Prolonged Asystole (Flat Line) In MG Patient Induced by Pyridostigmine. Successfully Treated with Hyoscyamine

Dr. Mohammad Saud Khan

Reversible acetylcholinesterase inhibitors are used as first-line treatment for myasthenia gravis (MG).

They improve symptoms by increasing concentration of acetylcholine at the neuromuscular junction and stimulating nicotinic receptors. Serious bradyarrhythmias can occur from muscarinic stimulation in heart, which in rare cases may progress to asystole (Flat Lining on ECG monitor).


These patients can initially be managed with hyoscyamine, a muscarinic antagonist. Persistence of bradyarrhythmias even after hyoscyamine treatment may warrant pacemaker placement. We present a case of 65-year-old female patient who presented with diplopia, dysphagia, and muscle weakness who was diagnosed with myasthenia gravis. She developed significant sinoatrial node block with prolonged asystole after starting treatment with pyridostigmine which was successfully treated with hyoscyamine, thus avoiding pacemaker placement.

Myasthenia gravis (MG) is an autoimmune disorder affecting the neuromuscular junctions. It is characterized by decrease in the number of available nicotinic acetylcholine receptors at postsynaptic membrane due to presence of pathogenic autoantibodies [1, 2]. Reversible acetylcholinesterase inhibitors are used as initial treatment for MG and pyridostigmine is the most widely used drug. They improve symptoms by increasing concentration of acetylcholine at the neuromuscular junction leading to stimulation of nicotinic receptors at postsynaptic membranes [2, 3]. However, use of these drugs is associated with potential adverse effects due to ... >>> Continue Reading Case Report