CCDS IBHRE LATEST UPDATE ALREADY GRADED A Rheobase ✔✔the lowest point on a strength duration curve at an infinitely long pulse duration Chronaxie time ✔✔the pulse width at twice the rheobase v alue. It approximates the most efficient stimulation pulse duration Charge (formula) ✔✔Charge= I(current) x T(time) Furman's formula ✔✔Energy(microjoules)= I(current)xV(voltage)xT(pulse width) Ohms law formula ✔✔Voltage(electromotive force)= I(current/flow of electrons) x R(resistance to current flow in ohms) Functional Refractory Period ✔✔the coupling interval which first results in a measurable degree of delay in impulse conduction Effective Refractory Period ✔✔the longest coupling interval to be associated with block Devices with NO interaction with pacers ✔✔1. microwave oven, 2. CT scan/Ultrasound 3. X -
rays (diagnostic) Devices that cause transient or 1 beat inhibition ✔✔1. EAS 2. Cellpho nes 3. Arc Welding 4. airport metal detector 5. TENS 6. Electric appliances such as electric blanket & power tools Devices that may damage the pacemaker ✔✔1. MRI 2. Defibrillator 3. Cardioversion 4. Cautery/RF Ablation 5. Radiation Therapy Resistance in Series ✔✔Series means the beginning of one resistance is connected to another Sum the resistances: R1+R2= total resistance. EX: A LEAD FRACTURE (fractures INCREASE impedance) Resistance in Parallel ✔✔Parallel means all the resistances are connected to th e same point. (R1xR2)/(R1+R2)= total resistance EX: LEAD INSULATION DEFECTS (insulation defects DECREASE impedance) Permanent pacemakers are constant voltage or constant current? ✔✔ALL permanent pacemakers are constant voltage devices. SOME temp pacema kers are constant voltage, most are constant current. LOAD ✔✔Load refers to impedance (or resistance) applied to a circuit. A system with a SMALL load (low impedance) applied to the circuit is said to be a constant current device A system with LARGE load is said to be a constant voltage device Guidelines for Permanent Pacing ✔✔1. Patient is symptomatic 2. The heart rate is less than 40 bpm 3. Asystole of greater than 3 seconds is documented NOTE: Pt may be asymptomatic with 2 or 3 Slew Rate ✔✔Slew rate = peak slope of an electrogram slew rate= change in voltage/ change in time Normal slew rate in atrium ✔✔>.3 V/s Normal slew rate in ventricle ✔✔>.5V/s Steroid used in electrodes ✔✔dexamethasone sodium phosphate in the silicone core(a corticosteriod) Steroid -Eluting Electrodes ✔✔1. The acute threshold is relatively flat compared to non -steroid electrodes 2. The initial capture threshold is similar to non -steroid leads Silicone Rubber lead insulation Pros ✔✔1. Can easily be rep aired
rays (diagnostic) Devices that cause transient or 1 beat inhibition ✔✔1. EAS 2. Cellpho nes 3. Arc Welding 4. airport metal detector 5. TENS 6. Electric appliances such as electric blanket & power tools Devices that may damage the pacemaker ✔✔1. MRI 2. Defibrillator 3. Cardioversion 4. Cautery/RF Ablation 5. Radiation Therapy Resistance in Series ✔✔Series means the beginning of one resistance is connected to another Sum the resistances: R1+R2= total resistance. EX: A LEAD FRACTURE (fractures INCREASE impedance) Resistance in Parallel ✔✔Parallel means all the resistances are connected to th e same point. (R1xR2)/(R1+R2)= total resistance EX: LEAD INSULATION DEFECTS (insulation defects DECREASE impedance) Permanent pacemakers are constant voltage or constant current? ✔✔ALL permanent pacemakers are constant voltage devices. SOME temp pacema kers are constant voltage, most are constant current. LOAD ✔✔Load refers to impedance (or resistance) applied to a circuit. A system with a SMALL load (low impedance) applied to the circuit is said to be a constant current device A system with LARGE load is said to be a constant voltage device Guidelines for Permanent Pacing ✔✔1. Patient is symptomatic 2. The heart rate is less than 40 bpm 3. Asystole of greater than 3 seconds is documented NOTE: Pt may be asymptomatic with 2 or 3 Slew Rate ✔✔Slew rate = peak slope of an electrogram slew rate= change in voltage/ change in time Normal slew rate in atrium ✔✔>.3 V/s Normal slew rate in ventricle ✔✔>.5V/s Steroid used in electrodes ✔✔dexamethasone sodium phosphate in the silicone core(a corticosteriod) Steroid -Eluting Electrodes ✔✔1. The acute threshold is relatively flat compared to non -steroid electrodes 2. The initial capture threshold is similar to non -steroid leads Silicone Rubber lead insulation Pros ✔✔1. Can easily be rep aired
