showed clot in heart/ I have a blood clot in my heart, and it was after taking the injection; atrial fibrillation persisting; experienced shortness of breath; general weakness; weakness in legs, especially thighs; soreness at the injection site; redness at the injection site; This spontaneous case was reported by a health care professional and describes the occurrence of ATRIAL FIBRILLATION (atrial fibrillation persisting) and THROMBOSIS (showed clot in heart/ I have a blood clot in my heart, and it was after taking the injection) in a 71-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch no. 002A21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     The patient's past medical history included Myocardial infarction (5 "MI"s) and Open heart surgery. Concurrent medical conditions included Diabetic retinopathy, Blindness, Atrial fibrillation (started about 2 years ago) and Type 2 diabetes mellitus. Concomitant products included TEMAZEPAM for Insomnia, DULAGLUTIDE (TRULICITY) for Type 2 diabetes mellitus, ASPIRIN [ACETYLSALICYLIC ACID], ATORVASTATIN CALCIUM (LIPITOR), DILTIAZEM, CARVEDILOL (COREG), SACUBITRIL VALSARTAN SODIUM HYDRATE (ENTRESTO), LOPERAMIDE HYDROCHLORIDE (IMODIUM), ISOSORBIDE MONONITRATE (ISOSORBIDE MONONITE), EMPAGLIFLOZIN (JARDIANCE), POTASSIUM CHLORIDE (KLOR-CON), FUROSEMIDE (LASIX [FUROSEMIDE]), LEVOTHYROXINE, MAGNESIUM OXIDE, PAROXETINE HCL and PARACETAMOL (TYLENOL) for an unknown indication.    On 26-Feb-2021, the patient received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 27-Feb-2021, the patient experienced VACCINATION SITE PAIN (soreness at the injection site) and VACCINATION SITE ERYTHEMA (redness at the injection site). In March 2021, the patient experienced DYSPNOEA (experienced shortness of breath), ASTHENIA (general weakness) and MUSCULAR WEAKNESS (weakness in legs, especially thighs). On 07-May-2021, the patient experienced THROMBOSIS (showed clot in heart/ I have a blood clot in my heart, and it was after taking the injection) (seriousness criterion medically significant). In May 2021, the patient experienced ATRIAL FIBRILLATION (atrial fibrillation persisting) (seriousness criterion medically significant). The patient was treated with WARFARIN SODIUM (JANTOVEN) ongoing from 07-May-2021 at an unspecified dose and frequency. At the time of the report, ATRIAL FIBRILLATION (atrial fibrillation persisting), THROMBOSIS (showed clot in heart/ I have a blood clot in my heart, and it was after taking the injection), DYSPNOEA (experienced shortness of breath), ASTHENIA (general weakness), MUSCULAR WEAKNESS (weakness in legs, especially thighs), VACCINATION SITE PAIN (soreness at the injection site) and VACCINATION SITE ERYTHEMA (redness at the injection site) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On 07-May-2021, Arteriogram: clot in heart (Inconclusive) clot in heart.     For mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular), the reporter did not provide any causality assessments.   Patient received first dose vaccine on 28Jan2021, and she had no problems. Patient was on pacer and defibrillator. Patient  had a nuclear stress test in May2021 which did not show anything.  Company comment: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.; Sender's Comments: Based on the current available information and temporal association between the use of the product and the start date of the events, a causal relationship cannot be excluded.