CCDS IBHRE EXAM 2025

CCDS IBHRE EXAM 2025

Rheobase - Answer the lowest point on a strength duration curve at an infinitely long pulse
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duration
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ty Chronaxie time - Answer the pulse width at twice the rheobase value. It approximates the most
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ty efficient stimulation pulse duration
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ty Charge (formula) - Answer Charge= I(current) x T(time)
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ty Furman's formula - Answer Energy(microjoules)= I(current)xV(voltage)xT(pulse width)
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ty Ohms law formula - Answer Voltage(electromotive force)= I(current/flow of electrons) x
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ty R(resistance to current flow in ohms) ty ty ty ty ty




ty Functional Refractory Period - Answer the coupling interval which first results in a measurable
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ty degree of delay in impulse conduction
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ty Effective Refractory Period - Answer the longest coupling interval to be associated with block
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Devices with NO interaction with pacers - Answer 1. microwave oven, 2. CT scan/Ultrasound 3. X-
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rays (diagnostic)
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ty Devices that cause transient or 1 beat inhibition - Answer 1. EAS 2. Cellphones 3. Arc Welding 4.
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ty airport metal detector 5. TENS 6. Electric appliances such as electric blanket & power tools
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ty Devices that may damage the pacemaker - Answer 1. MRI 2. Defibrillator 3. Cardioversion 4.
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ty Cautery/RF Ablation 5. Radiation Therapy ty ty ty ty

,ty Resistance in Series - Answer Series means the beginning of one resistance is connected to
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ty another



Sum the resistances: R1+R2= total resistance. EX: A LEAD FRACTURE (fractures INCREASE
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impedance)
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ty Resistance in Parallel - Answer Parallel means all the resistances are connected to the same point.
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(R1xR2)/(R1+R2)= total resistance ty ty




EX: LEAD INSULATION DEFECTS (insulation defects DECREASE impedance)
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ty Permanent pacemakers are constant voltage or constant current? - Answer ALL permanent
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ty pacemakers are constant voltage devices. ty ty ty ty




SOME temp pacemakers are constant voltage, most are constant current.
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ty LOAD - Answer Load refers to impedance (or resistance) applied to a circuit.
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A system with a SMALL load (low impedance) applied to the circuit is said to be a constant current
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device
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A system with LARGE load is said to be a constant voltage device
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ty Guidelines for Permanent Pacing - Answer 1. Patient is symptomatic
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2. The heart rate is less than 40 bpm
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,3. Asystole of greater than 3 seconds is documented
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NOTE: Pt may be asymptomatic with 2 or 3
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ty Slew Rate - Answer Slew rate = peak slope of an electrogram
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slew rate= change in voltage/ change in time
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ty Normal slew rate in atrium - Answer >.3 V/s
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ty Normal slew rate in ventricle - Answer >.5V/s
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ty Steroid used in electrodes - Answer dexamethasone sodium phosphate in the silicone core(a
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ty corticosteriod)



Steroid-Eluting Electrodes - Answer 1. The acute threshold is relatively flat compared to non-
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steroid electrodes ty




2. The initial capture threshold is similar to non-steroid leads
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ty Silicone Rubber lead insulation Pros - Answer 1. Can easily be repaired
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2. Flexible
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3. Proven performance history
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4. Easy to make
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ty Silicone Rubber lead insulation cons - Answer 1. high friction coefficient
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2. Absorbs lipids
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3. More thrombogenic and fibrotic
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, 4. Cuts easily
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5. Tears easily if suture tied too tightly
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6. Large diameter
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ty Polyurethane 80A - Answer BAD ty ty ty ty




ty Polyurethane 55D - Answer GOOD ty ty ty ty




ty polyurethane lead insulation pros - Answer 1. relatively nonthrombogenic/fibrotic
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2. thin walls
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3. high tear friction
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4. resists cutting
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5. low friction coefficient
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ty polyurethane lead insulation cons - Answer 1. cannot be repaired ty ty ty ty ty ty ty ty ty ty




2. relatively stiff
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3. hard to make
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ty Pacemaker Syndrome Causes - Answer 1. Loss of AV synchrony
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2. Sustained retrograde conduction
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3. A single ventricular rate when rate modulation is required for exercise
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Approx 25% of patients only paced from the ventricle may have some level of severity related to
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pacemaker syndrome
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ty Pacemaker syndrome diagnosis - Answer 1. Observe fluctuation in the peripheral blood pressure
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