This Article Full Text Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Permissions Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by Muller, J. E. Articles by Verrier, R. L. Search for Related Content PubMed PubMed Citation Articles by Muller, J. E. Articles by Verrier, R. L.

(Circulation. 1995;91:2508-2509.)
© 1995 American Heart Association, Inc.

Articles

Sympathetic Activity as the Cause of the Morning Increase in Cardiac Events

A Likely Culprit, but the Evidence Remains Circumstantial

James E. Muller, MD; Geoffrey H. Tofler, MD; Richard L. Verrier, PhD

From the Institute for Prevention of Cardiovascular Disease, Cardiovascular Division, Deaconess Hospital, Harvard Medical School, Boston, Mass.

Correspondence to James E. Muller, MD, Institute for Prevention of Cardiovascular Disease, Cardiovascular Division, Deaconess Hospital, Harvard Medical School, One Autumn St, Fifth Floor, Boston, MA 02215.

	Introduction

 
The well-documented morning increase in myocardial infarction, sudden cardiac death, and other cardiovascular disorders provides a new opportunity to identify the causes of disease onset. In this issue of Circulation, Middlekauff and Sontz¹ report on efforts to determine whether the sympathetic nervous system is responsible for the increase in disease onset in the morning. They have picked a prime candidate for a causal role, because (1) events associated with increased sympathetic discharge, such as heavy exertion, have been shown to trigger infarction onset² ; (2) morning is a time associated with a transition from low to high sympathetic activity³ ; and (3) both observational and randomized studies have demonstrated elimination of the morning peak of disease onset in individuals receiving ß-adrenergic blocking agents.^{4 5}

Middlekauff and Sontz directly measured firing rates of sympathetic nerves to skeletal muscle at rest and during stress in the morning and afternoon. The study was conducted in eight healthy subjects who had spent the previous night in the Clinical Research Center. The morning measurements (obtained between 6:30 and 8:30 AM) were compared with afternoon measurements (obtained between 2 and 4 PM). After basal levels were recorded, lower-body negative pressure was applied (to simulate the stress of assuming the upright posture), and a handgrip exercise was performed. The study convincingly demonstrates that, under these experimental conditions and in these supine subjects, there is no difference in basal or stressed sympathetic firing rate to skeletal muscles in morning versus afternoon testing.

Although this is a . . . [Full Text of this Article]

This article has been cited by other articles:

				C M Ryan, K Usui, J S Floras, and T D Bradley Effect of continuous positive airway pressure on ventricular ectopy in heart failure patients with obstructive sleep apnoea Thorax, September 1, 2005; 60(9): 781 - 785. [Abstract] [Full Text] [PDF]

				M. E. Otto, A. Svatikova, R. B. d. M. Barretto, S. Santos, M. Hoffmann, B. Khandheria, and V. Somers Early Morning Attenuation of Endothelial Function in Healthy Humans Circulation, June 1, 2004; 109(21): 2507 - 2510. [Abstract] [Full Text] [PDF]

				J. S. Rana, K. J. Mukamal, J. P. Morgan, J. E. Muller, and M. A. Mittleman Circadian Variation in the Onset of Myocardial Infarction: Effect of Duration of Diabetes Diabetes, June 1, 2003; 52(6): 1464 - 1468. [Abstract] [Full Text] [PDF]