Thoratec Corporation initiated a worldwide medical device correction of all serial numbers of the HeartMate II Left Ventricular Assist Systems (HM II LVAS) having Catalogue No. 1355 or 102139, which have been distributed since the beginning of clinical studies in November 2003. Over time, wear and fatigue of the percutaneous lead connecting the HeartMate II LVAS blood pump with the System Controller may result in damage that could interrupt pump function, require reoperation to replace the pump and potentially result in serious injury or death. The estimated probability of the need for pump replacement due to percutaneous lead damage is 1.3% at 12 months, 6.5% at 24 months and 11.4% at 36 months. Patients who are currently being supported by a HeartMate II LVAS should contact their doctors, who can assess the wear and fatigue of the percutaneous lead as well as provide proper instruction on management and care of the lead. Thoratec voluntarily issuied an Urgent Medical Device Correction notice after confirming 27 reports where wear and fatigue to the percutaneous lead necessitated pump replacement. These reports occurred over five years of clinical experience with 1,972 implants. All patients who have undergone a replacement of the HeartMate II pump survived the operation and were alive at least 30 days postoperatively. In five cases, pump replacement was not feasible and the patients expired. The affected systems were distributed to 153 hospitals and distributors throughout the United States, Europe, Canada and other countries. The HM II LVAS can be identified by the catalogue number located on the label of the package.