Emergence of Chloride as an Overlooked Cardiorenal Connector in Heart Failure

Several studies have recently challenged the sodium-centric view that has been dominating the field of heart failure (HF) and cardiorenal syndrome. The previously observed benefits of severe dietary restriction of salt do not seem to be consistently reproduced by contemporary studies. Moreover, there is evidence that too low intake may paradoxically lead to adverse outcomes in more advanced stages of HF. Facing the escalating controversy, investigators have shifted their focus from sodium to its often overlooked counter ion in salt, the chloride. Emerging data suggest that serum chloride levels could portend robust independent prognostic value in a wide range of HF syndromes possibly stronger than that of sodium. The untoward impact of hypochloremia on the outcomes could be mechanistically linked to renal tubular regulatory pathways, neurohormonal activation, and diuretic resistance. As such, it can be a potential target of therapy in this setting. In this article, the authors provide a brief overview of the role of serum chloride as a cardiorenal connector and explore the context in which the contemporary data should be interpreted. Implementation of predictive and therapeutic strategies incorporating the emerging evidence would be refined through discussion of nuances of such findings as well as their biological and clinical relevance.