Swedish Cardiac And Renal Failure Study-1

Inclusion Criteria: * The participant has given their written consent to participate * A diagnosis of HFrEF according to current criteria, for at least three months before the screening visit * Echocardiography within 24 months of the screening visit with ejection fraction ≤ 40%. The responsible investigator is allowed to order a new TTE at their own discretion if clinically indicated - e.g. following the initiation of markedly intensified HFrEF-treatment or in the event of significant clinical deterioration. If the new TTE shows an EF \> 40%, the participant will not be eligible for inclusion. However, a potential echocardiographic worsening should not, by itself, preclude enrollment * New York Heart Association class II-III * Optimally treated and stable HFrEF (according to the investigator) since at least four weeks before the screening visit. Treatment should include beta-blockers, sodium/glucose co-transporter 2 inhibitors, angiotensin-converting enzyme inhibitors, or angiotensin receptor blockers if eGFR ≥ 20 ml/min/1.73m2 according to the revised Lund-Malmö method. Participants should also have cardiac resynchronization therapy or an implantable cardioverter-defibrillator if the indication exists according to current guidelines * eGFR \< 30 ml/min/1.73m2 according to the revised Lund-Malmö method at least once during the 12 months before the screening visit, and eGFR \< 45 ml/min/1.73m2 at the time of inclusion Exclusion Criteria: * P-K ≥ 5.6 * For the first ten stu…