Myocardial fiber diameter and regional distribution in the ventricular wall of normal adult hearts, hypertensive hearts and hearts with hypertrophic cardiomyopathy.

Abstract

SUMMARY Myocardial fiber diameters were measured to determine their distribution throughout the ventricular wall in normal adult hearts, hypertensive hearts and hearts with hypertrophic cardiomyopathy (1HCM). In normal a'dult hearts and hypertensive hearts, the diameter decreased from the inner to the outer third of the left ventricular free wall and from the left ventricular side to the right ventricular side of the septum. In HCM, these regional differences were preserved in the left ventricular free wall, but not in the septum. The diameter was greatest in the middle third of the septum, where myocardial fiber disarray was widely distributed. The diameters of the fibers in the right ventricular side of the septum were significantly larger than those of the fibers in the left ventricular side of the septum in HCM. This finding, in contrast to that in normal adult hearts or hypertensive hearts, was considered to be related to the inward convex curvature of the left ventricular chamber. Although there was no significant difference in the diameter of myocardial fibers in the left ventricular free wall between hypertensive hearts and hearts with HCM, the diameters of those in the right ventricular free wall, in the right ventricular side of the septum and in the middle third of the septum were significantly larger in HCM than in hypertensive hearts. We conclude that there is a transmural variation of myocardial fiber diameter in the left ventricuar free wall and the ventricular septum, and such transmural variation in HCM is clearly different from that in hypertensive hearts.THE DIAMETERS of myocardial fibers in various heart diseases and in different regions of the heart have been recorded. However, little information is available on the regional variations throughout the ventricular wall. Studies on the regional distribution of intramyocardial pressure7-' and ventricular stress"-'2 lead one to expect that the diameter of myocardial fibers varies with their depth in the ventricular wall from the endocardial to the epicardial layers.Since the initial description by Brock,"3 there have been several reports of hypertrophic cardiomyopathy (HCM) coexisting with systemic hypertension. 1416 Moreover, asymmetric septal hypertrophy, which is one of the characteristic features of HCM, is not uncommon in patients with systemic hypertension.'719 Therefore, a differentiation between these two entities is clinically important when asymmetric septal hypertrophy coexists with systemic hypertension.In the present study we measured the diameters of myocardial fibers in different regions of the heart to determine the differences in their distribution throughout the ventricular wall in normal hearts, hypertensive hearts and hearts with HCM. trophy due to hypertension and 11 hearts with HCM.The age, sex and heart weights of the subjects are listed in table 1. A heart was considered normal if it had no evidence of clinical heart disease, the coronary arteries did not show more than 75% luminal narrowing and the heart weighed less t...

Quantitative analysis of myocardial fibrosis in normals, hypertensive hearts, and hypertrophic cardiomyopathy.

“…In the normal and hypertensive hearts we studied a slice from the middle third of the heart. Each slice was divided into [6][7][8] blocks, which were sectioned at a thickness of 4 sm. These sections were stained with Masson's trichrome and haematoxylin and eosin.…”

“…3) (NS). The percent of fibrosis were 2-3 (2 0), [2][3][4][5][6][7][8] (2 7), and 2-0 ( the right, middle, and the left thirds of the ventricular septum respectively; and 41 (2.6), 2-9 (1-7), and 141 (0 7)% in the inner, middle, and outer thirds of the left ventricular free wall respectively (Fig. 4).…”

Right Ventricular Endomyocardial Biopsy Findings in 25 Patients With Sick Sinus Syndrome

“…Comparison according to Rubenstein Classification: The SSS group was divided according to the Rubenstein Classification system 4) into two groups: types II and III, and the myocyte transverse diameter, fibrosis area ratio, mean lymphocyte count, and frequency of other cardiac lesions were compared. Comparison according to presence or absence of hypertension: Cardiac myocyte hypertrophy has been described in the hypertensive heart, not only in the left ventricle, but biventricularly as well, 7) so the myocyte transverse diameters in the four patients with SSS complicated with hypertension and the 21 normotensive patients were compared. Statistical analysis: Values are expressed as the mean ± standard deviation.…”

Dance Band on the Titanic

“…Accumulating experimental and clinical findings show association of cytoskeletal gene mutations with dilated cardiomyopathy. 113 The diversity of these mutations (involving components of the sarcomeric cytoskeleton [titin], the sarcolemmal cytoskeleton [eg, ␣, ␤, and ␦-sarcoglycan 114 ], the z-disk [eg, muscle LIM protein 115 ], intercalated disks [vinculin 116 ], and the intermediate filament system [desmin 117,118 ]) has led to the hypothesis that heart failure may be caused in this setting by an impairment of inside-out or outside-in mechanical signaling, although distinguishing these mechanisms is inherently difficult. This, in turn, would also suggest that similar mechanisms may be involved in acquired forms of heart disease triggered by altered mechanical loading of the heart.…”