0071643192.pdf

IMPLANTED CARDIAC DEFIBRILLATORS (ICD)

ICDs are placed in patients at high risk for sudden cardiac death from VT

and VFib. They are programmed to analyze the cardiac rhythm, perform anti-

tachycardia pacing, generate an electrical charge, and deliver an electrical

shock. All new generation ICDs have ventricular pacing abilities.

EVALUATION OF ADELIVEREDSHOCK

Patient-reported shocks may be appropriate (underlying VT or VFib), inappro-

priate, or phantom (patients think they got shocked but didn’t). Only interroga-

tion of the device or monitoring during an event can differentiate appropriate

from inappropriate shocks.

Appropriate shocks may result from associated:

■ Electrolyte abnormalities

■ Myocardial ischemia

■ Medications (proarrythmic drugs or med noncomplicance)

Inappropriate shocks may be a result of:

■ Nonsustained VT

■ SVT inappropriately sensed as VT

■ Oversensing T waves as QRS complexes

■ External interference sensed as impulses

■ Broken/displaced ventricular lead

DIAGNOSIS

■ Interrogation of the device

■ External cardiac monitoring during ICD event

■ ECG and labs to evaluate for ischemia or electrolyte abnormalities

■ CXR to evaluate leads

■ All patients with repetitive shock warrant diagnostic evaluation.

■ Stable patient with isolated shock may warrant less extensive evaluation.

TREATMENT

■ Identify and treat contributing conditions.

■ Inappropriate shocks may be prevented with magnet deactivation of the ICD.

■ Second-generation ICDs

■ Deactivate by placing ring magnet over generator for 30 seconds.

■ Reactivate by placing magnet over generator for another 30 seconds.

■ Third-generation ICDs

■ Presence of magnet deactivates ICD (removal reactivates it).

■ Reprogramming, as indicated, by cardiologist

IMPLANATEDCARDIACDEFIBRILLATORFAILURE

CAUSES

May be due to the following:

■ Component failure

■ Lead fracture/displacement

■ Battery depletion

■ Interference with pacemakers

RESUSCITATION