End-systolic stress-velocity and pressure-dimension  relationships by transthoracic echocardiography in mice

The purposes of this study were to assess load-independent, end-systolic relationships in mice and compare these relationships to ejection phase indexes in assessing contractility. In 13 mice, ejection phase indexes (shortening fraction and velocity of fiber shortening) and end-systolic relationships [pressure-dimension relationship (ESPDR) and stress-velocity relationship (ESSVR)] were determined using M-mode echocardiography and simultaneous left ventricular pressure. Load was altered with phenylephrine and nitroprusside. Contractility was increased with dobutamine and decreased by induction of hypothyroidism. Ejection phase indexes increased with dobutamine infusion but were not significantly decreased with hypothyroidism. However, end-systolic relationships changed significantly with both dobutamine ( y-intercepts: ESPDR from 22 to 48 mmHg, ESSVR from 3.7 to 6.6 circ/s, P < 0.05) and hypothyroidism ( y-intercepts: ESPDR from 22 to 11 mmHg, ESSVR from 3.7 to 3.2 circ/s, P< 0.05). We conclude that end-systolic indexes can be accurately measured in the intact mouse by echocardiography with simultaneous left ventricular pressure recording and appear to be more sensitive to inotropic state than ejection phase indexes.

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Impact of ejection on magnitude and time course of ventricular pressure-generating capacity

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1993.265.3.h899 ◽

1993 ◽

Vol 265 (3) ◽

pp. H899-H909 ◽

Cited By ~ 24

Author(s):

D. Burkhoff ◽

P. P. De Tombe ◽

W. C. Hunter

Keyword(s):

Time Course ◽

Cardiac Cycle ◽

Left Ventricular Pressure ◽

Left Ventricular ◽

Ventricular Pressure ◽

Time Varying ◽

Generating Capacity ◽

Ejection Phase ◽

Time Point ◽

Ventricular Dynamics

This study focuses on elucidating how ventricular afterloading conditions affect the time course of change of left ventricular pressure (LVP) throughout the cardiac cycle, with particular emphasis on revealing specific limitations in the time-varying elastance model of ventricular dynamics. Studies were performed in eight isolated canine hearts ejecting into a simulated windkessel afterload. LVP waves measured (LVPm) during ejection were compared with those predicted (LVPpred) according to the elastance theory. LVPm exceeded LVPpred from a time point shortly after the onset of ejection to the end of the beat. The instantaneous difference between LVPm and LVPpred increased steadily as ejection proceeded and reached between 45 and 65 mmHg near end ejection. This was in large part due to an average 35-ms prolongation of the time to end systole (tes) in ejecting compared with isovolumic beats. The time constant of relaxation was decreased on ejecting beats so that, despite the marked prolongation of tes, the overall duration of ejecting contractions was not greater than that of isovolumic beats. The results demonstrate a marked ejection-mediated enhancement and prolongation of ventricular pressure-generating capacity during the ejection phase of the cardiac cycle with concomitant acceleration of relaxation. None of these factors are accounted for by the time-varying elastance theory.

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Effects of arterial input impedance on mean ventricular pressure-flow relation

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1984.247.6.h978 ◽

1984 ◽

Vol 247 (6) ◽

pp. H978-H983 ◽

Cited By ~ 1

Author(s):

W. L. Maughan ◽

K. Sunagawa ◽

K. Sagawa

Keyword(s):

Characteristic Impedance ◽

Peripheral Resistance ◽

Left Ventricular Pressure ◽

Left Ventricular ◽

Ventricular Pressure ◽

Pressure Flow ◽

Inotropic State ◽

End Diastolic Volume ◽

State Compliance ◽

Slope Change

The mean left ventricular pressure-flow relationship (Pv-Fv), determined under a constant preload and variable peripheral resistance, has been proposed as a quantitative representation of ventricular pump function (9). We determined the Pv-Fv relation in seven isolated cross-perfused canine hearts by varying resistance of a simulated arterial load in five steps from 6.0 to 0.375 mmHg X s X ml-1 while keeping end-diastolic volume, inotropic state, compliance, and characteristic impedance at various constant values. All of the 27 Pv-Fv relations thus determined were moderately nonlinear. Varying end-diastolic volume at three levels shifted the relation curve in an approximately parallel fashion (P less than 0.0001). At three levels of inotropic state (mean LVP of isovolumic contractions 34.3 +/- 8.2, 48.0 +/- 6.3, and 59.2 +/- 9.6 mmHg), the Pv-Fv relation shifted with predominantly a slope change (P less than 0.0001). Changing compliance at three levels (0.2, 0.4, and 0.8 ml/mmHg) caused a statistically significant but quantitatively small crossover of the Pv-Fv curves (P less than 0.0001). Changing characteristic impedance to 0.1, 0.2, and 0.4 mmHg X s X ml-1 caused a highly significant (P less than 0.0001) divergence of Pv-Fv relation over the high Fv range. We conclude that this sensitivity of the Pv-Fv relation to characteristic impedance limits its use as a contractility index.

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Cardiac Mass and Myocardial Late Enhancement are Associated with Overall Disease Severity and Left Ventricular Pressure Load in Fabry Disease

Heart Lung and Circulation ◽

10.1016/j.hlc.2013.05.399 ◽

2013 ◽

Vol 22 ◽

pp. S167

Author(s):

R. Kozor ◽

M. Tchan ◽

D. Sillence ◽

S. Grieve ◽

G. Figtree

Keyword(s):

Fabry Disease ◽

Disease Severity ◽

Left Ventricular Pressure ◽

Late Enhancement ◽

Left Ventricular ◽

Cardiac Mass ◽

Ventricular Pressure ◽

Pressure Load

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Subepicardial fiber strain and stress as related to left ventricular pressure and volume

AJP Heart and Circulatory Physiology ◽

10.1152/ajpheart.1993.264.5.h1548 ◽

1993 ◽

Vol 264 (5) ◽

pp. H1548-H1559 ◽

Cited By ~ 5

Author(s):

T. Delhaas ◽

T. Arts ◽

P. H. Bovendeerd ◽

F. W. Prinzen ◽

R. S. Reneman

Keyword(s):

Left Ventricular Pressure ◽

Anterior Wall ◽

Left Ventricular ◽

Ventricular Pressure ◽

Stress And Strain ◽

Minor Importance ◽

Cavity Pressure ◽

Fiber Stress ◽

Optical Markers ◽

Ejection Phase

In a mathematical model of the mechanics of the left ventricle (LV) by Arts et al. (1), assuming uniformity of fiber stress (sigma f) and fiber strain (delta epsilon f) in the wall during the ejection phase, fiber stress and fiber strain were related to LV cavity pressure (Plv), LV cavity volume (Vlv) and wall volume (Vw) by the following pair of equations: sigma f = Plv (1 + 3 Vlv/Vw) and delta epsilon f = 1/3 delta ln (1 + 3 Vlv/Vw). The ratio of Vlv to Vw appeared to be the most important geometric parameter, whereas the actual LV shape was of minor importance. The relationships on fiber strain and stress were evaluated experimentally in six anesthetized open-chest dogs during normal and elevated (volume loading) end-diastolic LV pressure. Subepicardial fiber strain was measured simultaneously in 16 adjacent regions of the LV anterior wall, using optical markers that were attached to the epicardial surface and recorded on video. Changes in Vlv were measured by use of four inductive coils sutured to the LV in a tetrahedric configuration. Vw was measured postmortem. During control as well as hypervolemia the following results were found. At the anterior free wall of the LV, the slope of the estimated linear relationship between measured and calculated fiber strain was 1.017 +/- 0.168 (means +/- SD), which is not significantly different from unity. Calculated fiber stress corresponded qualitatively and quantitatively with experimental results reported on isolated cardiac muscle. Calculated subepicardial contractile work per unit of tissue volume was not significantly different from global pump work as normalized to Vw. These findings support the assumption of homogeneity of muscle fiber strain and stress in the left ventricular wall during the ejection phase. Furthermore, average values of fiber stress and strain can be estimated on the basis of measured left ventricular pressure and volume.

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