Responsibility of the SA Node.
Responsibility of the AV Node.
Responsibility of the Ventricular Pacemaker cells.
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
What are the conduction speeds for various cardiac conduction pathways?
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
In pacemakers what is AI and what is RP?
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)
Pacemakers have 5 settings to control. What are they and what can they be set to?
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]
What are some common issues with pacemakers (source of issues)?
Misplacement of the pacemaker resulting in regular arrhythmias
Recent studies suggest that cardiac resynchronization therapy is beneficial in what kind of patients?
n patients with reduced LVEF, heart failure symptoms, and prolonged QRS regardless of NYHA class. (2011)
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.
Defibrillators have 4 settings. What are they and what can they be set to?
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]
ICD-S: ICD with shock only
ICD-B: ICD with brady pacing and shock
ICD-T: ICD with tachy and brady pacing and shock
What does the ICD detect?
What is rate discrimination?
Method used by pacemakers to discriminate between atrial and ventricular rates.
If V rate > A rate, it detects V-Tach and shocks/advises chocks
What are the electrocautery guidelines for pts with a pacemaker?
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)
Are MRIs safe for pts with pacemakers?
Depends on their type of pacemakers.