CEREBRAL HEMODYNAMICS DURING INDUCED TACHYCARDIA IN ROUTINE ELECTROPHYSIOLOGIC STUDIES - A TRANSCRANIAL DOPPLER STUDY

Supraventricular and ventricular tachyarrhythmia are established cause s of syncope. We investigated the mean blood flow velocities (V-mean) of the middle cerebral arteries (MCA) during routine cardiac electroph ysiologic studies in patients with supraventricular and ventricular ta chyarrhythmias in order to evaluate the changes in cerebral hemodynami cs associated with pre-syncopal and syncopal states. Thirtytwo patient s with a history of supraventricular (n = 14) or ventricular (n = 18) tachyarrhythmias were investigated in the nonsedated, post-absorptive stare in supine position. V-mean was assessed in bath MCAs by means of transcranial Doppler under resting conditions, during atrial and vent ricular pacing at constant rates (n = 28) and during induction of tach yarrhythmia (n = 4). Mean arterial blood pressure (MABP) and heart rat e were also recorded. Seven patients suffered pre-syncope at a heart r ate of 187 +/- 45 bpm (mean +/- SD) with an average drop of 44% in the V-mean MCA, and statistically insignificant changes in MABP. Five pat ients suffered syncope during tachyarrhythmia (mean heart rate 283 +/- 42 bpm) with a reduction of 69% in the V-mean MCA. MABP could be asse ssed in two of those patients and showed a drop of 75 and 43 mmHg, res pectively. During tachyarrhythemia pre-syncope and syncope are associa ted with an average reduction in V-mean MCA by 44% and 69%, respective ly. The decrease in MCA blood flow velocity is a more important predic tive factor for the development of pre-syncope and syncope than the MA BP.