Introduction The European Society of Cardiology (ESC) produces clinical guidelines to standardise patient care by promoting evidence-based practice. Recently there has been focus upon financial conflicts of interest between study authors and Industry and also guideline authors themselves and Industry. We undertook this study to analyse the relationships between study and guideline authors and Industry for three ESC guidelines (heart failure [HF], valvular heart disease [VHD] and pericarditis [PD]).

Methods Regarding the research studies, we reviewed each pharmaceutical (i.e. medication-related) recommendation within the guidelines; the associated references were reviewed to ascertain if the study was funded by Industry and whether the authors had a conflict of interest with the Industry sponsor.

Regarding the guideline documents, we extracted the financial disclosures for each of the guidelines for all 165 contributors (authors and reviewers). We subdivided the relationships as described by the ESC: direct personal payments, institutional payments, receipt of royalties from intellectual property, institutional research funding and personal research funding.

Results There were 392 recommendations across the three guidelines of which 121 (31% – HF 72, VHD 23, PD 26) related to pharmaceutical agents. Table 1 outlines the frequency of industry sponsorship of studies and the frequency of competing interests amongst study authors. In the HF guideline, the proportion of references sponsored by industry was similar across the different classes of recommendation (1 – 50%; 2A – 44%; 2B – 47%; 3 – 43%).

The vast majority of guideline authors/reviewers themselves also had direct conflicts of interest with Industry, as shown in Table 2. The most common relationship with industry in the VHD and HF guidelines was a direct personal payment (72%–76%).

Conclusions Conflicts of interest amongst authors of guideline-influencing research studies are common, observed in the majority of cases. Furthermore, competing interests amongst guideline authors themselves are extremely common as well. Although positive strides have been made to declare competing interests in recent years, further research is required to determine the impact of competing interests amongst guideline committee authors and reviewers.