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At least 37 records · Page 2Linked to original sources
PubMed1995

Transesophageal echocardiography as an important tool in the diagnosis of postinfarction papillary muscle rupture.

Papillary muscle complicating acute myocardial infarction is an uncommon but potentially catastrophic event. We present 3 such cases to illustrate the difficulties in early identification of rupture. In each case, transesophageal echocardiography was employed providing rapid and unequivocal identification of the disorder. Prompt surgical intervention led to survival in 2 patients.

Echocardiography, Transesophageal↗
PubMed1985

Intercellular connections in rabbit heart as revealed by quick-frozen, deep-etched, and rotary-replicated papillary muscle.

Rabbit papillary muscles were ultrarapidly frozen, fractured, deep-etched, and rotary shadowed. These techniques revealed the interstitial space where the complex network of fine microthreads that connect myocytes to each other and to collagen fibrils can be seen in a three-dimensional array similar to scanning electron micrographs but at a resolution attainable in freeze-fracture microscopy.

Animals↗
PubMed1978

Leptomeric fibrils and T-tubule desmosomes in the Z-band region of the mouse heart papillary muscle.

The papillary muscle of the heart of adult white mice is investigated. Intrafibrillary located leptomeric fibrils, frequently encountered in the Z-band region of the myofibrils. The leptomeric fibrils are always running in a transverse direction and often in close proximity to the transverse tubules (which are also located at this level). There seems to be a close connection between the dense striae of the leptofibrils and the Z-bands of ordinary myofibrils. The leptomeric fibrils are spindle-shaped and have a length varying between 0.6 and 1.2 microgrometer. The banding periodicity of the fibrils is approximately 0.16 micrometer. Occasionally desmosomes are observed in the T-tubule system.

Animals↗
PubMed1982

Antagonism with dibenamine, D-600, and Ro 3-7894 to estimate dissociation constants and receptor reserves for cardiac adrenoceptors in isolated rabbit papillary muscles.

In papillary muscles isolated from reserpinized rabbits, positive inotropic responses to the alpha (alpha)-adrenergic agonist, (-)-phenylephrine in the presence of 10(7) M timolol and the beta (beta)-adrenergic agonist. (-)-isoproterenol were antagonized with the irreversible alpha-adrenergic antagonist, dibenamine, the irreversible beta-adrenergic antagonist. Ro 3-7894, and the calcium blocker, D-600. D-600 was employed as a functional antagonist of both alpha- and beta-adrenoceptor responses. Dissociation constants (Ka values) for drug-receptor interactions were calculated by the method of Furchgott and used to estimate fractional receptor occupancy and agonist efficacies. Comparison of responses showed that the receptor reserve for cardiac beta-adrenoceptors was greater than for alpha-adrenoceptors. D-600 was an effective inhibitor of both cardiac alpha- and beta-adrenoceptor responses; however, estimates of KA and receptor reserves were similar to estimates using an irreversible antagonist for alpha-but not beta-adrenoceptors.

Animals↗
PubMed1983

Age-dependent changes in electrophysiologic characteristics of fast and slow action potentials in rat papillary muscle.

Isolated papillary muscles from juvenile (about 2 months old, average weight of 250 g) and young adult rats (about 4 months old, average weight 485 g) were studied for age-dependent differences in the characteristics of fast and slow action potentials (APs). The fast and slow APs were recorded in 5.4 mM and 25 mM K+-Tyrode solutions, respectively (stimulation rate of 1 Hz). For the slow APs, the dose-response curves for isoproterenol versus Vmax (the maximum rate of rise of the APs), overshoot, and AP amplitude were linear between 10(-9) M and 10(-6) M (10(-5 M in some cases) in the juvenile and young adult rats. Isoproterenol pretreatment (1 mg/kg s.c., 1 h prior) decreased the slope of the dose-response curve, and saturation was achieved at a lower concentration. The Vmax, overshoot, and amplitude of both the fast and slow APs were somewhat smaller in the young adult rats than in the juvenile rats; there were no differences in the resting potential, AP duration, or threshold voltage. These results suggest that activation of a greater fraction of the beta-adrenergic receptors is coupled directly or indirectly to activation of a greater fraction of the slow channels. The pretreatment data suggest that down-regulation of the beta-adrenergic receptor may occur. The conductance per channel for the fast Na+ channels and slow channels, and (or) the number of both types of functional channels, may decrease with age.

Action Potentials↗
PubMed1995

Depressed regional deformation near anterior papillary muscle.

The role of the papillary muscle in left ventricular function has received new attention. We hypothesized that regional mechanics of the left ventricular wall near the anterior papillary muscle are influenced by the papillary muscle insertion. We therefore studied three-dimensional regional mechanics in and near the anterior papillary muscle in anesthetized, open-chest dogs, using implanted radiopaque markers and biplane cineradiography. In seven dogs, deformation differed little between an anterior papillary muscle insertion site (PMA) and a more basal site (PMB) overlying the anterior papillary muscle. However, local shortening and wall thickening were depressed in both locations relative to anterior free wall sites (FWA, FWB) studied in five additional dogs. A distinct structural border was observed at the junction between the myocardial wall and anterior papillary muscle, which may preclude the use of homogeneous strain in that region. Data from within the anterior papillary muscle indicated that uniaxial measurements in the papillary muscle are extremely sensitive to the orientation of the measurement axis, possibly explaining the variety of papillary muscle shortening patterns reported by previous investigators.

Animals↗
PubMed2003

Obstructive intramural coronary amyloidosis and papillary muscle rupture.

Mitral papillary muscle rupture is usually caused by ischaemia as a complication of myocardial infarction. In a 76 year old patient with no significant disease or major cardiovascular risk factors, papillary muscle rupture was caused by obstructive intramural coronary amyloidosis, an unusual cause.

Aged↗
PubMedDate not supplied

Echocardiographic recognition of partial papillary muscle rupture.

Acute papillary muscle rupture complicating acute myocardial infarction represents a potentially lethal complication of acute myocardial infarction. Survival depends on prompt recognition and institution of immediate medical and surgical therapy. We present two cases of partial papillary muscle rupture in the setting of acute myocardial infarction and describe the echocardiographic features that may allow early recognition of this condition before complete rupture.

Aged↗
PubMed1987

Ca2+-sensitizing effect of BM 14.478 on skinned cardiac muscle fibres of guinea-pig papillary muscle.

A concentration-dependent increase in force development was obtained with BM 14.478 (10(-9)-5 X 10(-4) M) in skinned fibres of guinea-pig papillary muscles. Guinea-pig papillary muscles are standard preparations for evaluating inotropic effects and they were also used in the present case for evaluating the positive inotropic effect of BM 14.478. We therefore conclude that a marked calcium-sensitizing effect contributes to the positive inotropic effect obtained with BM 14.478 even at very low concentrations.

Animals↗
PubMed1993

[Synchronous investigation of the effects of vesnarinone on action potential and muscle tension of isolated rabbit's ventricular papillary muscle].

This study adopted intracellular microelectrode technique to observe synchronously the effects of vesnarinone on intracellular potential and muscle tension of isolated rabbit's ventricular papillary muscle and analysed their variation. The results showed that vesnarinone increased the Tmax (P < 0.01) and Tdv/dt (P < 0.01) of isolated rabbit's ventricular papillary muscle and prolonged the action potential time (APT) without obvious effects on RP, APA and Vmax of papillary muscle. The relationship between them (r = 0.994, P < 0.05), suggesting that their changes be of the same mechanism and probably relate to the increase of inward calcium current.

Action Potentials↗
PubMed1995

The effect of cycle frequency on the power output of rat papillary muscles in vitro.

Papillary muscles were isolated from the right ventricles of rats and the length for maximum active force generation (Lmax) was determined isometrically. The work loop technique was used to derive the length for maximum work production (Lopt) at the cycle frequency, strain amplitude and stimulation phase shift found to be optimal for power output. Lopt was typically 7% shorter than Lmax and within the physiological length range (87.5% Lmax to Lmax). Net work and power output were measured during sinusoidal strain cycles around Lopt, over the cycle frequency range 1-9 Hz, strain amplitude and phase shift being optimised for work and power at each frequency. Experiments were performed at 37 degrees C. Distinct optima were found in both the work-frequency and the power-frequency relationships. The optimum cycle frequency for net work production was lower than the frequency for maximum power output. The mean maximum power output at 37 degrees C was 8.62 +/- 0.50 W kg-1 (mean +/- S.E.M., N = 9) and was achieved at a cycle frequency of approximately 6 Hz, close to the estimated resting heart rate of 5.8 Hz for the rats used (mean mass 223 +/- 25 g). The cycle frequency, strain amplitude and stimulation phase shift found to be optimal for power output produced an in vitro contraction closely simulating the basal in vivo contraction.

Animals↗
PubMed1975

The time course of the effects of beta- and alpha-adrenoceptor stimulation by isoprenaline and methoxamine on the contractile force and cAMP level of the isolated rabbit papillary muscle.

In the isolated papillary muscle of the rabbit the time course of the effects of selective beta- and alpha-adrenoceptor stimulation by isoprenaline and methoxamine, respectively, on the contractile force and on the level of 3',5'-cyclic AMP (cAMP) was determined. 1. Isoprenaline (3 times 10(-7) M) increased significantly the content of cAMP at 15 sec and elevated it to the maximal level-about twice the control value-at 30 sec after its administration, while the developed tension of the papillary muscle was also increased significantly at 15 sec and reached gradually its maximum at 90 sec. 2. Compared with isoprenaline methoxamine (10(-4) M) increased the developed tension very slowly: the maximal response was reached after 20 min. The level of cAMP, on the other hand, was changed neither before nor during the induction of the positive inotropic effect of methoxamine. 3. The phosphodiesterase inhibitor papaverine (10(-5) M) inhibited the PDE activity of the papillary muscle by about 40% after an incubation of 1 hr, and increased the level of cAMP significantly. The effects of isoprenaline on the contractile forced and on the level of cAMP were considerably enhanced by papaverine: the content of cAMP was increased by isoprenaline (3 times 10(-7) M) to about 3 times the control value and also its positive inotropic effect was significantly greater than in controls without papaverine. On the other hand, the positive inotropic effect of methoxamine (10(-4) M) was not affected by papaverine (10(-5) M). Furthermore, in the papillary muscle treated with papaverine the level of cAMP was significantly reduced by methoxamine: the papaverine-induced increase of cAMP was abolished by methoxamine. 4. The present results are compatible with the hypothesis that cAMP is involved as a mediator in the positive inotropic effect induced by beta-adrenoceptor stimulation, and indicate further that the stimulation of alpha-adrenoceptors evokes its positive inotropic effec through a mechanism other than that elicited by beta-adrenoceptor stimulation, i.e., independent of cAMP.

Animals↗
PubMed1984

Influence of chronic vagotomy on inotropic responses of isolated cat heart papillary muscle.

Isolated cat heart papillary muscle bathed at 37 degrees C, electrically driven at the rate of 30 per min, subjected to high voltage stimulation, or the addition of tyramine 1.7 microM, or high doses of acetylcholine (0.55mM) induced a positive inotropic effect revealed by an increase of peak tension developed (PTD). Papillary muscles obtained from cats after 7 to 8 days chronic bilateral cervical vagotomy showed a basic PTD (mg) similar to papillary muscles from non vagotomized control or sham operated cats. The inotropic effect of both tyramine and high voltage stimulation was absent in these animals as compared to controls or sham operated cats. Nevertheless, the inotropic effect of high acetylcholine concentration was still present and was of similar magnitude than in muscles of sham operated cats. The results suggest the existence of a neural cholinergic mechanism that is suppressed by chronic vagotomy which might be necessary for the synthesis, storage and/or release of adrenergic neurotransmitter in ventricular myocardium. It is suggested also, that suppression of general trophic function of vagus nerve might interfere with inotropic actions mediated by norepinephrine release.

Acetylcholine↗