Authors' objectives:

This review aims to assess the effectiveness and cost-effectiveness of the prophylactic use of implantable cardioverter defibrillators (ICDs) for patients with a prior myocardial infarction (MI); left ventricular dysfunction (defined as an ejection fraction (EF) less than 30 per cent); and no history of a cardiac arrest (which is caused in most cases by a fatal ventricular arrhythmia).

Authors' results and conclusions: To date, the MADIT II trial is the only study that evaluated patients with a prior MI and EF less than 30 per cent for prophylactic ICD therapy. Therefore, all evidence for the prophylactic use of ICDs for patients who fit the MADIT II inclusion criteria is based on one trial. MADIT II revealed a significant improvement in overall survival for patients receiving an ICD compared to patients in the conventional therapy group. However : - Exclusion criteria may not have been uniformly applied to all patients in the study. - The investigators reported only a portion of what was planned for the trial. Therefore, additional results are awaited. It is unknown whether the benefit from ICD implantation was greater in certain patients who had inducible ventricular arrhythmias that were documented during the trial. The effectiveness and safety of primary prevention ICD therapy in patients with very severe chronic heart failure is unknown. The study terminated early and the average follow-up was for only 20 months. Duration of follow-up can have an impact of outcome. Trials that end early may not reveal full treatment effects. The MADIT II trial did not specify how and where patients were recruited into the studies. It is possible that patients in the study may have been highly selected. The results of MADIT II may not be generalizable to all patients. It is unknown if all patients with any previous MI and an EF less than 30 per cent should receive an ICD. It is unclear what, if any, cutoff should be established for defining a prior MI. MADIT II was the first study to implant single and dual chamber ICDs in patients with prior MI and an EF less than 30 per cent. There was no stratification for the safety of single versus dual chamber ICDs. All previous trials assessing the prophylactic use of ICDs in patients used single chamber devices only. New approaches or techniques are needed that allow screening for markers of increased risk of fatal ventricular arrhythmias in large populations, where the relative risk is low but the number of deaths due to arrhythmia is high.

Authors' recommendations: There is unsatisfactory incomplete evidence to support the effectiveness of the prophylactic use of single and dual chamber ICDs for all patients with a previous MI and an EF less than 30 per cent. To date, all evidence is limited to one trial, MADIT II. The effectiveness and cost-effectiveness of single versus dual chamber ICDs for prophylactic use should be evaluated. The benefit of screening for arrhythmia markers in patients is unclear from MADIT II.

Authors' methods: Systematic review

Project Status: Completed

URL for project: http://www.health.gov.on.ca/english/providers/program/mas/tech/techlist_ mn.html

Year Published: 2003

English language abstract: An English language summary is available

Publication Type: Not Assigned

Country: Canada

Organisation Name: Medical Advisory Secretariat

Contact Address: Medical Advisory Secretariat, 20 Dundas Street West, 10th Floor, Toronto, ON M5G 2N6 CANADA. Tel: 416-314-1092l; Fax: 416-325-2364;

Contact Name: MASinfo.moh@ontario.ca

Contact Email: MASinfo.moh@ontario.ca

Copyright: Medical Advisory Secretariat, Ontario Ministry of Health and Long-Term Care