Experimental Myocardial Infarction

Pirzada, Farouk A.; Weiner, Jerold M.; Hood, William B.

doi:10.1378/chest.74.2.190

Cited by 46 publications

(7 citation statements)

References 25 publications

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“…Although systolic deformation was strongly reduced in both groups, diastolic myocardial stiffness increased only in the infarcted group. These modifications of systolic and diastolic function are in line with previously published results in both experimental animals and in humans 12 , 26 , 27 .…”

Section: Discussionsupporting

confidence: 92%

Shear Wave Imaging of Passive Diastolic Myocardial Stiffness

Pernot

Lee

Bel

et al. 2016

JACC: Cardiovascular Imaging

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ObjectivesThe aim of this study was to investigate the potential of shear wave imaging (SWI), a novel ultrasound-based technique, to noninvasively quantify passive diastolic myocardial stiffness in an ovine model of ischemic cardiomyopathy.BackgroundEvaluation of diastolic left ventricular function is critical for evaluation of heart failure and ischemic cardiomyopathy. Myocardial stiffness is known to be an important property for the evaluation of the diastolic myocardial function, but this parameter cannot be measured noninvasively by existing techniques.MethodsSWI was performed in vivo in open-chest procedures in 10 sheep. Ligation of a diagonal of the left anterior descending coronary artery was performed for 15 min (stunned group, n = 5) and 2 h (infarcted group, n = 5). Each procedure was followed by a 40-min reperfusion period. Diastolic myocardial stiffness was measured at rest, during ischemia, and after reperfusion by using noninvasive shear wave imaging. Simultaneously, end-diastolic left ventricular pressure and segmental strain were measured with a pressure catheter and sonomicrometers during transient vena caval occlusions to obtain gold standard evaluation of myocardial stiffness using end-diastolic strain-stress relationship (EDSSR).ResultsIn both groups, the end-systolic circumferential strain was drastically reduced during ischemia (from 14.2 ± 1.2% to 1.3 ± 1.6% in the infarcted group and from 13.5 ± 3.0% to 1.9 ± 1.8% in the stunned group; p <0.01). SWI diastolic stiffness increased after 2 h of ischemia from 1.7 ± 0.4 to 6.2 ± 2.2 kPa (p < 0.05) and even more after reperfusion (12.1 ± 4.2 kPa; p < 0.01). Diastolic myocardial stiffening was confirmed by the exponential constant coefficient of the EDSSR, which increased from 8.8 ± 2.3 to 25.7 ± 9.5 (p < 0.01). In contrast, SWI diastolic stiffness was unchanged in the stunned group (2.3 ± 0.4 kPa vs 1.8 ± 0.3 kPa, p = NS) which was confirmed also by the exponential constant of EDSSR (9.7 ± 3.1 vs 10.2 ± 2.3, p = NS).ConclusionsNoninvasive SWI evaluation of diastolic myocardial stiffness can differentiate between stiff, noncompliant infarcted wall and softer wall containing stunned myocardium.

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Section: Discussionsupporting

confidence: 92%

Shear Wave Imaging of Passive Diastolic Myocardial Stiffness

Pernot

Lee

Bel

et al. 2016

JACC: Cardiovascular Imaging

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“…In this study, infarcted reperfused myocardium was significantly stiffer (two to eight times) and more viscous (three to four times) than normal myocardium, consistent with previous observations using other (non-shear wave) techniques (Diamond and Forrester 1972; Hsu et al 2007; Luo et al 2007; Pirzada et al 1978; Pislaru et al 2004). Values of μ 1 > 4 kPa and μ 2 > 4 Pa·s fell outside the normal range for this animal model and physiologic levels of preload.…”

Section: Discussionsupporting

confidence: 91%

“…Myocardial elasticity and its changes with muscle contraction have been studied both in vitro and in vivo (Diamond and Forrester 1972; Little and Freeman 1987; Pirzada et al 1978; Suga and Sugawa 1974). At end-diastole, the myocardium is relaxed, and passive characteristics are dominant.…”

Section: Discussionmentioning

confidence: 99%

“…The second aim was to characterize differences in viscoelastic properties of the myocardium during systole and diastole in normal and infarcted myocardium. We hypothesized that alterations in myocardial stiffness caused by acute ischemia and re-perfusion (Diamond and Forrester 1972; Pirzada et al 1978) can be quantified in vivo by the shear wave method, SDUV. The effect of preload on viscoelastic estimates was also assessed.…”

Section: Introductionmentioning

confidence: 99%

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Viscoelastic Properties of Normal and Infarcted Myocardium Measured by a Multifrequency Shear Wave Method: Comparison with Pressure-Segment Length Method

Pislaru

Urban

Pislaru

et al. 2014

Ultrasound in Medicine & Biology

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Our aims were (i) to compare in vivo measurements of myocardial elasticity by shear wave dispersion ultrasound vibrometry (SDUV) with those by the conventional pressure-segment length method, and (ii) to quantify changes in myocardial viscoelasticity during systole and diastole after reperfused acute myocardial infarction. The shear elastic modulus (μ1) and viscous coefficient (μ2) of left ventricular myocardium were measured by SDUV in 10 pigs. Young’s elastic modulus was independently measured by the pressure-segment length method. Measurements made with the SDUV and pressure-segment length methods were strongly correlated. At reperfusion, μ1 and μ2 in end-diastole were increased. Less consistent changes were found during systole. In all animals, μ1 increased linearly with left ventricular pressure developed during systole. Preliminary results suggest that m1 is preload dependent. This is the first study to validate in vivo measurements of myocardial elasticity by a shear wave method. In this animal model, the alterations in myocardial viscoelasticity after a myocardial infarction were most consistently detected during diastole.

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“…Wall motion was tracked by an invasive technique (sonomicrometry) that has high precision and high spatial and temporal resolution necessary to track this fast wave propagation. To cover a wide range of myocardial stiffness, animals were studied before and after acute myocardial infarction, which is known to alter tissue properties [10, 34]. The feasibility of measuring this wave propagation in humans was tested using high frame rate tissue Doppler imaging (TDI).…”

Section: Introductionmentioning

confidence: 99%

Wave propagation of myocardial stretch: correlation with myocardial stiffness

2014

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The mechanism of flow propagation during diastole in the left ventricle (LV) has been well described. Little is known about the associated waves propagating along the heart wall s. These waves may have a mechanism similar to pulse wave propagation in arteries. The major goal of the study was to evaluate the effect of myocardial stiffness and preload on this wave transmission. Methods Longitudinal late diastolic deformation and wave speed (Vp) of myocardial stretch in the anterior LV wall were measured using sonomicrometry in sixteen pigs. Animals with normal and altered myocardial stiffness (acute myocardial infarction) were studied with and without preload alterations. Elastic modulus estimated from Vp (EVP; Moens-Korteweg equation) was compared to incremental elastic modulus obtained from exponential end -diastolic stress-strain relation (ESS). Myocardial distensibility and α-and β-coefficients of stress-strain relations were calculated. Results Vp was higher at reperfusion compared to baseline (2.6±1.3 m/s vs. 1.3±0.4 m/s; p=0.005) and best correlated with ESS (r 2=0.80, p<0.0001), β-coefficient (r2=0.78, p<0.0001), distensibility (r2=0.47, p=0.005), and wall thickness/diameter ratio (r2=0.42, p=0.009). Elastic moduli (EVP and ESS) were strongly correlated (r2=0.83, p<0.0001). Increasing preload increased Vp and EVP and decreased distensibility. At multivariate analysis, ESS, wall thickness, and end-diastolic and systolic LV pressures were independent predictors of Vp (r2model=0.83, p<0.0001). Conclusions The main determinants of wave propagation of longitudinal myocardial stretch were myocardial stiffness and LV geometry and pressure. This local wave speed could potentially be measured noninvasively by echocardiography.

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Experimental Myocardial Infarction

Cited by 46 publications

References 25 publications

Shear Wave Imaging of Passive Diastolic Myocardial Stiffness

Shear Wave Imaging of Passive Diastolic Myocardial Stiffness

Viscoelastic Properties of Normal and Infarcted Myocardium Measured by a Multifrequency Shear Wave Method: Comparison with Pressure-Segment Length Method

Wave propagation of myocardial stretch: correlation with myocardial stiffness

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