LETTER TO THE EDITOR
Scopolamine? Reply
David Selman, MDa
a 21 Omni Court,New York, New York 10956, USA
We thank the author for his interesting comment. Cumulating evidence indicates that vagomimetic agents enhance measures of cardiac parasympathetic activation, such as heart rate variability (HRV) (1,2). Compared to other agents affecting parasympathetic function, scopolamine has been most widely investigated in patients with documented coronary artery disease. In postmyocardial infarction patients, scopolamine increases HRV and baroreceptor reflex sensitivity (3,4). Transdermal scopolamine is also reported to reduce ambulatory ischemia and ischemic threshold during exercise testing in patients with severe coronary disease (5). Effects of vagomimetic agents other than scopolamine have not been systematically studied in patients with established coronary disease.
Consistent with the comment above, a recent investigation by Nobrega et al. (6) documented increased HRV in response to pyridostigmine in healthy individuals. However, despite beneficial effects on HRV and other indirect indices of autonomic nervous system activity, vagomimetic agents do not necessarily reduce arrhythmic vulnerability (1,2). Our data suggest that transient pre-ischemic vagal withdrawal may be specific to ischemic events triggered by mental stress (7). Further investigations are needed to examine the potential benefits of vagomimetic agents in preventing ischemia occurring at low cardiac demand thresholds, as commonly occurs with ischemia during ambulant monitoring and during mental stress in the laboratory (8).
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2. Vanoli E, Cerati D, Pedretti RF. Autonomic control of heart rate: pharmacological and nonpharmacological modulation. Bas Res Cardiol. 1998;93(Suppl 1):133–142
3. De Ferrari GM, Mantica M, Vanoli E, Hull SS Jr, Schwartz PJ. Scopolamine increases vagal tone and vagal reflexes in patients after myocardial infarction. J Am Coll Cardiol. 1993;22:1327–1334[Abstract]
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5. Kochiadakis GE, Rombola AT, Kanoupakis EM, Zuridakis EG, Skalidis EI, Vardas PE. Effect of transdermal scopolamine on heart rate variability in patients with severe coronary heart disease. Pacing Clin Electrophysiol. 1996;19:1867–1871[Medline]
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7. Kop WJ, Verdino RJ, Gottdiener JS, O’Leary ST, Bairey Merz CN, Krantz DS. Changes in heart rate and heart rate variability preceding ambulatory ischemic events. J Am Coll Cardiol. 2001;38:742–749[Abstract/Free Full Text]
8. Gottdiener JS, Krantz DS, Howell RH, et al. Induction of silent myocardial ischemia with mental stress testing: relation to the triggers of ischemia during daily life activities and to ischemic functional severity. J Am Coll Cardiol. 1994;24:1645–1651[Abstract]
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