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Abnormal myocardial adrenergic nerve function in orthostatic hypotension
M Nakamura1, T Yamazaki, K Hiramori
1Second Department of Internal Medicine, Iwate Medical University, Morioka, Japan. nkmrmoto@iwate-med.ac.jp
Cardiology
|January 20, 1999
Summary
Primary orthostatic hypotension in a 70-year-old man was linked to cardiac autonomic denervation. Impaired myocardial contractility and cerebral blood flow regulation contributed to his fainting spells.
Area of Science:
- Cardiology
- Neurology
- Nuclear Medicine
Background:
- Orthostatic hypotension (OH) is characterized by a significant drop in blood pressure upon standing.
- Primary OH involves autonomic nervous system dysfunction affecting blood pressure regulation.
- Diagnostic workup includes head-up tilt testing and autonomic function tests.
Observation:
- A 70-year-old male presented with recurrent syncope and faintness when upright.
- Head-up tilt testing and autonomic nerve function tests confirmed primary orthostatic hypotension.
- Myocardium scintigraphy using 201Tl showed no abnormalities.
Findings:
- 123I-metaiodobenzyl-guanidine (MIBG) uptake was significantly reduced in the heart.
- Reduced MIBG uptake indicates impaired cardiac sympathetic innervation (cardiac autonomic denervation).
- This suggests a globally denervated myocardium.
Implications:
- Globally denervated myocardium may limit the heart's ability to increase contractility promptly upon standing.
- This impairment can hinder the maintenance of adequate cerebral blood flow.
- These factors likely contribute to the development of postural hypotension in primary OH.