Skin fluid may reveal heart failure secrets without needles

Copied word for word from the study's registry entry, so the wording is the study team's rather than ours.

Inclusion Criteria: * Subject suffers from heart failure (according to ESC 2021 Heart Failure Guidelines). * Age of subject is ≥18 years. * Subject is female or male. * Signed written informed consent. * For female subjects: 1. Confirmed post-menopausal state, defined as amenorrhea for at least 12 months, or 2. If being of childbearing potential: 1. Negative highly sensitive urine or serum pregnancy test before inclusion, and 2. Practicing a highly effective birth control method (failure rate of less than 1%): 1. combined (estrogen and progestogen containing) hormonal contraception associated with inhibition of ovulation (oral/intravaginal/ transdermal), or 2. progestogen-only hormonal contraception associated with inhibition of ovulation (oral/injectable/implantable), or 3. intrauterine device (IUD), or 4. intrauterine hormone-releasing system (IUS), or 5. bilateral tubal occlusion, or 6. vasectomised partner, or 7. heterosexual abstinence. * Subject is capable to perform cardiopulmonary exercise testing. Exclusion Criteria: * Subject is breastfeeding. * Subject suffers from an addiction or from a disease that prevents the subject from recognizing nature, scope, and consequences of the study. * Subject is treated with immunosuppressive drugs at enrolment. * Subject requires renal replacement therapy. * Subject has a known colonisation or infection with multi-drug-resistant pathogens. * Subject has an open wound in or near the sampling area. * Subject has any type of tattoo or piercing anywhere in or near the sampling area. * Subject shows an inability to comply with all the study procedures and follow-up visits. * Subject is unwilling to consent to saving and propagation of pseudonymised medical data for study reasons. * Subject is legally detained in an official institution. * Subject is dependent on the sponsor, the investigator or the study sites. * Subject participates in a study according to AMG/CTR that investigates immunosuppressive or anticoagulant drugs at the time of this study.