Decreased liberation of noradrenaline from the heart following cold crystalloid cardioplegia

Reversible reduction of cardiac sympathetic innervation after coronary artery bypass graft surgery: an observational study using serial iodine 123-labeled meta-iodobenzyl-guanidine (MIBG) imaging

OBJECTIVES

Various types of surgical and interventional procedures have been reported to cause cardiac sympathetic denervation. We aimed at evaluating the effects of coronary artery bypass grafting (CABG) in cardiac sympathetic innervation through meta-iodobenzyl-guanidine (MIBG) imaging.

METHODS

MIBG imaging was performed in 21 patients with coronary artery disease (CAD) 1 day before and 1 week and 6 months after CABG with concomitant measurements of corrected QT interval. In each study we evaluated MIBG defect score in a 16-segment left ventricular model, MIBG-defect size (percent) from generated polar maps, and heart/mediastinum ratio.

RESULTS

Mean MIBG defect score and size were increased (32 ± 9.5 vs 24 ± 5, P < .0001, and 49.5% ± 20.4% vs 37% ± 8.7%, P = .004, respectively) and mean heart/mediastinum ratio was reduced (1.5 ± 0.4 vs 1.9 ± 0.3, P < .0001) at 1 week after CABG. At 6 months these indices had no significant differences compared with their pre-CABG values. Mean corrected QT interval demonstrated no significant changes. Increase in MIBG score in the second imaging was associated with adverse events related to arrhythmia and myocardial dysfunction during the 6-month follow-up period in a binary logistic regression model.

CONCLUSIONS

CABG is associated with clinically important but reversible reduction in cardiac sympathetic nerve function, with periprocedural effects (cardioplegia, hypothermia, ischemia, direct nerve injury) being possible mechanisms for this finding.