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PubMed1981

Two-dimensional echocardiographic diagnosis of papillary muscle rupture.

A 69-year-old man developed a rupture of the papillary muscle on the fifth day of acute posterior myocardial infarction. The two-dimensional echocardiographic features of ruptured papillary muscle included (1) mobile mass of echos attached to normal chordae tendineae in the left ventricle, (2) absent tip of papillary muscle, and (3) mitral valve prolapse. Noninvasive, two-dimensional echocardiography can reveal correct diagnosis of ruptured papillary muscle suspected clinically.

Acute Disease↗
PubMed1983

Guinea-pig and rabbit papillary muscles differ in their response to histamine.

Guinea-pig and rabbit papillary muscles differ in their response to histamine. 1. Basal developed force (BDF) and maximal developed force (MDF) following isoproterenol and histamine were determined in rabbit and guinea-pig papillary muscles under a variety of experimental conditions. Hypothermia and an increase in the calcium concentration increased the BDF in both tissues. 2. In the guinea-pig MDF increased to a similar extent following both agonists. In the rabbit the MDF response to histamine was much less than the response to isoproterenol. 3. In the guinea-pig papillary muscle, stimulation of both beta- and H2-receptors produces an increase in cyclic AMP. The rabbit papillary muscle contains H1-receptors, stimulation of which has no effect on cyclic AMP. The reduced MDF effect of histamine compared to isoproterenol in the rabbit may be due to the differing biochemical events following beta- or H1-stimulation.

Animals↗
PubMed1982

M mode and cross-sectional echocardiographic recognition of fibrosis and calcification of the mitral valve chordae and left ventricular papillary muscles.

The echocardiographic appearance of fibrotic thickening and calcification of mitral valve chordae tendineae and left ventricular papillary muscles in 17 patients is described. Pathologic proof of excessive fibrosis or calcification was obtained in five patients. In a sixth patient, calcium was demonstrated on angiography to extend from the chordae into papillary muscle. The characteristic feature of chordal and papillary muscle fibrosis and calcification is the presence of highly echogenic densities best visualized within the left ventricle at a level below the mitral valve leaflets. The more inferior location of these densities, within the body of the left ventricle, enables them to be easily differentiated from densities indicating fibrosis and calcification of the mitral valve anulus. The pattern of chordal and papillary muscle fibrosis and calcification was frequently associated with mitral anular calcification, aortic valve fibrosis or calcification and left atrial enlargement. One patient had rheumatic mitral valve disease. Many patients had mitral regurgitation and most had a history, physical examination and radiologic findings compatible with congestive heart failure. Although the origin and importance of the chordal and papillary muscle changes reported are not known, their frequent association with mitral regurgitation and with congestive heart failure suggests possible interrelations.

Aged↗
PubMed1984

Unidirectional block between Purkinje and ventricular layers of papillary muscles.

Previous work has characterized the Purkinje-ventricular junction (PVJ) of papillary muscles as a region of low safety factor with some delay between P and V activation. We have previously shown that the P strand action potential activates a layer of P cells over most of the papillary muscle surface, but activation of the underlying V cells occurs only at specific junctional sites, generally near the base of the muscle. Our present results from both dog and rabbit left papillary muscles show that the junctional regions for propagation from the V layer up into the P layer include not only these specific P-to-V sites but also other sites located more toward the apex of the muscle. These results show that the papillary muscles have regions of potential unidirectional block, although the manifestation of unidirectional block at these sites requires the premature excitation of the ventricular layer.

Action Potentials↗
PubMed1982

Mechanical restitution of the rat papillary muscle.

The experiments were performed on isometrically contracting rat papillary muscles paced at 1.0 Hz and at a temperature of 37 degrees C. The contractile response of a test contraction continuously rose when the duration of the preceding stimulus interval was gradually increased from 0.2 s. A maximum value was seen at intervals of 60--120 s. This phenomenon was called mechanical restitution of the papillary muscle. The insertion of a priming beat before the test contraction in order to increase the amount of contractile calcium elevated the mechanical restitution curve but it did not change the maximum contractile force seen after 60--120 s intervals. Lowering the extracellular calcium concentration from 2.0 mM to 1.0 mM, however, depressed this maximum contractile force to about 50%. The mechanical restitution is thought to reflect inflow of activator calcium to a cellular store, from which it is later released in response to the action potential. By using two test contractions a simple method is described to estimate the recirculating fraction of activator calcium between beats in this preparation. In 11 preparations the recirculating fraction of activator calcium was 0.72 +/- 0.03 (mean +/- SE). The results are consistent with the view that the same model of metabolism of activator calcium as previously proposed for rabbit papillary muscles is also applicable to the rat heart.

Action Potentials↗
PubMed1980

Papillary muscle necrosis in a neonatal autopsy population: incidence and associated clinical manifestations.

Papillary muscle necrosis was found in 24 of 84 neonates without congenital heart disease who died and were autopsied during a 17-month study period. The lesion was most prevalent in infants greater than or equal to 3,000 gm birth weight (59%), but papillary muscle necrosis was also noted in 25% of the infants of medium birth weight (1,500 to 2,999 gm) and in 19% of the very low-birth-weight infants (less than 1,500 gm). Papillary muscle necrosis in the highest birth-weight group correlated with five-minute Apgar scores of 6 or less, meconium aspiration syndrome, seizures, congestive heart failure, increased cardiothoracic ratio (greater than or equal to 0.60), and ischemic changes on electrocardiogram. In the medium- and very low-birth-weight groups, however, patients with papillary muscle necrosis could seldom be differentiated clinically from their birth-weight peers without the lesion, even in retrospect.

Autopsy↗
PubMedDate not supplied

Role of Na+/H+ exchange in the recovery of contractility during hypercapnia in cat papillary muscles.

Experiments were performed in cat papillary muscles contracting isometrically at a constant frequency (0.2 Hz) and temperature (29 degrees C). Contractility was evaluated by developed tension (T) and its first derivative (T). Hypercapnia was induced by switching the perfusate equilibrated with 5% CO2-95% O2 to a solution equilibrated with 12% CO2-88% O2. Composition of this second solution was either identical to the first one (pH0 6.90, experiments at variable pH0, vpH) or with a higher [NaHCO3] to keep pH0 constant at 7.4 during the hypercapnic period (experiments at constant pH0, cpH0). The increase in CO2 elicited a similar decrease in contractility at cpH0 and vpH0. Minimal mean +T values were 58.5 +/- 2.9% and 55.4 +/- 3.2% and occurred at 3.6 +/- 0.75 min and 4.5 +/- 1.52 min of hypercapnia, at cpH0 and vpH0 respectively. Contractility recovery after the initial fall, was significantly greater when hypercapnia occurred at cpH0. Return to normocapnia elicited an increase in contractility over control values (overshoot). When [Na+]e was decreased by 60%, hypercapnia produced a similar negative inotropic effect than at control [Na+]e but significantly diminished the degree of recovery at either cpH0 or vpH0. Hypercapnic acidosis at cpH0, in the presence of 5 x 10(-6)M ethylisopropylamiloride (EIPA), a specific inhibitor of Na+/H+ exchange, evoked a maximum negative inotropic effect significantly greater than in its absence and suppressed the recovery of contractility. In all cases the magnitude of the overshoot upon return to normocapnia paralleled the magnitude of contractility recovery during hypercapnia. The results suggest that the recovery of contractility during hypercapnic acidosis is entirely dependent upon the Na+/H+ exchanger.

Acidosis↗
PubMed1987

[Amplitude fluctuations in the contractile responses of small fragments of rat papillary muscle].

Contractile responses of small rat papillary muscle segments (length = 0.25 mm) superfused in a normal Tyrode's solution (t = 35 degrees C) and stimulated at a frequency of 0.16 Hz have been measured, using an original technique. The amplitude of contractile responses was found to fluctuate with the variation of 3.0 +/- 0.4 mu, though the contraction amplitude of the entire muscle remained constant from beat to beat. After the addition of caffeine (6 mM) the variation of contractile responses decreased up to 0.83--0.03 mu, demonstrating a crucial role of sarcoplasmic reticulum in the phenomenon. It is believed that contractility inhibition during calcium overload may be caused by the same reason.

Animals↗
PubMed1980

Effect of local anaesthetics (mesocain) on membrane properties of cat papillary muscle.

In 28 experiments on cat papillary muscles the effect of mesocain (generically related to lidocaine) was studied on transmembrane currents (rapid inward INa, slow inward Isi, outward Io), on the configuration and (dV/dt)max of the action potential, on the refractory period and on isometric tension. The experiments were performed using either voltage clamp method (double sucrose gap) or microelectrode technique. All three transmembrane currents are inhibited by mesocain in a dose-dependent manner. The effect becomes measurable at 10(-6) mol/1 on INa, at 10(-5) mol/1 on Isi and at 5 X 10(-5) mol/1 on Il. INa is blocked at 10(-3) mol/1 concentration. These changes correlate with the measured alterations of action potentials: i.e. a decreased (dV/dt) max and overshoot, lower voltage and shortening of the plateau phase, slower rate of late repolarizaion. The negative inotropic effect appeared with the same treshold concentration as Isi; at higher concentrations, however, this effect was relatively much greater. The recovery of excitability measured by the interval-dependence of (dV/dt) max was prolonged 5 times on the average by mesocain at 10(-4) mol/1 and the effective refractory period was delayed beyond complete repolarization. It is concluded that the main effect of mesocain also involves a delayed kinetics of recovery from inactivation of the Na carrying system.

Action Potentials↗
PubMed1995

[A case of mitral regurgitation due to partial papillary muscle rupture whose etiology was unknown].

The etiology of the papillary muscle rupture includes myocardial infarction, trauma, hypertension, myxomatous degeneration, endocarditis etc. We report a case of partial papillary muscle rupture whose etiology was unknown, in a 77-year-old woman. The preoperative catheterization and coronary angiography showed severe mitral regurgitation and no significant coronary stenosis. And we recognized the mass waving into the left atrium in systole with the echocardiogram. At surgery, we repaired the mitral valve by resecting quadrangular areas of the posterior leaflet including the attachment of the torn papillary muscle. Additionally a number 28 Carpentier-Edwards mitral annuloplasty ring was sewn in place. In pathologic specimen, there were focal fibrosis, necrotic muscle, lymphocytes, and no vegetation.

Aged↗
PubMed1989

Quantitative analysis of fiber disarray developing in papillary muscles unloaded after mitral valve replacement.

Muscle fiber disarray which developed in the papillary muscle released from its chordal attachment after mitral valve replacement (MVR) was analysed histometrically in 23 hearts. The degree of disarray, or how far the fiber arrangement deviated from an ideal condition in which the fibers are considered to be aligned in parallel, was evaluated in terms of the "disarray index". This index corresponds to the ratio of the minor to major axes of a regression ellipse which can be obtained histometrically by plotting the reciprocal of the number of muscle fibers intersected by a test line of equal length in every direction on a polar coordinate system. The index can vary continuously in a range from 0.00 for a completely parallel fiber alignment to 1.00 for a completely random distribution. The estimated index showed a gradual increase from 0.05 to 0.68 according to the postoperative survival period after MVR with a significant positive correlation (r = 0.793, p less than 0.01). The index was inversely correlated with the mean muscle fiber diameter (r = -0.433, p less than 0.05). These results indicate that the disarray which develops in the papillary muscle after MVR is a deformation of the normally parallel arrangement of fibers toward an isotropic texture under focal disruption of the normally longitudinally oriented tensile force.

Adult↗
PubMed1990

Decreased sensitivity of contraction to changes of intracellular pH in papillary muscle from diabetic rat hearts.

1. The relationship between intracellular pH (pHi) and contractile activity was investigated in papillary muscles isolated from right ventricle of normal and streptozotocin (STZ)-induced diabetic rats. pHi changes induced by 20 mM-NH4Cl were recorded with H(+)-sensitive microelectrodes. 2. An increase in pHi of approximately 0.20 pH units on exposure to NH4Cl led to an increase of the maximum developed tension, which was 707.8 +/- 57.5% (mean +/- S.E. of mean, n = 10) of control in normal muscles and 271 +/- 16.3% (n = 10) in diabetic muscles. On the other hand, acidosis induced by NH4Cl withdrawal was associated with a fall in developed tension to 48.2 +/- 6.7% of control in diabetic muscles, as compared to 79.2 +/- 8% in normal muscles. 3. The decrease in tension associated with acidosis was rapidly followed (in approximately 2 min) by a transient redevelopment of force, which peaked at 80.2 +/- 8.6% of control in the diabetic muscles as compared to 153.5 +/- 11.7% in normal papillary muscles. The peak of this secondary positive inotropy coincided in both groups of muscles with the maximum decrease of pHi, i.e. -0.40 +/- 0.02 and -0.28 +/- 0.04 pH units in diabetic and normal muscles, respectively. 4. Caffeine (10 mM), which had a marked positive inotropic effect in both groups of muscles, abolished the transient recovery of tension occurring after NH4Cl withdrawal. Ryanodine (2 microM) which had a marked negative inotropic effect on both normal and diabetic papillary muscles, also suppressed the transient recovery of tension. 5. The presence of amiloride (1 mM) during acidosis induced by NH4Cl withdrawal abolished the observed differences in developed tension, in particular the transient recovery of tension, between normal and diabetic muscles, as it abolished the differences in the amplitude of pHi decrease and in the time course of pHi recovery. 6. The presence of 2',4'-dichlorobenzamil amiloride (40 microM) significantly and similarly delayed and reduced the amplitude of transient recovery of tension in both normal and diabetic papillary muscles. 7. We conclude that STZ-induced diabetes induces a decrease in pHi sensitivity of contractile force. This may be the consequence of a change in sarcoplasmic reticulum (SR) composition and function, and may also indirectly result from changes in Na(+)-H+ exchange activity, particularly during intracellular acidosis.

Amiloride↗
PubMed2004

Electrophysiological effects of resveratrol on guinea pig papillary muscles.

The purpose of this study was to investigate the electrophysiological effects of resveratrol on guinea pig papillary muscles and the underlying mechanism. Action potentials were recorded by using intracellular microelectrode technique. The results obtained are as follows: (1) In normal papillary muscles, resveratrol (30, 60, and 120 micromol/L) shortened the duration of action potential (APD) in a concentration-dependent manner. (2) In partially depolarized papillary muscles, resveratrol (60 micromol/L ) not only shortened APD, but also decreased the amplitude of action potential (APA), overshoot (OS) and maximal rate of depolarization in phase 0 (Vmax). (3) Perfusion with Ca2+-free K-H solution, completely abolished the effects of resveratrol (60 micromol/L) on papillary muscles. (4) Application of potassium channel blocker tetraethylammonium chloride (TEA, 20 mmol/L) did not prevent the effect of resveratrol (60 micromol/L) on action potential. (5) Pretreatment with NG-nitro-L-arginine methyl ester (L-NAME, 1 mmol/L), a nitric oxide (NO) synthase inhibitor, failed to abolish the effect of resveratrol (60 micromol/L). All these results indicate that the electrophysiological effects of resveratrol on guinea pig papillary muscles are likely due to the reduction of calcium influx, which might not be mediated by NO.

Action Potentials↗
PubMed2001

Papillary muscles and tendinous cords of the right ventricle of the human heart: morphological characteristics.

A series of 79 normal human hearts was studied focusing on the morphological characteristics of the papillary muscles of the right ventricle and their tendinous cords (chordae tendineae). The number, incidence, length and shape of the anterior, septal and posterior papillary muscles were observed. The tendinous cords attached to each papillary muscle were counted at their origin. The papillary muscles and the tendinous cords were measured in situ and after the removal of the right atrioventricular valve (tricuspid valve). The anterior and posterior papillary muscles (apm, ppm) were present in 100% of the cases. The septal papillary muscle (spm) was absent in 21.5% of the hearts. The apm presented 1 head in 81% and 2 heads in 19%; it was 19.16 mm in length. The spm was one-headed in 41.7% and presented two heads in 16.5%; the presence of a 3 and 4 heads appeared in 12.7% and 7.6% respectively; the spm was 5.59 mm in length. The ppm had 1 head in 25.4%, 2 heads in 46.8%, 3 heads in 21.5% and 4 heads in 6.3% of the cases; it was 11.53 mm in length. Tendinous cords (TC) varied as follows: from 1 to 11 TC originated in the apm (mean 4.74); from 1 to 8 TC originated in the ppm (mean 2.67) and from 1 to 5 TC originated in the spm (mean 1.77).

Adolescent↗
PubMed1975

Papillary muscle shortening in the intact dog; a cinderadiographic study of tranquilized dogs in the upright position.

Shortening of the anterior papillary muscle of the left ventricle was demonstrated in six intact, tranquilized dogs. Two small metal markers that had been surgically implanted 3-50 months earlier were cineradiographically photographed during approximately ten sequential cardiac cycles in each of two orthogonal positions. Distances between markers were plotted for successive frames. The resulting curves were used to obtain maximum velocities of papillary muscle shortening and lengthening: 1.08 plus or minus 0.29 muscle lengths/sec and 1.39 plus or minus 0.48 muscle lengths/sec, respectively. From the two orthogonal planes, the average maximum spatial distance and the average minimum spatial distance between the markers were calculated. The mean percent shortening of 22.8 plus or minus 6.5% was surprisingly large: it approximated the distance from the foot to the peak of the ascending limb of the myocardial length-tension curve derived from isolated muscle studies. Mechanical studies on isolated papillary muscle have consistently shown reduced shortening with increasing loads. Since the in vivo dog papillary muscle has been reported to be under considerable tension during systole, there appears to be some contradiction between the degree of shortening found in the present study and the shortening observed in isolated papillary muscle studies.

Animals↗
PubMed1982

Experimental production of papillary muscle and mitral valve lesions by vagal manipulations in rabbits.

The present paper describes peculiar lesions in papillary muscles and mitral valves produced by vagal manipulations. In the 109 rabbits killed one week after clipping or crushing of their cervical vagi, papillary muscle and mitral valve lesions were found in 53 (48.6%) and 52 (47.7%) hearts respectively. The lesions were identified by visible deposits of colloidal carbon which had been injected intravenously during the first 3 postoperative days. The left ventricular free wall, interventricular septum and right ventricle were free of carbon deposits. The papillary muscles involved were characterized by swelling and increased stiffness which corresponded to degeneration of the myocardial cells and interstitial fibrosis on microscopic observation. Hydroxyproline content of the papillary muscles involved was 1.4 times more than that of normal hearts, while there was no significant difference in hydroxyproline content of either interventricular septum or left ventricular free wall between the manipulated and the normal preparations. Heart murmurs were heard in 23 animals studied. Phonocardiograms revealed mid to late systolic murmurs with or without midsystolic click. These results indicate that the vagus nerve plays an important role in the pathogenesis of some forms of papillary muscle and mitral valve lesions.

Animals↗
PubMed1989

Pimobendan increases calcium sensitivity of skinned human papillary muscle fibers.

The calcium sensitizing effects of the cardiotonic agent pimobendan on force production were investigated on chemically skinned human papillary muscle fibres. The papillary muscles were obtained from patients undergoing mitral valve replacement operations. Tension was produced by different free calcium concentrations and 100 mumol/l of pimobendan shifted the pCa-tension relationship significantly to the left. The effects of pimobendan were concentration dependent (10-300 mumol/l) but additionally also correlated with the state of left ventricular performance of the patients. Skinned papillary muscle fibres obtained from patients with reduced ventricular performance were more sensitive to calcium as well as pimobendan compared with fibres from patients with normal left ventricular performance. No differences in response to pimobendan were observed between fibres from NYHA II and NYHA III heart failure patients.

Calcium↗
PubMed1992

How lymph is drained away from the human papillary muscle: anatomical conditions.

The lymphatic and venous bed was evaluated in 42 human heart papillary muscles. The lymphatics form networks in the superficial and deep layers of the subendocardium and in the myocardium of the papillary muscles. In the apical area, the subendocardial lymphatics gradually merge with the fine myocardial, developing arcades at the origins of chordae tendineae. Thicker myocardial lymphatics leave the area passing along the connective tissue septa, often in close vicinity to the blood vessels. The injection method failed to reveal deep lymphatics in the connective tissue of chordae tendineae. Lymphovenous anastomoses were disclosed in the papillary muscle. The possible morphological pathways for lymphatic drainage of the papillary muscle are as follows: (1) the lymphatic bed subendocardial and myocardial, joining on the ventricular wall bed at the muscle base, and (2) lymphovenous anastomoses, passing along from the myocardial and subendocardial lymphatic bed into the ventricular wall veins and the sinus coronarius system, or into the thebesian veins and further directly into the heart ventricles.

Chordae Tendineae↗