Pacemakers (Leon-ruiz)

Question 1

Responsibility of the SA Node.

Responsibility of the AV Node.

Responsibility of the Ventricular Pacemaker cells.

Answer 1

SA: maintain NSR and dictate rate changes

AV: delay signal to ventricle, protect ventricular rate, replace SAN if it stops firing

VP cells: replace SAN and AVN if they fail

Question 2

What are the conduction speeds for various cardiac conduction pathways?

Answer 2

AV node: 0.05 m/sec

Atrial + ventricular muscles: 0.5 m/sec

Internodal tracts: 1 m/sec

His bundle branches: 2 m/sec

Purkinje fibers: 4 m/sec

Question 3

In pacemakers what is AI and what is RP?

Answer 3

AI: automatic interval; interval at which, if a pacemaker does not detect a stimulus, it fires - it resets if a pacemaker senses a signal

RP: refractory period; period in which pacemakers cannot do or sense anything (prevent oversensing)

Question 4

Pacemakers have 5 settings to control. What are they and what can they be set to?

Answer 4

I: Chamber being paced - O [none], A [atrium], V [ventricle], D [dual]

II: Chamber being sensed - O [none], A [atrium], V [ventricle], D [dual]

III: Response to sensing - O [none], T [trigger], I [inhibit], D [dual]

IV: Rate modulation - O [none], R [rate modulation]

V: Multisite pacing - O [none], A [atrium], V [ventricle], D [dual]

Question 5

What are some common issues with pacemakers (source of issues)?

Answer 5

Misplacement of the pacemaker resulting in regular arrhythmias

Question 6

Recent studies suggest that cardiac resynchronization therapy is beneficial in what kind of patients?

Answer 6

n patients with reduced LVEF, heart failure symptoms, and prolonged QRS regardless of NYHA class. (2011)

Question 7

A sudden cessation of cerebral blood flow for _ to _ s and/or decrease in SBP to __ mm Hg has been shown to be sufficient to cause complete loss of consciousness.

Answer 7

6, 8

60

Question 8

Defibrillators have 4 settings. What are they and what can they be set to?

Answer 8

I : Shock chamber - O [none], A [atrium], V [ventricle], D [dual]

II: Antitachycardia pacing chamber - O [none], A [atrium], V [ventricle], D [dual]

III: Tachycardia detection - E [electrogram], H [hemodynamic]

IV: Antibradycardia pacing chamber - O [none], A [atrium], V [ventricle], D [dual]

Abbreviations

ICD-S: ICD with shock only

ICD-B: ICD with brady pacing and shock

ICD-T: ICD with tachy and brady pacing and shock

Question 9

What does the ICD detect?

Answer 9

HR

AV dissociation

Interval stability

QRS waveform

Question 10

What is rate discrimination?

Answer 10

Method used by pacemakers to discriminate between atrial and ventricular rates.

If V rate > A rate, it detects V-Tach and shocks/advises chocks

Question 11

What are the electrocautery guidelines for pts with a pacemaker?

Answer 11

1. Contact manufacturer for specific guidelines regarding electrosurgery.
2. Ensure grounding pad is as far away from pacemaker unit and wires as possible
3. Path from electrosurgical tip to grounding pad should not cross pacemaker circuit.
4. Be prepared to reset pacemaker to asynchronous mode (artifact from electrosurgery can turn off/interfere with pacemaker function)
5. Have isoproterenol ready. (nonselective B-agonist similar to epi)

Question 12

Are MRIs safe for pts with pacemakers?

Answer 12

Depends on their type of pacemakers.