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  • 1
    Online Resource
    Online Resource
    Therapeutic Enigma of Unilateral Pulmonary Artery Coarctation in Pulmonary Hypertension
    Ovid Technologies (Wolters Kluwer Health) ; 1965
    In:  Annals of Surgery Vol. 162, No. 4 ( 1965-10), p. 702-723
    Details
    In: Annals of Surgery, Ovid Technologies (Wolters Kluwer Health), Vol. 162, No. 4 ( 1965-10), p. 702-723
    Type of Medium: Online Resource
    ISSN: 0003-4932
    URL: Article
    DOI: 10.1097/00000658-196510000-00013
    RVK:
    XA 23900
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 1965
    detail.hit.zdb_id: 2002200-1
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  • 2
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    Online Resource
    Left Ventricular Performance Following Correction of Free Aortic Regurgitation
    Ovid Technologies (Wolters Kluwer Health) ; 1970
    In:  Circulation Vol. 42, No. 5 ( 1970-11), p. 773-780
    Details
    In: Circulation, Ovid Technologies (Wolters Kluwer Health), Vol. 42, No. 5 ( 1970-11), p. 773-780
    Abstract: Left ventricular (LV) myocardial contractility, or inotropic state, was characterized in terms of the instantaneous relations between velocity of circumferential fiber shortening (V CF ), determined cineangiographically, and LV wall tension (hoop stress), calculated from LV dimensions and pressure, in five patients before and 7 to 10 mo after aortic valve replacement for free aortic regurgitation. Preoperatively the cardiac index was reduced or the LV end-diastolic pressure was markedly increased (or both occurred) in four patients, in each of whom depression of inotropic state was documented by a reduced V CF at maximum wall tension, ranging from 0.13 to 1.07 circumferences (circ)/sec (normal, 〉 1.40 circ/sec) at wall tensions of 318 to 464 g/cm 2 (normal, 178 to 417 g/cm 2 ). In one patient in whom LV end-diastolic pressure and cardiac index were normal preoperatively, V CF was 1.66 circ/sec at a maximum tension of 440 g/cm 2 . Following operation, LV end-diastolic pressure fell in the four patients with depressed inotropic state (average decrease, 23 mm Hg) and cardiac index increased (average increase, 0.93 L/min/m 2 ). However, no change in the tension-velocity relation was observed postoperatively, V CF ranging from 0.27 to 1.14 circ/sec in these patients, indicating that no change had occurred in the inotropic state. In addition, a fixed abnormality in diastolic LV pressure-volume characteristics, determined from preoperative and postoperative measurements of pressure and radius during diastole, had occurred in patients with depressed myocardial function. In contrast, in the patient with normal myocardial function, LV end-diastolic radius was reduced by 33% postoperatively while end-diastolic pressure was unchanged, suggesting reversal of stress relaxation, or creep, following relief of volume overload.
    Type of Medium: Online Resource
    ISSN: 0009-7322 , 1524-4539
    URL: Article
    DOI: 10.1161/01.CIR.42.5.773
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 1970
    detail.hit.zdb_id: 1466401-X
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  • 3
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    Online Resource
    Reduction of Cardiac Tyrosine Hydroxylase Activity in Experimental Congestive Heart Failure : Its Role In The Depletion Of Cardiac Norepinephrine Stores
    Ovid Technologies (Wolters Kluwer Health) ; 1967
    In:  Circulation Research Vol. 20, No. 3 ( 1967-03), p. 349-353
    Details
    In: Circulation Research, Ovid Technologies (Wolters Kluwer Health), Vol. 20, No. 3 ( 1967-03), p. 349-353
    Abstract: Although it is clear that cardiac norepinephrine stores are often markedly reduced in congestive heart failure, the mechanism responsible for this depletion has not been elucidated. The objective of this study was to investigate cardiac synthesis of norepinephrine in experimental right-sided heart failure by measuring the activity of tyrosine hydroxylase, the rate-limiting enzyme in the biosynthesis of norepinephrine. In homogenates of the right ventricles of 6 dogs with congestive heart failure and 2 with chronic cardiac denervation, myocardial tyrosine hydroxylase activity was severely reduced, averaging 0.4 ± 0.1 (SE) and 0.2 mµmole/g per hour respectively as compared to a normal value of 3.3 ± 0.7 mµmole/g per hour. Tyrosine hydroxylase activity was normal in reserpine-treated, norepinephrine-depleted dogs. These data provide evidence for a mechanism severely limiting norepinephrine biosynthesis in congestive heart failure.
    Type of Medium: Online Resource
    ISSN: 0009-7330 , 1524-4571
    URL: Article
    DOI: 10.1161/01.RES.20.3.349
    RVK:
    XA 10000
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 1967
    detail.hit.zdb_id: 1467838-X
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  • 4
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    Online Resource
    Enhanced Regional Deformation at the Anterior Papillary Muscle Insertion Site After Chordal Transsection
    Ovid Technologies (Wolters Kluwer Health) ; 1996
    In:  Circulation Vol. 93, No. 3 ( 1996-02), p. 585-593
    Details
    In: Circulation, Ovid Technologies (Wolters Kluwer Health), Vol. 93, No. 3 ( 1996-02), p. 585-593
    Abstract: Background Clinical and experimental studies of mitral valve replacement have shown a depression of ventricular function after chordal transsection; most recent studies have proposed that this is secondary to a depression of local function near the papillary muscle insertion site. However, there is no direct experimental evidence for changes in local fiber shortening in the wall of the left ventricle overlying the papillary muscle. Accordingly, we investigated the effect of chordal transsection on left ventricular shape and on three-dimensional regional deformation of the myocardium near the insertion of the anterior papillary muscle. Methods and Results In six open-chest dogs, two sets of three transmural columns of radiopaque markers were implanted in the anterior wall, one set at the tip of the papillary muscle (basal) and one at the site of papillary muscle fiber insertion (apical). A Björk-Shiley mitral valve was placed in the left atrium adjacent to the native valve. Markers were then tracked with biplane cineradiography, and deformation was quantified with the use of finite strain analysis. Chordal transsection resulted in reduced left ventricular end-systolic pressure and slowed relaxation. After chordal transsection, outward displacement of the ventricular wall and transverse shearing deformation were observed in the area of the papillary muscle during isovolumic contraction. Circumferential and radial strains during ejection were maintained at our basal site and enhanced on our apical site. Conclusions Chordal transsection led to enhanced local shortening and wall thickening and regional strain nonuniformity. These results indicate that chordal transsection induces an unloading of myocardium at the papillary muscle insertion site and that the resulting heterogeneity of regional function is the mechanism for the reduced global function and slowed ventricular relaxation.
    Type of Medium: Online Resource
    ISSN: 0009-7322 , 1524-4539
    URL: Article
    DOI: 10.1161/01.CIR.93.3.585
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 1996
    detail.hit.zdb_id: 1466401-X
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  • 5
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    Online Resource
    Effects of Acute Valvular Regurgitation on the Oxygen Consumption of the Canine Heart
    Ovid Technologies (Wolters Kluwer Health) ; 1968
    In:  Circulation Research Vol. 23, No. 1 ( 1968-07), p. 33-43
    Details
    In: Circulation Research, Ovid Technologies (Wolters Kluwer Health), Vol. 23, No. 1 ( 1968-07), p. 33-43
    Abstract: The effects on myocardial oxygen consumption and mechanics of acute, simulated aortic and mitral regurgitation were studied in open-chest, anesthetized dogs to determine how changes in the mechanical performance of the ventricle alter oxygen consumption. When regurgitation was induced acutely with effective stroke volume (total stroke volume less regurgitant volume) and heart rate held constant, left ventricular end-diastolic volume, total stroke volume, the ejection fraction, left ventricular wall tension, and the extent of shortening of the contractile element and the circumferential fibers all increased. With volumes of regurgitation approaching effective systemic blood flow, oxygen consumption increased only moderately, despite the increases in tension and shortening. When valvular regurgitation was induced while peak ventricular wall tension was held relatively constant, stroke volume doubled and the extent of both contractile element and circumferential fiber shortening increased. Contractile element work in generating tension was unchanged; that which led to fiber shortening increased substantially. Myocardial oxygen consumption did not increase significantly. Thus, marked increases in the efficiency of the contractile elements and myocardial fibers occurred. The low energy cost per unit of work expended in shortening as opposed to that used for tension development therefore allows the excess stroke volume of valvular regurgitation to be maintained at only a small added oxygen cost to the ventricle.
    Type of Medium: Online Resource
    ISSN: 0009-7330 , 1524-4571
    URL: Article
    DOI: 10.1161/01.RES.23.1.33
    RVK:
    XA 10000
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 1968
    detail.hit.zdb_id: 1467838-X
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  • 6
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    Structure and Mechanics of Healing Myocardial Infarcts
    Annual Reviews ; 2005
    In:  Annual Review of Biomedical Engineering Vol. 7, No. 1 ( 2005-08-15), p. 223-253
    Details
    In: Annual Review of Biomedical Engineering, Annual Reviews, Vol. 7, No. 1 ( 2005-08-15), p. 223-253
    Abstract: ▪ Abstract  Therapies for myocardial infarction have historically been developed by trial and error, rather than from an understanding of the structure and function of the healing infarct. With exciting new bioengineering therapies for myocardial infarction on the horizon, we have reviewed the time course of structural and mechanical changes in the healing infarct in an attempt to identify key structural determinants of mechanics at several stages of healing. Based on temporal correlation, we hypothesize that normal passive material properties dominate the mechanics during acute ischemia, edema during the subsequent necrotic phase, large collagen fiber structure during the fibrotic phase, and cross-linking of collagen during the long-term remodeling phase. We hope these hypotheses will stimulate further research on infarct mechanics, particularly studies that integrate material testing, in vivo mechanics, and quantitative structural analysis.
    Type of Medium: Online Resource
    ISSN: 1523-9829 , 1545-4274
    URL: Issue
    URL: Article
    DOI: 10.1146/bioeng.2005.7.issue-1
    DOI: 10.1146/annurev.bioeng.7.060804.100453
    Language: English
    Publisher: Annual Reviews
    Publication Date: 2005
    detail.hit.zdb_id: 2026771-X
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  • 7
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    Online Resource
    Comparison of Directly Measured Left Ventricular Wall Stress and Stress Calculated from Geometric Reference Figures
    Ovid Technologies (Wolters Kluwer Health) ; 1971
    In:  Circulation Research Vol. 28, No. 6 ( 1971-06), p. 611-621
    Details
    In: Circulation Research, Ovid Technologies (Wolters Kluwer Health), Vol. 28, No. 6 ( 1971-06), p. 611-621
    Abstract: Mean left ventricular wall force was determined with a calibrated transmural auxotonic strain gauge in the left ventricle of six anesthetized, open-chest dogs with intact circulation. The gauge was oriented in the plane of the minor left ventricular equator, midway between the papillary muscles. Left ventricular internal volume was derived from the passive pressure-volume curve of the arrested heart and calculated mean wall stress was derived both from spherical and ellipsoidal reference figures for the left ventricle and compared with measured forces. Control left ventricular end-diastolic pressure averaged 3.0 ± 0.6 mm Hg (SE). At this level of end-diastolic pressure, measured peak wall stress averaged 97.2±14.4 g/cm 2 , whereas calculated peak wall stress averaged 79.3±9.9 and 118.6±12.9 g/cm 2 , for the spherical and ellipsoidal models, respectively. Measured end-diastolic wall force values averaged 9.4±4.5 and 29.2±8.1 g/cm 2 at an end-diastolic pressure of 3.0 and 12.3 mm Hg, respectively. In all cases, stress values calculated from spherical reference figures for the left ventricle were significantly lower than those measured directly. In four other experiments, using right heart bypass, the ventricular septum was exposed and active wall force was determined at two or more sites on the left ventricular minor equator. Wall stress at these sites differed by an average of 15.3%, indicating that stresses around the minor equator are relatively uniform. These studies lend validity to the application of geometric models in the calculation of mean wall stress and favor the application of an ellipsoid for the geometric reference figure.
    Type of Medium: Online Resource
    ISSN: 0009-7330 , 1524-4571
    URL: Article
    DOI: 10.1161/01.RES.28.6.611
    RVK:
    XA 10000
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 1971
    detail.hit.zdb_id: 1467838-X
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  • 8
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    Online Resource
    Observations on Factors Affecting Local Forces in the Left Ventricular Wall during Acute Myocardial Ischemia
    Ovid Technologies (Wolters Kluwer Health) ; 1971
    In:  Circulation Research Vol. 29, No. 3 ( 1971-09), p. 306-316
    Details
    In: Circulation Research, Ovid Technologies (Wolters Kluwer Health), Vol. 29, No. 3 ( 1971-09), p. 306-316
    Abstract: The factors affecting local myocardial function in the presence of ischemic myocardial damage may considerably influence cardiac function and the extent of tissue damage resulting from the initial ischemic injury. However, previous attempts to study local wall forces in the ischemic myocardium have produced variable results. In the present study, a technique was developed for recording isometric left ventricular wall tension that minimized artifacts due to external forces acting on the ischemic area. Miniature isometric force gauges were implanted in 23 dogs in the left ventricular wall within a zone buffered by two rows of transmural prongs attached to a ring. During a test occlusion of a branch of the left anterior descending coronary artery, the ischemic area was defined by the presence of epicardial ST segment elevation, and force gauges were implanted in marginal or ischemic areas of the myocardium. During a subsequent coronary occlusion wall force in the ischemic area fell immediately by an average of 31 ± 8%. When the occlusion was repeated during isoproterenol infusion, wall tension decreased in previously unaffected areas of the myocardium, although in ischemic areas it remained above previous control ischemic levels. Arterial counterpulsation improved the development of wall tension in the ischemic area by 27% and decreased the extent and amount of ST segment elevation. Thus the present study clearly indicates a significant reduction but not elimination of active myocardial wall force in ischemic zones following experimental coronary occlusion. Moreover, force could be augmented by either isoproterenol or counterpulsation, and counterpulsation can produce a significant improvement in function of the ischemic myocardium while reducing the area of ischemic injury.
    Type of Medium: Online Resource
    ISSN: 0009-7330 , 1524-4571
    URL: Article
    DOI: 10.1161/01.RES.29.3.306
    RVK:
    XA 10000
    Language: English
    Publisher: Ovid Technologies (Wolters Kluwer Health)
    Publication Date: 1971
    detail.hit.zdb_id: 1467838-X
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  • 9
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    Online Resource
    Skeletal Muscle Deformation in the Lateral Muscle of the Intact Rainbow Trout Oncorhynchus Mykiss During Fast Start Maneuvers
    The Company of Biologists ; 1991
    In:  Journal of Experimental Biology Vol. 156, No. 1 ( 1991-03-01), p. 453-466
    Details
    In: Journal of Experimental Biology, The Company of Biologists, Vol. 156, No. 1 ( 1991-03-01), p. 453-466
    Abstract: Although there is an extensive body of information on the kinematics of the fast start response in teleosts, there is little information on the deformation of the skeletal muscle which produces the changes in body position during a fast start. This study presents preliminary information on the determination of skeletal muscle deformation with implanted ultrasonic dimension gauges in the intact fish during startle behavior. Deformation was measured in the lateral epaxial musculature of the rainbow trout Oncorhynchus mykiss during stage one of fast starts. The results show that ultrasound transit time dimension gauges can be implanted in the skeletal muscle of rainbow trout with minimum trauma and used to record local deformation along the length of the fish. Measurements remained stable over 4–8 h of implantation. Preliminary results show that: (1) muscle at different positions along the fish reaches its minimum length (average 9.6% shortening) at approximately the same time and coincident with the end of stage one of the fast start response; (2) the onset of concave curvature of the entire fish precedes the onset of local shortening at more caudal sites; (3) muscle on the convex side of a bend lengthens while muscle on the concave side shortens, and the two deformations follow a similar time course. These results indicate an asynchronous onset of skeletal muscle contraction in fast starts and support the hypothesis that local skeletal muscle deformation is transmitted caudally through skeletal or other structures.
    Type of Medium: Online Resource
    ISSN: 0022-0949 , 1477-9145
    URL: Article
    DOI: 10.1242/jeb.156.1.453
    Language: English
    Publisher: The Company of Biologists
    Publication Date: 1991
    detail.hit.zdb_id: 1482461-9
    SSG: 12
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  • 10
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    Online Resource
    Structural and mechanical factors influencing infarct scar collagen organization
    American Physiological Society ; 2000
    In:  American Journal of Physiology-Heart and Circulatory Physiology Vol. 278, No. 1 ( 2000-01-01), p. H194-H200
    Details
    In: American Journal of Physiology-Heart and Circulatory Physiology, American Physiological Society, Vol. 278, No. 1 ( 2000-01-01), p. H194-H200
    Abstract: Although large collagen fibers in myocardial infarct scar are highly organized, little is known about mechanisms controlling this organization. The preexisting extracellular matrix may act as a scaffold along which fibroblasts migrate. Conversely, deformation within the ischemic area could guide fibroblasts so new collagen is oriented to counteract the stretch. To investigate these potential mechanisms, we infarcted three groups of pigs. Group 1 served as infarct controls. Group 2 had the endocardium slit longitudinally to alter local systolic deformation. Group 3had a plug sectioned from ischemic tissue and rotated 90°. The slit altered systolic deformation in the infarcted tissue, changing circumferential strain from expansion to compression and increasing radial strain and shears and the variability of collagen fiber angles but not the mean angle. In the plug pigs, when deformation, matrix orientation, and continuity are altered in the infarct area, the result is complete disarray in the organization of collagen within the infarct scar.
    Type of Medium: Online Resource
    ISSN: 0363-6135 , 1522-1539
    URL: Article
    DOI: 10.1152/ajpheart.2000.278.1.H194
    RVK:
    WA 15000
    Language: English
    Publisher: American Physiological Society
    Publication Date: 2000
    detail.hit.zdb_id: 1477308-9
    SSG: 12
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