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CCDS IBHRE EXAM QUESTIONS AND ANSWERS
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CCDS IBHRE EXAM QUESTIONS AND ANSWERS
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CCDS IBHRE EXAM QUESTIONS AND ANSWERSRheobase - Answers-the lowest point on a strength duration curve at an infinitely long
pulse duration
Chronaxie time - Answers-the pulse width at twice the rheobase value. It approximates
the most efficient stimulation pulse duration
Charge (formula) - Answers-Charge= I(current) x T(time)
Furman's formula - Answers-Energy(microjoules)= I(current)xV(voltage)xT(pulse width)
Ohms law formula - Answers-Voltage(electromotive force)= I(current/flow of electrons) x
R(resistance to current flow in ohms)
Functional Refractory Period - Answers-the coupling interval which first results in a
measurable degree of delay in impulse conduction
Effective Refractory Period - Answers-the longest coupling interval to be associated with
block
Devices with NO interaction with pacers - Answers-1. microwave oven, 2. CT
scan/Ultrasound 3. X-rays (diagnostic)
Devices that cause transient or 1 beat inhibition - Answers-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 - Answers-1. MRI 2. Defibrillator 3.
Cardioversion 4. Cautery/RF Ablation 5. Radiation Therapy
Resistance in Series - Answers-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 - Answers-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? - Answers-ALL
permanent pacemakers are constant voltage devices.
,SOME temp pacemakers are constant voltage, most are constant current.
LOAD - Answers-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 - Answers-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 - Answers-Slew rate = peak slope of an electrogram
slew rate= change in voltage/ change in time
Normal slew rate in atrium - Answers->.3 V/s
Normal slew rate in ventricle - Answers->.5V/s
Steroid used in electrodes - Answers-dexamethasone sodium phosphate in the silicone
core(a corticosteriod)
Steroid-Eluting Electrodes - Answers-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 - Answers-1. Can easily be repaired
2. Flexible
3. Proven performance history
4. Easy to make
Silicone Rubber lead insulation cons - Answers-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 - Answers-BAD
Polyurethane 55D - Answers-GOOD
, polyurethane lead insulation pros - Answers-1. relatively nonthrombogenic/fibrotic
2. thin walls
3. high tear friction
4. resists cutting
5. low friction coefficient
polyurethane lead insulation cons - Answers-1. cannot be repaired
2. relatively stiff
3. hard to make
Pacemaker Syndrome Causes - Answers-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 - Answers-1. Observe fluctuation in the peripheral
blood pressure
2. Cannon "A" wave in the neck
3. History alone
Pacemaker syndrome management - Answers-Restore AV synchrony
in ventricular only PM -->lower the pacing rate to minimize ventricular only pacing
DO NOT increase the pacing rate
Fallback - Answers-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
Rate smoothing - Answers-1. Eliminated large cycle to cycle variations by preventing
paced rate from changing more than a certain percentage (3%, 6%, 12%, etc) from one
V-V interval to the next
2. Eliminates large fluctuations in rate during fixed-ratio or psuedo-Wenckebach block
FOUND IN GDT devices
sensor upper rate behavior - Answers-if the sinus rate is faster than the sensor
indicated rate, P synchronous pacing occurs
if the sensor indicated rate is faster, AV pacing at the sensor indicated rate occurs
mixed scenario: when the device is sensor driven AV pacing for a few cycles and a
sinus rate sudden emerges faster than the sensor indicated rate. The sensor driven
atrial output will be inhibited, a PR interval started, and a ventricular output will occur at
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