Systematic review and literature appraisal on methodology of conducting and reporting critical-care echocardiography studies: a report from the European Society of Intensive Care Medicine PRICES expert panel

This systematic review summarizes the research reporting practice in CCE for studies published between year 2000 and 2017. The aim of the systematic review was to inspect past studies in order to describe reporting attitude and to identify potential areas of weakness and insufficient reporting, finally providing a robust evidence base for the expert panel to design recommendations for standardized reporting of future studies. Our goal is not to judge the quality of the past studies, nor to create unreasonable standards that could limit in the future the publication of interesting studies unable to report all the necessary items. Of note, studies from authors of the PRICES panel were evaluated in the same manner in this systematic review, and we found many of them had the same weaknesses and insufficiencies in reporting as the other researchers.

Our systematic review identified a considerable heterogeneity between studies and between the different fields of interest. For instance, studies in FM topic reported items in a higher number while those on LVDF topic lacked many items. Several items were under-reported despite their importance from either a methodological or clinical perspective. A large volume of narrative information was collected during the course of this work, but the discussion of all these findings would make the manuscript unnecessarily long, so we chose to present a limited sample to illustrate the level of under-reporting of important items in CCE studies. For example—the presence of atrial fibrillation at the time of echocardiography was mentioned only in a minority of studies (mainly as exclusion criteria) while it is known that its incidence during critical illness is relatively high [11‐13] and that it may induce cardiac dysfunction (especially diastolic) and it complicates or invalidates most echocardiographic measurements. Moreover, it precludes the use of AET which requires normal sinus rhythm. Another example, despite the frequent use of vasoactive drugs in intensive care which are known to affect the interpretation of most echocardiographic variables, the presence and dosage of inotropes and vasopressors were sub-optimally reported (49%, 68% and 43%, respectively). This would clearly introduce a source of bias when comparing studies. Furthermore, the mode of ventilation was described by three-quarters of studies; however, the values of positive end-expiratory pressure, plateau pressure and tidal volume during the echocardiography examination were only reported in a minority of cases despite ventilation settings are known to affect heart performance and especially the RV function. Additionally, these omissions will limit the validity of echocardiography parameters in the investigation of fluid responsiveness [14].

We also evaluated methodological aspects of echocardiography studies and data analysis in each study. Among others, it appears that assessment for confounders, blinding, identification of the person responsible of both performing and reviewing the echocardiography studies are far from being systematically reported. We also found under-reporting of the “topic-specific” items, where one ideally would expect higher reporting due to their specificity for the area of interest. For instance, the LV ejection fraction was the most commonly used parameter to describe LVSF (76%), but information on LV size were provided in roughly half of studies. Information on RV dimensions were under-reported to a similar extent and RV wall thickness was seldom reported, despite the role of these measurements in signalling the effect of chronic lung disease on the RV [15]. Surprisingly, in the investigation of LVDF we found that in around one-third of cases the authors did not refer to existing guidelines [16, 17] and used their own criteria or quoted references other than guidelines. Similarly, in the study of the fluid management over one-quarter of studies did not provide sufficient information about the reference (“gold”) standard method used to assess fluid responsiveness.

After reporting these examples, we would like to emphasize that the purpose of the present systematic review is to provide solid evidence for the expert panel to design recommendations for the reporting of studies utilizing CCE, rather than to criticize the quality of the body of research or to create unreasonable standards. The information on the frequency of reporting will be of course weighted against the importance of each item with the target of establishing the essential items that need mandatory reporting in CCE studies. The ultimate aim is to guide future CCE researchers to pursue a standardized approach in study design and reporting to enhance reproducibility and data homogeneity. This will increase the external validity and the impact of individual studies, facilitating meaningful comparison and the pooling of data in meta-analyses. Similar to the rationale for the “PRISMA statement” [18], which provides structured guidance on the information that authors should report in systematic review and meta-analysis to improve data consistency and allowing meaningful pooling of results, the next step of the PRICES project is to construct recommendations based on this systematic review balanced with expert opinion on the importance of the appraised items.