Vasoplegia is a common complication after heart surgery for heart failure. With vasoplegia, the blood vessels can no longer squeeze properly, causing low blood pressure that is sometimes difficult to treat with medication. One of the causes of this complication is likely to be the use of the heart-lung machine, a device that takes over the function of the heart and lungs during surgery. The blood then comes into contact with a foreign environment and this can cause a reaction of the immune system. Patients with heart failure are extra sensitive to this reaction.

CytoSorb device is a filter that can be built into the heart-lung machine and can reduce the response of the immune system. Therefore, this study aims to investigate whether the use of this filter during heart surgery in patients with heart failure results in a less frequent occurrence of vasoplegia after surgery.

The incidence and prevalence of chronic heart failure is increasing. Despite the expansion of therapeutic options, overall survival and quality-of-life remain poor. When optimal medical therapy and cardiological interventions have failed to improve a patient's condition, surgical intervention may be a valid option in order to improve cardiac function. Different surgical treatments have improved clinical outcome. Unfortunately, heart failure surgery is associated with an increased risk of vasoplegia. This syndrome is characterized by hypotension and the continuous need of vasopressors, despite a normal or high cardiac index. The incidence of vasoplegia ranges from 11-31% in patients undergoing heart failure surgery. The prognosis of vasoplegia is poor. Prolonged hypotension and the accompanying hypoperfusion lead to end-organ dysfunction and is associated with an increased morbidity and mortality. The investigators hypothesise that the balance of the vascular system of patients with heart failure is fragile and therefore could easily be disturbed by a systemic inflammatory response syndrome (SIRS) caused by the cardiopulmonary bypass (CPB) and surgical trauma, making these patients more prone to develop vasoplegia. Minimising this SIRS reaction could be a strategy to prevent vasoplegia. Therefore, the objective of this single-center, investigator-initiated study is to analyse the efficacy and cost-effectiveness of using CytoSorb in preventing vasoplegia in patients with heart failure undergoing cardiac surgery on CPB.

CytoSorb treatment will be conducted intraoperatively and the device will be applied in a parallel circuit in the CPB. The total study intervention protocol takes 5 days and starts on the day of the surgery (day 0) and ends at day 4 postoperatively. Patient clinical data will be collected until day 30.

The vascular reactivity in response to a vasoconstrictor will be assessed in all patients at 3 different time points (after induction, after CPB, on day 1 postoperatively). During the vasoconstriction test, a bolus of 2 μg/kg phenylephrine is administered intravenously, after which the effect on the systemic vascular resistance is registered. At the same time points and in addition, before induction (baseline) and on day 4 the sublingual microcirculation will be monitored and blood samples will be collected.

Inclusion Criteria:

• Diagnosed with HF in line with the European Society of Cardiology (ESC) guidelines34;
• Left ventricular EF ≤35%;
• Undergoing cardiac surgery on CPB with an anticipated duration of >120 minutes;
• Age ≥18 years.

Exclusion Criteria:

• Incapacitated;
• Emergency operation;
• Need for moderate or high dosages of intravenous inotropic support (>4 gamma dobutamine or dopamine) and/or vasopression;
• Severe tricuspid regurgitation;
• Daily use of nitroglycerine or isosorbide dinitrate;
• Use of alpha blockers;
• Being heparin-induced thrombocytopenia (HIT) positive and citrate regional anticoagulation is unavailable as an alternative anticoagulation method;
• Platelet count <20,000/μL.

Perfusionists will not be blinded.