PLEASANTON, Calif - Thoratec Laboratories Corporation has announced that it will purchase Thermo Cardiosystmes, Inc. for $572 million in newly issued stock. Under the new deal, which is expected to close next year, Thoratec will exchange .835 a newly issued share for each share of Thermo Cardiosystems. Both companies are manufacturers of artificial heart devices. For more information visit www.thoratec.com.