Thoracentesis to Alleviate Cardiac Pleural Effusion

Inclusion Criteria: * Left ventricular ejection fraction (LVEF) ≤ 45% * Non- negligible pleural effusion by x-ray, ultrasound, CT or MRI, suspected to be due to heart failure * Age ≥ 18 years Exclusion Criteria: * Clinically indicated diagnostic thoracentesis (e.g. suspected malignant aetiology) * Suspected pulmonary or pleural infection (pneumonia symptoms with c- reactive protein\>100 mg/L or white blood count\>11) * Recent (\<3 months) intrathoracic procedure (including heart or lung surgery, transcatheter aortic valve implantation (TAVI) or thoracentesis) * Contraindications to thoracentesis according to local guidelines (such as spontaneously elevated international normalized ratio (INR) or thrombocytopenia), patients on oral anticoagulation may be randomized. * Severe aortic stenosis * Massive pleural effusion (equivalent to \>2/3 of lung on a standing chest x-ray) * Substantially affected hemodynamics (systolic blood pressure \< 85mmHg, need of inotropes) or high oxygen demand (\>7L/min) * Estimated glomerular filtration rate (eGFR) \<15ml/min/1.73m2 or dialysis treatment * Planned or expected admission \> 10 days for other condition than heart failure * Inability to give informed consent