Narrow Complex Tachycardia at a Rate of 220

40-something yo who is on flecainide and diltiazem had suddenonset chest pain, palpitations, shortness of breath and diaphoresis:Rate is 220.  What do you think?It is fast, narrow, and regular, without P-waves.  So it isnot atrial fib andnot VT.  It is a regular narrow complex tachycardia.  There is a lot of ST depression -- this is ischemia caused by the very fast rate and is an indication for emergent electrical cardioversion.What is the DDx?  ----PSVT (which includes AVNRT and orthodromic AV reciprocating tachycardia) [AVRT uses an accessory pathway, a " bypass tract " and thus is seen in WPW; about 30% of PSVT is orthodromic AVRT] ----Atrial Flutter with 1:1 conduction.Which is it?The fact that the patient is onFlecainide and Diltiazem is good evidence that this is atrial flutter with 1:1 conduction.  These medications are primarily given to patients with atrial fib or flutter (the flecainide keeps the patient in sinus rhythm, and the diltiazem prevents 1:1 AV conduction when the patient is in flutter).If you look closely at lead II across the bottom, it appears there are flutter waves.This is atrial flutter with 1:1 conduction.  The patient is not on anticoagulants, but the very fact that he is on flecainide is evidence that he probably spends most time in sinus rhythm.The providers thought this was AVNRT.He was given adenosine 6mg, then 12mg, with no change.  If AVNRT, then one would expect conversion...
Source: Dr. Smith's ECG Blog - Category: Cardiology Authors: Source Type: blogs