Midsummer Eve in Sweden: a natural fluid challenge in patients with heart failure.

Aims: Volume overload exacerbations in patients with chronic heart failure (HF) are associated with a dismal prognosis and are often triggered by dietary incompliance. We aimed to describe the effects of dietary changes on measures of fluid retention in HF patients.
Methods and Results: Thirty-one HF patients with an implantable defibrillator (age 64 ± 11 years, ejection fraction 25 ± 12%, median NT-proBNP 2090 ng/L, resynchronization therapy: n= 25) were followed by daily body weight (BW) (telemonitoring) and intrathoracic impedance (by the implanted device) around Swedish Midsummer 2009, a holiday traditionally celebrated with meals including salty fish dishes and ample intake of fluids. Midsummer Eve celebrations caused a distinct and rapid increase in BW and a decrease in impedance indicating increased fluid retention. Compared with baseline values, peak BW increased by 1225 g [interquartile range (IQR) 475-2013 g)] which was accompanied by a decrease in impedance (3 Ω; IQR -5.2 to -1.2) and a clear deflection on the impedance-based fluid detection algorithm (OptiVol) that crossed the preset fluid-alert threshold six times following Midsummer. Body weight and impedance values were normalized after a period of 20 and 8 days, respectively. A clustering of minor clinical events following Midsummer suggests a possible adverse impact of dietary incompliance. However, none of the patients were hospitalized for HF.
Conclusions: Dietary incompliance, e.g. on the occasion of a ceremonial meal, may lead to marked disturbances in the fluid balance of patients with HF reflected by increased BW and decreased intrathoracic impedance. These findings underline the importance of maintaining stable volume conditions in HF patients.