CCDS IBHRE Exam Questions & Answers 2023/2024
Rheobase - ANSWER-the lowest point on a strength duration curve at an infinitely long pulse duration
Chronaxie time - ANSWER-the pulse width at twice the rheobase value. It approximates the most efficient stimulation pulse duration
Charge (fo...
CCDS IBHRE Exam Questions & Answers 2023/2024
Rheobase - ANSWER-the lowest point on a strength duration curve at an infinitely long pulse duration
Chronaxie time - ANSWER-the pulse width at twice the rheobase value. It approximates the most efficient stimulation pulse duration
Charge (formula) - ANSWER-Charge= I(current) x T(time)
Furman's formula - ANSWER-Energy(microjoules)= I(current)xV(voltage)xT(pulse width)
Ohms law formula - ANSWER-Voltage(electromotive force)= I(current/flow of electrons) x R(resistance to
current flow in ohms)
Functional Refractory Period - ANSWER-the coupling interval which first results in a measurable degree of delay in impulse conduction
Effective Refractory Period - ANSWER-the longest coupling interval to be associated with block
Devices with NO interaction with pacers - ANSWER-1. microwave oven, 2. CT scan/Ultrasound 3. X-rays (diagnostic)
Devices that cause transient or 1 beat inhibition - 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 - ANSWER-1. MRI 2. Defibrillator 3. Cardioversion 4. Cautery/RF Ablation 5. Radiation Therapy Resistance in Series - 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 - 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? - ANSWER-ALL permanent pacemakers
are constant voltage devices.
SOME temp pacemakers are constant voltage, most are constant current.
LOAD - 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 - ANSWER-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 - ANSWER-Slew 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 - ANSWER-dexamethasone sodium phosphate in the silicone core(a corticosteriod)
Steroid-Eluting Electrodes - ANSWER-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 - ANSWER-1. Can easily be repaired
2. Flexible
3. Proven performance history
4. Easy to make
Silicone Rubber lead insulation cons - ANSWER-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 - ANSWER-BAD
Polyurethane 55D - ANSWER-GOOD polyurethane lead insulation pros - ANSWER-1. relatively nonthrombogenic/fibrotic 2. thin walls
3. high tear friction
4. resists cutting
5. low friction coefficient
polyurethane lead insulation cons - ANSWER-1. cannot be repaired 2. relatively stiff
3. hard to make
Pacemaker Syndrome Causes - ANSWER-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 - ANSWER-1. Observe fluctuation in the peripheral blood pressure
2. Cannon "A" wave in the neck
3. History alone
Pacemaker syndrome management - ANSWER-Restore AV synchrony
in ventricular only PM -->lower the pacing rate to minimize ventricular only pacing DO NOT increase the pacing rate
Fallback - ANSWER-1. Decouples atrial & ventricular events at the upper rate limit
2. The ventricular inhibited pacing rate then gradually decrements to a programmed lower or "fallback" rate over a programmed duration
3. When the fallback rate is reached, atrial synchrony is restored
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