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

1993 ◽  
Vol 265 (3) ◽  
pp. H899-H909 ◽  
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.

Coronary oscillatory flow amplitude is more affected by perfusion pressure than ventricular pressure

1990 ◽  
Vol 258 (6) ◽  
pp. H1889-H1898 ◽  
Author(s):  
R. Krams ◽  
P. Sipkema ◽  
N. Westerhof
Keyword(s):  
Oscillatory Flow ◽  
Perfusion Pressure ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Cardiac Contraction ◽  
Ventricular Pressure ◽  
Time Varying ◽  
Waterfall Model ◽  
Developed Pressure ◽  
Phasic Flow

In this study on the isolated, maximally vasodilated, blood-perfused cat heart we investigated the relation between left ventricular developed pressure (delta Piv) and coronary oscillatory flow amplitude (diastolic minus systolic flow, delta F) at different levels of constant perfusion pressure (Pp). We hypothesized that the effect of cardiac contraction on the phasic flow results from the changing elastic properties of cardiac muscle. The coronary vessel compartment can, as can the left ventricular lumen compartment, be described by a time-varying elastance. This concept predicts that the effect of left ventricular pressure on delta F is small, whereas the effect of Pp is considerable. Both the waterfall model and the intramyocardial pump model predict the inverse. The relation between delta Piv and delta F at a Pp of 10 kPa is delta F = (4.71 +/- 3.08).delta Piv + 337 +/- 75 (slope in ml.min-1.100 g-1.kPa-1 and intercept in ml.min-1.100 g-1; n = 7); the relation between (constant levels of) Pp and delta F at a constant delta Piv of 10 kPa is delta F = 51.Pp + 211 (slope in ml.min-1.100 g-1.kPa-1 and intercept in ml.min-1.100 g-1; n = 6). The differences in slope are best predicted by the time-varying elastance concept.

scholarly journals Synergistic Model of Cardiac Function with a Heart Assist Device

2019 ◽  
Vol 7 (1) ◽  
pp. 1
Author(s):  
Eun-jin Kim ◽  
Massimo Capoccia
Keyword(s):  
Cardiac Function ◽  
Heart Diseases ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Self Organization ◽  
Ventricular Pressure ◽  
Time Varying ◽  
Assist Device ◽  
Clinical Scenarios ◽  
Volume Relation

The breakdown of cardiac self-organization leads to heart diseases and failure, the number one cause of death worldwide. The left ventricular pressure–volume relation plays a key role in the diagnosis and treatment of heart diseases. Lumped-parameter models combined with pressure–volume loop analysis are very effective in simulating clinical scenarios with a view to treatment optimization and outcome prediction. Unfortunately, often invoked in this analysis is the traditional, time-varying elastance concept, in which the ratio of the ventricular pressure to its volume is prescribed by a periodic function of time, instead of being calculated consistently according to the change in feedback mechanisms (e.g., the lack or breakdown of self-organization) in heart diseases. Therefore, the application of the time-varying elastance for the analysis of left ventricular assist device (LVAD)–heart interactions has been questioned. We propose a paradigm shift from the time-varying elastance concept to a synergistic model of cardiac function by integrating the mechanical, electric, and chemical activity on microscale sarcomere and macroscale heart levels and investigating the effect of an axial rotary pump on a failing heart. We show that our synergistic model works better than the time-varying elastance model in reproducing LVAD–heart interactions with sufficient accuracy to describe the left ventricular pressure–volume relation.

In vivo murine left ventricular pressure-volume relations by miniaturized conductance micromanometry

1998 ◽  
Vol 274 (4) ◽  
pp. H1416-H1422 ◽  
Author(s):  
Dimitrios Georgakopoulos ◽  
Wayne A. Mitzner ◽  
Chen-Huan Chen ◽  
Barry J. Byrne ◽  
Huntly D. Millar ◽  
...  
Keyword(s):  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Genetically Engineered ◽  
Ventricular Pressure ◽  
Stroke Work ◽  
Time Varying ◽  
End Diastolic Volume ◽  
Novel Approach ◽  
Preload Reduction

The mouse is the species of choice for creating genetically engineered models of human disease. To study detailed systolic and diastolic left ventricular (LV) chamber mechanics in mice in vivo, we developed a miniaturized conductance-manometer system. α-Chloralose-urethan-anesthetized animals were instrumented with a two-electrode pressure-volume catheter advanced via the LV apex to the aortic root. Custom electronics provided time-varying conductances related to cavity volume. Baseline hemodynamics were similar to values in conscious animals: 634 ± 14 beats/min, 112 ± 4 mmHg, 5.3 ± 0.8 mmHg, and 11,777 ± 732 mmHg/s for heart rate, end-systolic and end-diastolic pressures, and maximum first derivative of ventricular pressure with respect to time (dP/d t max), respectively. Catheter stroke volume during preload reduction by inferior vena caval occlusion correlated with that by ultrasound aortic flow probe ( r 2 = 0.98). This maneuver yielded end-systolic elastances of 79 ± 21 mmHg/μl, preload-recruitable stroke work of 82 ± 5.6 mmHg, and slope of dP/d t max-end-diastolic volume relation of 699 ± 100 mmHg ⋅ s−1 ⋅ μl−1, and these relations varied predictably with acute inotropic interventions. The control normalized time-varying elastance curve was similar to human data, further supporting comparable chamber mechanics between species. This novel approach should greatly help assess cardiovascular function in the blood-perfused murine heart.

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

1993 ◽  
Vol 264 (5) ◽  
pp. H1548-H1559 ◽  
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.

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

1998 ◽  
Vol 274 (5) ◽  
pp. H1828-H1835 ◽  
Author(s):  
Richard V. Williams ◽  
John N. Lorenz ◽  
Sandra A. Witt ◽  
David T. Hellard ◽  
Philip R. Khoury ◽  
...  
Keyword(s):  
Transthoracic Echocardiography ◽  
Left Ventricular Pressure ◽  
Left Ventricular ◽  
Ventricular Pressure ◽  
Intact Mouse ◽  
Pressure Recording ◽  
Pressure Load ◽  
Inotropic State ◽  
Velocity Relationship ◽  
Ejection Phase

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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