Pressure-velocity relation in the isolated rabbit left ventricle.

Okuyama, Hiroshi

doi:10.2170/jjphysiol.33.507

Cited by 6 publications

(5 citation statements)

References 15 publications

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“…For the formulation of the new index, the LV was modeled as a pressurized thick-walled sphere. Similar geometric assumptions had been made by investigators studying LV pressure-volume dynamics in small animal models (14,26). This was done to reduce the mathematical complexity of calculation, which is especially pertinent in clinical cases.…”

Section: Discussionmentioning

confidence: 99%

Validation of a novel noninvasive cardiac index of left ventricular contractility in patients

Zhong¹,

Tan²,

Ghista³

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

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Although there are several excellent indexes of myocardial contractility, they require accurate measurement of pressure via left ventricular (LV) catheterization. Here we validate a novel noninvasive contractility index that is dependent only on lumen and wall volume of the LV chamber in patients with normal and compromised LV ejection fraction (LVEF). By analysis of the myocardial chamber as a thick-walled sphere, LV contractility index can be expressed as maximum rate of change of pressure-normalized stress (d*/dt max, where * ϭ /P and and P are circumferential stress and pressure, respectively). To validate this parameter, d*/dt max was determined from contrast cine-ventriculography-assessed LV cavity and myocardial volumes and compared with LVEF, dP/dt max, maximum active elastance (Ea,max), and singlebeat end-systolic elastance [E es(SB)] in 30 patients undergoing clinically indicated LV catheterization. Patients with different tertiles of LVEF exhibit statistically significant differences in d*/dt max. There was a significant correlation between d*/dt max and dP/dtmax (d*/ dt max ϭ 0.0075dP/dt max Ϫ 4.70, r ϭ 0.88, P Ͻ 0.01), E a,max (d*/dtmax ϭ 1.20Ea,max ϩ 1.40, r ϭ 0.89, P Ͻ 0.01), and Ees(SB) [d*/dtmax ϭ 1.60Ees(SB) ϩ 1.20, r ϭ 0.88, P Ͻ 0.01]. In 30 additional individuals, we determined sensitivity of the parameter to changes in preload (intravenous saline infusion, n ϭ 10 subjects), afterload (sublingual glyceryl trinitrate, n ϭ 10 subjects), and increased contractility (intravenous dobutamine, n ϭ 10 patients). We confirmed that the index is not dependent on load but is sensitive to changes in contractility. In conclusion, d*/dt max is equivalent to dP/dt max, Ea,max, and Ees(SB) as an index of myocardial contractility and appears to be load independent. In contrast to other measures of contractility, d*/dt max can be assessed with noninvasive cardiac imaging and, thereby, should have more routine clinical applicability. cardiac mechanics; ventricular elastance; ventriculography; wall stress THE QUEST TO DELINEATE and quantify myocardial inotropic function in humans, independent of ventricular loading conditions, is an ongoing preoccupation of researchers and clinicians (15-17, 19, 29, 45-47). In the left ventricle (LV), the peak first time derivative of LV intracavity pressure (dP/dt max ), which is reached just before aortic valve opening, is arguably the most sensitive cardiac index of inotropicity and is the "gold standard" (15, 16). Accurate determination of dP/dt max requires measurement of intraventricular LV pressure by invasive cardiac catheterization. In some individuals with mitral regurgitation, dP/dt max may be approximated from time-resolved mitral regurgitation velocities, which are acquired noninvasively using continuous-wave Doppler echocardiography (1). In general, however, accurate noninvasive assessment of ventricular pressure is very difficult.An additional difficulty with LV dP/dt max is that it is not preload independent (23). Conceivably, the LV pressure-volume relation and e...

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Section: Discussionmentioning

confidence: 99%

Validation of a novel noninvasive cardiac index of left ventricular contractility in patients

Zhong¹,

Tan²,

Ghista³

et al. 2007

American Journal of Physiology-Heart and Circulatory Physiology

View full text Add to dashboard Cite

show abstract

“…The stiffness of the ventricle may also reflect roughly the number of active cross-bridges in a whole ventricle, assuming that a small volume change causes a small length change in all wall muscles. Provided with a suitable geometrical model, the above results indicate that the pressure-volume and stiffness-pressure relations of the ventricle have close interrelations with the tension-length and stiffness-tension relations of the wall muscle, as the pressure-velocity relation does with the force-velocity relation of the wall muscle as described by OKUYAMA (1983). These studies will offer a way to analyze the ventricular performance on the basis of cardiac muscle mechanics.…”

Section: Discussionmentioning

confidence: 67%

“…Preparation procedures and the experimental setup were described in detail by OKUYAMA (1983). In brief, after the establishment of retrograde coronary perfusion, the heart was isolated and a thin latex balloon was inserted into the left ventricular cavity.…”

Section: Discussionmentioning

confidence: 99%

The pressure-volume and stiffness-pressure relations in the isolated rabbit left ventricle.

1983

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SummaryA balloon was introduced into the isolated rabbit left ven- Many studies have been done on cardiac muscle mechanics and on the ventricular performance, but few attempts have been made to elucidate the interrelation between both frameworks. One of the reasons has been the difficulty in controlling the intraventricular volume. Recently, SUGA and SAGAWA (1974) overcame this difficulty by adopting the intraventricular balloon method to the isolated dog heart. OKUYAMA (1983) has determined the hyperbolic relation between pressure and ejection velocity in the rabbit ventricle and has successfully shown the quantitative interrelation of force-velocity with ventricular wall muscle. This study was aimed at determining the pressure-volume and stiffness-pressure relations in the rabbit ventricle to compare them with the tension-length and stiffness-tension relations of wall muscle.Thirteen adult female rabbits, weighing 2.5-4.4 kg, were anesthetized with intravenous urethane (1.3-2.5 g/kg) administration, and under artificial ventilation the heart was exposed through midsternal thoracotomy. Preparation procedures and the experimental setup were described in detail by OKUYAMA (1983). In brief, after the establishment of retrograde coronary perfusion, the heart was isolated and a thin latex balloon was inserted into the left ventricular cavity. The balloon was connected to a volume control system, which consisted of a cylindrical chamber, a magnet shaker and an electrical feedback amplifier. The intraventricular volume could be changed at various velocities at any instant. The retrograde

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“…Twelve adult rabbits (2.2-3.2 kg) were anesthetized by intravenous urethane administration (1.3-2.5 g/kg), and, under artificial ventilation, the heart was exposed through a midsternal thoracotomy. The procedures for preparation and experimental set-up were described in detail elsewhere (OKUYAMA, 1983). Figure 1 illustrates the schematic experimental set-up.…”

Section: Methodsmentioning

confidence: 99%

Effects of ischemia on pressure-velocity and pressure-volume relationships in the isolated rabbit left ventricle.

Nakajima

1985

Jpn.J.Physiol

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The pressure-velocity and pressure-volume relationships were determined in the isolated rabbit left ventricle in order to evaluate ventricular function during global Ischemia (low pressure perfusion) and under reperfusion after a 10 min complete coronary occlusion (reperfusion after coronary occlusion). Reducing coronary perfusion pressure, the maximum isovolumic pressure (F0) decreased, but the maximum ejection velocity ( Vmag) did not. The slope of the end-systolic pressure-volume relationship (Emax) decreased without any significant change in the volume-axis intercept. On the other hand, under reperfusion after coronary occlusion, both Po and Vmag ware depressed considerably, but Emax quickly recovered to the control level. Thus, Vmax and Emax show different behavior depending on the ischemic conditions. To analyze the relaxation process under low pressure perfusion and reperfusion after coronary occlusion, the pressure-velocity relations during the relaxation phase were determined by the isovelocity method. Similar to the relation for contraction phase, the relation obtained here could be adequately approximated by a hyperbolic equation. Under the control condition, the relaxation velocity was always lower than the contraction velocity at the corresponding pressure level, and the ratio of the maximum filling velocity ('Lax) to Vmag was relatively constant. Although both 'Lax and Rmax/ Vmax were little affected by the low pressure perfusion, Vmax and 'Lax, especially Vmag, decreased when the ventricle was reperfused after coronary occlusion, resulting in an increased Rmax/Vmax.

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Pressure-velocity relation in the isolated rabbit left ventricle.

Cited by 6 publications

References 15 publications

Validation of a novel noninvasive cardiac index of left ventricular contractility in patients

Validation of a novel noninvasive cardiac index of left ventricular contractility in patients

The pressure-volume and stiffness-pressure relations in the isolated rabbit left ventricle.

Effects of ischemia on pressure-velocity and pressure-volume relationships in the isolated rabbit left ventricle.

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