Implantable cardioverter-defibrillator

This article needs additional citations for verification. Please help improve this article by adding citations to reliable sources. Unsourced material may be challenged and removed. Find sources: "Implantable cardioverter-defibrillator" – news · newspapers · books · scholar · JSTOR (July 2010) (Learn how and when to remove this template message)

Implantable cardioverter-defibrillator
Guidant Corporation ICD device
ICD-10-PCS	Z95.810
ICD-9	37.94-37.97
MeSH	D017147
MedlinePlus	007370
eMedicine	1971119
[edit on Wikidata ]

An implantable cardioverter-defibrillator (ICD) or automated implantable cardioverter defibrillator (AICD) is a device

"AICD" was trademarked by the Boston Scientific corporation, so the more generic "ICD" is preferred terminology.

On average ICD batteries last about six to ten years.^[2] Advances in technology, such as batteries with more capacity or rechargeable batteries,^[3] may allow batteries to last over ten years. The leads (electrical cable wires connecting the device to the heart) have much longer average longevity, but can malfunction in various ways, specifically insulation failure or fracture of the conductor; thus, ICDs and leads generally require replacement after every 5 to 10 years.^[4][5]

The process of implantation of an ICD system is similar to implantation of a

Just like pacemakers, ICDs can have a single wire or lead in the heart (in the right ventricle, single chamber ICD), two leads (in the right atrium and right ventricle, dual chamber ICD) or three leads (biventricular ICD, one in the right atrium, one in the right ventricle and one on the outer wall of the

, while ICDs are often permanent safeguards against sudden life-threatening arrhythmias.

Recent developments include the

Living with an ICD

People who have an implanted cardioverter-defibrillator can live full lives. Patients overall have either a sustained or improved quality of life after ICD implantation when compared to before ICD implantation.[9] It may provide a strong degree of reassurance. As with a pacemaker, however, living with an ICD does impose some restrictions on the person's lifestyle.

Physical activities

Almost all forms of physical activities can be performed by patients with an ICD with moderation.^[10] All forms of sports that do not pose a risk of damaging the ICD or because of the underlying cardiomyopathy can be undertaken by the patient. Special care should be taken not to put excessive strain on the shoulder, arm and torso area where the ICD is implanted. Doing so may damage the ICD or the leads going from the ICD generator to the patient's heart. Particularly to be avoided are exercises that cause the clavicle to be pulled down towards the ribs, such as lifting weights with the arm, on the ICD site, while standing.

Driving

ICD patients are prohibited from professional or commercial driving per the Cardiovascular Advisory Panel Guidelines for the Medical Examination of Commercial Motor Vehicle Drivers.^[11] A driving abstinence for private drivers is recommended following ICD implantation, but the timeframe is variable depending on the country (between 3 and 6 months for secondary prevention and 1–4 weeks for primary prevention). Following an appropriate ICD-therapy, a driving ban is recommended for 3–6 months depending on the country. After inappropriate ICD-therapy delivered for non-ventricular arrhythmias or due to the device malfunction, driving restrictions usually apply until the cause of the inappropriate therapy has been eliminated.^[12]

Electro-magnetic equipment

Equipment using large magnets or generating magnetic fields, or any similar environment, must be avoided by patients with an ICD. As with other metallic objects, an ICD is normally a contraindication to the use of magnetic resonance imaging (MRI). However, several ICD manufacturers have recently introduced MR-Conditional ICDs, which allow the use of MRI under specified safe operating conditions.

Quality of life

Implantable cardioverter defibrillators have demonstrated clear life-saving benefits, while concerns about patient acceptance and

Anxiety is a common psychological side effect, with approximately 13–38% of ICD patients reporting clinically significant anxiety.^[18][19] The primary etiological factors contributing to anxiety in ICD patients have not been determined, however. Depressive symptoms are also common, but the incidence of these problems has been shown to be similar to those observed in other cardiac patient groups, with approximately 24–41% of patients with ICDs experiencing depressive symptoms.^[19] Problems in psychosocial adjustment to ICDs, including the experience of anxiety, among spouses or other romantic partners are also prevalent.^[20] This phenomenon may be related, at least in part, to shared shock anxiety and avoidance of physical and sexual contact.^[21]

Follow Up

Patients are generally required to follow up with their electrophysiologist cardiologist at regular intervals, mostly 3 to 6 months. At this time, many device manufactures have some form of home monitoring to allow for device data to be sent in electronically to the physician.^[22] Recent advances include app integration for home interrogation and remote care has been correlated with some mortality benefit. ^[23]

Indications

Implantation of ICD is meant to prevent

Similarly, ICD use in primary prevention is to prevent cardiac death in patients who are at risk for sustained ventricular tachycardia or ventricular fibrillation. This population accounts for the bulk of all ICD implants. There are a multitude of guideline indications for ICD use in primary preventions with varying degree of supporting evidence. Periodically, both the American College of Cardiology (ACC)/American Heart Association (AHA) and European Society of Cardiology provide an update to this guideline. Some of the Class I indications are as follows:[24]

• With
  Left Ventricular Ejection Fraction
  (LVEF) ≤ 35% due to prior Myocardial Infarction (MI) who are at least 40 days post-MI and are in NYHA Functional Class II or III
• With Left Ventricular (LV) dysfunction due to prior MI who are at least 40 days post-MI, have an LVEF ≤ 30%, and are in NYHA Functional Class I
• With nonischemic Dilated cardiomyopathy (DCM) who have an LVEF ≤ 35% and who are in NYHA Functional Class II or III
• With nonsustained VT due to prior MI, LVEF < 40%, and inducible VF or sustained VT at electrophysiological study
• With structural heart disease and spontaneous sustained VT, whether hemodynamically stable or unstable
• With syncope of undetermined origin with clinically relevant, hemodynamically significant sustained VT or VF induced at electrophysiological study

Clinical trials

A number of clinical trials have demonstrated the superiority of the ICD over AAD (antiarrhythmic drugs) in the prevention of death from malignant arrhythmias. The SCD-HeFT trial (published in 2005)

patients that were implanted with an ICD had an all-cause death risk 23% lower than placebo and an absolute decrease in mortality of 7.2 percentage points after five years in the overall population.¹ Reporting in 1999, the Antiarrhythmics Versus Implantable Defibrillators (AVID) trial consisted of 1,016 patients, and deaths in those treated with AAD were more frequent (n = 122) compared with deaths in the ICD groups (n = 80, p < 0.001).^[26] In 2002 the MADITII trial showed benefit of ICD treatment in patients after myocardial infarction with reduced left ventricular function (EF<30).

Initially ICDs were implanted via thoracotomy with defibrillator patches applied to the

. The device was attached via subcutaneous and transvenous leads to the device contained in a subcutaneous abdominal wall pocket. The device itself acts as an electrode. Most ICDs nowadays are implanted transvenously with the devices placed in the left pectoral region similar to pacemakers. Intravascular spring or coil electrodes are used to defibrillate. The devices have become smaller and less invasive as the technology advances. Current ICDs weigh only 70 grams and are about 12.9 mm thick.

A recent study by Birnie and colleagues at the University of Ottawa Heart Institute has demonstrated that ICDs are underused in both the United States and Canada.[27] An accompanying editorial by Dr. Chris Simpson of Queen's University explores some of the economic, geographic, social and political reasons for this.^[28]

History

The development of the ICD was pioneered at Sinai Hospital in Baltimore by a team including Michel Mirowski, Morton Mower, Alois Langer, William Staewen, and Joseph "Jack" Lattuca. Mirowski teamed up with Mower and Staewen and together they commenced their research in 1969 but it was 11 years before they treated their first patient.^[29][30]

The work was commenced against much skepticism even by leading experts in the field of arrhythmias and sudden death. There was doubt that their ideas would ever become a clinical reality. In 1972

The problems to be overcome were the design of a system which would allow detection of ventricular fibrillation or ventricular tachycardia. Despite the lack of financial backing and grants, they persisted and the first device was implanted in February 1980 at Johns Hopkins Hospital by Dr. Levi Watkins Jr.^[29][32]

The first devices required the chest to be cut open and a mesh electrode sewn onto the heart; the pulse generator was placed in the abdomen.^[29]

Working mechanism

ICDs constantly monitor the rate and rhythm of the heart and can deliver therapies, by way of an electrical shock, when the heart rate exceeds a preset number. More modern devices have software designed to attempt a discrimination between ventricular fibrillation and ventricular tachycardia (VT), and may try to pace the heart faster than its intrinsic rate in the case of VT, to try to break the tachycardia before it progresses to ventricular fibrillation. This is known as overdrive pacing, or anti-tachycardia pacing (ATP). ATP is only effective if the underlying rhythm is ventricular tachycardia, and is never effective if the rhythm is ventricular fibrillation.

Many modern ICDs use a combination of various methods to determine if a fast rhythm is normal, supraventricular tachycardia, ventricular tachycardia, or ventricular fibrillation.

Rate discrimination evaluates the rate of the lower chambers of the heart (the ventricles) and compares it to the rate in the upper chambers of the heart (the atria). If the rate in the atria is faster than or equal to the rate in the ventricles, then the rhythm is most likely not ventricular in origin, and is usually more benign. If this is the case, the ICD does not provide any therapy, or withholds it for a programmable length of time.

Rhythm discrimination will see how regular a ventricular tachycardia is. Generally, ventricular tachycardia is regular. If the rhythm is irregular, it is usually due to conduction of an irregular rhythm that originates in the atria, such as atrial fibrillation. In the picture, an example of torsades de pointes can be seen; this represents a form of irregular ventricular tachycardia. In this case, the ICD will rely on rate, not regularity, to make the correct diagnosis.

Morphology discrimination checks the morphology of every ventricular beat and compares it to what the ICD knows is the morphology of normally conducted ventricular impulse for the patient. This normal ventricular impulse is often an average of a multiple of normal beats of the patient acquired in the recent past and known as a template.

The integration of these various parameters is very complex, and clinically, the occurrence of inappropriate therapy is still occasionally seen and a challenge for future software advancements.

cardiac rhythm

.

See also

Notes

References

• Bardy GH, Lee KL, Mark DB, et al. for the Sudden Cardiac Death in Heart Failure Trial (SCD-HeFT) Investigators. Amiodarone or an implantable cardioverter-defibrillator for congestive heart failure. N Engl J Med 2005; 352:225–237
• Stevenson W, Chaitman B, Ellenbogen K, Epstein A, Gross W, Hayes D, Strickberger S, Sweeney M (2004). "Clinical assessment and management of patients with implanted cardioverter-defibrillators presenting to nonelectrophysiologists". Circulation. 110 (25): 3866–69.
  PMID 15611390.Full text
• Kumar and Clarke. Internal Medicine. 2009.
• Sears S, Matchett M, Conti J. "Effective management of ICD patient psychosocial issues and patient critical events. J Cardiovasc Electrophysiol 2009; 20(11):1297–304.
• Sears SF Jr.; Todaro JF; Lewis TS; Sotile W; Conti JB. (1999). "Examining the psychosocial impact of implantable cardioverter defibrillators: a literature review". Clin Cardiol. 22 (7): 481–89.
  PMID 10410293
  .
• Burns JL, Serber ER, Keim S, Sears SF (2005). "Measuring patient acceptance of implantable cardiac device therapy: initial psychometric investigation of the Florida Patient Acceptance Survey". J Cardiovasc Electrophysiol. 16 (4): 384–90.
  S2CID 36667780
  .
• Mark DB, Anstrom KJ, Sun JL, Clapp-Channing NE, Tsiatis AA, Davidson-Ray L, Lee KL, Bardy GH (2008). "Quality of life with defibrillator therapy or amiodarone in heart failure". N Engl J Med. 359 (10): 999–1008.
  PMID 18768943
  .
• Bilge AK, Ozben B, Demircan S, et al. (Jun 2006). "Depression and anxiety status of patients with implantable cardioverter defibrillator and precipitating factors". Pacing Clin Electrophysiol. 29 (6): 619–26.
  S2CID 11982210
  .

External links

• A Defibrillator in Action Archived 2016-04-03 at the Wayback Machine
• Information on ICDs/S-ICDs from the charity Arrhythmia Alliance
• East Carolina Heart Institute at ECU, Cardiac Psychology Lab, Focus on ICD
• Samuel F. Sears, Jr., Ph.D., East Carolina University, Cardiac Psychology, ICD QoL Specialist
• Video, Coping with an ICD