Anger Increases Cardiac Sympathetic Heterogeneity as Measured by I-123 MIBG Imaging in Patients with Ischemic Cardiomyopathy

Objectives Anger can precipitate ventricular arrhythmias. Quantification of regional MIBG uptake to delineate heterogeneity of cardiac sympathetic activity during stress may help elucidate mechanisms.

Methods Five healthy men and five men with Ischemic Cardiomyopathy (ICM), age 50-80, underwent I-123 MIBG imaging during anger recall, then at rest on a second day. Images were acquired for 15 min in list-mode using a high-sensitivity and high-resolution SPECT/CT system (Discovery NM/CT 570c) then rebinned for 3-10 min followed by MLEM reconstruction with CT-based attenuation correction. Upper and lower limits of the heart were manually defined from CT co-registered with SPECT and myocardial (H) and mediastinal (M) volumes determined by semi-automated segmentation algorithm. Percent variability of count distribution derived from the circumferential count profiles of the LV was calculated by SD/mean.

Results Resting-HMR was greater in normals than ICM. Hemodynamic response to stress was similar. Stress decreased HMR significantly in the ICM patients, but not normals. Regional heterogeneity, as measured by percent variability, increased with stress in ICM patients in apical and mid-ventricular regions, but not normals. There was no change in tetrofosmin defect score with stress.

Conclusions Stress decreases HMR, and increases heterogeneity of uptake, in ICM patients, without changes in perfusion. Increases in heterogeneity of sympathetic activation may be one mechanism linking stress and ventricular arrhythmias.

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