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Cardiac iodine‐123‐metaiodobenzylguanidine scintigraphy may be useful to identify pathologic from physiologic sinus bradycardia
Author(s) -
Sunaga Akihiro,
Masuda Masaharu,
Fujita Masashi,
Iida Osamu,
Kanda Takashi,
Matsuda Yasuhiro,
Morozumi Takakazu,
Mano Toshiaki,
Uematsu Masaaki
Publication year - 2017
Publication title -
pacing and clinical electrophysiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.686
H-Index - 101
eISSN - 1540-8159
pISSN - 0147-8389
DOI - 10.1111/pace.13078
Subject(s) - medicine , sss* , bradycardia , sick sinus syndrome , sinus bradycardia , heart rate , cardiology , cardiac pacemaker , sinus (botany) , vagal tone , chest pain , anesthesia , heart rate variability , blood pressure , botany , biology , genus
Background Sinus bradycardia includes pathologic sick sinus syndrome (SSS) and physiologic bradycardia such as athletes’ heart. Pacemaker implantation is indicated for patients with symptomatic SSS; however, the indication remains difficult to determine in those with mild and/or unspecific symptoms. The sympathetic tone is increased in response to reduced cardiac output in SSS, whereas excessive vagal tone has been seen in physiological bradycardia. We sought to determine if cardiac iodine‐123‐metaiodobenzylguanidine scintigraphy ( 123 I‐MIBG) was useful in differentiating pathologic from physiologic sinus bradycardia. Methods Twenty consecutive patients presenting with continuous sinus bradycardia (heart rate of <50 beats/min) in our outpatient clinic (male, eight patients; age, 70 ± 12 years old) were enrolled. The indication for a pacemaker implantation was determined by an experienced electrophysiologist in compliance with the international guidelines. The sympathetic nervous tone was assessed by cardiac 123 I‐MIBG. Results Eight patients (40%) were clinically diagnosed as SSS (type I) including four suffering from obvious symptoms (syncope or dizziness) and four suffering from mild symptoms (fatigue), and had an indication for a pacemaker implantation. The patients with SSS indicated for a pacemaker implantation had a lower early heart‐to‐mediastinum ratio (2.0 ± 0.6 vs 2.5 ± 0.2, P = 0.043), lower delayed heart to mediastinum ratio (2.0 ± 0.8 vs 2.8 ± 0.3, P = 0.026), and higher washout rate (34 ± 6.0 vs 26 ± 6.0, P = 0.008) than those without. Conclusion Excessive sympathetic tone detected by 123 I‐MIBG may serve as an adjunct to determine the indication for a pacemaker implantation in sinus bradycardia.