QUINIDINE AND HIGH-AMPLIFICATION ECG

High-amplification EGG (HA EGG) is now used routinely to evaluate vent ricular tachycardia. The effects of 300 to 600 mg quinidine were deter mined in 26 heart disease patients with spontaneous and inducible vent ricular tachycardia. Programmed ventricular stimulation was performed and an HA ECG recorded (40 Hz high-pass filter) before and under treat ment, The stimulation became negative under treatment in-nine patients (group I), whereas the 17 others had persistent inducible tachycardia (group II). HA EGG tracings were modified in groups I and II, with a QRS duration increase of 7% and 8%, respectively, and RMS 40 decrease of 37 % and 29 %, and an LAS increase of 16 % and 17 %. Furthermore, o ne of the three group I and four of the seven group II patients who ha d a normal HA EGG tracing before treatment developed HA ECG abnormalit ies under treatment. An arrhythmia-inducing effect of the treatment wa s noted in three group II patients; this effect was not detected by HA EGG. In conclusion, changes in HA ECG tracings were seen during quini dine therapy of patients with ventricular tachycardia, and this effect was independent from the effect of antiarrhythmic agents on induction of the ventricular tachycardia. In addition, abnormalities of high-am plification ECG tracings developed in some patients under quinidine th erapy. These data suggest that class I anti-arrhythmic agents modify h igh-amplification ECG tracings and that these modifications fail to pr edict whether the treatment will prove effective.