Cardiac Complications of Refeeding Syndrome: Pathophysiological Mechanisms, Clinical Manifestations, and Preventive Strategies

Refeeding syndrome (RFS) is a potentially life-threatening metabolic disorder that occurs when nutrition is rapidly reintroduced after prolonged starvation or malnutrition. It is characterized by insulin-driven shifts of phosphate, potassium, and magnesium into cells, leading to severe hypophosphatemia, hypokalemia, and hypomagnesemia. These electrolyte derangements impair myocardial energy metabolism, contractility, and conduction, resulting in arrhythmias, heart failure, and sudden cardiac arrest. Thiamin deficiency and fluid overload further exacerbate cardiac instability, making cardiovascular complications the most fatal manifestations of RFS. Despite recognition for over 7 decades, RFS remains underdiagnosed due to inconsistent definitions, variable diagnostic criteria, and limited clinical awareness. Reported incidence ranges widely from 0% to 62%, with the highest rates in malnourished, critically ill, and elderly patients, as well as those with anorexia nervosa or chronic alcoholism. Prevention remains the cornerstone of management and includes risk stratification, gradual caloric initiation (10-20 kcal/kg/d), thiamin supplementation before feeding, and vigilant monitoring of phosphate, potassium, and magnesium levels during the initial refeeding period. Adherence to established guidelines has been shown to reduce morbidity and mortality. By summarizing the pathophysiological mechanisms, cardiac sequelae, and preventive strategies, this review underscores the importance of early recognition and standardized protocols to mitigate the cardiovascular consequences of RFS and improve outcomes in high-risk populations.