Narrow QRS complexes are formed due 1)reentry and in it is of two types. A) AVNRT and B)AVRT and in AVNRT we see "p" wave is submerged under QRS complex and we can see the rate will be 180 to 250/min in both AVNRT and AVRT. In AVRT, inverted "p" waves are after QRS complex and 'rp' interval is >100 ms.In AVRT the type is orthrodromic.
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