Microcirculation and Vascular Function After Fontan Surgery

Overview

Fontan Surgery is done for children with only one working lower chamber of the heart called the 'Single Ventricle'. This surgery involves making connections between the two big veins that drain oxygen deficient blood to the heart and the lung artery directly. Fontan patients may develop long-term complications such as reduced heart function or oxygen levels, increased pressure in the veins, liver or kidney problems etc. The reasons for these complications are poorly understood. The small blood vessels in the body or 'microcirculation' are tiny (can be seen only by microscope) and they supply food and oxygen to the tissues. Very little is known about what happens to the microcirculation in adult Fontan survivors . In this study the investigator want to understand why these adult Fontan survivors develop complications by looking at their microcirculation and comparing them with healthy people and those who were operated for other congenital heart diseases. The study will be conducted in East Midlands Congenital Heart Centre, Glenfield Hospital. Leicester.

In normal heart, there are two working lower chambers where one chamber pumps the blood to the lungs and other chamber pumps the blood to the body. However, some congenital heart conditions have only one working lower chamber of the heart called the 'Single Ventricle'. This condition is often associated with hole between the heart chambers with increased or decreased blood flow to the lungs. This can lead to mixing of blood in the heart with low oxygen levels in the body. The surgery for single ventricle is usually performed in stages starting from the infancy. Fontan surgery is the last stage where the two big veins that return the blood to the heart is connected to the lung artery directly. This surgery improves the oxygen levels in the blood and lessens the burden on the single ventricle. The blood is not pumped to the lungs by the heart but rather enters passively to the lungs through this new surgical connection. Some people operated for Fontan surgery have many short-term and long-term complications such as increased pressure in veins , poor heart function and low oxygen levels in the blood. In particular, the organs below the chest such as kidney, liver and gut are affected, and all of these predict poor outcomes. The reason for these complications are poorly understood. The small blood vessels in the body or 'microcirculation' are very tiny and are less than 150 microns in diameter. These includes arterioles, capillaries, and venules. Very little is known about the microcirculation in adult Fontan survivors and its association with aortic stiffness, late complications, and quality of life. In this study, The investigators want to look at the blood vessels in adult Fontan survivors, people operated for other congenital heart diseases, and healthy volunteers using a special microscope called Hand Held Capillary Microscopy. The investigators will visualize their blood vessel appearance, number, and size they have in their hands, feet, and under the tongue. This procedure is non-invasive and will not cause any pain. The aortic stiffness will be measured non-invasively using a special blood pressure monitor called Mobile 'O' Graph, which is about size of a pocket diary. 24 hour blood pressure monitoring is optional. The investigator will also collect the information about the quality of life using questionnaires as few studies have shown that the quality of life is affected in adult Fontan survivors and it was associated with poor vascular function. Age matched healthy controls and adults survivors of other congenital heart surgeries will also undergo these tests for comparison purpose. This study will be conducted at East Midlands Congenital Heart Centre, Glenfield Hospital, Leicester.