Cardiac Iodine-123-Meta-Iodo-Benzylguanidine Uptake in Carotid Sinus Hypersensitivity

Abstract

BackgroundCarotid sinus syndrome is the association of carotid sinus hypersensitivity with syncope, unexplained falls and drop attacks in generally older people. We evaluated cardiac sympathetic innervation in this disorder in individuals with carotid sinus syndrome, asymptomatic carotid sinus hypersensitivity and controls without carotid sinus hypersensitivity.MethodsConsecutive patients diagnosed with carotid sinus syndrome at a specialist falls and syncope unit were recruited. Asymptomatic carotid sinus hypersensitivity and non-carotid sinus hypersensitivity control participants recruited from a community-dwelling cohort. Cardiac sympathetic innervation was determined using Iodine-123-metaiodobenzylguanidine (123-I-MIBG) scanning. Heart to mediastinal uptake ratio (H:M) were determined for early and late uptake on planar scintigraphy at 20 minutes and 3 hours following intravenous injection of 123-I-MIBG.ResultsForty-two subjects: carotid sinus syndrome (n = 21), asymptomatic carotid sinus hypersensitivity (n = 12) and no carotid sinus hypersensitivity (n = 9) were included. Compared to the non- carotid sinus hypersensitivity control group, the carotid sinus syndrome group had significantly higher early H:M (estimated mean difference, B = 0.40; 95% confidence interval, CI = 0.13 to 0.67, p = 0.005) and late H:M (B = 0.32; 95%CI = 0.03 to 0.62, p = 0.032). There was, however, no significant difference in early H:M (p = 0.326) or late H:M (p = 0.351) between the asymptomatic carotid sinus hypersensitivity group and non- carotid sinus hypersensitivity controls.ConclusionsCardiac sympathetic neuronal activity is increased relative to age-matched controls in individuals with carotid sinus syndrome but not those with asymptomatic carotid sinus hypersensitivity. Blood pressure and heart rate measurements alone may therefore represent an over simplification in the assessment for carotid sinus syndrome and the relative increase in cardiac sympathetic innervation provides additional clues to understanding the mechanisms behind the symptomatic presentation of carotid sinus hypersensitivity.

Cardiac sympathetic innervation associates with autonomic dysfunction in chronic fatigue syndrome – a pilot study

“…Our findings of a relationship between cardiac sympathetic innervation and autonomic dysfunction are consistent with previous studies [ 7 ] and suggest that CFS subjects demonstrate disturbed myocardial adrenergic innervation and adrenergic innervation defects.…”

Should We Ever Pace for Carotid Sinus Syndrome?

“…Whether this reflects a generalized mild autonomic dysfunction associated with aging or a pathologic state remains unknown. We further explored the autonomic hypothesis through meta-iodo benzyl guanidine scanning of cardiac sympathetic activity in patients with CSS, patients with CSH, and asymptomatic controls (64). Cardiac sympathetic neuronal activity was increased in patients with CSS, but not in the other two groups (64), adding more weight to the suggestion that CSS is a clinical manifestation of autonomic dysregulation in older individuals.…”