she may have been panicked; she already has a pre-existing cardiac arrhythmia, but it seemed to have gotten worse after receiving the 1st dose/More arrhythmia problems; she already has a pre-existing cardiac arrhythmia, but it seemed to have gotten worse after receiving the 1st dose/More arrhythmia problems; left arm soreness; she felt ugh, like she was getting sick; sensation like she was going to pass out; Headache; This is a spontaneous report from a contactable nurse (patient). This 43-year-old female patient female received dose 1 of BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE) Lot number EM9810, intramuscular on left deltoid on 04Feb2021 as single dose (at the age of 43 years) for Covid-19 Immunization.  No medical history reported, and no concomitant medication reported.  Historical vaccine included BNT162B2 for Covid-19 Immunization.  Medical history included Pacemaker in Jun2019 and ongoing, sick sinus syndrome, and pre-existing cardiac arrhythmia ongoing.  Historical vaccine included Tetanus, Tetanus made her arm sore, the soreness from tetanus was worse than the soreness from COVID vaccine since it lasted a week with tetanus, no lot number reported.    No concomitant medication was reported. The patient experienced she already has a pre-existing cardiac arrhythmia, but it seemed to have gotten worse after receiving the 1st dose/More arrhythmia problems on 05Feb2021 considered medically significant with outcome of not recovered, Within 15 minutes after receiving the vaccine she felt like she was going to pass out three times on 04Feb2021 considered medically significant and recovered on 04Feb2021, she may have been panicked on unspecified date with outcome of unknown, left arm soreness on 05Feb2021 with outcome of recovered on Feb2021, and she felt ugh, like she was getting sick on 05Feb2021 with outcome of unknown.  The patient did not receive treatment for events.  She stayed an extra 30 minutes to be monitored after the initial waiting of 15 minutes since she had to drive home, then she felt better. She has not called her cardiologist since she has the history of arrhythmias.  She had the more arrhythmias start on the evening of the 05Feb2021, states it was weird because it seems to happen more in the evening between 6 and 9pm, sometimes as late as 10pm. However, 'yesterday' it started happening during the day, and it is more frequent, not constant, it just happens. States it is hard not think about it when her heart is having hiccups since that is what it feels like. She knows what it feels like because when her pacemaker goes off ventricularly she can feel it. She had arrhythmias before the vaccine but has not had issues with arrhythmias continuously. She was diagnosed with sick sinus syndrome and they do not know if it is cardiology or neurology, states it has been an issue for her for the last two years (2019). Lab data included weight of 284-286.  She is asking if there is any data that supports her getting the second dose on 25Feb2021. She has read that some people tend to have more side effects with the second dose. The patient had no prior vaccinations (within 4 weeks).; Sender's Comments: Based on vaccine-event chronological association, a causal relationship between events worsening arrhythmia and pre-syncope and BNT162B2 (PFIZER-BIONTECH COVID-19 VACCINE) cannot be excluded. The impact of this report on the benefit/risk profile of the Pfizer product is evaluated as part of Pfizer procedures for safety evaluation, including the review and analysis of aggregate data for adverse events. Any safety concern identified as part of this review, as well as any appropriate action in response, will be promptly notified to Regulatory Authorities, Ethics Committees and Investigators, as appropriate.