Faculty
Health Sciences
Supervisor Name
Dr. Kevin Shoemaker, Dr. Leena Shoemaker
Keywords
Vascular compliance, cerbrovascular control, vasovagal syncope, cerebral perfusion, cerebral blood flow
Description
Background: The rapid reduction in arterial pressure (AP) during VVS is associated with a decline in diastolic cerebral blood velocity (CBV) and maintained systolic CBV. We tested the hypothesis that this response may represent increased cerebrovascular compliance (Ci) in the presence of rapid hypotension.
Methods: AP and CBV were recorded from 14 otherwise healthy patients (34 ± 11 years) at rest and during head-up tilt (80°, 5-28 min). Baseline, mid-tilt, and VVS were analyzed. Individual AP and CBV waveforms were input into a modified Windkessel model to calculate Ci.
Results: Upright posture resulted in a decrease in CBV (-9 ± 8 cm/s; one-way ANOVA: P < 0.01 vs baseline), an increase in Ci (132 ± 72%; P < 0.01), but no change in AP (P = 0.14). Compared to mid-tilt, systolic (-34 ± 13%) and diastolic (-37 ± 10%) AP experienced similar reductions during VVS (P = 0.23 vs systolic CBV). In contrast, there was a reduction in diastolic CBV (-18 ± 9 cm/s; P < 0.01) in the presence of sustained systolic CBV (0 ± 12 cm/s; P > 0.99). CVR decreased by 14 ± 20% during VVS (P = 0.03 vs mid-tilt). The increase in CBV pulsatility during VVS (81 ± 50%; P < 0.01) occurred simultaneous to an increase in Ci (657 ± 410%; all P < 0.01).
Conclusions: An increase in CBV pulsatility is indicative of an increase in Ci, which may protect against reductions in cerebral perfusion during VVS.
Acknowledgements
Thank you to my supervisors, Dr. Kevin Shoemaker and Dr. Leena Shoemaker for their continuous guidance and support throughout this project and for allowing me to further my research experience.
Special thanks to Dr. Geoff Coombs and Dr. Ronald Schondorf for their support, guidance and feedback.
Creative Commons License
This work is licensed under a Creative Commons Attribution-Noncommercial 4.0 License
Document Type
Poster
Rapid changes in vascular compliance contribute to cerebrovascular adjustments during vasovagal syncope (VVS)
Background: The rapid reduction in arterial pressure (AP) during VVS is associated with a decline in diastolic cerebral blood velocity (CBV) and maintained systolic CBV. We tested the hypothesis that this response may represent increased cerebrovascular compliance (Ci) in the presence of rapid hypotension.
Methods: AP and CBV were recorded from 14 otherwise healthy patients (34 ± 11 years) at rest and during head-up tilt (80°, 5-28 min). Baseline, mid-tilt, and VVS were analyzed. Individual AP and CBV waveforms were input into a modified Windkessel model to calculate Ci.
Results: Upright posture resulted in a decrease in CBV (-9 ± 8 cm/s; one-way ANOVA: P < 0.01 vs baseline), an increase in Ci (132 ± 72%; P < 0.01), but no change in AP (P = 0.14). Compared to mid-tilt, systolic (-34 ± 13%) and diastolic (-37 ± 10%) AP experienced similar reductions during VVS (P = 0.23 vs systolic CBV). In contrast, there was a reduction in diastolic CBV (-18 ± 9 cm/s; P < 0.01) in the presence of sustained systolic CBV (0 ± 12 cm/s; P > 0.99). CVR decreased by 14 ± 20% during VVS (P = 0.03 vs mid-tilt). The increase in CBV pulsatility during VVS (81 ± 50%; P < 0.01) occurred simultaneous to an increase in Ci (657 ± 410%; all P < 0.01).
Conclusions: An increase in CBV pulsatility is indicative of an increase in Ci, which may protect against reductions in cerebral perfusion during VVS.