Problems with the outcome measures in randomized controlled trials of traditional Chinese medicine in treating chronic heart failure caused by coronary heart disease: a systematic review

Background Traditional Chinese medicine (TCM) has gained widespread application in treating chronic heart failure (CHF) secondary to coronary heart disease (CHD). However, the sound clinical evidence is still lacking. Corresponding clinical trials vary considerably in the outcome measures assessing the efficacy of TCM, some that showed the improvement of clinical symptoms are not universally acknowledged. Rational outcome measures are the key to evaluate efficacy and safety of each treatment and significant elements of a convincing clinical trial. We aimed to summarize and analyze outcome measures in randomized controlled trials (RCTs) of TCM in treating CHF caused by CHD, subsequently identify the present problems and try to put forward solutions. Methods We systematically searched databases including Embase, PubMed, Cochrane Library, CBM, CNKI, VIP and Wanfang from inception to October 8, 2018, to identify eligible RCTs using TCM interventions for treating CHF patients caused by CHD. Cochrane Database of Systematic Reviews (CDSR) was searched to include Cochrane systematic reviews (CSRs) of CHF. Two authors independently assessed the risk of bias of the included RCTs according to the Cochrane Handbook. Outcome measures of each trial were extracted and analyzed those compared with the CSRs. We also evaluated the reporting quality of the outcome measures. Results A total of 31 RCTs were included and the methodology quality of the studies was generally low. Outcome measures in these RCTs were mortality, rehospitalization, efficacy of cardiac function, left ventricular ejection fraction (LVEF), 6 min' walk distance (6MWD) and Brain natriuretic peptide (BNP), of which mortality and rehospitalization are clinical end points while the others are surrogate outcomes. The reporting rate of mortality and rehospitalization was 12.90% (4/31), the other included studies reported surrogate outcomes. As safety measure, 54.84% of the studies reported adverse drug reactions. Two trials were evaluated as high in reporting quality of outcomes and that of the other 29 studies was poor due to lack of necessary information for reporting. Conclusions The present RCTs of TCM in treating CHF secondary to CHD did not concentrate on the clinical end points of heart failure, which were generally small in size and short in duration. Moreover, these trials lacked adequate safety evaluation, had low quality in reporting outcomes and certain risk of bias in methodology. For objective assessment of the efficacy and safety of TCM in treating CHF secondary to CHD, future research should be rigorous designed, set end points as primary outcome measures and pay more attention to safety evaluation throughout the trial.