Vasis I mixed

There is a slow but progressive fall in blood pressure and pulse pressure which begins immediately after tilting and continues until the onset of syncope. Compared with the supine position, the heart rate increases during this phase by a variable amount. The vasovagal reaction occurs when a critical value of blood pressure is reached. The onset of the syncopal phase can be appreciated by a change in the slope of decline of blood pressure which coincides with a decrease of total peripheral resistance, as well as by a change in heart rate which starts decreasing, but does not fall to less than 40 bpm.