CCDS IBHRE EXAM QUESTIONS WITH
COMPLETE SOLUTIONS 2025
,Rheobase - ANSWERthe lowest point on a strength duration curve at an infinitely long
pulse duration
Chronaxie time - ANSWERthe pulse width at twice the rheobase value. It approximates
the most efficient stimulation pulse duration
Charge (formula) - ANSWERCharge= I(current) x T(time)
Furman's formula - ANSWEREnergy(microjoules)= I(current)xV(voltage)xT(pulse width)
Ohms law formula - ANSWERVoltage(electromotive force)= I(current/flow of electrons)
x R(resistance to current flow in ohms)
Functional Refractory Period - ANSWERthe coupling interval which first results in a
measurable degree of delay in impulse conduction
Effective Refractory Period - ANSWERthe longest coupling interval to be associated
with block
Devices with NO interaction with pacers - ANSWER1. microwave oven, 2. CT
scan/Ultrasound 3. X-rays (diagnostic)
Devices that cause transient or 1 beat inhibition - ANSWER1. 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 - ANSWER1. MRI 2. Defibrillator 3.
Cardioversion 4. Cautery/RF Ablation 5. Radiation Therapy
Resistance in Series - ANSWERSeries 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 - ANSWERParallel 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? - ANSWERALL
permanent pacemakers are constant voltage devices.
SOME temp pacemakers are constant voltage, most are constant current.
LOAD - ANSWERLoad 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 - ANSWER1. 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 - ANSWERSlew rate = peak slope of an electrogram
slew rate= change in voltage/ change in time
Normal slew rate in atrium - ANSWER>.3 V/s
Normal slew rate in ventricle - ANSWER>.5V/s
Steroid used in electrodes - ANSWERdexamethasone sodium phosphate in the silicone
core(a corticosteriod)
Steroid-Eluting Electrodes - ANSWER1. 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 - ANSWER1. Can easily be repaired
2. Flexible
3. Proven performance history
4. Easy to make
Silicone Rubber lead insulation cons - ANSWER1. high friction coefficient
2. Absorbs lipids
3. More thrombogenic and fibrotic
4. Cuts easily
5. Tears easily if suture tied too tightly
6. Large diameter
Polyurethane 80A - ANSWERBAD
COMPLETE SOLUTIONS 2025
,Rheobase - ANSWERthe lowest point on a strength duration curve at an infinitely long
pulse duration
Chronaxie time - ANSWERthe pulse width at twice the rheobase value. It approximates
the most efficient stimulation pulse duration
Charge (formula) - ANSWERCharge= I(current) x T(time)
Furman's formula - ANSWEREnergy(microjoules)= I(current)xV(voltage)xT(pulse width)
Ohms law formula - ANSWERVoltage(electromotive force)= I(current/flow of electrons)
x R(resistance to current flow in ohms)
Functional Refractory Period - ANSWERthe coupling interval which first results in a
measurable degree of delay in impulse conduction
Effective Refractory Period - ANSWERthe longest coupling interval to be associated
with block
Devices with NO interaction with pacers - ANSWER1. microwave oven, 2. CT
scan/Ultrasound 3. X-rays (diagnostic)
Devices that cause transient or 1 beat inhibition - ANSWER1. 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 - ANSWER1. MRI 2. Defibrillator 3.
Cardioversion 4. Cautery/RF Ablation 5. Radiation Therapy
Resistance in Series - ANSWERSeries 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 - ANSWERParallel 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? - ANSWERALL
permanent pacemakers are constant voltage devices.
SOME temp pacemakers are constant voltage, most are constant current.
LOAD - ANSWERLoad 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 - ANSWER1. 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 - ANSWERSlew rate = peak slope of an electrogram
slew rate= change in voltage/ change in time
Normal slew rate in atrium - ANSWER>.3 V/s
Normal slew rate in ventricle - ANSWER>.5V/s
Steroid used in electrodes - ANSWERdexamethasone sodium phosphate in the silicone
core(a corticosteriod)
Steroid-Eluting Electrodes - ANSWER1. 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 - ANSWER1. Can easily be repaired
2. Flexible
3. Proven performance history
4. Easy to make
Silicone Rubber lead insulation cons - ANSWER1. high friction coefficient
2. Absorbs lipids
3. More thrombogenic and fibrotic
4. Cuts easily
5. Tears easily if suture tied too tightly
6. Large diameter
Polyurethane 80A - ANSWERBAD
