Haemodynamic Determinants Of HYpertension In Children And Young People And Role Of The Sympathetic Nervous System: HY CYP

Background

Around a third of the adult population suffers from high blood pressure (medically known as "hypertension"). If left untreated, hypertension is a major risk factor for having a heart attack or a stroke. Put together these cause the largest number of deaths each year in the world.

A lot of research has been conducted into the changes that take place in the body in adults with hypertension but not much is known about what causes hypertension in children. More and more children are being diagnosed with high blood pressure - partly because doctors are checking for it more, but also because it is a common problem that develops alongside being overweight.

Children and young people are unfortunately becoming more overweight over time. This means it is becoming increasingly important to find out what causes hypertension in children and young people so we can offer the best treatment. It is also important because hypertension in children often leads on to hypertension in adults.

Hypertension can be caused either by the heart pumping too fast or too hard for the body's needs (cardiac overactivity), or by the blood vessels that carry the blood away from the heart becoming stiff or narrowed. Old studies suggest that hypertension is caused mainly by alterations in blood vessels. Some more recent evidence, including work from our group suggests that it is the heart beating harder and faster that is the main problem in young people.

We would like to look at this in more detail and try to ascertain the cause of any cardiac overactivity we find. We suspect that young people with hypertension have increased "fight or flight" activity (called sympathetic nervous system activity) and we will use breathing exercises and medication to try and block this activity to see what difference this makes to blood pressure in children and young adults with hypertension.

Aims:

This project will use state of the art blood pressure measurements and heart scans to measure the flow of blood in the heart and blood vessels of children and young people with hypertension and compare it to those without hypertension. We will also manipulate some of the messages getting from the brain to control the heart and blood vessels.

Objectives:

- We will use sophisticated imaging techniques (ultrasound and magnetic resonance imaging technology or MRI) to study in detail how the flow of blood through the heart and the blood vessels varies between young people with hypertension and with normal blood pressure.

- We will use breathing exercises to reduce the heart rate and volume of blood pumped during each heartbeat and see whether this has a greater effect in young people with hypertension or young people with normal blood pressure.

- We will use two medicines that work to reduce blood pressure in different ways and assess what effect these medications have on how the heart pumps and how the blood flows through the blood vessels. Impact

If we confirm our hypothesis that children and young people with high blood pressure have increased cardiac activity and not increased resistance in their blood vessels, it would lead to a shift in the way we think about high blood pressure in children and young adults. Many of the medications we use target the blood vessels and may therefore not be the best medications to use in young people.

We hope this research will lead to a clinical trial comparing how well different types of blood pressure medication work in this age group of patients. This research will also be one of the first studies to use MRI to study blood flows in hypertension in this age group, and the first study to manipulate the "fight or flight" response for children without using invasive and painful techniques.