Effects of asynchronous ventricular activation on myocardial adrenergic innervation in patients with permanent dual-chamber pacemakers: An I123-metaiodobenzylguanidine cardiac scintigraphic study

Abstract

Aims: To evaluate myocardial sympathetic innervation abnormalities in patients with DDD pacemakers for complete heart block. Methods: 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 I123-MIBG. The heart to mediastinum ratio was calculated to quantify cardiac I123-MIBG accumulation, while the SPECT study was performed to investigate the regional distribution of adrenergic innervation. All patients underwent a SPECT thallium201 myocardial study during the same week as the I123-MIBG study. Results: 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 I123-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 I123-MIBG abnormalities nor the perfusion defects were related to the duration of pacing. Conclusions: Stimulation from the apex of the right ventricle leads to regional disturbances of the adrenergic innervation of the left ventricular myocardium, as assessed by I123-MIBG activity. © 2001 The European Society of Cardiology.