Indications for ICD(Implantable Cardioverter- defibrillator)

Indications for ICD

ICD stands for Implantable Cardioverter- defibrillator. It is a particular device used to treat dysrhythmias and ventricular tachyarrhythmias. Implantable Cardioverter- defibrillator is used for the treatment of patients who are at higher risk for sudden cardiac death. It gives electrical shocks and creates cardiac contraction. All modern Implantable Cardioverter- defibrillator also function as pacemakers. 

Anatomy and Physiology of ICD

To overcome the risk of sudden cardiac attacks, the following subsequent trials are confirmed:

  • Antiarrhythmics versus Implantable Defibrillators (AVID)
  • Cardiac Arrest Study Hamburg (CASH)
  • The Canadian Implantable Defibrillators Study (CIDS)
  • Implantable Cardioverter-defibrillators or Implantable Cardioverter- defibrillator

Myocardial Infarction is caused in patients with severe heart attacks (NYHA), typically one, two, and three Ventricular tachyarrhythmias. 

The Implantable Cardioverter- defibrillator is used for better survival despite beta-blockage, surgical revascularization, or introduction (VT or VF). The patients with non-ischemic cardiomyopathies and coronary disease have no difference because both gained the same benefit. The prevention trials for this community include:

  • The famous multicentre automatic defibrillator trial for the comparison of conventional therapy.
  • The comparison occurs between guided and EP-guided therapy for unsustained multicentre tachycardia.

In the study of non-ischemic patients, the implantation of defibrillators prophylactic dilated trial occurs to stop a sudden cardiac attack, which is high risk in patients. The patients have different abnormalities such as heart attacks, syndrome defects, and dysplasia.

Indications of ICD

The different cardiology hospitals suggest a review of Implantable Cardioverter- defibrillator indications. The recommendations offered by experts are as follows:

Recommendations (class 1)

  • Patients with the left side of heart dysfunction caused by myocardial Infarction (less than forty days) receive chronic therapy that increases life chances for more than one year.
  • The unstable hemodynamically sustained VT occurs due to LV dysfunction.
  • The non-ischemic patients with LV dysfunction sustained VT and VF.
  • Heart Defects, Syncope, and VT occur.
  • Myocardial Infarction occurs in patients with monomorphic VT.
  • Pacemaker indication occurs in CRT patients with class one.
  • CRTD is suggested for the patient having sinus rhythm.
  • LQTS is suggested for patients with cardiac problems.
  • Sustained VF and VT are suggested in hypertrophic cardiology.
  • Life chance is greater than one year in NYHA type two and three with chronic medical therapy.
  • Patient with ventricular heart failure is suggested Implantable Cardioverter- defibrillator, which causes hemodynamic instability.

Class 2a recommendations:

  • 40 days life chances increase by NYHA medical therapy in patients.
  • One-year life expectancy increases in patients with the acute phase of myocarditis on medical therapy.
  • One-year life chances increase in patients who are not in the acute phase of arrhythmias.
  • Syncope occurs due to ECG. 
  • CRTD should examine the atrial fibration to decrease the risk of HF inpatients.

Class two Indications: 

  • CRT is suggested to reduce the risk of HF in atrial fibrillation patients. It requires pacing because the rate is less than 60 bpm during rest and less than 90 bpm during exercising.

Class three indications:

During severe myocarditis, the insertion of ICD should not be recommended:

Contraindications of ICD

Following are the contraindications:

  • The patients with less than a one-year life expectancy rate even after Implantable Cardioverter- defibrillator implantation are not suggested ICD again.
  • Implantable Cardioverter- defibrillator implantation is not recommended in VT and VF patients.
  • Implantable Cardioverter- defibrillator implantation is not recommended in psychiatric illnesses that occur by some other device implantation.
  • Implantable Cardioverter- defibrillator implantation is not recommended in congestive heart failure patients who do not have cardiac implantation.
  • Implantation of Implantable Cardioverter- defibrillator is not recommended in patients who have heart defects and ventricular tachyarrhythmias such as trauma and electrolyte imbalance caused by drugs. 


Following are the Implantable Cardioverter- defibrillator components: 

  • The ICD generators: 

The ICD generators are used for sensing, coordination, pacing, and defibrillation. It consists of electronic capacitors and a battery. 

  • The Battery: Every ICD consists of a battery. The battery’s lifespan depends on how much defibrillating and pacing the device is. The duration of an ICD battery is about four to seven years. 
  • The Circuit: The ICD circuit decides how and when both bradycardia pacing and anti-tachycardia therapies are conveyed. A large variety of programming options is facilitated by circuitry to function appropriately for each individual. A critical electrical element allowing for defibrillation is the ICD capacitor which stores the energy and releases it in a path across the heart.
  1. The ICD header and Can:

ICD generator communicates with LV electrodes and Defibrillators atrial through the heart. The header connects lead with ICD, and a hole exists in the title for the ventricular defibrillator’s lead. 

  • Ventricular ICD leads:

A ventricular defibrillator’s lead is made up of many metal wires. These wires are externally immured in polyurethane insulation or silicone. ICD lead and Pacemaker lead have the same functions. Mainly, the transmission of electrical pacing signals between the heart and generator also gives another pathway to participate in the delivery of shocks. This pathway is commonly called a lead coil. All elements of lead are connected to the ICD header by pin. All ventricular defibrillator lead has two or three pins connected to the ICD. One pin is used for sensing and pacing and the other for defibrillating. The ICD lead is significantly a bipolar lead.


  • https://www.ncbi.nlm.nih.gov/books/NBK459196/
  • https://www.textbookofcardiology.org/wiki/ICD_indications
  • https://dx.doi.org/10.1093/europace/eul108
  • https://dx.doi.org/10.1093/eurjhf/hfs105
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