<s>[INST] My 21 year old girl has a rapid heart beat, which started recently. she is takingContraceptive pill, 5 days ago we rushed her to A&E, her heart beat was very fast, they said she had inner ear infection and her tonsils were inflamed, so she was given Antibiotics but we had to stop as  the tablets were making her worse.(heart beat).while we were in hospital they recommend that she should take Magnesuim tablets. can you please advise why all of a sudden she is having this problem? [/INST] Hello thank you for posting here. By what you have explained, Lt looks like she is having sinus tachycardia supraventricular tachycardia (SVT). Sinus tachycardia is a condition when we have a heart beat due to running, exercising, stress and during infection in the body. So if it is sinus tachycardia then it is due to the infection. The other variant, SVT may also be triggered by infection in the body or due to abbe rant connections in the heart conduction system. It is a rarely harmful for the patient but required medications to settle down. Only an EKG will help to distinguish between them. Magnesium also helps in stabilizing a fast heart rate. But treating the cause - infection with a different antibiotic which doe snot worsen fast heart rate is advisable.it is usually a being problem, and after she recovers her normal heart rate she may probably not get it. However if she gets it on and off then there is a conduction pathway problem for which she should be on rate control medications. Thank you </s>