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CCDS IBHRE Exam Review
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CCDS IBHRE Exam Review CCDS IBHRE Exam Review CCDS IBHRE Exam Review
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CCDS IBHRE Exam ReviewRheobase - CORRECT ANS the lowest point on a strength duration curve at an infinitely long pulse
duration
Chronaxie time - CORRECT ANS the pulse width at twice the rheobase value. It approximates the most
efficient stimulation pulse duration
Charge (formula) - CORRECT ANS Charge= I(current) x T(time)
Furman's formula - CORRECT ANS Energy(microjoules)= I(current)xV(voltage)xT(pulse width)
Ohms law formula - CORRECT ANS Voltage(electromotive force)= I(current/flow of electrons) x
R(resistance to current flow in ohms)
Functional Refractory Period - CORRECT ANS the coupling interval which first results in a measurable
degree of delay in impulse conduction
Effective Refractory Period - CORRECT ANS the longest coupling interval to be associated with block
Devices with NO interaction with pacers - CORRECT ANS 1. microwave oven, 2. CT scan/Ultrasound 3. X-
rays (diagnostic)
Devices that cause transient or 1 beat inhibition - CORRECT ANS 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 ANS 1. MRI 2. Defibrillator 3. Cardioversion 4.
Cautery/RF Ablation 5. Radiation Therapy
,Resistance in Series - CORRECT ANS 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 ANS 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 ANS ALL permanent
pacemakers are constant voltage devices.
SOME temp pacemakers are constant voltage, most are constant current.
LOAD - CORRECT ANS 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 ANS 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 ANS Slew rate = peak slope of an electrogram
slew rate= change in voltage/ change in time
Normal slew rate in atrium - CORRECT ANS >.3 V/s
Normal slew rate in ventricle - CORRECT ANS >.5V/s
Steroid used in electrodes - CORRECT ANS dexamethasone sodium phosphate in the silicone core(a
corticosteriod)
Steroid-Eluting Electrodes - CORRECT ANS 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 ANS 1. Can easily be repaired
2. Flexible
3. Proven performance history
4. Easy to make
Silicone Rubber lead insulation cons - CORRECT ANS 1. 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 - CORRECT ANS BAD
Polyurethane 55D - CORRECT ANS GOOD
polyurethane lead insulation pros - CORRECT ANS 1. relatively nonthrombogenic/fibrotic
2. thin walls
3. high tear friction
4. resists cutting
5. low friction coefficient
polyurethane lead insulation cons - CORRECT ANS 1. cannot be repaired
2. relatively stiff
3. hard to make
Pacemaker Syndrome Causes - CORRECT ANS 1. Loss of AV synchrony
2. Sustained retrograde conduction
3. A single ventricular rate when rate modulation is required for exercise
Approx 25% of patients only paced from the ventricle may have some level of severity related to
pacemaker syndrome
Pacemaker syndrome diagnosis - CORRECT ANS 1. Observe fluctuation in the peripheral blood pressure
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