The conundrum of the complex relationship between acute kidney injury and cardiac arrhythmias.

Acute kidney injury (AKI) is defined by a rapid increase in serum creatinine levels, reduced urine output or both. Death may occur in 16-49% of patients admitted to an intensive care unit with severe AKI. Complex arrhythmias are a potentially serious complication in AKI patients with pre-existing or AKI-induced heart damage and myocardial dysfunction, with fluid overload, especially electrolyte and acid-base disorders, representing the pathogenetic mechanisms of arrhythmogenesis. Cardiac arrhythmias, in turn, increase the risk of poor renal outcomes, including AKI. Arrhythmic risk in AKI patients receiving kidney replacement treatment may be reduced by modifying dialysis/replacement fluid composition. The most common arrhythmia observed in AKI patients is atrial fibrillation. Severe hyperkalaemia, sometimes combined with hypocalcaemia, causes severe bradyarrhythmias in this clinical setting. Although the likelihood of life-threatening ventricular arrhythmias is reportedly low, the combination of cardiac ischaemia and specific electrolyte or acid-base abnormalities may increase this risk, particularly in AKI patients who require kidney replacement treatment. The purpose of this review is to summarize the available epidemiological, pathophysiological and prognostic evidence aiming to clarify the complex relationships between AKI and cardiac arrhythmias.