Case 27: Palpitations
Tuesday, September 13th, 2011Author: Dr Ian Stell
This 62 year old presented with a short history of palpitations. He had undergone several cardioversions in the past, and believed he had atrial fibrillation. His heart rate was 241 beats/min, he was hypotensive, but not shocked.
1. Could this be Wolf-Parkinson-White syndrome (WPW) with atrial fibrillation (AF)?
With an accessory pathway, patients with WPW and paroxysmal AF can have very fast ventricular response rates, particularly if the AV node is slowed by drugs and conduction is preferentially via the accessory pathway. (This is very dangerous, and can rapidly deteriorate to VF. It is the reason why most AV nodal blockers should be avoided in this situation – only procainamide and cardioversion are advised).
However WPW and AF passing through an accessory pathway produces variable QRS complex durations due to fusion with sinus beats. The QRS complexes seen here are very constant, making this very unlikely (thankfully!).
2. Could this be ventricular tachycardia?
Click to see the answerThis is unlikely for three reasons: Firstly the complexes, particularly in V4-V6 are not wide enough for VT. Secondly there are no ‘fusion’ or ‘capture’ beats; and finally the history of AF means that a supra-ventricular cause for the arrhythmia is likely.
3. How could the diagnosis be established?
Click to see the answerThis was thought to be a very fast supra-ventricular tachycardia. Adenosine was given to slow the ventricular response and reveal the underlying atrial activity. This showed atrial flutter at a rate around 250/min. Therefore the patient had atrial flutter with one-to-one block.
Attempts were made to increase the AV block (and hence slow the ventricular rate with beta-blockers). This was not successful, and cardioversion was undertaken to restore sinus rhythmn.