Cardiac Applications of 123I-mIBG Imaging

Cardiac autonomic innervation plays a key role in maintaining hemodynamic and electrophysiologic harmony. Cardiac sympathetic function is adversely altered in many disease states, such as congestive heart failure, myocardial ischemia, and diabetes. 123I-mIBG, a sympathetic neurotransmitter radionuclide analog, aids in the detection of sympathetic innervation abnormalities and can be imaged with planar and single-photon emission computed tomographic techniques. Cardiac 123I-mIBG uptake can be assessed by the heart mediastinal ratio (H/M), tracer washout rate, and focal uptake defects. These parameters have been widely studied and shown to correlate strongly and independently with congestive heart failure progression, cardiac arrhythmias, cardiac death, and all-cause mortality. There is accumulating evidence that 123I-mIBG imaging can help to monitor a patient's clinical course and response to therapy. The ability to predict potentially lethal ventricular arrhythmias promises to help more accurately select patients for implantable cardioverter defibrillators, limiting unnecessary devices and identifying additional patients at risk who do not meet current guidelines. 123I-mIBG shows potential to help determine whether greater risk and usually more expensive ventricular assist device therapies or cardiac transplantation might be needed. Although more investigation in larger populations is needed to strengthen previous findings, cardiac 123I-mIBG imaging shows promise as a new technique for recognizing and following potentially life-threatening cardiac conditions.