Application of Cardiac Neurohormonal Imaging to Heart Failure, Transplantation, and Diabetes

The neurohormonal system adapts to body demands, but in cardiac disease it can become maladaptive. A key component, the sympathetic nervous system, can be imaged with radiotracers such as iodine-123-meta-iodobenzylguanidine (¹²³I-mIBG), a norepinephrine analogue. Parameters assessed are the heart-to-mediastinal ratio (HMR), tracer washout, and regional single photon emission computed tomography (SPECT) defects. Much focus has been on heart failure that has a large neurohormonal pathophysiologic component. ¹²³I-mIBG imaging has powerful risk stratification ability for this high morbidity/mortality condition. A lower HMR increases the likelihood of clinical worsening, ventricular arrhythmias, and cardiac death. ¹²³I-mIBG imaging could potentially guide the use of biventricular pacemakers and ventricular assist devices. Much focus has been on better identifying patients likely to benefit from an implantable cardiac defibrillator. For patients with heart transplant, imaging with ¹²³I-mIBG or the positron emission tomographic (PET) tracer, ¹¹C-hydroxyephedrine (HED), can monitor recovery. In diabetes mellitus, imaging can recognize risk from cardiac autonomic dysfunction prior to clinical manifestations.