Contractile analysis and kinetic energy of the myocardium.
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Animals↗
Biomedical subjects
R M Shoucri
Publications and source records attributed to R M Shoucri.
Note on the way to quantify the pump function of the heart.
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Heart↗
A mathematical model of the dynamic geometry of the intact left ventricle and its application to clinical data.
In this paper we examine the relations that may exist between the geometric variables most frequently used to describe left ventricular contraction. The left ventricle is represented by a thick-walled cylinder contracting both radially and longitudinally. For this model, wall thickening, mid-wall radius shortening and longitudinal axis shorteining can be shown to be uniquely related during contraction, whereas it can be demonstrated that internal radius shortening is not uniquely related to these variables, but is also determined by the specific geometry of the cylinder, expressed in terms of the mid-wall radius-to-wall thickness (R/h) ratio of the cylinder. Detailed analysis of the same variables in 44 normal subjects, 32 patients with aortic stenosis and 54 patients with valvular regurgitation (33 aortic and 21 mitral), strongly suggests that the same relations are also clinically applicable. For instance, ventricular longitudinal axis shortening can be estimated with some accuracy from the standard M-mode echocardiogram. Also, wall thickening can be viewed as the direct reflection of the shortening that occurs in the circumferential and longitudinal directions, whereas internal radius shortening is significantly influenced by the R/h ratio of the ventricle, a consideration which becomes important when analyzing results in patients with left ventricular hypertrophy.
Angiocardiography↗
The dynamics of the ventricular wall and some observations on blood flow.
An expression for the energy of motion of the wall of the left ventricle is developed. A cylinderical model is assumed for the left ventricle, and symmetry is used to produce the problem to a two-dimensional problem. Result obtained indicate that consideration of the energy of motion can be useful in problems of clinical diagnosis. Some correlation between previously published experimental results is also made with the equations derived in this paper.
Blood Flow Velocity↗
Some observations on the kinetics of the Jaffé reaction for creatinine.
The Jaffé reaction for creatinine assay appears to follow pseudo-first-order kinetics; first-order rate constants are different for different samples. Rate constants for 10 different serum samples varied from a low value of 0.0040 +/- 0.0003 s-1 to 0.0084 +/- 0.0008 s-1. We describe an approach for determining first-order rate constants from kinetic data and discuss the effects of the above observations on the mathematical formulations required for reliable kinetic determinations of creatinine.
Autoanalysis↗
Clinical application of end-systolic pressure-volume relation.
On the basis of a mathematical formalism derived in previous studies, properties of the end-systolic pressure-volume (P-V) relation were analyzed to define indexes that can characterize a normal or failing left ventricle. Careful analysis of different areas under the P-V line can lead to new indexes that describe the performance of the left ventricle. The possibility to distinguish between normal, mildly depressed, or severely depressed left ventricles based on P-V relation is discussed. Implementation of the results for routine clinical work is examined.
Adult↗
Studying the mechanics of left ventricular contraction.
Several interesting aspects of the ESPVR have been discussed in this study, including: a) A possibility to introduce, in an explicit manner, the active force of the myocardium in the formalism describing the PVR of the left ventricle. b) A possibility to express the ventriculo-arterial coupling by using the ratio Emax/eam in a way to distinguish between the normal physiological state and the mildly or severely depressed state of the heart. The possibility of also expressing this coupling by using directly different areas under ESPVR has been indicated. A third method, not discussed here, is to use the windkessel model (see [27, 53]). c) The relationship between oxygen consumption and all the areas under ESPVR. d) A possible mechanism of adaptation to short- or long-term variation in load condition by changing ESPVR in a way to create an SWR (see Fig. 4 and Table 2). e) A possibility to use different areas under ESPVR for clinical diagnostic purposes (see [20]); an example for SWR and SWR/SW is given in Table. 2. f) A possibility of noninvasive clinical application of various results of this study. Item (f) depends on the possibility of noninvasive measurement of the left ventricular pressure, which has been reported by Bourguignon and Wagner [61], and Sato, et al. [62]. Noninvasive measurement of left ventricular dimensions has been discussed by Teichholz, et al. [63], Grassman, et al. [64], Dumesnil et al [65], Dumesnil and Shoucri [66, 67]. Measurement of ESPVR from one loop of the contraction cycle has also been discussed by Takeuchi, et al. [68] and Nakamoto, et al. [69]. Further readings can be found in [70] and [71]. The list of references is not exhaustive, but has been chosen to illustrate various related aspects of the topics discussed.
Adaptation, Physiological↗