Reversible HFrEF-The Pattern Five Specialties Missed, Lantern of Sulfur, Concept A, v12.3, March 2026

Reversible HFrEF: The Pattern Five Specialties Missed introduces Terrain-Induced Functional Cardiomyopathy (TIFC), a reversible phenotype of heart failure with reduced ejection fraction arising from coordinated physiologic instability along the Vertical Terrain Axis. This framework proposes that a subset of HFrEF presentations may represent downstream expression of terrain-level dysregulation involving bile signaling, RAAS interpretation, chloride handling, acid–base balance, mitochondrial voltage stability, and autonomic regulation rather than irreversible structural myocardial disease. Version 12.3 clarifies the clinical anomaly motivating the framework by foregrounding the observed electrolyte pattern—persistent hyperchloremia with chronically low CO₂ consistent with non–anion gap metabolic acidosis despite preserved renal function—before introduction of the TIFC model. The paper situates this phenotype within a broader systems-physiology architecture and links to companion preprints exploring bile-RAAS-chloride interactions, hydration-dependent hyperchloremia, and regulatory axis orientation within the Lantern of Sulfur framework. Version 12.3 update (March 2026):Abstract revised to introduce the clinical observation prior to presentation of the Terrain-Induced Functional Cardiomyopathy (TIFC) framework. This change clarifies the clinical anomaly that motivated the model while leaving the Vertical Terrain Axis architecture and conclusions unchanged. Minor language refinements were made to improve readability and indexing discoverability. No changes were made to the underlying framework This preprint it part of a triad with Circadian and Metabolic Timing in Electrolyte Regulation, Lantern of Sulfur, Concept A, v12, March 2026: 10.5281/zenodo.18896061