U5

Question 1

What is the relationship between voltage, current, and resistance?

Answer 1

Voltage, current, and resistance are related by Ohm’s Law: V = I * R.

Changes in any of these factors can significantly impact pacemaker function.

Question 2

How does a pacemaker sense intrinsic beats?

Answer 2

It uses an intracardiac signal to recognize intrinsic beats from the chamber where the pacemaker lead is positioned.

Question 3

What is the purpose of a pacemaker system?

Answer 3

To provide rate and rhythm to overcome bradyarrhythmia symptoms and meet the metabolic needs of the patient.

Question 4

What is capture in the context of pacing?

Answer 4

Capture refers to the depolarization of the myocardium by the pacemaker output.

Question 5

Define capture threshold.

Answer 5

The minimum electrical stimulus needed to consistently depolarize/capture the myocardium.

Question 6

What is the significance of pulse width in pacing?

Answer 6

Pulse width must be long enough for depolarization to propagate, affecting the success of capture.

Question 7

How does pulse amplitude affect myocardial capture?

Answer 7

Higher pulse amplitude increases the likelihood of myocardial depolarization.

Question 8

Fill in the blank: The _______ is the lowest amplitude with consistent capture at a given pulse width.

Answer 8

capture threshold

Question 9

What factors influence pacemaker longevity?

Answer 9

• Rate of pacing
• Percentage of time pacing
• Battery capacity
• Circuit efficiency
• Lead impedance

Question 10

What happens to pacemaker battery life if pulse width and amplitude are increased?

Answer 10

Battery life decreases due to an increase in total energy delivered.

Question 11

What is the typical range for normal lead impedance values?

Answer 11

300 – 1000 ohms.

Question 12

True or False: Sensing of intrinsic beats occurs in all pacemaker modes.

Answer 12

True

Question 13

What is the role of the strength-duration curve in pacing?

Answer 13

It illustrates the relationship between pulse amplitude and pulse width required for capture.

Question 14

What is the effect of lead integrity on sensing and capture?

Answer 14

Lead integrity affects stimulation threshold, reliability of capture, and pacemaker longevity.

Question 15

What is the importance of programming pulse amplitude to ≤ 2.5 V?

Answer 15

It maintains an adequate safety margin while ensuring effective pacing.

Question 16

What effect do steroid-eluting leads have on capture thresholds?

Answer 16

They reduce inflammation and maintain low chronic capture thresholds.

Question 17

Fill in the blank: A measured lead impedance of 750 ohms is indicative of _______.

Answer 17

Normal (intact) lead

Question 18

What occurs if there is an insulation break in the lead?

Answer 18

It results in low lead impedance values, potential loss of capture, and rapid battery depletion.

Question 19

What is the primary goal of programming pacemaker output?

Answer 19

To ensure patient safety and appropriate device performance.

Question 20

What does a high lead impedance condition indicate?

Answer 20

It can reduce battery current drain and increase pacemaker battery longevity.

Question 21

Describe the three-phase maturation process of a pacemaker lead.

Answer 21

• Acute phase: local inflammatory response increases capture threshold
• Peak phase: threshold peaks 1-3 weeks post-implant
• Chronic phase: threshold stabilizes lower than peak but higher than implant

Question 22

What is the clinical consequence of a fractured lead conductor?

Answer 22

Increased impedance may lead to loss of capture due to insufficient current flow.

Question 23

What is the relationship between programmed sensitivity and EGM amplitude?

Answer 23

If EGM amplitude is higher than programmed sensitivity, the signal will be sensed.

Question 24

Fill in the blank: A pacemaker’s sensitivity is the minimum size of signal it will _______.

Answer 24

sense

Question 25

What can electromagnetic interference affect in pacemaker function?

Answer 25

It can interfere with the pacemaker's ability to sense intrinsic beats.

Question 26

What does the height of the fence in the Fence Analogy represent?

Answer 26

The programmed sensitivity value ## Footnote The analogy illustrates how the programmed sensitivity determines whether a signal is detected.

Question 27

What occurs if the programmed sensitivity is set to a value higher than the EGM amplitude?

Answer 27

Undersensing ## Footnote This results in the pacemaker not sensing intrinsic signals, leading to inappropriate output.

Question 28

What happens when the programmed sensitivity value is set lower?

Answer 28

Increased sensitivity to signals ## Footnote This can lead to inappropriate detection of additional signals.

Question 29

What is oversensing?

Answer 29

Sensing inappropriate signals due to low programmed sensitivity ## Footnote This can include T-waves, electromagnetic interference, and myopotentials.

Question 30

True or False: Programming a higher sensitivity value makes the pacemaker less sensitive.

Answer 30

False ## Footnote A higher sensitivity value increases the pacemaker's sensitivity to signals.

Question 31

What is the guideline for programming the sensitivity of a pacemaker?

Answer 31

Program sensitivity value approximately ½ of measured EGM size ## Footnote This helps ensure that depolarization is sensed while avoiding inappropriate signals.

Question 32

What factors affect sensing accuracy in pacemakers?

Answer 32

* Electrophysiological properties of myocardium * Electrode placement within heart * Characteristics of electrode * Lead polarity * Sensing amplifier of pacemaker * EMI (electromagnetic interference) * Pacemaker circuit integrity ## Footnote Each factor can influence how well the pacemaker senses intrinsic cardiac signals.

Question 33

What does accurate sensing ensure for a pacemaker?

Answer 33

* Knows if it needs to pace * Delivers pacing at the right time * Provides accurate diagnostic data ## Footnote Ensuring proper sensing is critical for effective pacemaker function.

Question 34

What is the effect of lead conductor coil integrity on sensing?

Answer 34

Can cause undersensing or oversensing ## Footnote Undersensing occurs when signals cannot reach the pacemaker, while oversensing can happen when broken conductors create false signals.

Question 35

What should you do if a pacemaker is oversensing?

Answer 35

Decrease the sensitivity by programming a higher sensitivity setting ## Footnote This helps prevent the pacemaker from detecting inappropriate signals.

Question 36

What can lead insulation integrity issues cause?

Answer 36

Undersensing or oversensing due to conductor contact issues ## Footnote This may lead to incorrect interpretation of signals by the pacemaker.

Question 37

What is undersensing?

Answer 37

Occurs when intrinsic signals cannot be sensed by the pacemaker ## Footnote This may happen due to wire or conductor fractures.

Question 38

Fill in the blank: The pacemaker cannot discriminate signals based on _______.

Answer 38

shape/morphology or signal origin ## Footnote This limitation affects how signals are processed by the device.