End stage renal disease (ESRD) patients exhibit an extraordinarily high annual mortality. Cardiovascular (CV) causes account for almost half of all-cause mortality. Increased left ventricular mass (LVM) is a common finding in ESRD patients on dialysis and is an independent predictor of survival. Yet, to date there is no established medical treatment to reduce CV morbidity and mortality in ESRD patients on hemodialysis. Blockade of aldosterone action by means of mineralocorticoid receptor antagonists (MRA) provides cardioprotection and improves outcome in heart failure patients. Furthermore, the MRA spironolactone has recently been shown to reduce LVM in patients with mild-to-moderate chronic kidney disease (CKD). The investigators here hypothesize that spironolactone treatment is cardioprotective by reducing LVM in ESRD patients on dialysis.

Inclusion Criteria:

• Age >18 years
• Hemodialysis treatment for at least 3 months
• At least 3 dialysis sessions per week
• Written informed consent

Exclusion Criteria:

• Contraindications for cardiac magnet resonance imaging (CMR)
• Mineralocorticoid receptor antagonist treatment within the last 6 months
• Estimated life expectancy < 12 months as judged by the nephrologist
• History of hyperkalemia, defined as pre-dialysis potassium > 6.5 mmol/l occurring ≥ 3 times within the last 3 months prior to enrolment.
• High risk to develop hyperkalemia defined as pre-dialysis potassium > 6.0 mmol/l
• Hypotension (systolic blood pressure < 100 mmHg)
• Planned kidney transplantation (living donor) within the prospected study duration
• Any acute illness within the last 4 weeks precluding a study participation as judged by the nephrologist
• Non-amenorrheic women with child bearing potential without reliable contraception, pregnancy/lactation
• Allergy/hypersensitivity to spironolactone
• Non-compliance suspected or demonstrated