Funding outcome

Objective: Measure the relationship between heart function and brain blood flow in response to standing in patients with postural orthostatic tachycardia syndrome (POTS) compared with healthy participants. Rationale: POTS is a chronic condition that predominantly affects adolescents, young adults, and women. The core problem in POTS is patients cannot stand for long periods of time because of symptoms like lightheadedness and large increases in heart rate that causes them to sit down. Over months, many patients with POTS become very debilitated and usually cannot participate in normal activities like school, social activities, or sports. One of the worst symptoms that adolescents with POTS describe is 'brain fog' - a symptom that makes it difficult to concentrate, finish school assignments, or solve problems. The brain fog and other brain symptoms like lightheadedness are thought to be related to decreased brain blood flow while standing. However, brain blood flow has never been directly measured in POTS. With the state of art magnetic resonance (MR) technology at the Peter Allen MRI Center at the University of Alberta, brain blood flow can be measured directly for the first time using a specialized technique called 'arterial spin labelling'. In addition, the engineers at the MRI center are able to take live images of the heart while it is beating. The role of the heart in POTS has never been tested with MRI while standing because patients are required to lie down for the test. However using a specially constructed chamber that creates negative pressure in the legs, we will replicate the effect of standing (i.e. a shift of blood to the legs). So for the first time, we will be able to study the connection between the brain and heart in patients with POTS at rest and with simulated standing. Methods: Healthy adolescents and young adults less than 21 years and patients with POTS, most of whom are expected to be female, will be invited to participate. If it is safe for them to undergo an MRI, their brain blood flow and heart function will be evaluated at the Peter Allen MRI Center both at rest and with lower body negative pressure. In addition we will test their brain function using a standardized memory and concentration test that is easy to administer in the MRI machine. Anticipated Outcomes: Patients with POTS are often frustrated by the lack of understanding by care providers including clinicians because no one can 'measure' their symptoms. Understanding the cause of the brain symptoms in POTS and the relationship between brain blood flow and heart function will provide a clinically useful tool to diagnose and manage the condition. The objective measurement of both brain blood flow and heart function in POTS will also serve to test new treatments with reliable techniques.