Rheobase - Correct Answer-the lowest point on a strength duration curve at an infinitely long pulse duration Chronaxie time - Correct Answer-the pulse width at twice the rheobase value. It approximates the most efficient stimulation pulse duration Charge (formula) - Correct Answer-Charge= I(current) x T(time) Furman's formula - Correct Answer-Energy(microjoules)= I(current)xV(voltage)xT(pulse width) Ohms law formula - Correct Answer-Voltage(electromotive force)= I(current/flow of electrons) x R(resistance to current flow in ohms) Functional Refractory Period - Correct Answer-the coupling interval which first results in a measurable degree of delay in impulse conduction Effective Refractory Period - Correct Answer-the longest coupling interval to be associated with block Devices with NO interaction with pacers - Correct Answer-1. microwave oven, 2. CT scan/Ultrasound 3. X-rays (diagnostic) Devices that cause transient or 1 beat inhibition - Correct Answer-1. EAS 2. Cellphones 3. Arc Welding 4. airport metal detector 5. TENS 6. Electric appliances such as electric blanket & power tools Devices that may damage the pacemaker - Correct Answer-1. MRI 2. Defibrillator 3. Cardioversion 4. Cautery/RF Ablation 5. Radiation Therapy Resistance in Series - Correct Answer-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 - Correct Answer-Parallel means all the resistances are connected to the same point. (R1xR2)/(R1+R2)= total resistance EX: LEAD INSULATION DEFECTS (insulation defects DECREASE impedance) Permanent pacemakers are constant voltage or constant current? - Correct Answer-ALL permanent pacemakers are constant voltage devices. SOME temp pacemakers are constant voltage, most are constant current. LOAD - Correct Answer-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 - Correct Answer-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 - Correct Answer-Slew rate = peak slope of an electrogram slew rate= change in voltage/ change in time Normal slew rate in atrium - Correct Answer->.3 V/s Normal slew rate in ventricle - Correct Answer->.5V/s Steroid used in electrodes - Correct Answer-dexamethasone sodium phosphate in the silicone core(a corticosteriod) Steroid-Eluting Electrodes - Correct Answer-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 - Correct Answer-1. Can easily be repaired 2. Flexible 3. Proven performance history 4. Easy to make Silicone Rubber lead insulation cons - Correct Answer-1. high friction coefficient 2. Absorbs lipids 3. More thrombogenic and fibrotic 4. Cuts easily 5. Tears easily if suture tied too tightly