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PubMed2004

Passage in monolayer influences the response of chondrocytes to dynamic compression.

This study tests the hypothesis that expansion by passage in monolayer influences the response of isolated articular chondrocytes to dynamic compression. Chondrocytes, isolated from bovine articular cartilage, were seeded in monolayer and passaged 4 times (P1-4). For assessment of chondrocytic and fibroblastic phenotype, freshly isolated and passaged cells were seeded on glass coverslips or in 2% alginate beads and cultured for 7 days in DMEM + 10% FCS. Samples were assayed for DNA and GAG content and stained for collagen types I and II. In separate experiments, freshly isolated or passaged chondrocytes were seeded at 10 x 10(6) cells.ml(-1) in 4% cylindrical agarose constructs and subjected to 15% dynamic compressive strain at 1 Hz for 24 hours. [(3)H]-thymidine incorporation, SO(4) incorporation and nitrite release were analysed. Immediately following isolation (P0), chondrocytes seeded in alginate expressed high levels of type II collagen, but did not stain for type I collagen. Following repeat passage the cells expressed enhanced levels of type I collagen, with an associated reduction in type II collagen staining. These data indicate a modulation to a fibroblastic phenotype during monolayer expansion which was not rapidly reversed by culture in a 3D hydrogel. Dynamic compression down-regulated SO(4) incorporation at P0, but did not affect [(3)H]-thymidine incorporation. By contrast the incorporation of both SO(4) and [(3)H]-thymidine was enhanced by dynamic compression at both P1 and to a lesser extent P2. SO(4) and [(3)H]-thymidine incorporation were inhibited at P3 and P4. Nitrite release was down-regulated by dynamic compression at all passages. These data demonstrate a clear modulation in the response of bovine articular chondrocytes to dynamic compression following passage in monolayer.

Cartilage, Articular↗
PubMedDate not supplied

A survey of dynamical genetics.

The classical view of genetics is based on the central dogma of molecular biology that assigns to DNA a fundamental but static role. According to the dogma, DNA can be duplicated only in identical copies (except for random errors), and no smart mechanism can alter the information content of DNA: in more detail, the direction of transfer of the genetic information is only from DNA through RNA to proteins and never backwards. However, starting from the so-called dynamic genome (McClintock's jumping genes), and the so-called dynamic mutations (such as the trinucleotide expansion or, more generally, the instability of the number of tandem repeats of longer sequences), there is now a growing body of important cases where it is known that the DNA is altered in a more or less sophisticated way, often by smart enzymatic mechanisms. The study of all such dynamic phenomena and of their interpretations can be naturally called dynamical genetics. In this survey we examine a number of such dynamic phenomena, and also some phenomena of great biological importance that have no universally accepted explanation within a static approach to genetics, and for which a dynamical interpretation has been only proposed. Important examples are some controversial but interesting phenomena such as horizontal transmission and Creutzfeldt-Jakob Disease, and those peculiar DNA structures known as G-quadruplexes.

Creutzfeldt-Jakob Syndrome↗
PubMed2004

[Maximum likelihood analysis for mapping dynamic trait QTL in outbred population II. Simulation].

Based on the maximum likelihood analysis principle for dynamic trait QTL mapping, selecting three orders Legendre polynomial as sub-model,the effects of the individual number, the frequency of test day,the marker density and heritability on detecting power are investigated by Monte-Carlo simulation. Each factor is divided into three levels such as the high,middle and low,the combinations of which are arranged by using orthologal design. The simulating result shows that the high heritability needs less number of individuals and frequency of test day than the low one, but the number of individuals of more than 300 and the frequency of test day of 5% above can guarantee sufficient detecting power no matter what the heritability is like. The number of individuals has almost the same effect as the frequency of test day in dynamic traits QTL mapping and the number of individuals and the frequency of test day compensate each other under the same size of samples. As to the QTL detection for a dynamic point,simulation indicates that the presented dynamic trait QTL mapping method that focuses on the whole dynamic process is significantly superior to the classical mapping methods on each individual dynamic point.

Humans↗
PubMed2004

Dynamic monitoring system for full-scale wastewater treatment plants.

This paper proposes a new process monitoring method using dynamic independent component analysis (ICA), ICA is a recently developed technique to extract the hidden factors that underlie sets of measurements, whereas principal component analysis (PCA) is a dimensionality reduction technique in terms of capturing the variance of the data. Its goal is to find a linear representation of non-Gaussian data so that the components are statistically independent. PCA aims at finding PCs that are uncorrelated and are linear combinations of the observed variables, while ICA is designed to separate the ICs that are independent and constitute the observed variables. The dynamic ICA monitoring method is applying ICA to the augmenting matrix with time-lagged variables. The dynamic monitoring method was applied to detect and monitor disturbances in a full-scale biological wastewater treatment (WWTP), which is characterized by a variety of dynamic and non-Gaussian characteristics. The dynamic ICA method showed more powerful monitoring performance on a WWTP application than the dynamic PCA method since it can extract source signals which are independent of time and cross-correlation of variables.

Algorithms↗
PubMed2005

[Design of mechanical structure dynamic characteristics and development of verification system].

OBJECTIVE: To present an effective method for structural dynamic characteristics design, required design and test means for space products' development. METHOD: Computational modal analysis method was used to evaluate natural frequencies and modes of the products in the beginning of design, and test modal analysis method was used to identify the dynamic parameters of products in the test period. RESULT: The proposed computational modal analysis system is capable of making static and dynamic analysis, as well as natural frequencies and modes analysis of the structure, and this system could be applied in mechanical structure dynamic characteristics design. The proposed test modal analysis system could acquire real time force and acceleration signals, and obtain the basic modal parameters by processing the sampled data. This system could be used to modify mechanical products' dynamic characteristics and decrease vibration amplitude. CONCLUSION: The computational and test results of two test models demonstrated that the developed computational and test modal system is effective. The method can be used for design of structural dynamic characteristics of space products.

Acceleration↗
PubMed2005

[Comparative study between dynamic MRI and pelvic organography in diagnosis of pelvic floor disorders].

OBJECTIVE: To evaluate the clinical value of simultaneously combined pelvic floor dynamic MRI and pelvic organography in diagnosing female pelvic floor disorders and search for the best imaging model for diagnosing pelvic floor disorders. METHODS: Thirty women with pelvic floor disorders received pelvic floor dynamic MRI and simultaneously combined pelvic organography including cystourethrography, peritoneography, vaginography and defecography. Clinical diagnostic value was compared between this two methods. RESULTS: The diagnostic accuracy of pelvic floor dynamic MRI and simultaneously combined pelvic organograph for cystocele,anorectal junction abnormal descent, pelvic floor hernia,uterocervical prolapse was 100%, 95.2 %, 86.7%, 85.7% respectively. Rectocele and prolapse of rectal were diagnosed by pelvic organograph in 12 and 28 cases respectively, while only 6 and 0 cases were diagnosed by pelvic floor dynamic MRI respectively. The mean examining time of pelvic floor dynamic MRI and simultaneously combined pelvic organography was (16 +/- 3)min, (34 +/- 9)min respectively (P< 0.01). CONCLUSION: Pelvic floor dynamic MRI combined with defecography is the best imaging model for diagnosing pelvic floor disorders.

Adult↗
PubMedDate not supplied

Improvement after severe traumatic brain injury induced by coordination dynamics therapy: comparison with physiologic CNS development.

On the example of a 5-year longitudinal study of a boy who suffered severe traumatic brain injury, it is shown that there seems to be no limit as to the repair of the injured central nervous system (CNS) if Schalow Coordination Dynamics Therapy is administered. The treatment-induced improvement of CNS functioning was preceded by a transient worsening This observation is in accordance with the predictions of the theory of coordination dynamics. The dynamics of pattern formation are described in terms of the motion of low-dimensional order parameters. If the intrinsic coordination dynamics conflict with the trained movement patterns, a temporary increase in variability (loss of stability) of the required pattern can be observed. Such temporary worsening of coordination dynamics was observed during the repair of the injured CNS but not during the physiologic development of pupils between 7 and 19 years of age. The improvement achieved during 5 years of home treatment in the CNS functioning, as quantified by low-load coordination dynamics, was 11%; a further improvement of 38% could be achieved during 16 days of therapy under professional supervision. Therapy under professional supervision was approximately 100 times more efficient than the seemingly similar home therapy.

Brain Injuries↗
PubMed2006

Time-variant analysis of fast-fMRI and dynamic contrast agent MRI sequences as examples of 4-dimensional image analysis.

OBJECTIVES: Image sequences with time-varying information content need appropriate analysis strategies. The exploration of directed information transfer (interactions) between neuronal assemblies is one of the most important aims of current functional MRI (fMRI) analysis. Additionally, we examined perfusion maps in dynamic contrast agent MRI sequences of stroke patients. In this investigation, the focus centers on distinguishing between brain areas with normal and reduced perfusion on the basis of the dynamics of contrast agent inflow and washout. METHODS: Fast fMRI sequences were analyzed with time-variant Granger causality (tvGC). The tvGC is based on a time-variant autoregressive model and is used for the quantification of the directed information transfer between activated brain areas. Generalized Dynamic Neural Networks (GDNN) with time-variant weights were applied on dynamic contrast agent MRI sequences as a nonlinear operator in order to enhance differences in the signal courses of pixels of normal and injured tissues. RESULTS: A simple motor task (self-paced finger tapping) is used in an fMRI design to investigate directed interactions between defined brain areas. A significant information transfer can be determined for the direction primary motor cortex to supplementary motor area during a short time period of about five seconds after stimulus. The analysis of dynamic contrast agent MRI sequences demonstrates that the trained GDNN enables a reliable tissue classification. Three classes are of interest: normal tissue, tissue at risk for death, and dead tissue. CONCLUSIONS: The time-variant multivariate analysis of directed information transfer derived from fMRI sequences and the computation of perfusion maps by GDNN demonstrate that dynamic analysis methods are essential tools for 4D image analysis.

Cerebrovascular Circulation↗
PubMed1991

The effects of dynamic tension and reduced graft size on muscle regeneration in rabbit free muscle grafts.

In a study of 28 adult New Zealand White rabbits, the influence of tension and size on muscle regeneration in tibialis anterior free muscle grafts (without vascular anastomoses) was examined 6 months after transplantation. Three laboratory models were studied: (1) whole dynamic (WD) graft (allowing ankle excursion and, therefore, variable dynamic physiologic tension), (2) whole static (WS) graft (constant, fixed length and, thus, only isometric tension), and (3) longitudinally sliced (reduced radius) dynamic (SD) model. Bilateral orthotopic grafts of the tibialis anterior muscle were performed in 24 rabbits (eight animals in each of the three different model groups). Controls consisted of normal tibialis anterior muscle from four age-matched rabbits. All tibialis anterior muscle grafts were examined histologically (fiber counts) and functionally (determined by in situ contractile properties under maximal stimulation conditions). The WD grafts demonstrated a significantly higher number of regenerated fibers per muscle cross section (4819 +/- 589) than the WS (2221 +/- 603) or SD (1919 +/- 732) grafts. The amount of tetanic tension in the WD grafts was 35 percent of the control and twice as much as that of the WS grafts (WD 1.0 +/- 0.2 kg versus WS 0.5 +/- 0.4 kg; p less than 0.05). The SD grafts produced approximately one-third as much maximum tetanic tension as the WD grafts (0.3 +/- 0.1 kg versus 1.0 +/- 0.2 kg), demonstrating that the amount of recovery was similar in these two dynamic models, since only the longitudinal middle third of the muscle was grafted in the SD model. Free muscle grafts under dynamic tension, which allows excursion, have shown a greater amount of muscle-fiber regeneration and restoration of function compared with a graft with fixed length. The positive effect of dynamic mechanical tension on small autogenous free muscle grafts (without vascular anastomoses) is clinically significant in the reconstruction of facial and hand neuromuscular deficits when blood vessels are not available for reanastomosis. Future studies using the tibialis anterior WD and SD transplant models will strengthen our understanding of the events of spontaneous revascularization and skeletal muscle regeneration.

Analysis of Variance↗
PubMed1989

Understanding natural dynamics.

When making dynamical judgments, people can make effective use of only one salient dimension of information present in the event. People do not make dynamical judgments by deriving multidimensional quantities. The adequacy of dynamical judgments, therefore, depends on the degree of dimensionality that is both inherent in the physics of the event and presumed to be present by the observer. There are two classes of physical motion contexts in which objects may appear. In the simplest class, there exists only one dynamically relevant object parameter: the position over time of the object's center of mass. In the other class of motion contexts, there are additional object attributes, such as mass distribution and orientation, that are of dynamical relevance. In the former class, objects may be formally treated as extensionless point particles, whereas in the latter class some aspect of the object's extension in space is coupled into its motion. A survey of commonsense understandings showed that people are relatively accurate when specific dynamical judgments can be accurately based on a single information dimension; however, erroneous judgments are pervasive when simple motion contexts are misconstrued as being multidimensional, and when multidimensional quantities are the necessary basis for accurate judgments.

Attention↗
PubMed1988

Molecular-dynamics simulations of [Met5]- and [D-Ala2,Met5]-enkephalins. Biological implication of monomeric folded and dimeric unfolded conformations.

To investigate the biologically active conformation of enkephalin, molecular-dynamics simulations were applied to [Met5]- and [D-Ala2,Met5]-enkephalins. The dynamic trajectory of monomeric extended [Met5]-enkephalin was analysed in terms of relative mobility between respective torsions of backbone chain. After 10 ps of the dynamics simulation, the conformational transition was converged into a stationary state among the beta-bend folded forms, where they are stabilized by several intramolecular hydrogen-bond formations. Similar conformational transition was also observed in the dynamics simulation of [D-Ala2,Met5]enkephalin, which is a more mu-receptor-specific peptide than [Met5]enkephalin. The geometrical correspondence between the monomeric enkephalin conformation in the stationary state and morphine molecule (a mu-specific rigid opiate) was surveyed by virtue of the triangular substructures generated by choosing three functional atoms in each molecule, and good resemblances were observed. On the other hand, the dynamics simulation of the antiparallel extended [Met5]enkephalin dimer showed a trajectory different from that of the monomeric one. Two intermolecular hydrogen bonds at Tyr1 (NH3+)...Met5(CO2-) end residues were held throughout the 100 ps simulation, the dimeric structure being consequently kept. The conformational transition of the backbone chains from the antiparallel extended form to the twisted one took place via an intermediate state. Many conformations revealed during the dynamics simulation showed that the relative orientations of each two Tyr1, Gly3, Phe4 and Met5 residues in the dimer are nearly related by a pseudo-C2-symmetry respectively, and both halves of the dimer structure could be further fitted to the monomeric folded enkephalin conformation. The monomeric and dimeric conformations of enkephalin at their stationary states are discussed in relation to the substrate-specificity for mu- and delta-opioid receptors.

Computer Simulation↗
PubMed1986

Recognizing people seen in events via dynamic "mug shots".

This study examined effects of an event and dynamic mug shots on facial recognition. Witnesses saw either a film of a liquor store holdup staged by six perpetrators, slides of the same targets, or freeze-framed views from the filmed event. Slides of different facial views of targets among 12 foils, or dynamic 180 degrees mug shots of the same men, or multiple static views were administered 24 hr later in yes-no recognition tests. Recognition (d') was poorer for the same men seen in the event than in slides, but better for dynamic than for static mug shots. Nondynamic event characteristics were responsible for poor recognition of people seen in events, whereas dynamic aspects of facial transformations, not multiple views, seemed responsible for the superiority of dynamic mug shots. The implications of these results for issues of ecological validity of traditional face recognition methodology and for static feature models vs. dynamic transformation models of face recognition are discussed.

Adult↗
PubMed1984

[Dynamic computed tomography of brain tumor].

Dynamic computed tomography (CT) has been widely used because of its simplicity, but regional cerebral perfusion of brain tumors has not critically been evaluated. This study was conducted to evaluated parameters obtained from the dynamic perfusion study in brain tumors and to clarify the usefulness of the dynamic CT comparing with Xe-enhanced CT. Dynamic CT was performed on 20 patients with brain tumor (three meningiomas, one pineal tumor, three metastatic brain tumors, thirteen gliomas). Dynamic CT consisted of performing six rapid sequential scans after a bolus intravenous injection of 40 ml of iodinated contrast medium. In this study, five parameters (corrected first moment, area, peak, time to peak, percent terminal height) were obtained from computer analysed curve fit on time density curve profile of serial scanning. In Xe-enhanced CT, serial CT was taken every three or five minutes during inhalation of 40 to 50 percent stable xenon. Flow rate constant (K), partition coefficient (lambda) and cerebral blood flow (CBF) for each pixel were calculated from delta HU (Hounsfield unit) and end-tidal air curve and displayed on CRT as images. In patients with meningioma, values of area and percent terminal height of the tumor were much higher than those of contralateral gray matter, and these findings show excessive increase of the intratumoral blood volume and extreme extravasation of iodinated contrast medium respectively. In patients with metastatic brain tumor or malignant glioma, which were enhanced by contrast medium, the values of all parameters of the tumors were higher than contralateral gray matter. Increase of intratumoral blood volume and destruction of blood brain barrier are suggested in these tumors. In the remaining patients with glioma, which was not enhanced, the values of corrected first moment and time to peak of the tumors were higher but area and peak were lower than contralateral gray matter. These findings show decrease of intratumoral blood volume and delay of mean transit time and arrival time of the bolus. Compared with CBF measured by Xe-enhanced CT, it was suggested that high density area of metastatic brain tumor or malignant glioma consisted of viable tumor cells, and in patients with glioma, low density area adjacent to the tumor with contrast enhancement was the invasive site of the tumor. Using dynamic CT, we were also able to distinguish the tissue contains viable tumor cells from the other part of brain by the differences in the parameter value.

Adult↗
PubMed1983

[Usefulness of dynamic computed tomography in the diagnosis of thoracic aortic aneurysms].

Five patients with thoracic aortic aneurysms, two saccular and three dissecting aneurysms, were examined by dynamic computed tomographic (CT) scanning. A Siemens Somatom 2 was employed. Dynamic scanning is the method by which plural serial images can be obtained in single operation. We used three serial images in a 5-second scan following a 3-second interval. After rapid manual injection of 30 ml of 76% megluminc amidotrizoate sodium into the right antecubital vein, scans of 4 mm section were performed three times and subsequently conventional scans four times. Serial changes in the same section and changes in the CT number against time in regions of interest in the image were investigated. Saccular aneurysms was difficult to distinguish from mediastinal tumors on the plain chest X-ray films. However, it was confirmed by the dynamic CT scanning demonstrating free communication between the aorta and the abnormal lumen, because the latter was filled with contrast medium, and the time of appearance, and the peak and washout of a contrast medium were almost the same between two lumens. In dissecting aneurysms, it was able to recognize both the false and true lumens as double channels in the aorta. We observed the different mode of dissection between the ascending and descending aorta in one case, and observed the twisting of an intimal flap in variable parts of the aorta in another case. Furthermore, it was possible to confirm the difference of blood flow pattern between the false and true lumens by dynamic CT. Because CT has a high quality image resolution, and especially, dynamic CT provides the serial changes in the same section after injection of contrast medium, both CT and dynamic CT are useful non-invasive imaging techniques for evaluating thoracic aortic aneurysms.

Adult↗
PubMed1995

Test time and efficiency of the dynamic strategy in glaucoma perimetry.

The dynamic strategy is a perimetric measurement procedure where by the luminance-step sizes are optimized according to physiological data. In contrast to the traditional 4- to 2-dB strategy, the step sizes are not constant but vary between 2 and 10 dB depending on the sensitivity. We examined 40 eyes of 40 glaucoma patients with both the traditional and the dynamic strategy using a modified Octopus 1-2-3 perimeter. A total of 16 visual field locations were examined using both strategies 3 times each in alternation. The order of the initial strategy was randomized. The variance of the three measurements was calculated as a measure of reproducibility. The quantity of presented stimuli was recorded as a measure of test time. After the elimination of starting points, absolute scotomata, and series of fields showing a significant trend during the session, 255 measured locations of 27 series were available for evaluation. The mean number of presentations (indicating test time) was 46% (dynamic strategy versus traditional strategy). The variance of the three measurements depended on the sensitivity. In the normal sensitivity range, the dynamic strategy had a markedly lower variance (58%). For relative defects, the variance was higher (141%-156%). According to a benefit/cost calculation, the efficiency of the dynamic strategy was better in all sensitivity ranges and reached a factor of 3 for high sensitivities. The dynamic strategy is considerably more efficient than the traditional strategy using fixed step sizes.

Adult↗
PubMed1995

Factor analysis for extraction of blood time-activity curves in dynamic FDG-PET studies.

UNLABELLED: Arterial sampling in dynamic PET studies can be eliminated by using left ventricular or aortic time-activity curves (TAC) obtained from user drawn regions of interest (ROIs) after appropriate spillover correction. In this study, we evaluated the feasibility of extracting the "pure" arterial TAC from dynamic PET images using factor analysis of dynamic structures (FADS). METHODS: Computer simulations were used to study the performance of the FADS algorithm with positivity constraints. Ten canine 13N-ammonia and two human FDG-PET dynamic studies were used to extract the blood TACs from FADS. Plasma samples and compartmental model fittings were used to validate the accuracy of the FADS-generated blood factors. RESULTS: We found that FADS with positivity constraints was sufficient to extract the blood factor from the composite dynamic images. The "pure" blood-pool TACs that matched well with the arterialized well counter measurements were generated from FADS in the canine and human studies. CONCLUSION: FADS has the potential to accurately extract "pure" blood TAC from dynamic PET images, allowing reliable quantitation of biological information from PET studies without blood sampling, ROI drawing or spillover correction.

Algorithms↗
PubMed1994

Nerve growth dynamics. Quantitative models for nerve development and regeneration.

The quantitative analysis of nerve growth dynamics is critical to our understanding of nerve development and regeneration, but only recently has a quantitative framework begun to emerge to help define key objectives and to direct experimental measurements towards achieving this goal. Conceptually, the framework centers on the dynamic processes commonly observed for individual growth cones of growing neurites at the phase microscopy level, namely lamellipodial and filopodial extension and retraction. Because these activities essentially define the position of the axon tip, understanding how they are regulated offers to yield direct insight into factors governing the growth trajectory of the axon. In addition, much biological interest and effort is focused on the lamellipodial and filopodial behavior of the growth cone, which should facilitate experimental quantitation. Characterization of lamellipodial and filopodial activity has not been straightforward, however, because their inherent randomness leads to a requirement for considerable data and for less common mathematical techniques, such as time-series analysis. The work reviewed above has identified key analytical tools and experimental parameters needed to develop an integrated model of growth cone dynamics. Detailed measurement and analysis will be required to carry this development process to the next step. The cellular model of growth cone motility resulting from the characterization of lamellipodial and filopodial dynamics represents an intermediate description that can be extended to encompass both molecular mechanisms of growth cone behavior and axonal growth in multicellular tissue environments. For example, on the molecular level, filopodia contain a central core of actin filaments whose polymerization and depolymerization is thought to correspond to filopodial extension and retraction, with significant regulation possible through receptor-mediated effects on actin dynamics. By rewriting the parameters of filopodia dynamics in the current model in terms of these molecular events, one can begin to investigate their effects on growth cone behavior and to examine hypotheses of molecular mechanisms. Processes underlying lamellipodial behavior can be examined in a similar manner. At the tissue level, the effects of environmental factors on model parameters can be incorporated to yield predictions of the neurite outgrowth response to a particular environment. Such predictions offer a basis for designing microenvironments with optimal characteristics for enhancing nerve regeneration or manipulating the nerve growth response. Although the quantitative framework described here has focused on growth by peripheral nerve cells, it represents concepts known to apply to neurons of the central nervous system, as well.(ABSTRACT TRUNCATED AT 400 WORDS)

Animals↗
PubMed1994

The effects of dynamic cardiac compression on ventricular mechanics and energetics. Role of ventricular size and contractility.

The purpose of this study was to determine the role of ventricular size or contractility in the effectiveness of dynamic cardiac compression in terms of the pressure-volume relationship and myocardial oxygen consumption. In 10 isolated cross-circulated dog hearts, the ventricle was directly compressed during systole. For the volume run, measurements for slope of the end-systolic pressure-volume relation, pressure-volume area, external work, coronary blood flow, and myocardial oxygen consumption were achieved before and during a fixed amount of dynamic cardiac compression. Left ventricular volume was then increased while stroke volume was kept constant, and measurements were repeated. For the contractility run, after the control measurements were taken, left ventricular contractility was significantly increased or decreased by infusion of either dobutamine or propranolol into the coronary circulation. Measurements were repeated before and during dynamic cardiac compression at the control level of end-diastolic and stroke volumes. Dynamic cardiac compression significantly increased slope of the end-systolic pressure-volume relation, pressure-volume area, and external work (p < 0.01), whereas coronary blood flow and myocardial oxygen consumption were not affected. The increase in pressure-volume area caused by dynamic cardiac compression was greater with the larger volume. Despite the significant differences in the native left ventricular contractility, the increases in slope of the end-systolic pressure-volume relation, pressure-volume area, and external work did not differ among the three groups. We conclude that dynamic cardiac compression enhances left ventricular systolic function independent of ventricular contractility and without affecting coronary blood flow or myocardial oxygen consumption. Mechanical enhancement is more effective in the dilated heart.

Animals↗