isovolumic relaxation

i·so·vol·u·mic re·lax·a·tion

that part of the cardiac cycle between the time of aortic valve closure and mitral opening, during which the ventricular muscle decreases its tension without lengthening so that ventricular volume remains unaltered; the heart is never precisely isovolumetric (vs. isovolumic) except during long diastoles with a midiastolic period of diastasis.
References in periodicals archive ?
Mitral E velocity (ME), mitral A velocity (MA), mitral E wave deceleration time (MEDT), and LV isovolumic relaxation time (IVRT), defined as time period between the termination of aortic systolic wave and beginning of ME, were measured by locating the sampling volume cursor of pulsed Doppler in the apical four chamber position at 5 mm above the mitral leaflets tips.
The correlations between isovolumic relaxation time, P wave duration and LA size and coronary ectasia may reflect, indirectly, the element of diastolic dysfunction in this cohort.
We measured left ventricle Ejection Fraction (EF) and Fractional Shortening (FS) to survey left ventricle systolic function, and left ventricle Isovolumic Relaxation Time (LV IVRT) and also Early rapid filling/Atrial contraction (E/A ratio) in mitral valve blood flow to survey left ventricle diastolic function.
Isovolumic relaxation time and isovolumic contraction time from the basal part of the left ventricle, myocardial rate during the systole, myocardial rate during the erly diastole, the rate during the late diastole, ejection time, isovolumic contraction acceleration and acceleration of the ventricle at the time of isovolumic contraction were measured.
8 in individuals >55 years, DT >220 ms, IRT >100 ms; pseudonormal: 1 < E/A < 2,150 ms < DT < 200 ms, IRT <100 ms; restrictive filling, E/A >2, DT <150 ms, IRT <60 ms, where E is the peak E-wave velocity and A is the peak A-wave velocity of the mitral inflow, DT is the deceleration time of the E wave, and IRT is the left ventricular isovolumic relaxation time (13).
There was a restrictive physiology pattern of the left ventricle, however, with isovolumic relaxation time of 50 milliseconds, deceleration time of 160 milliseconds, and early to late diastolic filling ratio of 2.
The results showed that there were a good agreement for mitral inflow E and S, deceleration time, isovolumic relaxation and contraction times, myocardial performance index, ejection time, systolic and diastolic mitral annular pulse-wave velocities from TTE and TEE.
Peak early filling velocity (E wave), peak atrial systolic velocity (A wave), early-to-late diastolic flow ratio (E/A), deceleration time (dTE), isovolumic relaxation time (IVRT) and isovolumic contraction time (IVCT) were measured for the tricuspid valve (26).
After infusion, diastolic parameters like velocity of propagation (Vp) and isovolumic relaxation time (IVRT) improved almost to same extent in both groups but deceleration time (DT) did not.
The relevant echocardiographic parameters were measured in both subject groups: myocardial performance index (MPI), isovolumic relaxation time (IRT), isovolumic contraction time (ICT), pre-ejection period (PEP), ejection time (ET), PEP/ET ratio, deceleration time (DT) and acceleration time (AT).
Although the entire time course of LVP cannot be converted to certain equations because of the variability in aortic properties, some equations have been proposed for isovolumic contraction and isovolumic relaxation phases, which are the periods that the aortic valve is not open, and therefore, aortic pressure is not equal to the left ventricular pressure.