The purpose of this study is to determine if siltuximab has an effect on the heart function measured by ECG recordings and more specifically to determine if siltuximab has an effect on the QT interval in patients with Monoclonal Gammopathy of Undetermined Significance (MGUS), Smoldering Multiple Myeloma (SMM) or Indolent Multiple Myeloma (IMM). The study will also look to see if siltuximab may be useful in treating patients with MGUS, SMM or IMM.