Cerebral blood flow velocity declines before arterial pressure in patients with orthostatic vasovagal presyncope
Dan Dan, MDa,
Jeffrey B. Hoag, MDa,
Kenneth A. Ellenbogen, MD, FACCa,
Mark A. Wood, MD, FACCa,
Dwain L. Eckberg, MDb,* and
David M. Gilligan, MD, FACCa
a Departments of Medicine and Physiology, Medical College of Virginia at Virginia Commonwealth University, Richmond, Virginia, USA
b Hunter Holmes McGuire Department of Veterans Affairs Medical Center, Richmond, Virginia, USA
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Figure 1 Recording from one patient indicating the measurements made. Sbp, map, dbp = systolic, mean arterial and diastolic pressures. Bottom panel shows middle cerebral artery velocity (V) and calculations of indexes of cerebral blood flow velocity (CBFV). CBFVC = cerebral blood flow velocity corrected for RR interval (RRI); PI = pulsatility index.
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Figure 2 Break-point of mean arterial pressure and total middle cerebral artery blood flow velocity/RR interval (left) and sum of squared errors from iterative least squares linear regression (right) for one patient. Break-point analyses indicated that, in this patient, total cerebral blood flow/RR interval began to fall 28 s before mean arterial pressure.
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Figure 3 Average of all systemic hemodynamic and cerebrovascular indices of last 300 s of tilt in syncopal and nonsyncopal patients. Time "0" (vertical dashed line) represents the time of syncope for the syncopal patients, and 2 min before the end of tilt for nonsyncopal patients.
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Figure 4 Average differences among break-points of onset of symptoms, cerebrovascular indexes, and mean arterial pressure. Open circles are individual values for the tilt-positive subjects, and the closed circles are means ± SEM. Negative values signify break-points occurring before the mean arterial pressure break-point. RRI = RR interval.
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