From Syndrome to Disease: Reconsidering Heart Failure Through the 2026 Universal Definition and ICD-10/ICD-11

Heart failure remains one of the central clinical realities of cardiovascular medicine. The recent 2026 AHA/ACC/ESC/WHF Expert Consensus Document, Second Universal Definition of Heart Failure, defines heart failure as a clinical syndrome with diverse causes, recognized through a combination of symptoms, signs, biomarkers, imaging, and structural or functional cardiac abnormalities. This is correct and clinically useful. Yet this definition does not fully exhaust the nature of heart failure across its entire course.

There is an important distinction between the origin of heart failure and its later clinical status. Heart failure may initially arise as a syndrome of ischemic heart disease, hypertension, valvular pathology, cardiomyopathy, arrhythmia, pulmonary disease, renal disease, or systemic disorders. In this sense, it is indeed secondary. However, at later stages heart failure often becomes the principal determinant of the patient’s health, symptoms, functional capacity, repeated decompensations, hospitalization risk, response to treatment, and prognosis. At that point, it no longer behaves merely as a syndrome attached to another disease. It behaves as a disease in its own right.

This idea is not new. In my earlier work on chronic heart failure, I argued that medicine already recognizes analogous transitions in other fields. A primary disease may generate a syndrome, and that syndrome may then grow into a new disease entity when it acquires independent clinical dominance. The example of chronic kidney disease is especially instructive. Diverse renal insults may initiate the process, but over time the shared functional disorder of the kidney becomes a disease category with its own stages, prognostic implications, and therapeutic strategy. The original cause remains important, but it is no longer the only organizing principle of care. The same reasoning can be applied to chronic heart failure.

The 2026 universal definition partly confirms this view, even if it does not state it explicitly. The document presents heart failure not only as a syndrome, but also as a staged and dynamic condition. It distinguishes individuals at risk for heart failure, those with pre-heart failure, those with symptomatic heart failure, and those with advanced disease. It emphasizes that once symptomatic heart failure is established, the diagnosis is generally considered permanent, even if the patient improves. It also recognizes trajectories such as worsening heart failure, decompensated heart failure, improvement, remission, and recovery. This is far more than the language of a transient syndrome. It is the language of a chronic disease state with its own natural history.

The consensus is especially valuable in showing that heart failure has a longitudinal identity. It is not merely a momentary expression of another disease. It progresses, stabilizes, worsens, remits, or partially recovers according to its own internal dynamics and according to therapeutic intervention. It demands surveillance over time. It requires repeated reassessment. It shapes quality of life and survival. All of this suggests that the syndrome language, while formally correct at the level of definition, becomes conceptually incomplete when applied to advanced stages.

International disease classification supports this broader interpretation. In ICD-10, heart failure is already classified among diseases of the heart, under the I50 category. In ICD-11, this position becomes even more explicit, with heart failure occupying its own block within diseases of the circulatory system and including distinct subcategories such as congestive heart failure, left ventricular failure, right ventricular failure, biventricular failure, and unspecified heart failure. Thus, international classification systems already recognize heart failure as a disease entity for purposes of nosology, statistics, coding, and health-system organization.

This convergence between classification and clinical practice is important. It indicates that medicine, perhaps implicitly, already understands that heart failure is not only a syndrome of other diseases. Once symptomatic and especially once advanced, it becomes a disease state with relative clinical autonomy. The etiologic disease does not disappear, but it descends to the level of cause, while heart failure itself rises to the forefront as the condition most immediately governing the patient’s life.

The practical importance of this conceptual shift lies in treatment strategy. In early stages, the main priority is naturally the treatment of causal and predisposing diseases. Hypertension, coronary artery disease, diabetes, obesity, valvular abnormalities, toxic exposures, genetic conditions, and other risk factors must be corrected early to prevent or delay the emergence of heart failure. In these stages, therapeutic logic is primarily etiologic.

But once chronic symptomatic heart failure becomes established, and especially when it enters advanced stages, the therapeutic center of gravity changes. The first priority is no longer only correction of the original causal disease. The first priority becomes treatment of heart failure itself. Decongestion, neurohormonal modulation, phenotype-directed therapy, rhythm and conduction management, device therapy where indicated, prevention of recurrent decompensation, and in some patients advanced therapies or palliative care come to the forefront. In such patients, heart failure is no longer simply one expression of another disease; it is the dominant disease process that demands primary therapeutic attention.

This is where the current consensus may still underestimate heart failure conceptually. It organizes the syndrome very well, but it does not fully articulate the transition by which the syndrome becomes a disease in clinical reality. As a result, the reader may still think of heart failure mainly as derivative, even when the document itself describes a permanent, staged, progressive, and therapeutically autonomous condition. In that sense, the universal definition is internally very close to the disease concept, but it stops one step short of saying so.

A more complete formulation would preserve both sides of the truth. Heart failure is a syndrome in origin and definition, because it emerges from multiple diseases and is recognized through a constellation of findings rather than by a single lesion. Yet heart failure can become a disease in its own right in the later course, when it acquires dominance over symptoms, prognosis, hospitalizations, and treatment strategy. The categories are not mutually exclusive. Rather, they describe different moments within the same clinical evolution.

Such a formulation would also help clinicians think more clearly. It would clarify when the management of causal disease remains primary and when heart failure itself must take first place. It would align guideline language more closely with ICD-10 and ICD-11. Most importantly, it would reflect real bedside medicine, where many patients are no longer governed principally by ischemia, hypertension, or valvular pathology as isolated entities, but by the chronic and recurrent disease state of heart failure that these pathologies have produced.

In this sense, recognizing the transition from syndrome to disease is not a semantic exercise. It has direct implications for diagnosis, staging, therapeutic prioritization, prognosis, and communication. The 2026 universal definition is a major step forward, but it can be read more deeply than it states itself. If read in that way, it supports the conclusion that heart failure begins as a syndrome and, in many patients, becomes a disease.