount of current that flows through a pacemaker system is very small: Use milliamps as a unit of measurement rather than amp. Convert amps to milliamps by multiplying amps by 1000 (or move the decimal three places to the right). Instructor Notes The clinical significance of increasing the current: Ask: What effect will this have on device longevity? It will increase battery drain and decrease device longevity. Ask: Will the pacemaker reliably capture the myocardium? The higher the current the more likely it is to capture the myocardium. Ask: Could the patient notice any ill effects from increasing the current? Yes, other muscles in the area of the pacing leads could be stimulated as well, for example the diaphragm.

Other terms Cathode: A negatively charged electrode For example, the electrode on the tip of a pacing lead Anode: A positively charged electrode Examples: The “ring” electrode on a bipolar lead The IPG case on a unipolar system More on this later (see: Pacemaker Basics) Anode Cathode Student Notes The cathode (more commonly called the tip electrode) is negatively charged, and the other electrode is positively charged. The anode may be the ring electrode on the lead, or it may be the case of the pacemaker when a unipolar lead system is used. If the cathode is negative, and the anode is positive – what is the path the current (or electrons) take? From cathode to anode. Some other terms used are: Charge: The quantity of electricity that has flowed Charge (Coulombs or watt/hrs) = I x T (time) Since voltage is relatively constant over battery life, “Charge” is essentially what is consumed as the battery depletes Energy: The result of multiplying the force times the time Energy (Joules) = V x I x T Instructor Notes

Battery Basics So where does the current come from? A battery produces electricity as a result of a chemical reaction. In its simplest form, a battery consists of: A negative electrode (anode) An electrolyte, (which conducts ions) A separator, (also an ion conductor) and A positive electrode (cathode) Negative terminal Anode Separator Cathode Positive terminal Student Notes Using a typical “D” cell battery as an illustration: When the battery is connected to an external load (e.g., myocardium): A chemical reaction in the battery is initiated when a load is applied to the battery For example, when a pacing pulse is applied This reaction frees up electrons on the cathode The electrons pass through the separator, and are conducted to the anode via the electrolyte where they collect on the anode They flow from the anode through the myocardium and return back to the cathode Via the myocardium This electrons depolarize the muscle cells causing them to contract When the external load is removed (i.e., the pacing stops), the chemical reaction in the battery ceases. Obviously, pacemakers and defibrillators do not use “D” cell or even wet-cell batteries, but the concepts for generating and moving electrons is the same. Instructor Notes Ask: Why not use rechargeable batteries? The re-charging circuitry takes up space, making the devices ultimately significantly larger They are not reliable enough to be used as a power source in circumstances that might be life-saving

Brief Statements Indications Implantable Pulse Generators (IPGs) are indicated for rate adaptive pacing in patients who ay benefit from increased pacing rates concurrent with increases in activity and increases in activity and/or minute ventilation. Pacemakers are also indicated for dual chamber and atrial tracking modes in patients who may benefit from maintenance of AV synchrony. Dual chamber modes are specifically indicated for treatment of conduction disorders that require restoration of both rate and AV synchrony, which include various degrees of AV block to maintain the atrial contribution to cardiac output and VVI intolerance (e.g. pacemaker syndrome) in the presence of persistent sinus rhythm. Implantable cardioverter defibrillators (ICDs) are indicated for ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life-threatening ventricular arrhythmias. Cardiac Resynchronization Therapy (CRT) ICDs are indicated for ventricular antitachycardia pacing and ventricular defibrillation for automated treatment of life-threatening ventricular arrhythmias and for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy and have a left ventricular ejection fraction less than or equal to 35% and a QRS duration of ≥130 ms. CRT IPGs are indicated for the reduction of the symptoms of moderate to severe heart failure (NYHA Functional Class III or IV) in those patients who remain symptomatic despite stable, optimal medical therapy, and have a left ventricular ejection fraction less than or equal to 35% and a QRS duration of ≥130 ms. Contraindications IPGs and CRT IPGs are contraindicated for dual chamber atrial pacing in patients with chronic refractory atrial tachyarrhythmias; asynchronous pacing in the presence (or likelihood) of competitive paced and intrinsic rhythms; unipolar pacing for patients with an implanted cardioverter defibrillator because it may cause unwanted delivery or inhibition of ICD therapy; and certain IPGs are contraindicated for use with epicardial leads and with abdominal implantation. ICDs and CRT ICDs are contraindicated in patients whose ventricular tachyarrhythmias may have transient or reversible causes, patients with incessant VT or VF, and for patients who have a unipolar pacemaker. ICDs are also contraindicated for patients whose primary disorder is bradyarrhythmia.

Brief Statements (continued) Warnings/Precautions Changes in a patient’s disease and/or medications may alter the efficacy of the device’s programmed parameters. Patients should avoid sources of magnetic and electromagnetic radiation to avoid possible underdetection, inappropriate sensing and/or therapy delivery, tissue damage, induction of an arrhythmia, device electrical reset or device damage. Do not place transthoracic defibrillation paddles directly over the device. Additionally, for CRT ICDs and CRT IPGs, certain programming and device operations may not provide cardiac resynchronization. Also for CRT IPGs, Elective Replacement Indicator (ERI) results in the device switching to VVI pacing at 65 ppm. In this mode, patients may experience loss of cardiac resynchronization therapy and / or loss of AV synchrony. For this reason, the device should be replaced prior to ERI being set. Potential complications Potential complications include, but are not limited to, rejection phenomena, erosion through the skin, muscle or nerve stimulation, oversensing, failure to detect and/or terminate arrhythmia episodes, and surgical complications such as hematoma, infection, inflammation, and thrombosis. An additional complication for ICDs and CRT ICDs is the acceleration of ventricular tachycardia. See the device manual for detailed information regarding the implant procedure, indications, contraindications, warnings, precautions, and potential complications/adverse events. For further information, please call Medtronic at 1-800-328-2518 and/or consult Medtronic’s website at www.medtronic.com. Caution: Federal law (USA) restricts these devices to sale by or on the order of a physician.

Brief Statement: Medtronic Leads Indications Medtronic leads are used as part of a cardiac rhythm disease management system. Leads are intended for pacing and sensing and/or defibrillation. Defibrillation leads have application for patients for whom implantable cardioverter defibrillation is indicated Contraindications Medtronic leads are contraindicated for the following: ventricular use in patients with tricuspid valvular disease or a tricuspid mechanical heart valve. patients for whom a single dose of 1.0 mg of dexamethasone sodium phosphate or dexamethasone acetate may be contraindicated. (includes all leads which contain these steroids) Epicardial leads should not be used on patients with a heavily infracted or fibrotic myocardium. The SelectSecure Model 3830 Lead is also contraindicated for the following: patients for whom a single dose of 40.µg of beclomethasone dipropionate may be contraindicated. patients with obstructed or inadequate vasculature for intravenous catheterization.

Brief Statement: Medtronic Leads (continued) Warnings/Precautions People with metal implants such as pacemakers, implantable cardioverter defibrillators (ICDs), and accompanying leads should not receive diathermy treatment. The interaction between the implant and diathermy can cause tissue damage, fibrillation, or damage to the device components, which could result in serious injury, loss of therapy, or the need to reprogram or replace the device. For the SelectSecure Model 3830 lead, total patient exposure to beclomethasone 17,21-dipropionate should be considered when implanting multiple leads. No drug interactions with inhaled beclomethasone 17,21-dipropionate have been described. Drug interactions of beclomethasone 17,21-dipropionate with the Model 3830 lead have not been studied. Potential Complications Potential complications include, but are not limited to, valve damage, fibrillation and other arrhythmias, thrombosis, thrombotic and air embolism, cardiac perforation, heart wall rupture, cardiac tamponade, muscle or nerve stimulation, pericardial rub, infection, myocardial irritability, and pneumothorax. Other potential complications related to the lead may include lead dislodgement, lead conductor fracture, insulation failure, threshold elevation or exit block. See specific device manual for detailed information regarding the implant procedure, indications, contraindications, warnings, precautions, and potential complications/adverse events. For further information, please call Medtronic at 1-800-328-2518 and/or consult Medtronic’s website at www.medtronic.com. Caution: Federal law (USA) restricts this device to sale by or on the order of a physician.

Disclosure NOTE: This presentation is provided for general educational purposes only and should not be considered the exclusive source for this type of information. At all times, it is the professional responsibility of the practitioner to exercise independent clinical judgment in a particular situation.