HEART-RATE DURING SPONTANEOUS AND INDUCED PAROXYSMAL SUPRAVENTRICULARTACHYCARDIA

It is generally assumed that paroxysmal supraventricular tachycardia ( PSVT) induced during invasive electrophysiological study reproduces th e patient's spontaneous, clinical arrhythmia. Even in the absence of a ntiarrhythmic drugs, however, there may be significant differences in characteristics of the induced and spontaneous arrhythmias. We compare d the heart rate of PSVT in 38 patients who had undergone electrophysi ological study with induction of PSVT who also had a spontaneous episo de of PSVT documented by transtelephonic ECG monitoring during a perio d when all antiarrhythmic drugs were withheld. The heart rate during s pontaneous PSVT was faster than the heart rate of PSVT induced during electrophysiological study; the mean difference was 16 beats/min (P < 0.001). We conclude that heart rate of PSVT induced during electrophys iological study generally underestimates the heart rate of spontaneous PSVT in the antiarrhythmic drug-free state. This may be due to differ ences in the autonomic and hemodynamic states during spontaneous and i nduced arrhythmias.