CCDS IBHRE (Guaranteed To Pass Concepts)
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 DO NOT increase the pacing rate
Fallback ✔ Ans - 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 ✔ Ans - 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 ✔ Ans - 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
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 DO NOT increase the pacing rate
Fallback ✔ Ans - 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 ✔ Ans - 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 ✔ Ans - 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
