While many antibiotics, such as azithromycin and levofloxacin are associated with certain types of arrhythmia, amoxicillin is not associated with cardiac side effects such as heart palpitations or flutter. In fact, the prescribing information for amoxicillin doesn't list any cardiac side effects. In addition, a history of abnormal heart beats (e.g. PVCs) or arrhythmia is not a contraindication to amoxicillin therapy.
There is a chance your cardiac side effects were a coincidence or it could be secondary to other side effects of amoxicillin. Although uncommon, amoxicillin therapy has been associated with certain central nervous system effects such as nervousness, anxiety and agitation. These could make you more susceptible to cardiac problems, especially in those with a history of them.
Lastly, there is always the chance that you are experiencing rare and under-reported side effects. The FDA's Adverse Event Reporting System (FAERS) has listed over 70 cases of cardiac problems reported in 2017 alone with amoxicillin but it is important to know that there is no certainly that the reported events in the FAERS were due to the medication.
It is important to let your doctor know about the symptoms you experienced while taking amoxicillin so you can be properly evaluated.