Fiber orientation across the left ventricular myocardial wall has been studied. Specimens were obtained from 18 dog hearts rapidly fixed in situ in systole, in diastole, and in dilated diastole. Fiber orientation was determined across the free wall at eight sites from a T-shaped specimen by measurements with light microscopy in serial paraffin sections. Results indicate: (1) The wall has a well-ordered distribution of fiber angles varying from about 60° (from the circumferential direction) at the inner surface to about -60° on the outer surface. The greatest change in angle with respect to wall thickness occurs at the two surfaces (endocardial and epicardial). (2) Fiber angles did not change significantly during the transition from diastole to systole, despite a 28% increase in wall thickness (except in the papillary muscle root region). (3) The proportion of fibers lying in the sector of fiber angles oriented circumferentially (0±22.5°) to those oriented longitudinally (67.5 to 90° and -67.5 to -90°) is approximately 10:1. This ratio increases toward the base and diminishes toward the apex of the left ventricle. (4) All fiber angles in the lateral wall of hearts in systole increased through the wall by approximately 7° near the base and 19° near the apex relative to their counterparts in diastole, indicating bending or torsion of the left ventricle during contraction.

Fiber Orientation in the Canine Left Ventricle during Diastole and Systole

Rationale: Right ventricular (RV) function is an important determinant of prognosis in pulmonary hypertension. However, noninvasive assessment of the RV function is often limited by complex geometry and poor endocardial definition.Objectives: To test whether the degree of tricuspid annular displacement (tricuspid annular plane systolic excursion [TAPSE]) is a useful echo-derived measure of RV function with prognostic significance in pulmonary hypertension.Methods: We prospectively studied 63 consecutive patients with pulmonary hypertension who were referred for a clinically indicated right heart catheterization. Patients underwent right heart catheterization immediately followed by transthoracic echocardiogram and TAPSE measurement.Results: In the overall cohort, a TAPSE of less than 1.8 cm was associated with greater RV systolic dysfunction (cardiac index, 1.9 vs. 2.7 L/min/m2; RV % area change, 24 vs. 33%), right heart remodeling (right atrial area index, 17.0 vs. 12.1 cm2/m), and RV–left ventricular (L...

https://www.atsjournals.org/doi/pdf/10.1164/rccm.200604-547OC

Tricuspid annular displacement predicts survival in pulmonary hypertension.

Assessment of right ventricular function using two-dimensional echocardiography☆

An eight-electrode conductance catheter previously developed by us and used to determine stroke volume in dogs was applied in human beings and dogs to measure absolute left ventricular volume quantitatively. For calibration we developed the formula V(t) = (1/alpha)(L2/sigma b)G(t) - Vc, where V(t) is time-varying left ventricular volume, alpha is a dimensionless constant, L is the electrode separation, sigma b is the conductivity of blood obtained by a sampling cuvette, and G(t) is the measured conductance within the left ventricular cavity. Vc is a correction term caused by the parallel conductance of structures surrounding the cavity and is measured in two ways. The first method, applicable in the anesthetized animal, consists of temporary reduction of volume to zero by suction. The second method uses a transient change in sigma b by injection of a small bolus of hypertonic saline (dogs) or 10 ml of cold glucose (humans) into the pulmonary artery. The validity of the formula was previously established for the isolated postmortem canine heart. The predicted linearity, slope constant alpha, and accuracy of Vc for the left ventricle in vivo were investigated by comparing the conductance volume data with results from independent methods: electromagnetic blood flow measurement for stroke volume and indicator dilution technique for ejection fraction (dogs), thermal dilution for cardiac output (12 patients), and single-plane cineventriculography for V(t) (five patients). In all comparisons, linear regression showed high correlation (from r = .82 [n = 46] to r = .988 [n = 20]) while alpha, with one exception, ranged from 0.75 to 1.07 and the error in Vc ranged from 0.5% to 16.5% (mean 7%). After positioning of the catheter, no arrhythmias were observed. It is concluded that the conductance catheter provides a reliable and simple method to measure left ventricular volume, giving an on-line, time-varying signal that is easily calibrated. Together with left ventricular pressure obtained through the catheter lumen, the instrument may be used for instantaneous display of pressure-volume loops to facilitate assessment of left ventricular pump performance.

Continuous measurement of left ventricular volume in animals and humans by conductance catheter.

Hypertrophic cardiomyopathy. The importance of the site and the extent of hypertrophy. A review

Changes in dimensions of the ventricular chambers and the displacement of specific points on the walls of the heart have been studied by the cinefluorographic technic. The contributions of the various myocardial layers to ventricular ejection have been considered in terms of the anatomic architecture of the heart. The mechanical effectiveness of myocardial contraction is closely related to the degree of diastolic distension and the magnitude of the stroke volume. During contraction, the various layers must exert tension on the connections between them. Energy expended in this manner does not contribute to ventricular ejection but could theoretically promote rapid filling during the early diastolic period.

The Functional Anatomy of Ventricular Contraction

Left ventricular dimensions have been directly measured for extended periods of time in intact unanesthetized dogs under various conditions. The diameter of the left ventricle during diastole is very large in relation to the change in diameter during each cycle. Thus, considerable quantities of blood remain within the chamber at the end of systolic ejection. The stroke output can be increased by either more complete systolic ejection during exercise or by greater diastolic filling during a startle reaction. Accelerated heart rate occurs in both cases. Changes in left ventricular diameter occur very rapidly, often being manifest within the duration of a single cardiac cycle. Mechanisms by which changes in ventricular size can be directly affected by neural and hormonal influences are briefly considered.

Continuous Measurements of Left Ventricular Dimensions in Intact, Unanesthetized Dogs

Intracardiac impedance plethysmography.

Changes in length and circumference of the left ventricle were recorded simultaneously by variable resistance gages on its external surface in intact dogs. The absolute changes in circumference were considerably greater than the changes in length, but the relative changes in these dimensions were similar (averaging around 2 to 3 per cent). Under most circumstances, the length and circumference vary in the same direction but occasionally inexplicable differences in response were observed.

Length-Circumference Relations of the Left Ventricle

There is a theoretical ideal to be achieved in the construction of a simple, practical membrane oxygenator. Direct contact between blood and oxygen common to many current artificial lungs is unphysiologic and entails the obvious possibility of air embolism in addition to suspected but not well-defined damage to blood elements at gas-fluid interfaces.1Contemporary membrane oxygenators2-4necessitate relatively high pressure pumping of venous blood into sandwich-like devices which must use membranes which are undesirably thick. In all of the currently employed machines the primary problem would appear to be that of securing enough contact between blood and oxygen without excessive recurrent damage to the blood which must be returned to the patient's systemic circulation. Our primary intent has been to employ membrane substances which are as thin as possible. As suggested by Crescenzi5,6and Kylstra,7these require that only gravity flow be used to avoid rupture

Clyde Wagner

Papers

The Functional Anatomy of Ventricular Contraction

Continuous Measurements of Left Ventricular Dimensions in Intact, Unanesthetized Dogs

Intracardiac impedance plethysmography.

Length-Circumference Relations of the Left Ventricle

A gravity-flow membrane oxygenator.