anxiety and panic are the first possibilities. sudden onset of palpitations is a very unusual sign of heart attack. none of the investigation and symptoms are compatible with the heart attack. although there are some ecg changes like q waves which can be present are indicative of heart damage in case of heart attack. but your echo is normal and so no need to worry at all. there is also t-wave insertion in lead 3 and non-significant elevation in avr. so given these changes i would advise for some stress test like treadmill test or stress thallium which you did not mention anything about. if you have not undergone it then you can have it to rule out the possibility of inducible ischemia. the qrs prolonging of such mild degree is not significant and this much variation may normally occur with different ecg. it is not very common with omeprazole. for further information consult a cardiologist online --><link>
could omeprazole cause changes in ecg and increase the heart rate?