NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Ventricular filling slows epicardial conduction and increases action potential duration in an optical mapping study of the isolated rabbit heartINTRODUCTION: Mechanical stimulation can induce electrophysiologic changes in cardiac myocytes, but how mechanoelectric feedback in the intact heart affects action potential propagation remains unclear. METHODS AND RESULTS: Changes in action potential propagation and repolarization with increased left ventricular end-diastolic pressure from 0 to 30 mmHg were investigated using optical mapping in isolated perfused rabbit hearts. With respect to 0 mmHg, epicardial strain at 30 mmHg in the anterior left ventricle averaged 0.040 +/- 0.004 in the muscle fiber direction and 0.032 +/- 0.006 in the cross-fiber direction. An increase in ventricular loading increased average epicardial activation time by 25%+/- 3% (P < 0.0001) and correspondingly decreased average apparent surface conduction velocity by 16%+/- 7% (P = 0.007). Ventricular loading did not significantly alter action potential duration at 20% repolarization (APD20) but did at 80% repolarization (APD80), from 179 +/- 7 msec to 207 +/- 5 msec (P < 0.0001). The dispersion of APD20 was decreased with loading from 19 +/- 2 msec to 13 +/- 2 msec (P = 0.024), whereas the dispersion of APD80 was not significantly changed. These electrophysiologic changes with ventricular loading were not affected by the nonspecific stretch-activated channel blocker streptomycin (200 microM) and were not attributable to changes in myocardial perfusion or the presence of an electromechanical decoupling agent (butanedione monoxime) during optical mapping. CONCLUSION: Acute loading of the left ventricle of the isolated rabbit heart decreased apparent epicardial conduction velocity and increased action potential duration by a load-dependent mechanism that may not involve stretch-activated channels.
Document ID
20040087558
Document Type
Reprint (Version printed in journal)
Authors
Sung, Derrick (University of California San Diego 9500 Gilman Drive, La Jolla, CA 92093-0412, United States)
Mills, Robert W.
Schettler, Jan
Narayan, Sanjiv M.
Omens, Jeffrey H.
McCulloch, Andrew D.
McCullough, A. D.
Date Acquired
August 21, 2013
Publication Date
July 1, 2003
Publication Information
Publication: Journal of cardiovascular electrophysiology
Volume: 14
Issue: 7
ISSN: 1045-3873
Subject Category
Life Sciences (General)
Funding Number(s)
CONTRACT_GRANT: P41 RR 08065
CONTRACT_GRANT: T32 HL 07444
Distribution Limits
Public
Copyright
Other
Keywords
NASA Program Biomedical Research and Countermeasures
NASA Discipline Cardiopulmonary
Non-NASA Center