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Myasthenia Gravis

MuSK antibody MG and ECG changes

05/22/2009

Question:

Hello, I am a 54yr old female and was recently diagnosed with MuSK antibody MG. I was also investigated for an abnormal exercise stress test which was followed by a Sestamibi myocardial perfusion scan by a cardiologist. This test confirmed a right bundle branch block and reversible ST depression. Ischaemic heart disease has been ruled out. My question is - could there be relationship between MG and ECG changes?

Answer:

Myasthenia is not directly related to heart arrhythmias. Myasthenia is a disease that affects the neuromuscular junction of skeletal muscle, which is a different type of muscle than cardiac muscle. People with myasthenia definitely can have cardiac arrhythmias, but we do not think the changes seen on the EKG represent the effect of acetylcholine receptor blockade at the cardiac muscle neuromuscular junctions. Theoretically, the medications that we treat myasthenia may cause heart rhythm problems (e.g. pyridostigmine), but probably not right bundle branch block.

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Response by:

Robert W Neel, IV, MD Robert W Neel, IV, MD
Assistant Professor of Neurology
College of Medicine
University of Cincinnati