Cardiac Rhythm Management Devices Flashcards
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Read the first 7 Cardiac Rhythm Management Devices flashcards as text
A CRT device shows less than 98% biventricular pacing on follow-up. What is the most appropriate first intervention?
Answer: Optimize AV delay and manage causes of native conduction (e.g., AF)
Maximizing biventricular pacing percentage—by programming AV delay shorter than intrinsic PR and treating AF that competes with pacing—is the first step before hardware revision.
The subcutaneous ICD (S-ICD) is contraindicated in patients who require what function?
Answer: Antitachycardia pacing or bradycardia pacing support
Because the S-ICD has no transvenous leads, it cannot provide antitachycardia pacing or chronic bradycardia pacing, limiting its use to patients with no pacing indication.
Magnet application to a permanent pacemaker in a non-dependent patient typically results in which response?
Answer: Asynchronous pacing at a fixed magnet rate
Magnet application causes most pacemakers to switch to asynchronous (AOO, VOO, or DOO) pacing at a manufacturer-specific magnet rate, bypassing sensing functions.
Which electrogram (EGM) characteristic best distinguishes supraventricular tachycardia (SVT) from VT in a dual-chamber ICD?
Answer: Atrial rate equal to or faster than ventricular rate with 1:1 AV relationship at onset
When the atrial rate meets or exceeds the ventricular rate with a 1:1 relationship, SVT is favored; VT typically shows VA dissociation or slower atrial rate than ventricular rate.
What is the primary purpose of the post-ventricular atrial refractory period (PVARP) in a dual-chamber pacemaker?
Answer: To prevent sensing of far-field R-waves on the atrial channel
PVARP prevents the atrial channel from sensing the ventricular event or its far-field signal, thereby avoiding pacemaker-mediated tachycardia and inappropriate tracking.
A patient with a transvenous ICD develops recurrent inappropriate shocks due to atrial fibrillation with rapid ventricular response. Which programming change is most appropriate?
Answer: Increase the VT/VF detection interval (number of intervals to detect)
Increasing the number of intervals required to confirm tachycardia (NID) reduces inappropriate therapy by allowing time for spontaneous AF rate slowing or discrimination algorithms to operate.
Impedance trending for an ICD lead shows a sudden rise from 500 Ω to >2000 Ω. This most likely indicates:
Answer: Lead fracture or insulation breach near the connector
A sudden, marked increase in impedance typically signals a lead fracture or conductor discontinuity, which can also cause oversensing and inappropriate shocks.