Supplementary Material for: Prognostic Value of Time in Serum potassium Target Range Among Patients With Heart Failure and preserved ejection fraction

Introduction: Heart failure (HF) imposes a substantial disease burden, where dyskalemia is an established prognostic factor. Although time in therapeutic range (TTR) demonstrates clinical utility across cardiovascular conditions, its prognostic significance for potassium in heart failure with preserved ejection fraction (HFpEF) remains poorly characterized. Methods: This secondary analysis of the Treatment of Preserved Cardiac Function HF with an Aldosterone Antagonist (TOPCAT) trial (n=2,953 HFpEF patients) evaluated potassium TTR using Rosendaal's linear interpolation method (target range: 4.0-5.0 mmol/L). The primary composite endpoint included cardiovascular death, and HF hospitalization. Analyses employed multivariable Cox regression. Results: A total of 373 primary composite endpoint events (12.6%) occurred after the initial 12-month follow-up period post-enrollment. Patients in the highest TTR tertile demonstrated a significantly lower cumulative incidence of the primary composite endpoint compared to lower tertile. Multivariable regression analyses revealed an inverse relationship between potassium TTR levels and primary composite endpoint risk (HR 0.60, 95% CI 0.46-0.79, P<0.001), with consistent protection observed for secondary outcomes, including cardiovascular mortality, all-cause mortality, and any hospitalization. Conclusion: Potassium TTR represents a potent independent predictor of outcomes in HFpEF, demonstrating its potential value in the management of HF.