Normally my heart rate in 80s but when i'm sick it can get upto. 150/160. why? did ultra sound , cat scan on heart and both normal any ideas ?

SVT: It's possible that you have a supraventricular tachycardia (or other arrhythmia), but it's also possible that it's simply sinus tachycardia (normal heart rhythm, elevated due to stress or fever). If you can anticipate a spell (eg when you're sick), ask your doc for a 24 hour holter recorder to document exactly what your heart rhythm is doing.