A Pilot Study Comparing the Programmed Delay Between the Atrial and Ventricle Interval

There are different kinds of pacemakers and different ways they can be set up to try to make
the heart beat regularly. A normal heart has four chambers; these four chambers pump in a
co-ordinated way to move blood effectively. When pacemakers were first invented, they told
the heart when to pump, but didn't make the four chambers work well together. Newer
pacemakers can give more detailed instructions, so the chambers work together more
effectively. We already know that the newer (bi-ventricular) pacemakers work better for some
patients with heart failure.

There are blood tests (often referred to as "markers") that give us information about how
well your heart is working and about how your body is responding to heart failure. The idea
of this study is to compare different ways of setting up a pacemaker, using these blood
tests to give us information about how well it's working. We hope to learn if we can use
this approach to figure out the best pacemaker setup ("programming") for each individual
patient.

Usually pacemakers have two wires or leads, one is in the top right chamber and the other in
the bottom right chamber of the heart. The newer pacemakers, which are given to patients
with heart failure, have an additional lead or wire, which goes to the left side of the
heart. So when heart contracts the lead from top chamber sends impulses to bottom chambers
and the leads in right and left sides of bottom chamber responds by sending impulses in a
co-ordinated way enabling heart to contract efficiently.

Currently, the standard way of treating patients with heart failure is by pacing the top and
then bottom chambers, based on a timing interval determined by ultrasound, while also pacing
the two bottom chambers in a coordinated manner. There are differences of opinion among
experts and by previous studies regarding this method. Pacing is accomplished through
pacemaker wires, which are placed in the right top chamber, the right bottom chamber and the
left bottom chamber of the heart.

The setting we propose to adjust is the timing between the impulse sent between top and
bottom chambers.