Document Detail


Active myocyte shortening during the 'isovolumetric relaxation' phase of diastole is responsible for ventricular suction; 'systolic ventricular filling'.
MedLine Citation:
PMID:  16567105     Owner:  NLM     Status:  MEDLINE    
Abstract/OtherAbstract:
OBJECTIVE: To study the 'isovolumetric relaxation' phase of rapid ventricular filling by analysis of the shortening of cardiac muscle in the endocardial and epicardial segments of the left ventricle in the dual helical model of the ventricular band, described by Torrent-Guasp. METHODS: In 10 pigs (27-82 kg), temporal shortening by sonomicrometer crystals was recorded while recording ECG, and measuring intraventricular pressure and dP/dt with Millar pressure transducers. RESULTS: The following sequence was observed; shortening began in descending or endocardial segment, and 82+/-23 ms later it was initiated in the epicardial or ascending segment of the band. The descending segment stops shortening during the rapid filling phase of fast descent of ventricular pressure, but the ascending segment shortening continues for 92+/-33 ms, so that active shortening continues during the period of isovolumetric relaxation. During the rapid filling phase, dopamine decreased the interval between completion of endocardial and termination of epicardial contraction from 92+/-20 to 33+/-8 ms. Conversely propranolol delayed the start of epicardial shortening from 82+/-23 to 121+/-20 ms, and prolonged the duration of endocardial contraction, causing a closer (21+/-5 ms vs 92+/-20 ms) interval between termination of contraction of endocardial and epicardial fibers. The resultant slope of the rapid descent of the left ventricular pressure curve became prolonged. CONCLUSIONS: These time sequences show that ongoing unopposed ascending segment shortening occurs during the phase of rapid fall of ventricular pressure. These active shortening phases respond to positive and negative inotropic stimulation, and indicate the classic concept of 'isovolumetric relaxation', IVR, must be reconsidered, and the new term 'isovolumetric contraction', IVC, or systolic ventricular filing may be used.
Authors:
Gerald D Buckberg; Manuel Castellá; Morteza Gharib; Saleh Saleh
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Publication Detail:
Type:  Journal Article     Date:  2006-03-29
Journal Detail:
Title:  European journal of cardio-thoracic surgery : official journal of the European Association for Cardio-thoracic Surgery     Volume:  29 Suppl 1     ISSN:  1010-7940     ISO Abbreviation:  Eur J Cardiothorac Surg     Publication Date:  2006 Apr 
Date Detail:
Created Date:  2006-04-18     Completed Date:  2007-01-10     Revised Date:  -    
Medline Journal Info:
Nlm Unique ID:  8804069     Medline TA:  Eur J Cardiothorac Surg     Country:  Germany    
Other Details:
Languages:  eng     Pagination:  S98-106     Citation Subset:  IM    
Affiliation:
Option on Bioengineering, California Institute of Technology, Pasadena, CA, USA. gbuckberg@mednet.ucla.edu
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MeSH Terms
Descriptor/Qualifier:
Animals
Cell Size
Diastole / physiology*
Electrocardiography
Endocardium / cytology,  physiology
Models, Cardiovascular
Muscle Cells / cytology,  physiology*
Myocardial Contraction / drug effects
Pericardium / cytology,  physiology
Propranolol / pharmacology
Swine
Systole / physiology*
Transducers, Pressure
Vasodilator Agents / pharmacology
Ventricular Function, Left / physiology*
Chemical
Reg. No./Substance:
0/Vasodilator Agents; 525-66-6/Propranolol

From MEDLINE®/PubMed®, a database of the U.S. National Library of Medicine


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