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CCDS IBHRE EXAM|247 QUESTIONS AND ANSWERS|100% VERIFIED
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CCDS IBHRE EXAM|247 QUESTIONS ANDANSWERS|100% VERIFIED
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
-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
,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
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
2. Flexible
3. Proven performance history
4. Easy to make
-Silicone Rubber lead insulation cons - -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 - -BAD
-Polyurethane 55D - -GOOD
-polyurethane lead insulation pros - -1. relatively nonthrombogenic/fibrotic
2. thin walls
3. high tear friction
4. resists cutting
5. low friction coefficient
-polyurethane lead insulation cons - -1. cannot be repaired
2. relatively stiff
3. hard to make
-Pacemaker Syndrome Causes - -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 - -1. Observe fluctuation in the peripheral
blood pressure
2. Cannon "A" wave in the neck
3. History alone
-Pacemaker syndrome management - -Restore AV synchrony
in ventricular only PM -->lower the pacing rate to minimize ventricular only
pacing
DO NOT increase the pacing rate
-Fallback - -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 - -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
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