Neuromuscular Assessment of Heart Failure Patients

The exercise intolerance and accelerated fatigue experienced by patients with congestive heart failure (CHF) may not be solely dictated by their cardiac dysfunction. Failure in the neuromuscular system may also play a role. Specific techniques can characterize the origin(s) of neuromuscular failure as being neural (central fatigue), muscular (peripheral fatigue), or involving the junction of these two (neuromuscular transmission failure). Only three studies have attempted to investigate neuromuscular failure in CHF patients, and the interpretation of the results from the most thorough investigation may be confounded. If we are to increase our understanding of the exercise intolerance and accelerated fatigue experienced by these patients, the evaluation of the neuromuscular system of CHF patients needs to be improved.Patients with congestive heart failure (CHF) have a reduced exercise tolerance and experience accelerated fatigue during exercise. Previous studies have shown that the exercise capacity of these patients correlates with muscle dysfunction rather than cardiac dysfunction [1–4]. While abnormalities in metabolism [5–8], morphology [8–10], and blood flow [1,11,12] of skeletal muscles have been documented to contribute to muscle dysfunction in CHF patients, the role of the neuromuscular system remains to be evaluated. Electromyographic changes, detected by surface electrodes on the quadriceps, have suggested that muscle fatigue occurs relatively sooner in CHF patients than in healthy subjects [13]. The central nervous system, the contractile apparatus of the muscles, and the junction of the neural and muscular systems each play a role in neuromuscular function and may be affected by the chronic heart failure state of individuals and, thus, may play a role in their exertional intolerance. This chapter will discuss the components of neuromuscular fatigue and the methods by which they can be assessed. A brief review of the current literature pertaining to neuromuscular fatigue assessment of CHF patients will follow.