Basic Concept of Pacemaker :Basic Concept of Pacemaker


Basic Concept of Pacemaker :Over view Pacemaker System Pacemaker Function NBG Code Lead Impedance The magnet Mode & Electromagnetic Interference Information for patient ‘s pacemaker Basic Concept of Pacemaker


Basic Concept of Pacemaker :Over view Pacemaker System Basic Concept of Pacemaker


What is a pacemaker ? :What is a pacemaker ? A device for increaseing a slow HR A device used primarily to correct some types of bradycardia, or slow heart rhythms.


Who need it ? :Who need it ? Indications for Pacing Sick Sinus Syndrome Heart Block Post RF Ablation


How does it work ? :How does it work ? Attach the pacemaker system Pulse generator Sensing and Pacing leads Make it into a circuit Put the system into the body / under the skin and join to the heart by pacing wire Program it’s function by the programmer


Pacing Systems : Pacing Systems Pulse generator Sensing and Pacing lead


The Pacemaker System :The Pacemaker System Patient Lead Pacemaker Programmer


Leads :Leads Epicardial Endocardial


Connection to Pacemaker :Connection to Pacemaker


Just a Simple Lead :Just a Simple Lead


Lead System :Lead System A lead is the insulated wire used to connect the pulse generator to the cardiac tissue The lead transmits the energy to the myocardium and relays intrinsic cardiac signals back to the sensing circuit


Components of a Pacing Lead :Components of a Pacing Lead Connector Proximal Ring Electrode Lead Body Active Fixation Mechanism Suture Sleeve Distal Tip Electrode


Fixation Mechanisms :Fixation Mechanisms Active fixation Screw-in lead Passive fixation Tined tip Passive fixation Finned tip


Slide 15:Suture On Sutureless Epicardial Leads


Pacemaker Circuit :Pacemaker Circuit Unipolar VS Bipolar


Unipolar Vs. Bipolar :Bipolar Unipolar Unipolar Vs. Bipolar + + -


Bipolar Pathway :Bipolar Pathway - +


Unipolar Pathway :Unipolar Pathway + + -


Unipolar :Unipolar


Bipolar Configuration :Bipolar Configuration


Unipolar Versus Bipolar :Unipolar Versus Bipolar


Slide 23:UNIPOLAR vs BIPOLAR


Unipolar Leads :Unipolar Leads Advantage Smaller size Easier to implant? Larger spike on surface ECG Theoretically more reliable Disadvantages Possibility of pocket stimulation Possibility of myopotential inhibition Susceptible to EMI Susceptible to cross-talk


Bipolar Leads :Bipolar Leads Advantages Torque control Noise Rejection Programming flexibility No Pocket stimulation Disadvantages Larger Diameter Stiffer Small ECG Artifact in surface ECG


Lead Placement :Lead Placement Ventricular Lead Right Ventricular Apex (RVA) or Right Ventricular Outflow Tract (RVOT) Ventricular Bradycardia Pacing Sensing Intrinsic Rhythm Atrial Lead Right Atrial Appendage or Atrial Septal Wall Atrial Pacing Atrial Sensing


Ventricular Lead Placement :Ventricular Lead Placement


Ventricular Lead Placement :Ventricular Lead Placement


Ventricular Lead Placement :Ventricular Lead Placement


Atrial Lead Placement :Atrial Lead Placement The atrial lead should be implanted on the septal wall of the atrial appendage Once the lead is in the proper position it will have a “wagging” appearance


Atrial Endocardial Placement :Atrial Endocardial Placement


Atrial Endocardial Placement :Atrial Endocardial Placement


Atrial Endocardial Placement :Atrial Endocardial Placement Ventricle Atrium


Atrial Endocardial Placement :Atrial Endocardial Placement


Basic Concept of Pacemaker :Over view Pacemaker System Pacemaker Function Basic Concept of Pacemaker


Single Chamber Pacing :Single Chamber Pacing One Lead One Circuit / Pacemaker One Patient


Dual-Chamber Pacing :Dual-Chamber Pacing


Basic Function :Basic Function Energy Output Parameters Cardiac Stimulation Threshold Impedance


Energy :Energy Ohm's Law Voltage Current Resistance


Ohm’s Law :Ohm’s Law V = IR V = Voltage I = Current R = Resistance


Voltage :Voltage The difference in potential energy between two points Unit of measure = volt (V)


Current :Current The rate of transfer or flow of electricity Unit of measure – milliampere (mA)


Resistance :Resistance The opposition to the flow of electrical current through a material Unit of measure = ohm (O)


Slide 44:V = IR V = IR CONSTANT VOLTAGE


Output Pulse Duration in Milliseconds :Output Pulse Duration in Milliseconds Pulse Amplitude Pulse Begins Pulse Width Pulse Ends Pulse Wave Form


Pacing Technology “Secret” :Pacing Technology “Secret” Pacemakers do only 2 things: Pace Sense


Capture :Definition:Cardiac depolarization and resultant contraction caused by pacemaker stimulus Capture


Pacing (Stimulation) threshold :The lowest amount of energy to capture the myocardium 100 % of the time Pacing (Stimulation) threshold


Pacing Thresholds :Pacing Thresholds Suggested Intraoperative Values Atrium Less than 1.5 Volts Ventricular Less than 1.0 Volts Pacing Impedance 300-1500 O Depending on lead type


Sensing Thresholds :Sensing Thresholds Suggested Intraoperative Values Atrium Greater than 2.0 mV Ventricular Greater than 5.0 mV


Suggested Chronic Pacing Thresholds :Suggested Chronic Pacing Thresholds Atrium Less than 2.5 Volts Ventricular Less than 2.5 Volts


Suggested Chronic Sensing Thresholds :Suggested Chronic Sensing Thresholds Atrium Greater than 2.0 mV Ventricular Greater than 5.0 mV


Cardiac Stimulation Threshold :Cardiac Stimulation Threshold The minimum amount of electrical energy required to produce consistent cardiac depolarizations through a given electrode May be expressed in terms of voltage, current, energy or charge


The Strength Duration Curve :The Strength Duration Curve


Strength Duration Curve :Strength Duration Curve The rheobase is the least voltage needed to depolarise the heart at an infinite pulse duration. The chronaxie is the shortest pulse duration required to depolarise the heart at a voltage twice the rheobase.


Acute To Chronic Threshold Change :Acute To Chronic Threshold Change Historically reported to occur between 2-8 weeks post implant Thresholds may increase 2-5 times Virtual Electrode - Myocardial Interface


Pacing Thresholds :Pacing Thresholds Hayes, D. et. al. Cardiac Pacing and Defibrillation: A Clinical Approach. Futura. Armonk, NY. 2000:7. 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 1 2 3 4 5 6 7 13 26 52 Time After Implant Chronic Pacing Threshold, Pulse Width (ms)


Chronic Electrode :Excitable Tissue Non-Excitable Tissue Virtual Electrode Electrode Chronic Electrode


Pacing Thresholds :Pacing Thresholds How do we decrease the inflammation process to obtain even lower thresholds? Steroids


Acute Changes in Pacing Threshold :Hayes, D. et. al. Cardiac Pacing and Defibrillation: A Clinical Approach. Futura. Armonk, NY. 2000:7. Acute Changes in Pacing Threshold 0 0.5 1 1.5 2 2.5 3 3.5 4 4.5 5 1 2 3 4 5 6 7 13 26 52 Time After Implant Chronic Pacing Threshold, Pulse Width (ms) Steroid No Steriod


Other Factors ImpactingCapture Threshold :Other Factors ImpactingCapture Threshold Activity Level Posture Time of Day Co-morbid illness Heart Failure Elevated Potassium Acidosis After a Meal Drugs Disease progression


Sensing :Definition: The ability of the pacemaker to sense an intrinsic electrical signal Sensing


Sensing :Sensing When programming sensitivity, as you lower the number you make the pacemaker more sensitive, (allow it “see” more). 1 mV 2 mV 5 mV Sensing


Sensing :Sensing Sensing Threshold: indicates the minimum intracardiac signal that will be sensed by the pacemaker to initiate the pacemaker response (inhibited or triggered) Sensing


Sensing :8 mV 6 mV 4 mV 2 mV 0 mV R-wave 7 mV R-wave 3 mV Pacemaker programmed to 4 mV Sensing Sensing


Sensing :Sensing Pacemaker programmed to 2 mV 8 mV 6 mV 4 mV 2 mV 0 mV R-wave 7 mV R-wave 3 mV Sensing


Slide 67:UNDERSENSING


Slide 68:Automatic Interval Undersensing Intrinsic Refractory Period 800 ms Capture Capture Capture Capture UNDERSENSING


Slide 69:OVERSENSING


Slide 70:Automatic Interval Capture Capture Capture Capture Lack of Pacing Spike Lack of Pacing Spike OVERSENSING


Slide 71:OVERSENSING Sources Myopotentials Environment Intrinsic Cardiac Signals Lack of Pacing Spike Lack of Pacing Spike


Problems with PacemakersFailure to Capture :Problems with PacemakersFailure to Capture Causes: Threshold rise (electrolytes, drugs) Lead dislodgement Lead fracture RV infarct Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.


Problems with PacemakersFailure to Pace :Problems with PacemakersFailure to Pace Causes: Oversensing Battery failure Internal insulation failure Conductor coil fracture Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.


Problems with PacemakersFailure to Sense :Problems with PacemakersFailure to Sense Causes: Undersensing Lead Fracture Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005.


Basic Concept of Pacemaker :Over view Pacemaker System Pacemaker Function NBG Code Basic Concept of Pacemaker


Slide 76:The NASPE/BPEG Generic (NBG) Code Position Category Letters Used Manufac- turer’s Designation Only I II III Chamber(s) Paced Chamber(s) Sensed Response to Sensing Rate modulation Multisite pacing O-None P-Simple Programmable M-Multi- Programmable C-Communicating R-Rate modulation O-None A-Atrium V-Ventricle D-Dual (A+V) S- Single (A or V) S- Single (A or V) O-None A-Atrium V-Ventricle D-Dual (A+V) O-None T-Triggered I-Inhibited D-Dual (T+I) O-None A-Atrium V-Ventricle D-Dual (A+V) IV V Version 2001


Common Pacemaker Modes :Common Pacemaker Modes - Ventricular pacing - No sensing - No response to sensing


Common Pacemaker Modes :Common Pacemaker Modes - Ventricular pacing - Ventricular sensing - Inhibited when sensing a ventricular event


Common Pacemaker Modes :Common Pacemaker Modes - Ventricular pacing - Ventricular sensing - Inhibited when sensing a ventricular event - Rate response capabilities


Common Pacemaker Modes :Common Pacemaker Modes - Dual (Atrial & Ventricular) pacing - Dual (Atrial & Ventricular) sensing - Dual (Inhibited & Triggered) response to sensing


Common Pacemaker Modes :Common Pacemaker Modes Programmability & Rate Response - Dual (Atrial & Ventricular) pacing - Dual (Atrial & Ventricular) sensing - Dual (Inhibited & Triggered) response to sensing - Rate Response Capabilities


Pacemaker ConfigurationsVOO :Pacemaker ConfigurationsVOO Indications Temporary mode some-times used during surgery to prevent interference from electrocautery


Pacemaker ConfigurationsVVI :Pacemaker ConfigurationsVVI


Pacemaker ConfigurationsAAI :Pacemaker ConfigurationsAAI Indications Sick sinus syndrome in the absence of AV node disease or atrial fibrillation.


Pacemaker ConfigurationsVDD :Pacemaker ConfigurationsVDD Indications AV block with intact sinus node function (particularly useful in congenital AV block).


Pacemaker ConfigurationsDDD :Pacemaker ConfigurationsDDD


Intrinsic P and R-waves :Intrinsic P and R-waves


Atrial Capture :Pacemaker Stimulus Atrial Capture


Pace Atrium Sense Ventricle :Pace Atrium Sense Ventricle


Pace and Sense in AtriumSense in Ventricle :Pace and Sense in AtriumSense in Ventricle


Pacemaker ECG :Pacemaker ECG Should be LBBB …. pacing from right ventricle Should be superior axis …. pacing from apex Pacing spike may be seen Heart rate must faster than the lower rate


DDDR Pacing :DDDR Pacing Example of Dual-Chamber


Basic Concept of Pacemaker :Over view Pacemaker System Pacemaker Function NBG Code Lead Impedance Basic Concept of Pacemaker


Lead Impedance :Lead Impedance Assessment of lead integrity Not lead position


Lead Resistance/Impedance Changes :Lead Resistance/Impedance Changes High Resistance > 2500 ohms Also called an “Open Circuit” Chronic lead system Fractured lead conductor coil Acute lead system Loss of contact between the terminal pin of the lead and the pacemaker header set screw


Lead Resistance/Impedance Changes :Lead Resistance/Impedance Changes


Slide 97:Low Resistance < 250 ohms Also called “Shorted Circuit” Insulation Break-Down Insulation cut by suture Degradation of the insulation Subclavian Crush Syndrome Lead Resistance/Impedance Changes


Lead Resistance/Impedance Changes :Lead Resistance/Impedance Changes


Insulation Break :Insulation Break Current is escaping Decreased Resistance Increased Current Drain Pacing and sensing problems


Lead Fracture :Lead Fracture Current cannot reach heart Increased Resistance Decreased Current Drain Pacing and sensing problems


Basic Concept of Pacemaker :Over view Pacemaker System Pacemaker Function NBG Code Lead Impedance The magnet Mode & Electromagnetic Interference Basic Concept of Pacemaker


The magnet mode :The magnet mode


Magnets & Device Function :Magnets & Device Function To alter pacemaker or ICD function, a magnet has to have a field strength of >= 10 gauss next to the surface of the device. To compare - a magnet in a stereo speaker has a field strength of 100 gauss at the surface, but 0 gauss 6 inches away.


How does magnet application affect a pacemaker? :How does magnet application affect a pacemaker? Magnet application disables the sensing amplifier, causing it to pace asynchronously. Dual chamber pacemakers will pace in DOO Single chamber pacemakers will pace in VOO/AOO Magnet rates vary manufacturer to manufacturer


Magnetic Interference :Magnetic Interference 6 Inch Rule. It is recommended that patients with a pacemaker or defibrillator keep at least 6 inches away from possible sources of interference. e.g. mobile phones, magnetic pain therapy, stereo speakers * Patients are advised to keep safe distance from anti-theft devices, arc welding equipment and to have manual security checks at airports *NASPE news and press release May 17, 2000 www.naspe.org.


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Electromagnetic Interference :Electromagnetic Interference Cardioversion / Defibrillation Electrocautery Magnetic Resonance Imaging (MRI) Extracorporeal Shock Wave Lithotripsy (ESWL) Therapeutic Radiation Radiofrequency Ablation


Cardioversion / Defibrillation :Cardioversion / Defibrillation Prior to any electrical procedure, device interaction must be analyzed Pacemaker interference is possible with cardioversion / defibrillation Paddles for cardioversion / defibrillation or electrocautery should be 4-6 inches away Paddles should be placed anterior / posterior if possible


Magnetic Resonance Imaging (MRI) :Magnetic Resonance Imaging (MRI) Generally contraindicated Asynchronous pacing


Basic Concept of Pacemaker :Over view Pacemaker System Pacemaker Function NBG Code Lead Impedance The magnet Mode & Electromagnetic Interference Information for patient ‘s pacemaker Basic Concept of Pacemaker


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