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- Title
Cardiac iodine-123-metaiodobenzylguanidine scintigraphy may be useful to identify pathologic from physiologic sinus bradycardia.
- Authors
Sunaga, Akihiro; Masuda, Masaharu; Fujita, Masashi; Iida, Osamu; Kanda, Takashi; Matsuda, Yasuhiro; Morozumi, Takakazu; Mano, Toshiaki; Uematsu, Masaaki
- Abstract
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 (123I-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 123I-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 123I-MIBG may serve as an adjunct to determine the indication for a pacemaker implantation in sinus bradycardia.
- Subjects
BRADYCARDIA treatment; BRADYCARDIA diagnosis; SICK sinus syndrome; BRADYCARDIA; CARDIAC pacemakers; CARDIOVASCULAR system physiology; DIZZINESS; ELECTROPHYSIOLOGY; FATIGUE (Physiology); RADIONUCLIDE imaging; SYNCOPE; BENZENE derivatives; DESCRIPTIVE statistics; IODINE radioisotopes; SYMPTOMS; DIAGNOSIS
- Publication
Pacing & Clinical Electrophysiology, 2017, Vol 40, Issue 6, p632
- ISSN
0147-8389
- Publication type
Article
- DOI
10.1111/pace.13078