Effects of asynchronous ventricular activation on myocardial adrenergic innervation in patients with permanent dual-chamber pacemakers; an I(123)-metaiodobenzylguanidine cardiac scintigraphic study.

Abstract

To evaluate myocardial sympathetic innervation abnormalities in patients with DDD pacemakers for complete heart block. We studied 39 patients, chronically paced in DDD mode because of complete atrioventricular block. Twenty-three healthy individuals served as a control group. All patients underwent planar and single-photon emission computed tomography (SPECT) myocardial imaging 4 h after intravenous infusion of 185 MBq I(123)-MIBG. The heart to mediastinum ratio was calculated to quantify cardiac I(123)-MIBG accumulation, while the SPECT study was performed to investigate the regional distribution of adrenergic innervation. All patients underwent a SPECT thallium(201)myocardial study during the same week as the I(123)-MIBG study. The heart to mediastinum ratio was significantly smaller in paced patients than in the controls (P<0.001). 89.7% of paced patients had regional abnormalities of I(123)-MIBG uptake, mainly in the inferior (92.3%) and apical (38.5%) wall. 46.2% of paced patients had regional perfusion defects, also mainly in the inferior (46.2%) and apical (10.3%) wall. Neither the I(123)-MIBG abnormalities nor the perfusion defects were related to the duration of pacing. Stimulation from the apex of the right ventricle leads to regional disturbances of the adrenergic innervation of the left ventricular myocardium, as assessed by I(123)-MIBG activity.