cardioversion 3 times/arrhythmia/went back into arrhythmia 6 months later; heart attack; This spontaneous case was reported by a patient family member or friend and describes the occurrence of ARRHYTHMIA (cardioversion 3 times/arrhythmia/went back into arrhythmia 6 months later) and MYOCARDIAL INFARCTION (heart attack) in a male patient of an unknown age who received mRNA-1273 (Moderna COVID-19 Vaccine) for COVID-19 vaccination.     No Medical History information was reported.   On an unknown date, the patient received fourth dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) 1 dosage form. On an unknown date, received third dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form, second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form and first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On an unknown date, the patient experienced ARRHYTHMIA (cardioversion 3 times/arrhythmia/went back into arrhythmia 6 months later) (seriousness criterion medically significant) and MYOCARDIAL INFARCTION (heart attack) (seriousness criterion medically significant). The patient was treated with Surgery (cardioversion) for Arrhythmia. At the time of the report, ARRHYTHMIA (cardioversion 3 times/arrhythmia/went back into arrhythmia 6 months later) and MYOCARDIAL INFARCTION (heart attack) outcome was unknown.            Patient had 2 doses of the moderna vaccine and 2 moderna boosters. No concomitant medications were reported. Patient had  a heart attack. He went back into arrhythmia 6 months later. Treatment reported included Cardioversion 3 times. "The patient was treated with Surgery (cardioversion) for Arrhythmia".  Company comment: This spontaneous case concerns a male patient of an unknown age, with no reported medical history, who experienced the unexpected serious (medically significant) AESIs of Arrhythmia and Myocardial Infarction. Patient received 2 doses of mRNA-1273 vaccine as primary series and 2 booster doses of mRNA-1273 vaccine on unknown dates. The onset dates of events Arrhythmia and Myocardial Infarction were not reported, hence, latency cannot be properly assessed. It was reported that patient had cardioversion 3 times and a heart attack. And there was recurrence of arrhythmia 6 months later. Clinical course and laboratory details were not reported. The outcome of events was unknown. The benefit-risk relationship of mRNA-1273 is not affected by this report. Events' seriousness was assessed as per medical judgement.; Sender's Comments: This spontaneous case concerns a male patient of an unknown age, with no reported medical history, who experienced the unexpected serious (medically significant) AESIs of Arrhythmia and Myocardial Infarction. Patient received 2 doses of mRNA-1273 vaccine as primary series and 2 booster doses of mRNA-1273 vaccine on unknown dates. The onset dates of events Arrhythmia and Myocardial Infarction were not reported, hence, latency cannot be properly assessed. It was reported that patient had cardioversion 3 times and a heart attack. And there was recurrence of arrhythmia 6 months later. Clinical course and laboratory details were not reported. The outcome of events was unknown. The benefit-risk relationship of mRNA-1273 is not affected by this report. Events' seriousness was assessed as per medical judgement.