Evaluation of the VU-AMS device in pediatric cardiology

The VU-AMS (Vrije Universiteit Ambulatory Monitoring System) is developed at
the VU University and is designed to record four different signals: the
electrocardiogram, impedance cardiogram, movement, and hand skin conductance.
Until today, this device is mainly used to study stress and emotion, both in
laboratory and naturalistic environments. The current study is designed to
evaluate the clinical usefulness of the VU-AMS device in pediatric cardiology.

In order to do this, we first need to gather reference values and validate the
device on several modalities that are of interest in the clinical evaluation of
pediatric cardiac patients. Stroke volume and cardiac autonomic nervous
activity will be measurements of interest.

Therefore, 150 healthy children will be recruited from the outpatient clinic
(1-4 years), primary schools (4-12 years) and secondary schools (12-18 years)
in Leiden. Detailed echocardiogram will be performed and subsequently, the
VU-AMS device will be worn for 24 hours. Stroke volume measures from the VU-AMS
device and echocardiography will be compared. Also, 24 hour fluctuations in
stroke volume and autonomic nervous activity will be studied.

To evaluate the clinical usefulness of the VU-AMS in pediatric cardiology.

To validate and improve the measures of stroke volume from the VU-AMS device.
VU-AMS stroke volume measures will be compared with stroke volume measured by
echocardiography.

To develop reference values in a normal population of children for sympathetic-
and parasympathetic nervous indices, and stroke volume changes during rest and
exercise.

The design of the study is observational. 150 healthy children with an age
range of 1-18 years will be recruited. Children from 1-4 years will be
recruited from the outpatient department of pediatric cardiology. Those who
have an innocent murmur or other complaints that turns out to be unrelated to a
cardiac disorder can be included. Children from 4-12 years will be recruited
from a primary school, and from 12-18 years from a secondary school. Children
who have any chronic disorder or use medication cannot be included. Five to ten
children of each year-group will be included.

The children will detailed echocardiography will be performed, including 2- and
3-dimensional strain and tissue Doppler imaging, jointly with VU-AMS recording
to test the validity of stroke volume measures by the VU-AMS in this
population. Subsequently, the VU-AMS device will be used to measure 24 hour
fluctuations in cardiac sympathetic- and parasympathetic nervous activity and
stroke volume in all children. An i-pod or i-phone running a program to keep
an electronical diary designed at the VU University will be used to monitor
activities and posture and location during the 24 hour ambulatory measurement.
Reference values in a healthy population will be developed and the VU-AMS will
be validated.

All children will undergo echocardiogarphy during a 30-minute period and will
wear the VU-AMS device during 24 hours. During that period there are no
restrictions except from bathing and swimming.

Since we are studying the normal variability and usefulness of the VU-AMS
device in the pediatric population it is only possible to answer these
questions by studying children.

There is a huge amount of experience of echocardiography and 24-hour Holter
monitoring in children. Usually there are no problems in performing these
studies.