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