Cardiopulmonary exercise testing in mild generalized myasthenia gravis: an exploratory pilot feasibility study

Area of Science:

• Neurology
• Exercise Physiology
• Clinical Medicine

Background:

• Generalized myasthenia gravis (gMG) is a chronic autoimmune disorder affecting neuromuscular junctions.
• Assessing exercise capacity in gMG patients is challenging due to potential neuromuscular fatigability.
• Understanding the drivers of exercise limitation is crucial for effective management.

Purpose of the Study:

• To evaluate the safety and feasibility of cardiopulmonary exercise testing (CPET) in patients with mild gMG.
• To determine if CPET termination is caused by systemic exertion or MG-specific neuromuscular fatigue.
• To assess the short-term effects of CPET on patient fatigue levels.

Main Methods:

• An exploratory pilot study involving nine patients with mild gMG.
• Maximal incremental CPET on a cycle ergometer with detailed gas exchange and lactate measurements.
• Repetitive nerve stimulation (RNS) and Chalder Fatigue Scale (CFS) assessments before and after CPET.

Main Results:

• All participants completed CPET safely without adverse events, with symptoms resolving within 30 minutes.
• Most participants met multiple predefined exertion criteria, indicating significant systemic effort.
• Neuromuscular junction transmission showed decremental responses pre- and post-CPET, but fatigue scores did not significantly change post-exercise.

Conclusions:

• CPET is a safe and feasible diagnostic tool for individuals with mild gMG.
• Exercise limitation during CPET in mild gMG is primarily attributed to systemic factors rather than neuromuscular fatigue.
• CPET can aid in clinical evaluations, informing individualized exercise prescriptions and identifying cardiopulmonary limitations.