## 1 Introduction  
The market has always turned its attention towards the impact of innovation. Over the past 30 years, the technology moved such quick steps that many consolidated products and services have been replaced to provide better solutions. The role of computer science and engineering in this process is incontrovertible, forcing many industries to go along with it, often making it the company's core business, sometimes resulting in new products and services, but also new professions and improvements. In this fascinating context, the Digital Health sector is rising, in some ways, represented by the combination of computer science and healthcare to empower professionals and address the well-being of people with innovative systems.  
The healthcare sector is already taking advantage of the introduction of digital technologies. However, there are some specific issues, as privacy and security issues that still needs attention: i.e., the sharing of information in a trust-less scenario. Particularly sensitive to this topic are the Internet of Medical Things (IoMT) solutions, those solutions that usually exploit devices like smartphones to increase the well-being of an individual. Nevertheless, what makes IoMT promising for the future is the scientific contribution that it could bring. In fact, while a patient sees a medical device as a solution to its problems, professionals(i.e., doctors, researchers) can use it as a source of data to exploit in order to discover new diseases and treatments. Thus, imagining a world equipped with IoMT solutions, the crowd could build one of the most significant opportunities for healthcare: an interplanetary dataset representing all the clinical stories of the individuals from which to learn. However, as said previously, without firstly enabling a trusted context in a trust-less scenario would imply to neglect some potential risks: health data of an individual are considered sensitive, and they should be secured in any possible way [1].  
A technology that seems promising a secure context in a trust-less scenario is the Distributed Ledger Technology (DLT). The technology is usually disclosed as capable of preserving three significant properties: decentralization, immutability, and transparency. These three features could not only give to health data the security it deserves, but also they could allow a shift in data ownership, giving to data creators full access power control over their data, basically shifting from a system-centric position (where the data are created by a user, owned by the provider of a service and the decisions over data are taken together with the provider) to a user-centric position (where the data are created by the user, owned by the user, and the decisions over data are totally up to himself). Advancements in this field often make use of distributed data storage services as the InterPlanetary File System (IPFS), with the attempt of decentralizing data management [2].  
In this review, we will illustrate the advancements of the IoMT implementations combined with DLTs. Since we find out that those implementations could be still considered in the early stage of their real potential, we will first describe the state-of-the-art of the Internet of Medical Things, discussing the implementations proposed as capable of preserving privacy and security, finally labeling the proposed architectures regarding the ability to provide a user-centric system. Our final goal is to understand what is needed in order to go towards a user-centric solution for data management with respect to actual implementations.  
This contribution is structured as follows: Section 1 contains the introduction; Section 2, the background over the IoMT; Section 3, our position compared to the other surveys; Section 4, the research papers analysis; Section 5, the discussion over user-centricity; Section 6, the future vision; Section 7, the conclusions.