Many years have elapsed since the human body was attempted to be described. Though the human body remains the same, the understanding of it has changed immensely and continues to do so. Research works carried out in various parts of the world contribute newer information everyday. As the other fields of science, the field of Anatomy is also changing day by day. With advances in imaging techniques, understanding of body structures has changed to a great extent. The present study is a step towards adding some more information to existing data on the possible variations in the Anatomy of cardiac papillary muscles.
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muscle to the total LV mass is markedly increased com- pared to healthy controls. The inclusion of papillary muscles in myocardial volume improves accuracy of volumetric measures of LV stroke volume when com- pared with the internal reference measure taken from velocity encoded flow data at the aortic outflow. These findings may have significant implications for assessment and targeted therapy of patients with Fabry disease, as well as other conditions associated with cardiac hyper- trophy, and should prompt a move toward more consist- ent standards in reporting volumetric data.
comprehensive review, see Sagawa et al. (Sagawa et al., 1988)]. It is unclear, from in situ strain and length change recordings, whether the papillary muscles remain isometric during the isovolumic relaxation phase, with reports indicating varying degrees of shortening (Hirakawa et al., 1977; Marzilli et al., 1985; Semafuko and Bowie, 1975), lengthening (Rayhill et al., 1994) or no significant length change (Hirakawa et al., 1977; Rayhill et al., 1994). Regardless of the disagreement in the literature, if papillary muscles are to be used as a linear model of ventricular muscle, the addition of an isometric relaxation phase would enhance the realism of the model. To determine whether this feature could easily be incorporated into the protocols used in this study, an experiment was carried out in which the muscle length was held constant during part of the relaxation phase. The isometric relaxation phase was incorporated into the length change pattern by selecting a time for shortening to end and by holding the length constant until relaxation was complete (Fig. 10). The results from these experiments are shown in Table 2. As the absolute shortening amplitude was increased, work output per twitch also increased. This result is in agreement with the findings of experiment 1. Once again, the enthalpy output per twitch varied over only a small range and, thus, ε Net reflected the
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Several studies on skeletal muscles using the work loop technique have demonstrated that muscles in vitro produce maximum power output at cycle frequencies corresponding to their normal operating frequencies in vivo (see, for example, Stokes and Josephson, 1988; Josephson and Stokes, 1989; Altringham and Young, 1991; James et al. 1995). These studies support some of the ideas proposed by Hill (1950) on the evolution of an optimal design for muscles. Hill included the heart in his review and, since cardiac muscle has fundamental similarities to skeletal muscle, it is not unreasonable to propose that it too will be optimised for power production at an operating frequency similar to the in vivo situation. The present investigation examines this hypothesis by studying the relationship between power output and operating frequency in mammalian cardiac muscle, using rat papillary muscles.
and de Tombe, 1993). Titin is a huge, striated muscle protein that binds to the thick filaments, linking them to the Z disc, and is important in positioning the thick filaments within the sarcomere (Horowits et al. 1989). The titin molecule consists of a series of large macromolecular domains coupled to each other by shorter protein domains. The large macromolecular domains can be enormously extended by unfolding and it is this property which led to the suggestion that titin may account for the viscous load of shortening cardiac muscle (ter Keurs and de Tombe, 1993). The authors emphasized that further investigation was required to support this proposal. However, for the purposes of the present study, one could speculate that increasing muscle length may result in the deformation and unfolding of the titin macromolecular domains, which may explain the observed increase in energy loss (hysteresis) with increasing muscle length. The greater energy losses for rat papillary muscles compared with skeletal muscles (Heerkens et al. 1987; Syme, 1990) could be related to the greater titin content in cardiac muscle compared with skeletal muscle (Brady, 1991).
Many investigations of ventricular energetics have used isolated papillary muscles as a model of ventricular muscle. These muscles have myocytes arranged in parallel along their length, can be readily dissected and can have ties or clips attached to either end, allowing them to be attached to apparatus for measuring mechanical properties. The most common protocols used in vitro have involved either isometric or afterloaded isotonic contractions, with muscle length set to that giving maximum active force output. As a model of ventricular function, isometric contraction protocols are less than ideal since, unlike the contracting ventricle, no mechanical work is performed during contraction. However,
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The present study was performed on a group of 96 formalin-fixed adult human hearts, which ranged in age from 18 to 90 years and gave no evidence of con- genital malformations or pathological changes. The valves were divided into five types according to earlier studies and analysis was made in terms of these types. The tendinous chords and their ramifications were counted. The surfaces of particular leaflets were measured. The ratio of marginal to ventricular leaflets was counted for each type of leaflet in particular types of valves. The parts of the main leaflets supported by specific papillary muscles were counted for types 1, 2 and 3.
The valves were divided into types and subtypes depending on the number of leaflets and the loca- tion of accessory leaflets [14, 20–22] (Fig. 1). The papillary muscles of the right ventricle were classi- fied according to an earlier scheme [11, 21] (Fig. 2). The types of connection leaflets between the tricus- pid valve and the papillary muscles were classified according to a scheme drawn up earlier for verte- brates [24, 27]. Connection type 1, typical for birds, was a straight connection between the leaflet and the papillary muscles, type 2 was a membranous connection recorded in the literature as characteris-
The types which represent uncomplicated forms (1, 2 and 3) or segmental forms (1, 2, 5 and 10) dominate among the posterior papillary muscles. The incidence of these types is a little lower than in Gro- chowski’s study  among the hearts of young peo- ple and higher for the hearts of the elderly. We did not divide hearts into age-dependent groups as, ac- cording to earlier authors, they do not change in shape during ontogenesis [11, 12]. Absence of a posterior muscle occurred in 3.73% of the hearts studied by us and in 6% in Grochowski’s study. The results of the two studies are similar, with segmen- tal forms 1, 2 and 3 dominating in both.
The region where the papillary muscles are found covers a sizeable surface of the septum, from the conus arteriosus up to the back angle of the right cham- ber. Depending on their location the following septal papillary muscles (mus- culi papillares septales, MPS) were singled out: 1) lying on the front wall of the septum (anterior papillares septales), 2) in the central part of the septum (cen- tral muscles), and 3) in the posterior section of the septum (posterior papillares septales). A trial to determine the types of MPS was based on this diversity of location. Consequently, five types of MPS were specified: type I: anterior–central (44.1%); type II: anterior (15.3%); type III: anterior–posterior (13.5%); type IV: anterior–central–posterior (24.3%); and type V: uniform (2.75%).
Moderate alcohol intoxication in man, a ubiqitious social event, causes acute but reversible myocardial depression, the mechanism of which is unknown. We investigated whether this depression could be due to a direct effect of ethanol on the process of electromechanical coupling by simultaneously measuring the transmembrane action potential and contraction, or the cytosolic calcium transient (via aequorin photoluminescence) and contraction in isolated ferret right ventricular papillary muscle. Ethanol, in concentrations that are similar to plasma levels in man during intoxication (0.15 vol %), depressed the force of contraction approximately 10%. The step in the electromechanical process that was affected appeared to be the calcium-myofilament interaction, as there was no change in the transmembrane action potential or cytosolic calcium transient. This inhibition was quickly reversed by removal of the ethanol from the perfusate. On the other hand, higher concentrations of ethanol produced changes in contraction, the calcium transient, and the action potential, suggesting multiple levels of inhibition of electromechanical coupling. Increasing the perfusate calcium or use of the calcium channel agonist, BAY-K 8644, increased cytosolic calcium to near maximum but had little effect on contractility, confirming that the relationship between calcium and the myofilaments had been altered. These data suggest that the acute depression in ventricular function seen with alcohol consumption may be due to a direct effect on electromechanical coupling […]
reflects both changes in developed tension as well as relaxation and (b) the relaxation process is highly sensitive to temperature and previous papillary muscle studies have been conducted under hypothermic conditions. The present study examines the effect of hypoxia on the relaxation process of 31 isometrically contracting kitten papillary muscles at
As observed in the chinchillas studied, some nerve fibres from the valve cusps connect with the plexus on the tendinous cords and papillary muscles. A simi- lar situation exists in the human heart . This is explained by other study results [1, 10, 14] on the adrenergic innervation of the atrioventricular valves in the guinea pig. The authors demonstrated the presence of the two main plexuses: a) a larger, dense plexus located in the basal part of the valve cusps, along the annulus fibrosus, with branches to the central and marginal area of the cusps, b) a smaller one, moving upward from the tendinous cords and connecting with the distal region of the larger plexus.
nonexercised controls. Right ventricular papillary muscles were removed from young adult (9 mo) and old (24-26 mo) male Fischer 344 rats that were chronically exercised on a rodent treadmill and from their age-matched, nonexercised controls. During isometric contraction, hypoxia depressed contraction and relaxation in all muscles, but to a lesser extent in the exercised groups. A significant exercise effect was observed in the following variables: the maximum developed tension, the maximum rate of tension development, the maximum rate of tension decline, and the time required for the hypoxia to reduce maximum tension by 20%. The maximum rate of tension decline was more sensitive to hypoxia than was the maximum rate of tension development in all groups. Exercise also had an effect on the temperature dependence of cardiac performance during hypoxia. Thus, chronic exercise results in the preservation of both contraction and relaxation during hypoxia for aged as well as young adult hearts.
Regional myocardial function is better assessed with TDI than any other method of echocardiography. Quantitative assessment is an important prerequisite for complete description of the dynamic changes that occur during ischemia .Conventional assessment of wall motion based on visual assessment is highly subjective and semi quantitative. Accurate assessment of regional contractile function is important for prognosis and management in patients with coronary artery disease. It has been demonstrated that wall thickening is a useful measure of regional function and is more precious than wall motion analysis . However the differentiation of regions with abnormal contractile function from regions with normal contractile function by planar method in patient with coronary artery disease is difficult because of wide range of thickening in normal and abnormal regions. The low temporal resolutions used in stress echocardiographic studies together with the limited ability of human vision to discern small differences in myocardial asynchrony, do not allow an objective quantitative assessment of complex wall motion. Tissue Doppler velocity and SRI can accurately quantify Local mechanical function with higher temporal accuracy than any current clinical method. Two dimensional strain analyses is more accurate than wall thickening analysis in discriminating dysfunctional from functional myocardium and therefore it improves the detection of regional difference in function. Two dimensional tissue Doppler and strain Doppler echocardiographic techniques used in this study allowed processing of simultaneous velocity and strain traces from apical two chamber view in the same cine loop. The Doppler ultrasonic beam was placed in mid inferior region of inferior wall of left ventricle and mid point of both papillary muscles. The Doppler ultrasonic beam was also placed in the anterior septum of left ventricle.
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We tested the hypothesis that the intracellular Ca2+ overload of ventricular myocardium during the period of posthypoxic reoxygenation is mediated by transsarcolemmal Ca2+ influx via Na+/Ca2+ exchange. In aequorin-loaded, ferret right ventricular papillary muscles, blockers of the sarcolemmal and the sarcoplasmic reticulum Ca2+ channels, slowed the Cai2+ transient, producing a convex ascent during membrane depolarization, followed by a concave descent during repolarization. The magnitude of the Cai2+ transient was affected by changes in the membrane potential, Nai+, Nao+, and Cao2+, and was blocked by Ni2+, or dichlorbenzamil. The calculated Na+/Ca2+ exchange current was in the reverse mode (Ca2+ influx) during the ascending phase of the Cai2+ transient, and was abruptly switched to the forward mode (Ca2+ efflux) at repolarization, matching the time course of the Cai2+ transient. During hypoxic superfusion, the Cai2+ transient was abbreviated, which was associated with a shorter action potential duration. In contrast, immediately after
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Myocardial oxygen consumption is regulated by interrelated mechanical and inotropic conditions; there is a parallel increase in the aerobic metabolism and inotropic state during beta-adrenergic stimulation under fixed mechanical conditions. In contrast, there is some evidence that beta-blockade may reduce oxygen consumption through effects independent of its influence on mechanical conditions and contractile state, and that prolonged beta- blockade may sensitize the myocardium to beta-adrenergic stimulation. To clarify these two points, the present study examined the relationship of myocardial energetics to mechanics and inotropism during acute beta-blockade and after the withdrawal of long-term beta- blockade, whereupon the basis for any effect observed was sought by characterizing the number, affinity, and affinity states of the beta-receptors as well as the coupling of activated beta-receptors to cyclic AMP generation. Studies of right ventricular papillary muscles from control and chronically beta-blocked cats demonstrated contractile and energetic properties as well as dose-response behavior and inotropic specificity suggestive of an increase in myocardial sensitivity to beta-adrenoceptor stimulation in the latter group. Assays of cardiac beta-adrenoceptors from further groups of control and pretreated cats, both in cardiac tissue and in isolated cardiac muscle cells, failed to define a difference between the two groups either in terms of receptor number and affinity or in terms of the proportion of receptors in the high-affinity state. However, coupling of the activated […]
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Figure 1 Cardiac magnetic resonance measurements. (A) Six long-axis images were obtained, with a 30˚ angulation between each plane, as indicated by the blue lines. (B) Three-chamber view of a patient with mitral annulus disjunction (MAD), with prolapse of the mitral valve leaflets. (C) Zoom of (B): the yellow-dotted line represents the mitral annulus. The blue line represents the longitudinal MAD. This image shows the presence of prolapsing mitral leaflets, indicated by the two green arrows. (D) Late gadolinium enhancement on the basal left ventricular wall (red arrow) and the papillary muscles (green arrows).
The study was performed on 32 adult male Wistar rats of line with mass 200 - 250 g. All procedures with the ex- perimental animals were performed in accordance with the National Guidance on the Operation of the experi- mental animals (1977). Papillary muscles were rapidly isolated from the left ventricle of rat heart. The following groups of papillary muscles have been studied: I group- intact papillary muscles perfused with Krebs-Henseleit solution; II group-intact papillary muscles, perfused with Krebs-Henseleit solution, containing amiodarone in dose of 1 μМ/l (Sanofi Pharma, France), in 15 min.; III group- papillary muscles of rats, which obtained preliminary amiodarone in dose 20 mg/kg/day during 14 days and perfused with Krebs-Henseleit solution.
Sodium-dependent calcium exchange may be an important mediator of calcium reperfusion damage during the calcium paradox phenomenon. We measured intracellular sodium activity with ion-selective electrodes during a 15-min period of calcium reperfusion in isolated ferret papillary muscles. During the calcium-free period, alpha Nai increased from 9.0 +/- 0.9 to 18.9 +/- 4.3 mM. With reinstitution of calcium there was a significant