chest pain; pain in my left breast especially under the breast; felt like a large weight had been placed on my center chest causing my breathing to be very uncomfortable; felt like heart arrhythmia; does feel like someone hit her with brass knuckles in the arm; The pain in my left arm was much more painful than the first; This spontaneous case was reported by a consumer and describes the occurrence of ARRHYTHMIA (felt like heart arrhythmia) in a 72-year-old female patient who received mRNA-1273 (Moderna COVID-19 Vaccine) (batch nos. 028A21A and 025A21A) for COVID-19 vaccination. The occurrence of additional non-serious events is detailed below.     Concurrent medical conditions included Sulfonamide allergy, Drug allergy, Food allergy, Drug allergy and Reaction to drug preservatives. Concomitant products included CURCUMA LONGA RHIZOME (TURMERIC CURCUMIN [CURCUMA LONGA RHIZOME]), LEVOTHYROXINE SODIUM (SYNTHYROID), COLECALCIFEROL (D3) and RESVERATROL for an unknown indication.   On 28-Feb-2021, the patient received first dose of mRNA-1273 (Moderna COVID-19 Vaccine) (Intramuscular) 1 dosage form. On 29-Mar-2021, received second dose of mRNA-1273 (Moderna COVID-19 Vaccine) (unknown route) dosage was changed to 1 dosage form. On 30-Mar-2021, the patient experienced FEELING ABNORMAL (does feel like someone hit her with brass knuckles in the arm) and VACCINATION SITE PAIN (The pain in my left arm was much more painful than the first). On 31-Mar-2021, the patient experienced ARRHYTHMIA (felt like heart arrhythmia) (seriousness criterion medically significant), BREAST PAIN (pain in my left breast especially under the breast) and DYSPNOEA (felt like a large weight had been placed on my center chest causing my breathing to be very uncomfortable). On an unknown date, the patient experienced CHEST PAIN (chest pain). In April 2021, ARRHYTHMIA (felt like heart arrhythmia), BREAST PAIN (pain in my left breast especially under the breast) and DYSPNOEA (felt like a large weight had been placed on my center chest causing my breathing to be very uncomfortable) had resolved. At the time of the report, FEELING ABNORMAL (does feel like someone hit her with brass knuckles in the arm), CHEST PAIN (chest pain) and VACCINATION SITE PAIN (The pain in my left arm was much more painful than the first) had resolved.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): In 2021, Computerised tomogram: abnormal (abnormal) Minimal leaky valve issue. In 2021, Echocardiogram: abnormal (abnormal) Minimal leaky valve issue..         It was reported that the pain in patient's left arm was much more painful than the first, followed by 36 hours later, what she felt like heart arrhythmia, in her left breast especially under the breast, and she felt like a large weight had been placed on her center chest causing her breathing to be very uncomfortable. She had to see DR once again. After a CAT scan, cardiogram & ECHO cardio, doctor came up with a minimally leaky valve issue, which was known and was not a problem. She is happy and relieved to say that she have none of the side effects of the Moderna vaccine. She reported that it took at least 3 weeks for the breast pain & chest pain and weird heart flutters to completely fade.  No treatment medications were provided.     This case was linked to US-MODERNATX, INC.-MOD-2021-064049 (E2B Linked Report).   Most recent FOLLOW-UP information incorporated above includes: On 13-May-2021: Updated Patient details, medical history, concomitant medications, batch or lot number, updated events.; Sender's Comments:  US-MODERNATX, INC.-MOD-2021-064049:1st dose