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Postnatal myocardium remodelling generates inhomogeneity in the architecture of the ventricular mass.

ABSTRACT: The 3D architecture of the ventricular mass is poorly known, although in vivo imaging techniques show the physiological inhomogeneity of ventricular walls mechanics. Polarized light imaging makes it possible to quantitatively analyse the myosin filament orientation.In this paper, we focus on the study the 3D architecture and regional isotropy of myocardial cells.Twenty normal human hearts, 10 from the perinatal period and 10 from the post-neonatal period were studied by polarized light microscopy. In each voxel of the ventricular mass (90 × 90 × 500 µm) the principal orientation segment was automatically and unambiguously extracted as well as a regional isotropy index (regional orientation tensor of the voxel neighbourhood).During the first months of postnatal age, the median regional isotropy values decreased in the ventricular mesh. This global decrease was not homogeneous across the ventricular walls. From the perinatal to the neonatal period, this decrease was more marked in the inner two-third of the lateral left ventricular wall and in the right part of the interventricular septum. There was a progressive post-neonatal appearance of a particularly inhomogeneous secondary arrangement of myocardial cells with alternation of thick low-RI and thin high-RI areas.This study has shown a postnatal change in ventricular myocardial architecture, which became more inhomogeneous. The cell rearrangements responsible for the inhomogeneity in ventricular myocardial architecture are revealed by a variation of the regional isotropy index. These major changes are probably an adaptive consequence of the major haemodynamic changes occurring after birth during the neonatal period that generates major parietal stress variations and parietal remodelling.

SUBMITTER: Jouk PS

PROVIDER: S-EPMC5820407 | biostudies-literature | 2018 Jan

REPOSITORIES: biostudies-literature

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Postnatal myocardium remodelling generates inhomogeneity in the architecture of the ventricular mass.

Jouk Pierre-Simon PS Truong Ba Luu BL Michalowicz Gabrielle G Usson Yves Y

Surgical and radiologic anatomy : SRA 20171128 1

<h4>Background</h4>The 3D architecture of the ventricular mass is poorly known, although in vivo imaging techniques show the physiological inhomogeneity of ventricular walls mechanics. Polarized light imaging makes it possible to quantitatively analyse the myosin filament orientation.<h4>Aims</h4>In this paper, we focus on the study the 3D architecture and regional isotropy of myocardial cells.<h4>Methods</h4>Twenty normal human hearts, 10 from the perinatal period and 10 from the post-neonatal ...[more]

PMID: 29181565

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Project description:BackgroundAbnormal QT intervals, long QT or short QT, have been epidemiologically linked with sudden cardiac death because of ventricular fibrillation (VF). Consequently, Food and Drug Administration recommends testing all pharmacological agents for QT toxicity as a risk factor for cardiac toxicity. Such tests assess QT/QTc interval, which represents ventricular depolarization and repolarization. However, the current QT toxicity analysis does not account for the well-known anisotropy in cardiac tissue conductivity. Mines demonstrated in 1913 that cardiac wavelength (λ) determines inducibility of reentrant arrhythmia, where both repolarization time or action potential duration and conduction velocity determine λ=action potential duration×conduction velocity. We aimed to determine the role of anisotropic wavelength in inducibility of VF in explanted human left ventricular preparations. We tested the hypothesis that 3-dimensional cardiac wavelength, which takes into account anisotropic cardiac tissue conductivity, can accurately predict VF sustainability.MethodsWe conducted panoramic optical mapping of coronary perfused human left ventricular wedge preparations subjected to pharmacologically induced shortening and prolongation of action potential duration, by IK,ATP agonist pinacidil and antagonist glybenclamide, respectively. This measured action potential duration, conduction velocity, and thus determined pacing cycle length-dependent wavelengths in longitudinal (λL), transverse (λTV), and transmural (λTM) directions using S1S1 pacing protocol, from which wavelength volume (Vλ) was determined, as Vλ=λL×λTV×λTM, and compared with tissue volume. We tested a hypothesis that tissue volume/Vλ ratio can predict VF sustainability.ResultsAt baseline, at pacing rate of 240 beats per minute, the wavelengths were λL=9.6±0.6 cm, λTV=4.2±0.3 cm, and λTM=5.8±0.2 cm, respectively (n=7), and thus Vλ=246.4±42.1 cm3. Administration of pinacidil at escalating concentrations progressively decreased Vλ, and VF became sustained, when tissue volume/Vλ was above safety factor κ=4.4±0.6 (n=9) during rapid pacing. Treatment with glybenclamide decreased VT/Vλ below κ at any pacing rate and prevented VF sustainability.ConclusionsSustained VF was only sustained in ventricular volume exceeding critical Vλ=λL×λTV×λTM.

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Postnatal myocardium remodelling generates inhomogeneity in the architecture of the ventricular mass.

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Postnatal myocardium remodelling generates inhomogeneity in the architecture of the ventricular mass.

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