Cardiac sympathetic activity in hypertrophic cardiomyopathy and Tako-tsubo cardiomyopathy

123I-meta-iodobenzylguanidine (123I-mIBG) scintigraphy has been established as an important technique to evaluate cardiac sympathetic function and it has been shown to be of clinical value, especially for the assessment of prognosis, in many cardiac diseases. The majority of 123I-mIBG scintigraphy studies have focused on patients with cardiac dysfunction due to hypertension, ischemic heart disease, or valvular disease. However less is known about the role of 123I-mIBG scintigraphy in primary cardiomyopathies. This overview shows the clinical value of 123I-mIBG scintigraphy in two types of primary cardiomyopathy: The genetic hypertrophic cardiomyopathy (HCM) and the acquired Tako-tsubo cardiomyopathy (TCM). Cardiac sympathetic activity is increased in HCM and correlates to the septal wall thickness and consequently to the LVOT obstruction. Moreover, increased cardiac sympathetic activity correlates with impaired diastolic and systolic LV function. In addition, 123I-mIBG scintigraphy may be useful for determining the risk of developing congestive heart failure and ventricular tachycardia in these patients. In TCM 123I-mIBG scintigraphy can be used to assess cardiac sympathetic hyperactivity. In addition, 123I-mIBG scintigraphy may identify those patients who are prone to TCM recurrence and may help to identify responders to individual (pharmacological) therapy.