Improvement in cardiac sympathetic nerve activity in responders to resynchronization therapy

Aims To assess changes in cardiac adrenergic activity with cardiac resynchronization therapy (CRT), and to investigate whether these changes are related to improvement in left ventricular ejection fraction (LVEF). Methods and results Sixteen patients (13 males, age 66+7 years) were studied at baseline and after 6 months of CRT (mean follow-up 9.2+3.2 months). LVEF was assessed by nuclear angiography. Responders were defined as patients showing 5 % absolute increase in LVEF þ improvement in 1 NYHA class þ absence of heart failure hospitalization. Cardiac sympathetic nerve activity was studied by 123I-metaiodobenzyl-guanidine (123I-MIBG) scintigraphy. Responders (n 8) showed lower 123I-MIBG washout at follow-up when compared with non-responders (P 0.002), indicating lower cardiac sym-pathetic nerve activity. The decrease in 123I-MIBG washout at follow-up when compared with baseline was only seen in the responder group (P 0.036). There was a moderate correlation between increase in LVEF and decrease in 123I-MIBG washout (r 0.52, P 0.04). Conclusion CRT induces a reduction in cardiac sympathetic nerve activity in responders, that parallels an improvement in LVEF, whereas non-responders do not show any significant changes