Transcranial Doppler monitoring during head upright tilt table testing in patients with suspected neurocardiogenic syncope

Abstract

The aim of the present study was to evaluate the mechanism of cerebrovascular autoregulation in patients with neurocardiogenic syncope using bilateral transcranial Doppler (TCD) monitoring during head upright tilt table testing (HUT). Two hundred and six patients were prospectively studied. One hundred and fifty-nine subjects (77%) had a prior history of syncope and 47 (23%) had presyncope. Ninety-nine patients (48%) had syncope or presyncope during HUT with a 76% fall in diastolic middle cerebral artery blood flow velocity (D-MCA-BFV). Systolic MCA-BFV (S-MCA-BFV) fell by 33%. Deepening of the dicrotic notch in the Doppler waveform always preceded the fall in D-MCA-BFV. Patients without syncope or presyncope (n=96) had smaller changes in cerebral blood flow velocities during HUT and only twenty-two subjects had transient deepening of the dicrotic notch. Eleven subjects had presyncope during HUT due to an exaggerated response to nitrates with progressive arterial hypotension without bradycardia and changes during TCD monitoring that were intermediate between positive and negative HUT. In conclusion, patients with neurocardiogenic syncope have changes in cerebral blood flow during the event. TCD monitoring during HUT helps to assess these alterations.

Regulation of middle cerebral artery blood velocity during recovery from dynamic exercise in humans

“…The findings provide important information regarding grayor black-out incidents that occur immediately at the cessation of exercise (5,8) and are consistent with previous studies (2,22) that have reported that syncope was related to impaired regulation of the diastolic phase of MCA V. When blood pressure decreases during syncope, MCA Vd diminishes, whereas MCA Vs may be well maintained (22). In addition, during head-up tilt, MCA Vs and MCA Vd fall significantly.…”

“…Rather, our findings suggest that the influence of CA on MCA Vd is different from MCA Vs during exercise and recovery. These differential CA influences may be important physiologically because previous studies have already demonstrated that there is a different response of MCA V to change in perfusion pressure between systolic and diastolic phases during specific conditions, such as orthostatic stress (2,22) and exercise (18,21). Although both transfer function phase and gain are used as an index of dynamic CA, changes in gain were not consistent with changes in phase in the present study.…”

Early Childhood Gender Differences in Anterior and Posterior Cerebral Blood Flow Velocity and Autoregulation

“…Previously established age-appropriate depths were used to insonate both the MCAs and BAs. 4 During steady-state conditions, Vmca, Vbas, mean arterial pressure (MAP), heart rate, and respiratory rate were recorded in each position.…”

HOBOE (Head-of-Bed Optimization of Elevation) Study: Association of Higher Angle With Reduced Cerebral Blood Flow Velocity in Acute Ischemic Stroke

“…6,[13][14][15][16] Transcranial Doppler ultrasound has been used in several studies investigating autoregulation. 3,8,14,[17][18][19] However, TCD studies of orthostatic blood flow changes in patients with stroke are limited. 20,21 Ischemic stroke typically is caused by occlusion of a cerebral blood vessel 22 (commonly the middle cerebral artery [MCA]).…”