IMPLANTABLE CARDIOVERTER-DEFIBRILLATOR

INTRODUCTION


                                   

                                                                                      An implantable cardioverter -defibrillator(ICD) or automated implanted cardioverter - defibrillator(AICD) is a device implantable inside the body ,able to perform cardioversion,defibrillation,and pacing of heart.The device is therefore capable of correcting most life -threatening cardiac arrhythmias.The ICD is the first -line treatment and prophylactic therapy for patients at risk for sudden cardiac death due to ventricular tachycardia.

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

PHENOMENON

                             

The process of implantation of an ICD system is similar to implantation of a pacemaker .In fact ,ICDs are composed of an ICD generator and of wires. The first component or generator ,contains a computer chip or circuitry with RAM (memory),programmable software,a capacitor and a battery;this is implanted typically under the skin in the left upper chest.

The second part of the system is an electrode wire or wires that,similar to pacemakers ,are connected to the pacemakers,are connected to the generators and passed through a vein to the right chambers of the heart.The lead usually loadges in the apex of septum of the right ventricle.

SIMILARITIES BETWEEN ICDs &PACEMAKERS

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 left ventricle).

DIFFERENCE BETWEEN ICDs & PACEMAKERS

The difference between ICDs & pacemakers is that pacemakers are also available as temporary unit and are generally designed to correct slow heart rates ,i.e bradycardia,while ICDs are often permanent safegaurds against sudden life -threatening arrhythmias.

INDICATIONS

Implantation of ICDs is meant to prevent sudden cardiac death and is indicated under various conditions.Two broad but distinct categories are primary and secondary prevention

.

Primary prevention refers to the patients who have not suffered a life-threatening arrhythmia episodes.

Secondary prevention has the strongest evidence for benifits and it refers to survivors of cardiac arrest secondary to ventricular fibrillation or hemodynamically unstable sustained ventricular tachycardia after reversible causes are excluded.

LIVING WITH AN ICD

                                    

People who have an implanted cardioverter defibrillator can live full lives. Usually the ICD may not improve the quality of life of the patient, although 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, outlined below:

PHYSICAL ACTIVITIES  Almost all forms of physical activities can be performed by patients with an ICD. 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.

ELECTRO-MAGNETIC EQUIPMENT  Equipment using large magnets of generating magnatic fields, or any similar environment, must be avoided by patients with an ICD. As with othe 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 crdioverter defibrillators have demonstrated clear life-saving benefits, but concerns about patient acceptance and psychological adjustment to the ICD have been the focus of much research.

Researchers, including those from the field of cardiac psychology, have concluded that the quality of life (QoL) of ICD patients is at least equal to, or better than, that of those taking anti-arrhythmic medications. The largest study of examined 2,521 patients with stable heart failure in the SCD-HeFT trial. Results indicated that there were no differences between ICD-treated and medication-treated groups at 30 months in patient-reported QoL.