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Active myocyte shortening during the 'isovolumetric relaxation' phase of diastole is responsible for ventricular suction; 'systolic ventricular filling'

Buckberg, Gerald D. and Castellá, Manuel and Gharib, Morteza and Saleh, Saleh (2006) Active myocyte shortening during the 'isovolumetric relaxation' phase of diastole is responsible for ventricular suction; 'systolic ventricular filling'. European Journal of Cardio-Thoracic Surgery, 29 (S1). S98-S106. ISSN 1010-7940. doi:10.1016/j.ejcts.2006.02.043.

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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.

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Additional Information:© 2006 Elsevier B.V. Received 17 February 2006; accepted 27 February 2006.
Subject Keywords:Isovolumetric relaxation; Isovolumetric contraction; Helical heart; Ventricular myocardial band; Systolic ventricular filling
Issue or Number:S1
Record Number:CaltechAUTHORS:20130920-081636233
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:41434
Deposited By: Tony Diaz
Deposited On:20 Sep 2013 19:33
Last Modified:10 Nov 2021 04:30

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