28-Cardiac Pacemaker-22-Feb-2019Reference Material I_Pacemakers.ppt - Pacemakers Outline 1 Energy calculation 2 Pacemaker codes 3 Pacemaker

28-Cardiac Pacemaker-22-Feb-2019Reference Material I_Pacemakers.ppt

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Unformatted text preview: Pacemakers Outline 1. Energy calculation 2. Pacemaker codes 3. Pacemaker configurations 4. Indications for pacemakers 5. Problems with pacemakers 6. Examples 7. Battery 8. Recent trends 9. Leads and electrode Implantable pacemakers Fixed Rate Demand R-Wave triggered Ventricular inhibited Atrial triggered Dual chamber Pacemakers Energy Calculation Ep=(Vs2/RH) TD + VS IDT Ep - Energy delivered by the pacemaker to the heart during each pulse Vs – Voltage RH – Electrode – heart resistance TD – Pulse duration ID – Drain current T- time period between successive pulse Pacemaker Codes Position Function 1 Chambers Paced 2 Chambers Sensed 3 Response to Sensed Stimulus 4 Rate Modulation? O (none) O O O (non-rate responsive) A (atrium) A T (triggered) R (rate responsive) V (ventricle) V I (inhibited) D (both atrium & ventricle) Pacemaker Configurations VOO Indications Temporary mode some-times used during surgery to prevent interference from electrocautery Pacemaker Configurations VVI Indications The combination of AV block and chronic atrial arrhythmias (particularly atrial fibrillation). Pacemaker Configurations AAI Indications Sick sinus syndrome in the absence of AV node disease or atrial fibrillation. Pacemaker Configurations VDD Indications AV block with intact sinus node function (particularly useful in congenital AV block). Pacemaker Configurations DDD Indications 1. The combination of AV block and SSS. 2. Patients with LV dysfunction and LV hypertrophy who need coordination of atrial and ventricular contractions to maintain adequate CO. Indications for Pacemaker Class I 1. Sinus node dysfunction with documented symptomatic bradycardia 2. Symptomatic chronotropic incompetence (failure to increase HR with exercise or increased metabolic demand) 3. 3° and advanced 2° AV block associated with any of the following: Arrhythmias that require drugs resulting in symptomatic bradycardia Sinus pauses > 3 seconds Asymptomatic escape rate < 40bpm while awake 4. 3° or 2° AV block with associated symptomatic bradycardia 5. Type II 2° AV block with wide QRS, regardless of symptoms Indications for Pacemaker Class IIa 1. Syncope of unexplained origin when major abnormalities of sinus node function are discovered or provoked during EP studies. 2. Asymptomatic 3° AV block with an awake ventricular rate > 40bpm 3. Asymptomatic type II 2° AV block Problems with Pacemakers Failure to Capture Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005. Causes: • • • • Threshold rise (electrolytes, drugs) Lead dislodgement Lead fracture RV infarct Problems with Pacemakers Failure to Pace Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005. Causes: • • • • Oversensing Battery failure Internal insulation failure Conductor coil fracture Problems with Pacemakers Failure to Pace Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005. Causes: • Crosstalk Problems with Pacemakers Failure to Sense Braunwald's Heart Disease: A Textbook of Cardiovascular Medicine, 7th ed., 2005. Causes: • Undersensing • Lead Fracture Example 1 The Alan E. Lindsay ECG Learning Center ; Ventricular sensed, ventricular paced Consistent with VVI Example 2 The Alan E. Lindsay ECG Learning Center ; Atrial sensed, ventricular paced Consistent with DDD or VDD Example 3 The Alan E. Lindsay ECG Learning Center ; Atrial paced Consistent with AAI or DDD Example 4 The Alan E. Lindsay ECG Learning Center ; Failure to Pace Example 5 The Alan E. Lindsay ECG Learning Center ; Failure to Sense Pacemaker Battery Mercury Batteries Biological power sources Nuclear batteries – Plutonium 238 (Half life of 87 years) Lithium cells – 2Li+I2= 2LiI+e Battery energy in joule (A-H Rating)* VS * 3600 (s/h) Joules Life time of a battery (battery energy in joule/Energy delivered in each pulse)* T Sec Life time * (1/3600)* (1/24) *(1/365) Years Recent trends Programmable Pacemakers Rate –responsive A Cardiac pacemaker delivers 5 V Pulses of 2 ms duration to bipolar electrodes, which drives a 500 Ω – resistive load. The mean pulse rate of the pacemaker is 70 per min. What is the total energy supplied to this load over 10 years period? (Neglect the energy drain losses). Assume that the power supply is two 2.8 V lithium batteries. What must be the milliamp –hour (mAh) capacity of each battery to be operating the same pacemaker for 10 years? Leads and electrode Myo cardial – Outside wall Endo cardial – inside wall – Sutureless – Tined – Porous tip – Steriod eluting ...
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