Fatigue in Heart Failure

Definition and Pathophysiology

Fatigue in heart failure is a complex symptom with origins in both physiological and psychological factors, including low cardiac output, peripheral hypoperfusion, and skeletal muscle deconditioning 1
The origins of fatigue are multifaceted, making it challenging to quantify and assess clinically 1, 2

Fatigue is one of the cardinal manifestations of heart failure, alongside dyspnea, and is explicitly defined as such in major heart failure guidelines, according to the American College of Cardiology 3, 4
Fatigue may limit exercise tolerance and significantly impair the functional capacity and quality of life of affected individuals, as noted by the American College of Cardiology 3, 2

Fatigue may present independently of fluid retention - some patients have exercise intolerance with little evidence of fluid retention, while others primarily complain of edema with few symptoms of fatigue, as described by the American College of Cardiology 3, 4
Fatigue can manifest at different levels of exertion, which forms the basis of the NYHA classification system:
- Class I: No fatigue with ordinary physical activity, according to the American College of Cardiology 5
- Class II: Fatigue occurs with ordinary physical activity, according to the American College of Cardiology 5
- Class III: Fatigue occurs with less than ordinary activity, according to the American College of Cardiology 5
- Class IV: Fatigue present even at rest, according to the American College of Cardiology 5

There is a poor relationship between symptoms (including fatigue) and the severity of cardiac dysfunction, as noted by the American College of Cardiology 4, 2
The New York Heart Association (NYHA) functional classification uses fatigue as a key symptom to classify heart failure severity, but this is subjective and can fluctuate over time, according to the American College of Cardiology 3, 6

Relying solely on the presence or absence of fatigue at rest is insufficient for heart failure diagnosis or management, as stated by the American College of Cardiology 3, 4
Fatigue may be attributed to beta-blocker therapy, but other causes should be considered, including sleep apnea, overdiuresis, or depression, according to the American Heart Association, as published in Circulation 7