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.