Cardiac Radiopharmaceuticals

• DEFINITION:
  CARDIAC RADIOPHARMACEUTICAL: a radioactive drug which, when administered for purpose of diagnosis of heart disease, typically elicits no physiological response from the patient. Even though non-radioactive thallium is extremely cardiotoxic, it is not dangerous to administer a 3 mCi IV dose of Tl-201 thallous chloride to a patient since the dose only contains ~40 ng of Tl¹⁺.
   

• PROPERTIES OF AN IDEAL CARDIAC AGENT
   

  • Uptake proportional to blood flow
  • High heart/background ratio
  • No redistribution, no clearance
  • Isotope energy optimal for imaging and dosimetry
  • Readily available commercially
  • Suitable for myocardial perfusion with SPECT
  • Xenon-like compound (inert)
  • Lipid soluble, crosses cell membranes
     

• PROPERTIES OF IDEAL MYOCARDIAL PERFUSION IMAGING AGENT
   

  • High myocardial extraction efficiency at all flows
  • No pharmacologic effects
  • Short t _biological and t _physical allow repeated studies over short time span
  • Minimizes radiation dose
  • Rapid blood clearance
  • Instant kit Tc-99m agent with ideal photon energy, low-cost, and wide availability
     

• CATEGORIES OF RADIOPHARMACEUTICALS FOR MYOCARDIAL IMAGING
   

  • Myocardial perfusion agents (Tl-201, Rb-82, Tc-99m agents)
  • Blood Pool agents (Tc-RBC)
  • Myocardial Viability Agents, e.g., F-18 FDG
  • Myocardial metabolism agents, for example, labeled fatty acids
  • Myocardial necrosis agents, for example, labeled monoclonal antibodies
  • Labeled lipoproteins for imaging atherosclerosis, e.g., I-123 HDL, I-123 LDL

   

• OTHER CARDIAC IMAGING

  • Infarct Imaging
  • Other Uses of 99mTc Sestamibi