Regional sympathetic innervation of the heart by means of metaiodobenzylguanidine imaging in silent ischemia.

Metaiodobenzylguanidine was used to determine regional cardiac sympathetic innervation and whether it is reduced in silent ischemia. Patients with silent ischemia (group 1, n = 6) and angina (group 2, n = 5) and normal subjects (n = 6) underwent single-photon emission tomography at 4 hours. From base to midventricle, uptake increased in group 1 (p < 0.006), group 2 (p < 0.01), and the normal subjects (p < 0.004). In group 1 anterior ventricular uptake was greater than inferior uptake at the midventricle (p < 0.03) and apex (p < 0.05). In group 2 the same relationship was demonstrated at midventricle (p < 0.01) and apex (p < 0.05). Group 2 uptake was only significantly greater than group 1 at midventricle (p < 0.05). Innervation is greatest in midventricle and the apex of the left ventricle and greater in the anterior wall compared with the inferior wall. There is no evidence of reduced innervation in silent ischemia.