title: [Analysis of the phase of left ventricular isovolumic relaxation time in healthy people using dual-channel echocardiography].
abstract: OBJECTIVE
  To exacted analysis each time interval in isovolumic relaxation time (IVRT) of normal subjects through observin the changes of cardiac structure and hemodynamics during the IVRT. Then to provide the evidence of cardiac resynchronization therapy.
  
  
  METHODS
  Quantitative analysis was performed for 60 subjects. The dual-channel echocardiography(DCE), pulse wave doppler (PW) and tissue wave dapper (TDI) examination of all the subjects were recorded, and IVRT was divided into two intervals, isovolumic relaxation time of early intervals (IVRTe) and isovolumic relaxation time of late interval (IVRT1). Then measured the time of each interval. Indicators were used including: (1) IVRT; (2) IVRTe; (3) IVRTI; (4) IVRTI/IVRT; calculating the data after heart rate corrected; (5) cIVRT; (6) clVRTe; (7) clVRTI; (8) clVRTI/clVRT; (9) measuring the time difference in mitral blood and tissue (TE-é) of DCE group.
  
  
  RESULTS
  The i-wave within IVRT in PW images was found in 45 subjects, and the i-wave was about 1/2 of IVRT (49.17 +/- 5.37) ms. IVRT was divided into IVRTe and IVRTI by a turning point at descending branch of i-wave as t-point. The j-wave was observed in 84% TDI images, and the j-wave was about 1/2 of IVRT (43.13 +/- 4.83) ms. IVRT was divided into IVRTe and IVRTI by a turning point of the onset of j-wave as t-point. A significant difference was found between PW and TDI with measurement of IVRT, IVRTe, IVRTI (P < 0.05). There were no significant differences between the common group and DCE group (P > 0.05). After heart rate corrected, the data showed no significant difference using pairwise comparisons among the three groups (P > 0.05). The mean and standard deviation of IVRTI/IVRT, cIVRTI/clVRT were (0.50 +/- 0.12) ms. There were little difference of time intervals and good consistenc using DCE measured IVRT with multiple tests confinmed.
  
  
  CONCLUSIONS
  The study found that IVRT might be divided into IVRTe and IVRT1 phases. There were i-wave in IVRTe and j-wave in IVRT1. The t-point was nearly midpoint inisovolumic relaxation time.
authors.forename: Dan-Dan
authors.initials: DD
authors.lastname: Wang
authors.forename: Yao
authors.initials: Y
authors.lastname: Chen
authors.forename: Liang-Hua
authors.initials: LH
authors.lastname: Xia
authors.forename: Min
authors.initials: M
authors.lastname: Xu
authors.forename: Ming
authors.initials: M
authors.lastname: Chen
mesh_terms: D000328:Adult; D003971:Diastole / Q000502:physiology*; D004452:Echocardiography; D005260:Female; D064368:Healthy Volunteers; D006801:Humans; D008297:Male; D008875:Middle Aged; D016277:Ventricular Function, Left / Q000502:physiology*