The study will investigate, if inflammatory and cardio-circulatory biochemical biomarkers are detectable in dermal interstitial fluid (dISF) of heart failure patients, and if there are detectable kinetics of these biomarkers during a cardiopulmonary exercise test. For dISF extraction the PELSA System - an investigational device - will be used.

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.