Technology and Health Care - Volume 5, issue 1-2

Authors: Redmann, K. | Lunkenheimer, P.P. | Scheld, H.H. | Dietl, K.-H. | Fischer, St. | Cryer, C. | Whimster, W.F. | Stroh, N.

Article Type: Research Article

Abstract: Microergometry is a method which we have developed as a tool to measure local mesh-tension within the myocardial weave at any measuring site of both ventricles and the septum on the beating heart in situ. In a mapping procedure on pig and dog hearts, both in control conditions and in the hypertrophied state after aortic banding, local mesh-tension was measured in several areas and in up to eight depths proceeding from the epicardium to the endocardium: Probe-to-fibre coupling is definitely more stable in the canine myocardium than in the porcine heart muscle, probably due to a more effective connective tissue …fettering of the canine myocardial weave. The observed longitudinal gradient, with the highest tension in the base, of control dog hearts was levelled out in the hypertrophied hearts. Furthermore, in control dog hearts mesh-tension in the subepi- and subendocardial layers was higher than in the midlayers. This pronounced midlayer-hypotension was smoothed in the hypertrophied hearts. Further studies will be dedicated to the question of whether the impact of ventricular size and shape on intersegmental stress transmission is determined by the Frank–Starling mechanism alone or whether protracted remodelling processes on the level of the local fibre weave cause slow coupling alterations. Show more

DOI: 10.3233/THC-1997-51-211

Citation: Technology and Health Care, vol. 5, no. 1-2, pp. 123-134, 1997

Authors: Palladino, Joseph L. | Rabbany, Sina Y. | Mulier, Jan P. | Noordergraaf, Abraham

Article Type: Research Article

Abstract: Myocardial contractile properties form the cornerstone of the heart’s ability to pump blood. Efforts have been made to characterize these properties via classic elasticity theory concepts, which can lead to spurious results, as demonstrated by experiments measuring intramyocardial pressure. Two ways out of these difficulties are identified. One is to start at the cellular level, the other at the chamber level. The latter allows separation of ventricle (source) and arterial (load) effects on measured pressure and flow, distinct from previous definitions of ventricular contractility which tended to lump the two.

DOI: 10.3233/THC-1997-51-212

Citation: Technology and Health Care, vol. 5, no. 1-2, pp. 135-144, 1997

Authors: Rabbany, Sina Y. | Kresh, J. Yasha | Noordergraaf, Abraham

Article Type: Research Article

Abstract: To characterize the complex force field generated in the ventricular myocardium, intramyocardial pressure (IMP) measurement is used as an indirect means of assessing the distribution of regional wall stress. To resolve the long term confusion associated with this measurement, IMP is divided into its two dominant components: intramyocardial fluid pressure (IFP) and intramyocardial fiber stress (IFS). The intramyocardial response to regional and global contractile function is examined in terms of changes in the magnitude and transmural gradient of IMP recording. The experimental results support the theoretical concept proposed where the hydraulic properties of the myocardium proved to have an influence …on cardiac function. To gain a deeper understanding of myocardial function, cellular and subcellular components must be considered. Show more

DOI: 10.3233/THC-1997-51-213

Citation: Technology and Health Care, vol. 5, no. 1-2, pp. 145-157, 1997

Authors: Kresh, J. Yasha | Armour, J. Andrew

Article Type: Research Article

Abstract: In the past the study of mechanical and electrical properties of the heart has been disjointed with minimal overlap and unification. The fact remains that these features are tightly coupled and central to the functioning heart. The maintenance of adequate cardiac output relies upon the highly integrated autoregulatory mechanisms and modulation of cardiac myocyte function. Regional ventricular mechanics and energetics are dependent upon muscle fiber stress–strain rate, the passive properties of myocardial collagen matrix, adequate vascular perfusion, transcapillary transport and electrical activation pattern. Intramural hydraulic “loading” is regulated by coronary arterial and venous dynamics. All of these components are under …the constant influence of intrinsic cardiac and extracardiac autonomic neurons, as well as circulating hormones. A brief overview of the putative regulation of these various components is presented in this paper. Show more

DOI: 10.3233/THC-1997-51-214

Citation: Technology and Health Care, vol. 5, no. 1-2, pp. 159-169, 1997

Authors: Djavakhishvili, N.

Article Type: Research Article

Abstract: As the myocardial capillaries drain tassel-like into the peripheral end of sinusoids, the venous system of the myocardium begins in the sinusoids and plays an important role in the regulation of myocardial circulation. The sinusoids dilate in response to inadequacy of the arterial vascularization and their expansion has been found to be inversely proportional to the blood flow in the coronary arteries. The sinusoids become more dilated and prominent with coronary dilators and reinforcement of myocardial vascularization by cardiopexy techniques, causes the sinusoids to become dilated.

DOI: 10.3233/THC-1997-51-215

Citation: Technology and Health Care, vol. 5, no. 1-2, pp. 171-175, 1997