Effects of asynchronous ventricular activation on myocardial adrenergic innervation in patients with permanent dual-chamber pacemakers - An I-123-metaiodobenzylguanidine cardiac scintigraphic study

Aims To evaluate myocardial sympathetic innervation abnormalities in patien ts with DDD pacemakers for complete heart block. Methods We studied 39 patients, chronically paced in DDD mode because of co mplete atrioventricular block. Twenty-three healthy individuals served as a control group. All patients underwent planar and single-photon emission co mputed tomography (SPECT) myocardial imaging 4 h after intravenous infusion of 185 MBq I-123-MIBG. The heart to mediastinum ratio was calculated to qu antify cardiac I-123-MIBG accumulation, while the SPECT study was performed to investigate the regional distribution of adrenergic innervation. All pa tients underwent a SPECT thallium(201) myocardial study during the same wee k as the I-123-MIBG study. Results The heart to mediastinum ratio was significantly smaller in paced p atients than in the controls (P < 0.001). 89.7% of paced patients had regio nal 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 dura tion of pacing. Conclusions Stimulation from the apex of the right ventricle leads to regio nal disturbances of the adrenergic innervation of the left ventricular myoc ardium, as assessed by I-123-MIBG activity. (Eur Heart J 2001; 22: 323-332, doi:10.1053/euhj.2000.2482) (C) 2001 The European Society of Cardiology.