CRM IBHRE UPDATED ACTUAL Exam
Questions and CORRECT Answers
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)
Energy (formula) - CORRECT ANSWER - Energy(microjoules)= I(current)xVxT
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
Questions and CORRECT Answers
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)
Energy (formula) - CORRECT ANSWER - Energy(microjoules)= I(current)xVxT
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
