Effectiveness of psychological intervention as add-on to standard cardiac rehabilitation: Time to adopt new methods or keep doing more of the same?

Cardiac rehabilitation (CR) is a multidisciplinary and multifaceted effort focused on physical training, risk factor management and patient education targeted to minimise the impact of heart disease on patient outcomes and restore physical capacity and health as far as it is possible. The evidence for CR is consistent, with significant cardiovascular mortality reductions even in the era of acute revascularisation and improved pharmacotherapy. Hence, in the European guidelines on cardiovascular disease prevention, CR is indicated with a class Ia recommendation, which is the highest level of evidence. In this issue of the journal, Albus et al. published a systematic review and meta-analysis on CR controlled trials and controlled cohort studies to evaluate the additional benefit of psychological interventions, in comparison to exercise-based CR alone, on depression, anxiety, quality of life, cardiovascular morbidity and cardiovascular and all-cause mortality. The authors are to be commended for this effort and it provides much food for thought for CR researchers, cardiologists, psychologists and other mental health professionals in the field. In 20 studies of 4450 patients, they showed nonsignificant trends, with small to moderate effect sizes, for reducing depression and cardiovascular morbidity, with no evident associations with other outcomes. As the authors rightly point out, there is a number of limitations to these findings, including the low to moderate quality of the included studies, and heterogeneity with respect to the interventions in terms of content, duration, intensity – both in the intervention and comparator groups – along with heterogeneity in outcomes and follow-up periods. Furthermore, interpretation of the findings is especially problematic given that the psychological content of both the intervention and comparator groups is difficult to discern, define and quantify. Given the heterogeneity across almost all methodological aspects that need to be considered when designing a randomised controlled trial and the level of quality of the studies, it is important, however, that we do not jump to the conclusion that psychological interventions in the context of CR are not worthwhile. This would be tantamount to throwing away the baby with the bathwater. In 2018, Richards et al. published a systematic review and meta-analysis in this journal based on their 2017 Cochrane review on the effectiveness of psychological interventions as the sole intervention in patients with coronary heart disease. The systematic review and meta-analysis had similar problems (e.g. low to moderate quality of studies included and heterogeneity across studies, etc.) to the current systematic review and meta-analysis by Albus et al., as outlined in an associated editorial. The review and meta-analysis by Richards et al. found an effect on cardiovascular mortality, but only small to moderate improvements in anxiety, depression and stress, and no effects on total mortality and major adverse cardiac events. On a broader level, the results of these two systematic reviews and meta-analyses leave the question open as to whether we see a progression in the literature, or whether we are merely producing ‘more of the same’? When we design new studies, we base the power calculation on the effect sizes of existing studies that may in fact be underpowered or not comparable with respect to methodological aspects, such as those differences found by Albus et al. From that point of view, we are producing ‘more of the same’ and repeating our mistakes. For example, when comparing the oldest study (i.e. the 1998 study by Black et al.) with the most recent study