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Evidence summaries

Implantable Cardiac Defibrillators

Implantable cardiac defibrillators are effective in reducing mortality in both secondary and primary prevention as compared to pharmacotherapy. Cost per life-year gained is high which implies careful patient selection. Level of evidence: "A"

Several technology assessment reports 1 2 3 4 on implantable cardioverter defibrillators (ICDs) are abstracted in the Health Technology Assessment Database.

Three prospective, randomized trials patients have compared ICD with pharmacotherapy in secondary prevention in nearly 2,000 patients who have survived cardiac arrest, ventricular tachycardia or syncope, ventricular tachycardia with seriously affected circulation and concomitant reduced heart function. The largest study found a one-year mortality of 11 percent in the ICD group as compared to 18 percent in the control group. Combined results from the three studies show a significant reduction in annual mortality, from 12.3% to 8.8%. Number of patients needed to treat (NNT) for one year to avoid one death is 29.

Four randomized trials of ICD in primary prevention, including some 3,000 patients, have been identified. The largest trial included 1,232 patients with pronounced impaired left ventricle function following myocardial infarction. After an average time of 20 months of follow-up, the mortality rate was 14.2 percent in the ICD group compared to 19.8 percent in the control group.

The risks associated with ICD treatment include perioperative death, infections, thromboembolytic complications, cardiopulmonary perforation, and misinterpretation of heart rate by the pulse generator, resulting in inadequate shocks. With modern implantation techniques the perioperative mortality rate and the risk of later mechanical complications are low.

The cost per life-year gained by ICD treatment compared to pharmacotherapy in secondary prevention varies substantially depending on patients risk profiles; rough estimates are in the range of 75,000 to 200,000 euros.

A systematic review 1 including 34 studies (3 RCTs) for efficacy review and about 100 studies for adverse effects was abstracted in DARE 2. All patients had had ventricular fibrillation, usually with underlying ischaemic heart disease. Peri-operative mortality is less than 1%. Failure to insert the device is less than 10%. Lead dislodgement occurs in up to 10% of recipients. Infection occurs in less than 4% of recipients. Thromboembolic events occurred in 15.7% of patients when thrombosis was specifically looked for, but only in 3.1% of patients when clinically significant emboli were considered. Inappropriate shocks were received by 10 to 30% of the patients. The device reduces the incidence of sudden cardiac death to less than 1% annually. Comparative studies using a control group found no significant difference in survival after 1 year. Four randomised studies found a favourable survival advantage for patients treated with the device compared to drugs. Two studies found that quality of life declined during the first 6 months after implantation but was restored by the end of follow-up. Several authors concluded that ICDs fall within the range of $20,000 - $40,000 cost per year of life saved.

A systematic review 5 including 8 studies with a total of 5207 subjects was abstracted in DARE. Studies of patients with NICM, resuscitated cardiac arrest, documented or symptomatic tachyarrhythmia, or depressed left ventricular function at risk of developing lethal cardiac arrhythmia, were eligible for inclusion. ICD therapy was associated with a statistically significant reduction in all-cause mortality compared with medication (RR 0.69, 95% CI 0.55, 0.87, P=0.002).

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    References

    • Aass H, Hegrenaes L, Heldal M, Ohm O J, Tande P, Myhre K I. Implantable defibrillator. Oslo: The Norwegian Centre for Health Technology Assessment (SMM). 2002. The Norwegian Centre for Health Technology Assessment (SMM). www.sintef.no/smm/ [HTA-20020556 ].
    • Swedish Council on Technology Assessment in Health Care. Implantable defibrillator - early assessment briefs (Alert). Swedish Council on Technology Assessment in Health Care (SBU). 2003. Swedish Council on Technology Assessment in Health Care (SBU). www.sbu.se [HTA-20030972 ].
    • Parkes J, Bryant J, Milne R. Implantable cardioverter defibrillators: arrhythmias. A rapid and systematic review. Health Technology Assessment Vol.4: No.26. 2000. 69. The National Coordinating Centre for Health Technology Assessment (NCCHTA) on behalf of Southampton Health Technology Assessments Centre. www.ncchta.org [HTA-20000925 ].
    • L'Agence Nationale d'Accreditation d'Evaluation en Sante. Implantable cardioverter defibrillators: update. Paris: L'Agence Nationale d'Accreditation d'Evaluation en Sante (ANAES). 2001. 4. L'Agence Nationale d'Accreditation d'Evaluation en Sante (ANAES). www.anaes.fr [HTA-20030002 ].
    • Desai AS, Fang JC, Maisel WH, Baughman KL. Implantable defibrillators for the prevention of mortality in patients with nonischemic cardiomyopathy: a meta-analysis of randomized controlled trials. JAMA 2004 Dec 15;292(23):2874-9. [PubMed] [DARE]

Primary/Secondary Keywords