Some patients who are treated with methotrexate may develop a cardiac arrhythmia. The precise mechanism is unclear.


Clinical features:

(1) onset of a cardiac arrhythmia in a patient being treated with methotrexate

(2) temporal relationship between the arrhythmia and the timing of methotrexate administration or an increase in dose

(3) disappearance of the arrhythmia on discontinuation of methotrexate or reduction in dose

(4) no other explanation for the arrhythmia is identified


Types of arrhythmias reported:

(1) ventricular tachycardia

(2) ventricular ectopy

(3) ventricular fibrillation

(4) supraventricular tachyarrhythmia

(5) sinus bradycardia


Some patients may undergo cardiac arrest with sudden death.


Differential diagnosis:

(1) myocardial infarction (risk increased in autoimmune disorders treated with methotrexate)


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