Oscillatory cerebral blood flow in postural tachycardia syndrome (1183.7)

Abstract

Measureable upright cognitive loss occurs in postural tachycardia syndrome (POTS). Some POTS patients have impaired cognition associated with an excessive decrease in mean cerebral blood flow (CBF) equivalent to a loss of static autoregulation. More often, however, CBF is not decreased but a demonstrable loss of neurovascular coupling occurs and may result from time dependent changes in CBF. We tested the hypothesis that CBF changes comprise increased oscillatory CBF in POTS (N=10, age 17‐28 y) compared to healthy volunteers (N=9) by measuring changes in CBF velocity (CBFv) using transcranial Doppler ultrasound of the left middle cerebral artery during a 70° upright tilt. Total amplitude and peak power of heart rate, BP, and CBFv variability (V) were measured over an extended frequency range of 0.01 to 0.5 Hz using Welch’s method. Nonlinear methods were used to compute phase synchronization between MAP and CBFv. Upright HR was increased in POTS (128±7 vs 85±3 bpm), as was diastolic BP (74±3 vs 64±3 mmHg) Peripheral resistance, cardiac output, and mean CBFv were not different. Upright amplitude, peak power, and peak frequency of HRV were increased in POTS (p<.01) (11.1±1.2 centered at .088 Hz vs 7.6±1.1ms/Hz centered at 0.068Hz and 8.3±1.1 vs 4.2±0.7•!08ms2), as for BPV (p<.01) (9.2±0.8 vs 6.0±0.7mmHg/Hz centered at .086 Hz and 15.4±4.7 vs 3.0±1.1•!08mmHg2 centered at 0.70Hz), and for CBFV (pCBFv phase synchronization was much larger in POTS compared to control (P<.004) (0.97±0.01 vs 0.76±0.11).When upright POTS patients have increased BP oscillations (Mayer) waves with disproportionately increased oscillations of CBFv occurring at a higher frequency than control. These observations cannot be interpreted within the framework of a linear Ohmic relationship between BP and CBF but rather indicate increased coupling of BP to CBFv in POTS when upright. Large oscillatory CBF has been shown to subvert neurovascular coupling in animal models.Grant Funding Source: NHLBI