Signs and symptoms of heart failure can occur at any time. Differences between acute heart failure (AHF) patients who present at nighttime vs daytime and their outcomes have not been well studied. Our objective was to determine if there are differences in baseline characteristics and clinical outcomes between AHF patients presenting during daytime vs nighttime hours within an international, clinical trial.

This is a post hoc analysis of the RELAX AHF trial, which randomized 1,161 AHF patients to serelaxin vs placebo, both in addition to usual AHF therapy. Prespecified end points of the primary trial were used: dyspnea, 60-day heart failure/renal failure rehospitalization or cardiovascular (CV) death, and 180-day CV death. Both unadjusted and adjusted analyses for outcomes stratified by daytime vs nighttime presentation were performed.

Of the 1,161 RELAX-AHF patients, 775 (66.8%) patients presented during daytime and 386 (33.2%) at nighttime. Baseline characteristics were largely similar, although daytime patients were more likely to be male, have greater baseline body weight, have higher New York Heart Association class, have history of atrial fibrillation, and have more peripheral edema compared with nighttime patients. No differences in dyspnea relief or 60-day outcomes were observed. However, daytime presentation was associated with greater risk for 180-day CV death after adjustment (hazard ratio 2.28, 95% CI 1.34-3.86; c statistic = 0.82, 95% CI 0.78-0.86).

In this secondary analysis of the RELAX-AHF trial, baseline characteristics suggest that daytime-presenting patients may have more gradual worsening of chronic HF. Patients with AHF who presented at night had less risk for 180-day CV death, but similar risk for 60-day CV death or rehospitalization and symptom improvement for patients who presented during the daytime.