Antagonism of contractile forces in left ventricular hypertrophy: a diagnostic challenge for better pathophysiological and clinical understanding.

Cardiac function is characterised by haemodynamic parameters in the clinical scenario. Due to recent development in imaging techniques, the clinicians focus on the quantitative assessment of left ventricular size, shape and motion patterns mostly analysed by echocardiography and cardiac magnetic resonance. Because of the physiologically known antagonistic structure and function of the heart muscle, the effective performance of the heart remains hidden behind haemodynamic parameters. In fact, a smaller component of oblique transmural netting of cardiac muscle fibres simultaneously engenders contracting and dilating force vectors, while the predominant mass of the tangentially aligned fibres only acts in one direction. In case of hypertrophy, an increased influence of the dilating transmural fibre component might counteract systolic wall thickening, thereby counteract cardiac output. A further important aspect is the response to inotropic stimulation that is different for the tangentially aligned fibre component in comparison to the transmural component. Both aspects highlight the importance to integrate the analysis of intramural fibre architecture into the clinical cardiac diagnostics.

Hierarchy and inhomogeneity in the systematic structure of the mammalian myocardium: towards a comprehensive view of cardiodynamics.

In order to visualise the mammalian myocardial structure in its entirety, we distended excised porcine left ventricles by inflating the coronary arteries with compressed air, using rising pressures between 100 and 300 kPa. The ventricular walls became elongated, and left ventricular cavity widened with rising pressure albeit with insignificant changes in their mural thickness. High resolution computed tomographic analysis subsequent to pneumographic distension revealed a hierarchical structure. First, a feathered arrangement of the cardiomyocytes aggregated together mainly within the equatorial area of the ventricle, giving an overall appearance of systematically arranged spatially netted lamellar structures with pronounced local inhomogeneity. Second, histological examination in orthogonal planes, analysing samples dividing the ventricular walls into 18 segments, showed the lamellae themselves to be made up of aggregated chains of myocytes, the alignment of these chains producing the well-recognised change in so-called helical angle when traced through the thickness of the walls. Transmural length sections removed from the same positions in the ventricular walls showed inter-lamellar connections aligned in the direction from the ventricular base to the apex which were definitely longer than those we observed in transmural cross-sections. Electron-microscopy exposed the two compartments of interstitial connective tissue, suggesting the endomysium to bind long chains of myocytes to lamellar aggregates, while the loose perimysium strengthens the structure of the lubricating medium which eases the gliding of the lamellar aggregates relative to one another.

Ventriculectomia parcial esquerda: ponte para transplante? / Partial left ventriculectomy: bridge to transplantation?

OBJETIVO: Analisar os resultados e a viabilidade da ventriculectomia parcial esquerda (VPE) como ponte para transplante cardíaco (TX). DELINEAMENTO: Estudo de coorte histórica e prospectivo. CASUISTICA E MÉTODOS: Cinquenta e três pacientes (pts) foram submetidos a VPE em um período de 5 anos. Destes, 7 pts com contra-indicação inicial ao TX, idades variando de 37 a 64 anos, 5 homens e 2 mulheres, com miocardiopatia dilatada, foram subseqüentemente relistados e transplantados. Foram analisados a fração de ejeção (FE), o diâmetro diastólico final do ventrículo esquerdo (DDFVE), a CF da NYHA, o consumo máximo de oxigênio (VO2 máx) e os escores de qualidade de vida (QV) antes da VPE, aos 3 e 6 meses, e pré-transplante...