An overview of Postural Orthostatic Tachycardia Syndrome Standing up is something most of us take for granted; we've been doing it since childhood. Our bodies automatically adjust to the pull of gravity by increasing vascular tone, heart rate, and cardiac output. Blood vessels contract, heart rates increase and our systolic blood pressure remains the same or decreases slightly while diastolic pressure increases slightly (Brunner & Suddarth, 2000, p. 546). Our bodies operate in perfect h