SUPRAVENTRICULAR TACHYCARDIA WITH WIDE QR S COMPLEXES DURING VAUGHAN-WILLIAMS CLASS-I ANTIARRHYTHMICS - DIAGNOSTIC AND THERAPEUTIC IMPLICATIONS

The authors report 8 cases of regular tachycardia with wide QRS comple xes during treatment with Vaughan-Wiiliams class 1 antiarrhythmic drug s. These antiarrhythmics, prescribed to prevent atrial fibrillation (3 patients) and atrial flutter (5 patients), were flecainide in 4 cases , propafenone in 2 cases and cibenzoline and hydroquinidine respective ly associated with digitoxine and propranolol. These wide complex tach ycardias were regular atrial tachycardias with 1/1 conduction to the v entricle. The action of the drug, more pronounced on intra-atrial cond uction velocities than on atrioventricular node refractoriness resulte d in transformation of flutter at 300 cycles/min with 2/1 conduction a nd a ventricular rate of 150 cycles/min to atrial flutter at 210 cycle s/min with 1/1 ventricular conduction. This acceleration of the Ventri cular rate was accompanied by widening of the QRS complex. Using the n ew ventricular tachycardia criteria recently published by Brugada resu lted in a diagnostic error in 7 out of the 8 cases. The recording of a wide QRS complex tachycardia in a patient on class 1 antiarrhythmic t herapy for an atrial arrhythmia should alert the physician to 1/1 atri al tachycardia despite morphological electrocardiographic criteria of ventricular tachycardia. The 1/1 atrial tachycardia may be poorly tole rated and require emergency treatment. The preventive association of a drug which stows conduction through the atrioventricular node is not always effective.