Journal of Applied Physiology, Vol 59, Issue 3 890-897, Copyright © 1985 by American Physiological Society

ARTICLES

Cardiac response to submaximal exercise in dogs susceptible to sudden cardiac death

G. E. Billman, P. J. Schwartz, J. P. Gagnol and H. L. Stone

The hemodynamic response to submaximal exercise was investigated in 38 mongrel dogs with healed anterior wall myocardial infarctions. The dogs were chronically instrumented to measure heart rate (HR), left ventricular pressure (LVP), LVP rate of change, and coronary blood flow. A 2 min coronary occlusion was initiated during the last minute of an exercise stress test and continued for 1 min after cessation of exercise. Nineteen dogs had ventricular fibrillation (susceptible) while 19 animals did not (resistant) during this test. The cardiac response to submaximal exercise was markedly different between the two groups. The susceptible dogs exhibited a significantly higher HR and left ventricular end-diastolic pressure (LVEDP) but a significantly lower left ventricular systolic pressure (LVSP) in response to exercise than did the resistant animals. (For example, response to 6.4 kph at 8% grade; HR, susceptible 201.4 +/- 5.1 beats/min vs. resistant 176.2 +/- 5.6 beats/min; LVEDP, susceptible 19.4 +/- 1.1 mmHg vs. resistant 12.3 +/- 1.7 mmHg; LVSP, susceptible 136.9 +/- 7.9 mmHg vs. resistant 154.6 +/- 9.8 mmHg.) beta-Adrenergic receptor blockade with propranolol reduced the difference noted in the HR response but exacerbated the LVP differences (response to 6.4 kph at 8% grade; HR, susceptible 163.4 +/- 4.7 mmHg vs. resistant 150.3 +/- 6.4 mmHg; LVEDP susceptible 28.4 +/- 2.1 mmHg vs. resistant 19.6 +/- 3.0 mmHg; LVSP, susceptible 122.2 +/- 8.1 mmHg vs. resistant 142.8 +/- 10.7 mmHg). These data indicate that the animals particularly vulnerable to ventricular fibrillation also exhibit a greater degree of left ventricular dysfunction and an increased sympathetic efferent activity.

This article has been cited by other articles:

				K P Savonen, T A Lakka, J A Laukkanen, T H Rauramaa, J T Salonen, and R Rauramaa Workload at the heart rate of 100 beats/min and mortality in middle-aged men with known or suspected coronary heart disease Heart, April 1, 2008; 94(4): e14 - e14. [Abstract] [Full Text] [PDF]

				B. J. Holycross, M. Kukielka, Y. Nishijima, R. A. Altschuld, C. A. Carnes, and G. E. Billman Exercise training normalizes beta-adrenoceptor expression in dogs susceptible to ventricular fibrillation Am J Physiol Heart Circ Physiol, November 1, 2007; 293(5): H2702 - H2709. [Abstract] [Full Text] [PDF]

				G. E. Billman Heart rate response to onset of exercise: evidence for enhanced cardiac sympathetic activity in animals susceptible to ventricular fibrillation Am J Physiol Heart Circ Physiol, July 1, 2006; 291(1): H429 - H435. [Abstract] [Full Text] [PDF]

				J. A. Sala-Mercado, R. L. Hammond, J.-K. Kim, N. F. Rossi, L. W. Stephenson, and D. S. O'Leary Muscle metaboreflex control of ventricular contractility during dynamic exercise Am J Physiol Heart Circ Physiol, February 1, 2006; 290(2): H751 - H757. [Abstract] [Full Text] [PDF]

				G. E. Billman Aerobic exercise conditioning: a nonpharmacological antiarrhythmic intervention J Appl Physiol, February 1, 2002; 92(2): 446 - 454. [Abstract] [Full Text] [PDF]

				M. S. Houle, R. A. Altschuld, and G. E. Billman Enhanced in vivo and in vitro contractile responses to {beta}2-adrenergic receptor stimulation in dogs susceptible to lethal arrhythmias J Appl Physiol, October 1, 2001; 91(4): 1627 - 1637. [Abstract] [Full Text] [PDF]

				M. O'Neill, C. E. Sears, and D. J. Paterson Interactive effects of K+, acid, norepinephrine, and ischemia on the heart: implications for exercise J Appl Physiol, April 1, 1997; 82(4): 1046 - 1052. [Abstract] [Full Text] [PDF]