The overall goal of this work is to study the autonomic control of atrioventricular (AV) and ventriculoatrial (VA) conduction. Two projects are concerned with potential vagal contributions to common arrhythmias, and the third project is a detailed study of vagal-sympathetic-heart period interactions on AV conduction. Specifically, the AV nodal Wenckebach arrhythmia will be studied as a function of: a) brief vagal stimulus bursts and the timing of these bursts in the cardiac cycle, b) the time after the onset of vagal stimulus trains, c) background sympathetic activity, d) the interaction of basic cycle length (heart period) and a) above, and e) a comparison of VA vs. AV conduction for a) to d) above. Secondly, facilitated conduction of a premature depolarization will be studied. That is, with AV sequential pacing the AV junctional refractory period is """"""""peeled back,"""""""" and a premature depolarization (PD) is conducted more rapidly (facilitated) than with single chamber pacing. Facilitated conduction will be studied as a function of: a) basic cycle length of the paced beats and coupling intervals of the premature beats, b) brief bursts of vagal activity and the timing of that vagal activity in a cardiac cycle, c) different levels of sympathetic activity, and d) the interaction of a) and b) above for both AV and VA conduction. The third project concerns the effects of brief bursts of sympathetic activity, and the dynamic beat-by-beat interactions of vagal activity, sympathetic activity, and heart period on AV and VA conduction. In each dog, each effect will be studied separately and in various simultaneous combinations to provide quantitative conclusions. The results of these three projects should provide basic new insights into the physiology of the control of AV conduction, and how the control of VA conduction importantly differs. This information is additionally important for the design and clinical optimization of artifical cardiac pacemakers where serious problems now arise from our poor understanding of these phenomena.

Agency
National Institute of Health (NIH)
Institute
National Heart, Lung, and Blood Institute (NHLBI)
Type
Research Project (R01)
Project #
5R01HL022484-10
Application #
3336893
Study Section
Cardiovascular Study Section (CVA)
Project Start
1978-07-01
Project End
1989-06-30
Budget Start
1987-07-01
Budget End
1988-06-30
Support Year
10
Fiscal Year
1987
Total Cost
Indirect Cost
Name
Mount Sinai Medical Center
Department
Type
DUNS #
City
Cleveland
State
OH
Country
United States
Zip Code
44106
Hill, M R; Wallick, D W; Mongeon, L R et al. (1995) Vasoactive intestinal polypeptide antagonists attenuate vagally induced tachycardia in the anesthetized dog. Am J Physiol 269:H1467-72
Kuguoglu, A F; Wallick, D W; Martin, P J (1995) Facilitated ventriculoatrial conduction: effects of sequential pacing interval and basic cycle length. Am J Physiol 268:H384-90
Hill, M R; Wallick, D W; Martin, P J et al. (1995) Effects of repetitive vagal stimulation on heart rate and on cardiac vasoactive intestinal polypeptide efflux. Am J Physiol 268:H1939-46
Carlson, M D; White, R D; Trohman, R G et al. (1994) Right ventricular outflow tract ventricular tachycardia: detection of previously unrecognized anatomic abnormalities using cine magnetic resonance imaging. J Am Coll Cardiol 24:720-7
Hill, M R; Wallick, D W; Martin, P J et al. (1993) Frequency dependence of vasoactive intestinal polypeptide release and vagally induced tachycardia in the canine heart. J Auton Nerv Syst 43:117-22
Wallick, D W; Xu, R G; Martin, P J (1992) Dynamic interaction of vagal activity and heart rate on atrioventricular conduction. Am J Physiol 262:H792-8
Carlson, M D; Geha, A S; Hsu, J et al. (1992) Selective stimulation of parasympathetic nerve fibers to the human sinoatrial node. Circulation 85:1311-7
Yang, T N; Cheng, J; Martin, P et al. (1991) Effects of spatial dispersion of acetylcholine release on AV conduction responses to vagal stimulation in dogs. Am J Physiol 261:H392-7
Furukawa, Y; Wallick, D W; Martin, P J et al. (1990) Chronotropic and dromotropic responses to stimulation of intracardiac sympathetic nerves to sinoatrial or atrioventricular nodal region in anesthetized dogs. Circ Res 66:1391-9
Furukawa, Y; Wallick, D W; Carlson, M D et al. (1990) Cardiac electrical responses to vagal stimulation of fibers to discrete cardiac regions. Am J Physiol 258:H1112-8

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