Skip to main content
NCBI home page
British Heart Journal logoLink to British Heart Journal
. 1980 Aug;44(2):179–183. doi: 10.1136/hrt.44.2.179

Effect of myocardial shortening velocity on duration of electrical and mechanical systole. S2T interval as measure of shortening rate.

L E Ford, N P Campbell
PMCID: PMC482379  PMID: 6107092

Abstract

To determine the effect of myocardial shortening velocity on the duration of electrical and mechanical systole, five healthy men, ages 32 to 41, were studied. Carotid message and atropine were used to define the effects of changes in heart rate without changes in shortening rate. The effects of amyl nitrite, which produced approximately the same degree of tachycardia as atropine but a significantly higher maximum shortening rate, were compared with those of atropine to assess the effects of faster shortening velocities. The increased heart rate produced by both agents caused a substantial decrease in both the QT and the S1S2 intervals, but the QT interval was longer and the S1S2 interval shorter with the amyl nitrite. Thus, the S2T interval was substantially longer after amyl nitrite. The results are in keeping with the finding in isolated cardiac muscle that active shortening increases action potential duration and decreases the duration of mechanical activation. These observations raise the possibility that longer QT intervals and shorter S1S2 intervals would also be seen in patients with hypokinetic ventricular segments when the healthy muscle contracts more vigorously to compensate for the weaker segments.

Full text

PDF
179

Images in this article

180Image
on p.180

Selected References

These references are in PubMed. This may not be the complete list of references from this article.

  1. Abildskov J. A. Adrenergic effects of the QT interval of the electrocardiogram. Am Heart J. 1976 Aug;92(2):210–216. doi: 10.1016/s0002-8703(76)80256-6. [DOI] [PubMed] [Google Scholar]
  2. Allen D. G., Jewell B. R., Murray J. W. The contribution of activation processes to the length-tension relation of cardiac muscle. Nature. 1974 Apr 12;248(449):606–607. doi: 10.1038/248606a0. [DOI] [PubMed] [Google Scholar]
  3. Brady A. J. Onset of contractility in cardiac muscle. J Physiol. 1966 Jun;184(3):560–580. doi: 10.1113/jphysiol.1966.sp007931. [DOI] [PMC free article] [PubMed] [Google Scholar]
  4. Brutsaert D. L., de Clerck N. M., Goethals M. A., Housmans P. R. Relaxation of ventricular cardiac muscle. J Physiol. 1978 Oct;283:469–480. doi: 10.1113/jphysiol.1978.sp012513. [DOI] [PMC free article] [PubMed] [Google Scholar]
  5. DeMaria A. N., Neumann A., Schubart P. J., Lee G., Mason D. T. Systematic correlation of cardiac chamber size and ventricular performance determined with echocardiography and alterations in heart rate in normal persons. Am J Cardiol. 1979 Jan;43(1):1–9. doi: 10.1016/0002-9149(79)90036-5. [DOI] [PubMed] [Google Scholar]
  6. Diamant B., Killip T. Indirect assessment of left ventricular performance in acute myocardial infarction. Circulation. 1970 Oct;42(4):579–592. doi: 10.1161/01.cir.42.4.579. [DOI] [PubMed] [Google Scholar]
  7. Dominguez G., Fozzard H. A. Effect of stretch on conduction velocity and cable properties of cardiac Purkinje fibers. Am J Physiol. 1979 Sep;237(3):C119–C124. doi: 10.1152/ajpcell.1979.237.3.C119. [DOI] [PubMed] [Google Scholar]
  8. Doroghazi R. M., Childers R. Time-related changes in the Q-T interval in acute myocardial infarction: possible relation to local hypocalcemia. Am J Cardiol. 1978 Apr;41(4):684–688. doi: 10.1016/0002-9149(78)90818-4. [DOI] [PubMed] [Google Scholar]
  9. Heikkilä J., Luomanmäki K., Pyörälä K. Serial observations on left ventricular dysfunction in acute myocardial infarction. II. Systolic time intervals in power failure. Circulation. 1971 Sep;44(3):343–354. doi: 10.1161/01.cir.44.3.343. [DOI] [PubMed] [Google Scholar]
  10. Kaufmann R. L., Hennekes R., Lab M. J. Demonstration of an "excitation-contraction recoupling" mechanism in mammalian ventricular myocardium. Nat New Biol. 1971 Mar 31;230(13):150–151. doi: 10.1038/newbio230150a0. [DOI] [PubMed] [Google Scholar]
  11. Nathan D., Beeler G. W., Jr Electrophysiologic correlates of the inotropic effects of isoproterenol in canine myocardium. J Mol Cell Cardiol. 1975 Jan;7(1):1–15. doi: 10.1016/0022-2828(75)90002-4. [DOI] [PubMed] [Google Scholar]
  12. Patterson S. W., Piper H., Starling E. H. The regulation of the heart beat. J Physiol. 1914 Oct 23;48(6):465–513. doi: 10.1113/jphysiol.1914.sp001676. [DOI] [PMC free article] [PubMed] [Google Scholar]
  13. Proudfit W. L., Bruschke A. V., Sones F. M., Jr Natural history of obstructive coronary artery disease: ten-year study of 601 nonsurgical cases. Prog Cardiovasc Dis. 1978 Jul-Aug;21(1):53–78. doi: 10.1016/s0033-0620(78)80004-8. [DOI] [PubMed] [Google Scholar]
  14. SONNENBLICK E. H. Force-velocity relations in mammalian heart muscle. Am J Physiol. 1962 May;202:931–939. doi: 10.1152/ajplegacy.1962.202.5.931. [DOI] [PubMed] [Google Scholar]
  15. Schwartz P. J., Wolf S. QT interval prolongation as predictor of sudden death in patients with myocardial infarction. Circulation. 1978 Jun;57(6):1074–1077. doi: 10.1161/01.cir.57.6.1074. [DOI] [PubMed] [Google Scholar]
  16. Weissler A. M., Harris W. S., Schoenfeld C. D. Systolic time intervals in heart failure in man. Circulation. 1968 Feb;37(2):149–159. doi: 10.1161/01.cir.37.2.149. [DOI] [PubMed] [Google Scholar]

Articles from British Heart Journal are provided here courtesy of BMJ Publishing Group

RESOURCES