Short run of ventricular tachycardia and atrial fibrillation

Short run of ventricular tachycardia and atrial fibrillation

Short run of ventricular tachycardia and atrial fibrillation: Underlying rhythm is atrial fibrillation as there are no P waves and it is an irregular rhythm.  Short run of wide QRS tachycardia should be considered as a run of ventricular tachycardia. Alternate possibility is Ashman phenomenon and concealed transseptal conduction maintaining aberrancy [1]. But the short run is much faster than the basic ventricular rate of the atrial fibrillation. Yet a long-short sequence as in Ashman phenomenon is evident at the onset with cycle lengths of 480 and 320 ms. Moreover, the cycle length of the tachycardia beats is almost constant at 320 ms. Cycle lengths would have been irregular if it was Ashman phenomenon and concealed transseptal conduction. The pause of 600 ms after termination of the tachycardia is also in favor of ventricular ectopic activity causing a ventricular tachycardia. This can be considered like a full compensatory pause which is not part of the Fisch criteria for Ashman phenomenon.

One possibility to be considered when a run of ventricular tachycardia occurs in the setting of atrial fibrillation is digoxin toxicity. Digoxin is still being used for control of ventricular rate in atrial fibrillation, though its use has come down much compared to yesteryears when it was the sheet anchor of treatment. One would expect some ST – T changes (reverse correction mark sign) in the baseline rhythm in case of digoxin toxicity, which is not seen here. Moreover, the ventricular rate of atrial fibrillation is not that slow as we expect when toxic levels of digoxin are present. But these are not absolute criteria which can confidently rule out digitoxicity as a cause in this case. Other possibilities for increased myocardial irritability like electrolyte imbalance and myocardial ischemia are more likely for this type of rhythm on the monitor in the current scenario.

References

1. Gouaux JL, Ashman R. Auricular fibrillation with aberration simulating ventricular paroxysmal tachycardia. Am Heart J. 1947;34:366.
2. Fisch C. Electrocardiography of arrhythmias: from deductive analysis to laboratory confirmation–twenty-five years of progress.  J Am Coll Cardiol. 1983;1:306-16.