Iodine-123 metaiodobenzylguanidine myocardial scintigraphy for prediction of response to β-blocker therapy in patients with dilated cardiomyopathy

What will be the role of I-123 MIBG in improving the outcome of medically treated heart failure patients?

“…In 30 NYHA class II or III HF patients treated with 16 ± 4 mg/day of carvedilol for 12 ± 1 months, Kasama et al 38 noted that an improvement from baseline in B-type natriuretic peptide from 270 ± 249 to 148 ± 125 (P = .002) and in LVEF from 33 ± 6 to 39 ± 6 (P = .003) was paralleled by an improvement in late I-123 MIBG HMR from 1.66 ± 0.16 to 1.88 ± 0.23 (P \ .001). Similar concordant improvement in cardiac sympathetic nerve function with improvement in clinical status and/or LVEF has also been observed in response to treatment with metoprolol, 39 carvedilol, 40,41 bisoprolol, 42 enalapril, 43 candesartan, 44 and spironolactone. 45 Improvement in LVEF in response to b-blocker therapy has been documented in HF patients with a broad range of baseline sympathetic neural impairment.…”

Polymorphisms of norepinephrine transporter and adrenergic receptor α1D are associated with the response to β-blockers in dilated cardiomyopathy

“…Interestingly, it is reported that the response to b-blocker therapy in patients with non-ischemic DCM could be predictable using MIBG myocardial scintigraphy. 5,6 Since MIBG NET and ADRA1D polymorphisms in b-blocker response S Nonen et al scintigraphy is influenced by norepinephrine uptake via NET, functional analysis of this polymorphism, especially by using MIBG, would be informative. Our results suggest that ADRA1D T1848A and A1905G polymorphisms correlate with the response to b-blockers.…”

“…It is also reported that iodine-123 metaiodo benzyl guanidine (MIBG) image is a predictable marker for the outcome of b-blocker therapy. 5,6 The proportion of the responders is smaller in the patients with impaired MIBG uptake. These findings suggest that the response to b-blockers depends on the pathophysiological status of cardiac remodeling, including the activation of neurohumoral signals.…”

Cardiac autonomic imaging with SPECT tracers

“…For example, numerous studies have shown that cardiac 123 I-mIBG images improve after therapy with b-blockers. 48,50,[78][79][80][81][82][83] Gerson et al 50 showed that the H/M improved significantly after the use of carvedilol, especially in patients with an H/M ratio\1.40. Toyama et al 84 showed favorable changes of symptoms, functional class, cardiac function, and H/M in those treated with metoprolol.…”

“…92 Many ask if 123 I-mIBG imaging might help direct medical therapy. Such investigations in terms of bblockers have shown that imaging does not provide sufficient separation between those who do or do not benefit, 83,93 and given the high benefit/risk and relatively low cost of medical therapies, an 123 I-mIBG study is unlikely to preclude their use. 94 123 I-mIBG imaging could instead be used to determine whether or not a particular therapy is working, perhaps increase doses more aggressively or determine if device therapies or transplantation are needed.…”