Transcatheter aortic valve implantation improves cardiac sympathetic nerve activity on ¹²³ I-metaiodobenzylguanidine myocardial scintigraphy in severe aortic valve stenosis

Background: There is a consensus that overactivation of the cardiac sympathetic nervous system (CSN) proportionately increases the severity of heart failure and is accompanied by worse prognosis. Because it is unknown whether patients with aortic valve stenosis (AS) have similar CSN activation, we investigated the effect of transcatheter aortic valve implantation (TAVI). Methods and Results: We enrolled 31 consecutive patients with AS treated by TAVI. ¹²³ I-metaiodobenzylguanidine (MIBG) myocardial scintigraphy was performed at baseline and at 2 weeks after TAVI. At baseline, the early heart-mediastinum ratio (H/M) was within normal limits (3.0±0.5), but the delayed H/M was low (2.6±0.6) and the washout rate (WR) was high (34±13%). WR negatively correlated with aortic valve area (r=−0.389, P<0.01) and cardiac output (r=−0.595, P<0.01) and positively correlated with norepinephrine (r=0.519, P<0.01) and log NT-proBNP level (r=0.613, P<0.01). After TAVI, there were significant decreases in the norepinephrine level (366±179 ng/mL vs. 276±125 ng/mL, P<0.01) and WR (34±13 vs. 26±11%, P<0.01). Conclusions: The WR of MIBG was a useful marker of CSN activity and severity of AS. Immediate improvement of CSN activity after TAVI implied that AS hemodynamics per se enhanced CSN.