A catheter is provided that has a basket-shaped electrode assembly with an improved
mechanism for expanding and contracting the electrode array. The expansion mechanism
is designed to permit reproducible reintroduction of the catheter into the heart.
The catheter comprises an elongated catheter body having at least one lumen therethrough.
A basket-shaped electrode assembly is mounted at the distal end of the catheter
body. The basket assembly comprises a plurality of spines connected at their proximal
and distal ends, each of which comprises at least one electrode. The basket assembly
has an expanded arrangement wherein the spines bow radially outwardly and a collapsed
arrangement wherein the spines are arranged generally along the axis of the catheter
body. An expander is attached at or near its distal end to the distal ends of the
spines and extends through the catheter body. The expander has a proximal end that
extends out the proximal end of the catheter body a lumen extending therethrough.
In use, the expander can be moved longitudinally relative to the catheter body
to expand and contract the basket-shaped electrode assembly. The lumen that extends
through the expander permits the catheter to be introduced into the heart over
a guidewire. If the catheter is removed and subsequently reintroduced over the
guidewire, the basket-shaped electrode assembly can be easily reintroduced to its
original position.