CCDS IBHRE Questions with solutions
100% solved
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(cur...
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
Effective Refractory Period the longest coupling interval to be associated with block
, CCDS IBHRE Questions with solutions
100% solved
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.
(R1xR2)/(R1+R2)= total resistance
, CCDS IBHRE Questions with solutions
100% solved
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
, CCDS IBHRE Questions with solutions
100% solved
NOTE: Pt may be asymptomatic with 2 or 3
Slew Rate Slew rate = peak slope of an electrogram
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
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