Palpitations; Symptomatic ventricular extrasystoles; Mild prolapse of the mitral valve anterior leaflet with little regurgitation; This spontaneous case was reported by a consumer and describes the occurrence of PALPITATIONS (Palpitations), VENTRICULAR EXTRASYSTOLES (Symptomatic ventricular extrasystoles) and MITRAL VALVE PROLAPSE (Mild prolapse of the mitral valve anterior leaflet with little regurgitation) in a  patient of an unknown age and gender who received mRNA-1273 (Spikevax) for COVID-19 vaccination.     No Medical History information was reported.    On an unknown date, the patient received dose of mRNA-1273 (Spikevax) (unknown route) 1 dosage form. On an unknown date, the patient experienced PALPITATIONS (Palpitations), VENTRICULAR EXTRASYSTOLES (Symptomatic ventricular extrasystoles) and MITRAL VALVE PROLAPSE (Mild prolapse of the mitral valve anterior leaflet with little regurgitation). The patient was treated with BISOPROLOL FUMARATE (CONGESCOR) ongoing since an unknown date at a dose of 1.25 milligram once a day. At the time of the report, PALPITATIONS (Palpitations), VENTRICULAR EXTRASYSTOLES (Symptomatic ventricular extrasystoles) and MITRAL VALVE PROLAPSE (Mild prolapse of the mitral valve anterior leaflet with little regurgitation) outcome was unknown.      DIAGNOSTIC RESULTS (normal ranges are provided in parenthesis if available): On an unknown date, Blood pressure measurement: 120/85 mmhg (normal) 120/85 mmHg. On an unknown date, Cardiac function test: normal and rhythmic sounds (normal) normal and rhythmic sounds. On an unknown date, Chest scan: vesicular murmur (abnormal) vesicular murmur. On an unknown date, Electrocardiogram: normal (normal) Normal.     The action taken with mRNA-1273 (Spikevax) (Unknown) was unknown.       No concomitant medications were reported.  Company comment: This spontaneous case concerns a patient of unknown age and gender with no reported medical history, who experienced the unexpected, non-serious AESI of Ventricular extrasystoles along with other non-serious events of Palpitations and Mitral valve prolapse. The date of administration of mRNA-1273 and onset date of events were not specified, hence, latency could not be assessed. On an unknown date, Blood pressure measurement was 120/85 mmhg (normal), Cardiac function test was normal with normal rhythmic sounds, Chest scan showed vesicular murmur and Electrocardiogram was normal. Mitral valve prolapse could be a confounder to the events. The patient was treated with Bisoprolol Fumarate (Congescor) ongoing since an unknown date at a dose of 1.25 milligram once a day, however the outcome of the event was unknown. The benefit-risk relationship of mRNA-1273 is not affected by this report.   Most recent FOLLOW-UP information incorporated above includes: On 15-Mar-2022: Translation document received on 18 Mar 2022 contains Lab data, event verbatim and treatment details.; Sender's Comments: This spontaneous case concerns a patient of unknown age and gender with no reported medical history, who experienced the unexpected, non-serious AESI of Ventricular extrasystoles along with other non-serious events of Palpitations and Mitral valve prolapse. The date of administration of mRNA-1273 and onset date of events were not specified, hence, latency could not be assessed. On an unknown date, Blood pressure measurement was 120/85 mmhg (normal), Cardiac function test was normal with normal rhythmic sounds, Chest scan showed vesicular murmur and Electrocardiogram was normal. Mitral valve prolapse could be a confounder to the events. The patient was treated with Bisoprolol Fumarate (Congescor) ongoing since an unknown date at a dose of 1.25 milligram once a day, however the outcome of the event was unknown. The benefit-risk relationship of mRNA-1273 is not affected by this report.