Implantable Cardioverter-Defibrillators

In USA, more than 300,000 people have an ICD and more than 180,000 ICDs are implanted annually, based on CMS registry data.

Given current implant and survival rates, nearly 700,000 people in USA may have an ICD by the year 2020.

ICD implant is indicated for any-cause cardiomyopathy with EF ≤35% and without evidence of dysrhythmia; thus some pts undergo ICD implantation for “primary prevention.”

All conventional ICDs can provide pacing for bradycardia; some pts are pacing dependent.

Some ICDs also have atrial, RV, and LV pacing capability for CRT. LV leads can be transvenous in the coronary sinus or epicardial.

Newer subcutaneous ICDs use a subcutaneous electrode instead of traditional transvenous or epicardial leads. These devices are less invasive but have limited functionality; for example, they have no permanent antibradycardia pacing capability and cannot deliver antitachycardia pacing.

Premature ICD failure rates might approach 2%. For the ICD pt without evidence of pacing, determining battery function is difficult. ^∗

∗ Some ICDs allow demonstration of battery function without interrogation:

In USA, 450,000 pts/y suffer SCA; 550,000 new cases/y of CHF.

ICD therapy for SCA, VT, and VF and primary prevention is superior than medical management.

Associated diseases include cardiomyopathy, CAD, long QT syndrome, arrhythmogenic right ventricular dysplasia, Brugada syndrome, hypertrophic cardiomyopathy, and LV noncompaction. Some ICD pts also have sinus and/or AV node disease.

Robust data is lacking; however, the presence of an ICD might increase periop risk.

Inappropriate HVT can induce tachydysrhythmia, injure the myocardium releasing troponin, and is associated with increased mortality.

Incorrect interpretation of device type (i.e., confusing an ICD for a pacemaker) or events (i.e., pseudomalfunction) during the periop period might lead to pt harm.

Risk might also be increased in these pts owing to associated disease(s).

EMI on the ICD’s ventricular channel resulting in inappropriate HVT including shock(s) and/or antitachycardia pacing. For the pacing-dependent pt, EMI-induced ventricular oversensing with pacing inhibition can also result in asystole

Intraop increase in ventricular pacing owing to EMI entering a dual chamber ICD and causing atrial lead oversensing and ventricular tracking

Intraop increases in pacing rates owing to activation of the “exercise sensor,” whether due to direct mechanical stimulation (such as preparation of the chest) or pressure on the device (personnel leaning). The cause of this undesirable tachycardia might be mistaken as inadequate anesthetic depth

Failure to capture (i.e., pacing output without myocardial depolarization) due to inappropriate programmed parameters (i.e., inadequate safety margin), or abrupt increase in pacing threshold from myocardial ischemia/infarction, drug administration, or lyte shifts. Note that any or all chambers can undergo failure to capture with possible hemodynamic derangement, even without apparent outright pacing failure

Magnet ∗ placement will never change the pacing mode (i.e., produce asynchronous pacing) of an ICD and will change pacing rates only in ICDs from ELA (Sorin, Milan, Italy). Only Boston Scientific (BOS) ^§ ICDs emit ongoing tones confirming appropriate magnet placement. No ongoing confirmation of magnet placement is available in Medtronic, St Jude Medical ^§ (SJM), or Biotronik ICD. ICDs from BOS and St. Jude Medical can have their magnet switch disabled by programming. Indeed, some older ICDs from BOS (with the “GDT” or “CPI” x-ray code) can undergo permanent disabling of HVT by magnet placement

Disabling HVT during central access procedures in the thorax to prevent inappropriate shocks due to guidewire contact with the RV lead. For 6 weeks after lead implant central venous catheterization in the thorax is relatively contraindicated