Cardiac rehabilitation attendance as a predictor of long-term survival

Background

Previous research has shown that CRP attendance is associated with improved outcomes including lower mortality, lower morbidity rates and better quality of life among patients who have experienced acute cardiac events. The evidence for these claims for secondary prevention has been reported in a few studies, from meta-analyses and is summarised in the Heart Research Centre's Best Practice Guidelines for Cardiac Rehabilitation and Secondary Prevention. The reduction in mortality is largely demonstrated in randomised controlled trials conducted in Finland, the United Kingdom and other European countries during the 1970s and 1980s. Most of the evidence to support these endorsements comes from studies in patients who have had MI. Pooled data from numerous randomised trials of CR after MI have documented a 20% to 25% reduction in all-cause and cardiovascular mortality over three years. It may be that the benefits arise not only from the exercise component of these programs, but from the comprehensive nature of the interventions which also include risk factor modification, education and counselling.

The present study involves a follow-up of 573 (88%) of 652 patients consecutively admitted to three Melbourne hospitals for a study of attendance patterns at CRPs conducted in 1996-1997. Of the 652 eligible patients, 573 were tracked four months after their acute event to determine whether or not they had attended and completed a CRP. There were 79 patients who could not be located.  Thus, there was an 88% follow-up rate among known survivors in the study.  Of these patients, 284 (49.6%) had attended a CRP, while 272 (47.5%) had not. Amongst attenders, 67 (23.6%) patients discontinued the program. All patients interviewed at baseline consented to participate in a follow-up study.

Aim

The primary aim of this follow-up study is to investigate whether attendance at a cardiac rehabilitation program (CRP) predicts lower mortality at 12 years patients after acute myocardial infarction (AMI), coronary artery bypass graft surgery (CABGS) or percutaneous coronary intervention (PCI). It is anticipated that patients who did not attend CRPs or who dropped out after initial attendance will have greater cardiovascular disease (CVD) and total mortality than other patients at 12 years.

Methods

This follow-up study will be undertaken in stages. The first step will be to determine the mortality status of men and women in the cohort. The Australian National Death Index (ANDI) will be used to identify deceased subjects and cause of death (CVD or non CVD).  For those persons who are not identified as deceased according to ANDI, efforts will be made to track the remaining men and women via hospital records, and cardiologists, surgeons or general practitioners (GPs) who treated these patients during the period of the original study and subsequently. If these enquiries fail to establish the mortality status of participants, the third and final stage will be to contact the last known residence of each patient.

It is expected that approximately 30% of the patients will have died over the 12 year follow-up period. The relationship between mortality and CRP attendance and other independent variables will be examined using survival analysis, both with and without adjustment, for potential confounders.