CCDS IBHRE Questions and Correct Answers the Latest Update

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CCDS IBHRE Questions and
Correct Answers the Latest Update
Rheobase


✓ the lowest point on a strength duration curve at an infinitely long pulse duration



Chronaxie time


✓ the pulse width at twice the rheobase value. 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
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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. 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


✓ 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 the same point.
✓

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✓ (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 pacemakers 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

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✓
✓ 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 repaired
✓ 2. Flexible
✓ 3. Proven performance history
✓ 4. Easy to make



Silicone Rubber lead insulation cons


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