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PubMed1976

Effects of prostaglandin E1 on the positive inotropic actions of noradrenaline, nerve stimulation and calcium in the isolated blood-perfused papillary muscle of the dog.

The effects of PGE1 on the dog heart were studied using the blood-perfused sinus node and papillary muscle preparations isolated separately from the same animal. PGE1 administered into the papillary muscle artery as bolus injections in doses of 1-1000 ng caused a dose-dependent increase of the developed tension and dT/dt of the papillary muscle. The effect was not inhibited by the beta-adrenoceptor blocking agent pindolol. PGE1 injected into the sinus node artery in doses of 3-300 ng did not change the rate of contraction of the sinus node preparation. PGE1 in the blood concentrations of 4.4 X 10(-9) to 1.7 X 10(-7) M enhanced the positive inotropic responses to noradrenalin and field stimulation as well as to calcium. The influence of PGE1 on the positive inotropic effect of perivascular nerve stimulation was not consistent: the action of perivascular nerve stimulation was enhanced by PGE1 in the majority of preparations but was reduced in one third of preparations. PGE1 in the same blood concentrations as used in the papillary muscle significantly depressed the positive chronotropic responses to noradrenaline and dopamine. The present results indicate that PGE1 induces multiple actions on the dog heart. Its predominant effect on the ventricular myocardium appears to be enhancement of the adrenergic stimuli probably via the facilitation of calcium movement through the myocardial cell membrane. In addition, PGE1 may decrease the sensitivity of beta-adrenoceptors to adrenergic stimuli in the sinus node.

Animals↗
PubMed1989

Effects of l-carnitine on membrane potential derangements induced by palmitoylcarnitine and anoxia in isolated superfused guinea-pig papillary muscle.

We examined in isolated superfused guinea-pig papillary muscle whether palmitoylcarnitine caused electrophysiological derangements similar to those caused by anoxia, and whether l-carnitine was similarly effective in improving membrane potential characteristics in both cases. Superfusion with Krebs-Henseleit solution containing 3 x 10(-4) M palmitoylcarnitine for 30 min caused gradual reduction of resting membrane potential and amplitude of action potential, and marked shortenings of the duration of action potential and absolute refractory period. On the other hand, aeration with 95%N2-5%CO2 for 30 min caused the same electrophysiological changes as those caused by palmitoylcarnitine. In both deteriorated preparations with palmitoylcarnitine superfusion and with 95%N2-5%CO2 aeration, l-carnitine (3 x 10(-3) M) prevented the papillary muscle from these derangements and restored the membrane potential at 10(-2) and 3 x 10(-2) M. It is concluded from these results that acylcarnitines such as palmitoylcarnitine, the accumulation of which has been thought to inhibit oxidative phosphorylation in ischemic heart, induce electrophysiological derangements quite similar to those found under anoxia, and that the application of l-carnitine is an effective solution to improve the electrophysiological derangements.

Animals↗
PubMed1988

[Anterolateral papillary muscle motion before and after septal myotomy in hypertrophic obstructive cardiomyopathy].

The left ventricular outflow pressure gradient in hypertrophic cardiomyopathy results from systolic anterior motion of the mitral valve (SAM). This abnormal orientation of the valve was previously proposed to be caused by inappropriately hypertrophied papillary muscles which protrude to the interventricular septum (IVS). Septal myotomy can alter the orientation of the papillary muscles and resolve the pressure gradient, without myectomy. Recently, we have experienced two instructive cases to prove our previously advocated hypothesis. Case 1: This 54-year-old man complained of effort dyspnea, and his echocardiogram disclosed marked SAM, and a thickened IVS (28 mm) and left ventricular posterior wall (16 mm). The intraventricular pressure gradient was 134 mmHg, and there was mitral regurgitation of grade 2/4. A longitudinal incision via the aorta on the anterior portion of the IVS, toward the base of the anterolateral papillary muscle, resolved the pressure gradient and mitral regurgitation, and two-dimensional echocardiography demonstrated that the SAM resolved at the lateral aspect of the valve, but it remained on the medial side. Case 2: This 57-year-old man complained of dyspnea during effort. He had marked SAM. The intraventricular pressure gradient was 65 mmHg, and there was grade 3/4 mitral regurgitation. Longitudinal incisions on the anterior, medial and posterior parts of the IVS abolished the SAM and reduced mitral regurgitation to grade 1/4. In both cases, during systole, the anterolateral papillary muscle protruded into the left ventricular ontflow tract, causing SAM. After surgery, the direction of the muscle axis moved toward the mitral orifice during systole, resulting in alleviation of SAM on the same side of the location of septotomy. This further confirmed our concept that disoriented papillary muscles play essential roles in causing SAM. If the Venturi forces previously stressed by other investigators cause SAM, the latter should resolve on both the medial and lateral aspects, even by septotomy. Thus, the Venturi theory seems untenable.

Cardiomyopathy, Hypertrophic↗
PubMed1990

Effects of ketamine on the cardiac papillary muscle of normal hamsters and those with cardiomyopathy.

The effect of ketamine (10(-5) and 10(-4) M) on the intrinsic contractility of left ventricular papillary muscle from normal hamsters and those with cardiomyopathy (BIO 82.62, 6-month old) was investigated. At these concentrations, ketamine induced a positive inotropic effect on normal papillary muscle, as shown by an increase in maximum unloaded shortening velocity (+19 +/- 4 and +34 +/- 5%, P less than 0.05), active isometric force (+32 +/- 8 and +57 +/- 11%, P less than 0.05), and peak power output (+40 +/- 8 and +80 +/- 16%, P less than 0.05), and induced a slight decrease in sarcoplasmic reticulum function. Ketamine had no effect on the curvature of the total force-velocity curve, suggesting that it does not modify myothermal economy. Contractility of papillary muscle from hamsters with cardiomyopathy was less than that of controls, as shown by the decrease in isometric active force (-41%, P less than 0.02), peak power output (-33%, P less than 0.05), and sarcoplasmic reticulum function. The positive inotropic effect of ketamine on papillary muscle from hamsters with cardiomyopathy was less marked than in controls and almost suppressed in some cases: only the maximum unloaded shortening velocity was significantly increased with 10(-5) M ketamine (+7 +/- 6%, P less than 0.05), whereas no significant changes were observed in active isometric force (+14 +/- 8 and +13 +/- 11%; nonsignificant [NS]) and peak power output (+9 +/- 5 and +13 +/- 8%; NS) with ketamine (10(-5) and 10(-4) M, respectively).(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed2001

Comparison of the efficiency of rat papillary muscles during afterloaded isotonic contractions and contractions with sinusoidal length changes.

The results of previous studies suggest that the maximum mechanical efficiency of rat papillary muscles is lower during a contraction protocol involving sinusoidal length changes than during one involving afterloaded isotonic contractions. The aim of this study was to compare directly the efficiency of isolated rat papillary muscle preparations in isotonic and sinusoidal contraction protocols. Experiments were performed in vitro (27 degrees C) using left ventricular papillary muscles from adult rats. Each preparation performed three contraction protocols: (i) low-frequency afterloaded isotonic contractions (10 twitches at 0.2 Hz), (ii) sinusoidal length change contractions with phasic stimulation (40 twitches at 2 Hz) and (iii) high-frequency afterloaded isotonic contractions (40 twitches at 2 Hz). The first two protocols resembled those used in previous studies and the third combined the characteristics of the first two. The parameters for each protocol were adjusted to those that gave maximum efficiency. For the afterloaded isotonic protocols, the afterload was set to 0.3 of the maximum developed force. The sinusoidal length change protocol incorporated a cycle amplitude of +/-5% resting length and a stimulus phase of -10 degrees. Measurements of force output, muscle length change and muscle temperature change were used to calculate the work and heat produced during and after each protocol. Net mechanical efficiency was defined as the proportion of the energy (enthalpy) liberated by the muscle that appeared as work. The efficiency in the low-frequency, isotonic contraction protocol was 21.1+/-1.4% (mean +/- s.e.m., N=6) and that in the sinusoidal protocol was 13.2+/-0.7%, consistent with previous results. This difference was not due to the higher frequency or greater number of twitches because efficiency in the high-frequency, isotonic protocol was 21.5+/-1.0%. Although these results apparently confirm that efficiency is protocol-dependent, additional experiments designed to measure work output unambiguously indicated that the method used to calculate work output in isotonic contractions overestimated actual work output. When net work output, which excludes work done by parallel elastic elements, rather than total work output was used to determine efficiency in afterloaded isotonic contractions, efficiency was similar to that for sinusoidal contractions. The maximum net mechanical efficiency of rat papillary muscles performing afterloaded isotonic or sinusoidal length change contractions was between 10 and 15%.

Animals↗
PubMed1992

Acute and subacute effects of doxorubicin on postextrasystolic potentiation in guinea pig papillary muscles.

To investigate the effects of doxorubicin on postextrasystolic potentiation (PESP), isolated guinea pig papillary muscles were field-stimulated and the resulting isometric force was recorded. Postextrasystolic contraction was evoked following trains of 37 regular stimulations. The effects of acute doses of doxorubicin (0.2 mM) on regular contractions and postextrasystolic contractions were examined for 2 hr. The effects of subacute doses of doxorubicin (total dose 5 mg/kg intraperitoneally) on the relationship between %PESP (postextrasystolic/regular contraction) and both the extra-stimulus coupling interval and the postextrasystolic interval were examined. Acute administration of doxorubicin decreased the amplitude of postextrasystolic contractions more than that of regular contractions. Thus, %PESP in the doxorubicin-treated group decreased significantly over time. There was no similar decrease in the control papillary muscles. Both the extra-stimulus coupling interval and the postextrasystolic interval had less of an effect on %PESP in doxorubicin-treated animals than in control animals. Since PESP depends upon sarcoplasmic reticulum activity, our results indicate that acute and subacute exposure to doxorubicin impairs the activity of the sarcoplasmic reticulum of guinea pig papillary muscles.

Animals↗
PubMed2002

Surgical management of acute mitral valve regurgitation due to post-infarction papillary muscle rupture.

BACKGROUND AND AIM OF THE STUDY: Acute myocardial infarction associated with mitral papillary muscle rupture and cardiogenic shock carries a high mortality. Data relating to early and late survival after emergency mitral valve surgery and concomitant complete coronary artery revascularization in this patient population were analyzed. METHODS: Between January 1988 and December 1998, 21 consecutive patients (mean age 62+/-9.7 years) underwent emergency coronary and concomitant mitral valve surgery for acute myocardial infarction and mitral papillary muscle rupture associated with cardiogenic shock. Mitral valve replacement was performed in 19 patients (90%), and mitral valve repair in two (10%). An average of 2.2 distal anastomoses per patient was performed. Revascularization was complete in 19 patients (90%). Preoperatively, intra-aortic balloon pumping was used in 11 patients (52%), and two (10%) had salvage surgery when arriving at the operating room under cardiopulmonary resuscitation. Early and late follow up was complete; mean follow up was 5+/-3 years (range: 16 months to 12 years). RESULTS: Thirty-day mortality was 19% (4/21), with two cardiac-related early deaths (10%). Early morbidity included perioperative stroke in 6% (1/17), myocardial infarction in 6% (1/17), and need for hemodialysis in 18% (3/17). There were three late deaths; one was cardiac-related. Actuarial survival at one, five and 10 years was 81, 68 and 56%, respectively. All survivors were in NYHA class I or II. CONCLUSION: Emergency surgery for acute post-infarction mitral papillary muscle rupture is justified, even as a salvage procedure. Concomitant mitral valve surgery and complete coronary artery revascularization achieve acceptable survival rates and satisfactory functional results.

Acute Disease↗
PubMed1989

Effects of barium on spontaneous mechanical and electrical oscillations in rat papillary muscle.

In experiments on isolated rat papillary muscles the effects of Ba2+ (0.2-1 mM) on spontaneous resting tension oscillations (RTO) and membrane potential oscillations (MPO) were investigated. In normal Tyrode's solution the muscles were not spontaneously active, however, the addition of barium (1 mM) after a delay of 3-5 min induced the spontaneous excitations of the preparations. During this time period the amplitudes of RTO and MPO of the quiescent muscle increased gradually, and just before the first spontaneous beat their values were many fold above control levels. It was noted that just before the first spontaneous excitation the RTO became very synchronous and resembled the sinusoidal oscillations. By means of a special transducers the displacements of two adjacent points (distance, 1.0 mm) on a muscle surface were continuously recorded at the resting state. The correlation coefficient between these displacement signals was shown to increase from zero (before Ba2+ addition) to 0.5-0.7 (just before the first spontaneous beat). It was suggested that the enhancement of the RTO and MPO is a result of the synchronization of subthreshold electrical and mechanical activities of all muscle cells after the addition of barium.

Animals↗
PubMed2005

Resting metabolism of mouse papillary muscle.

The aims of this study were to measure the resting metabolic rate of isolated mouse papillary muscles and to determine whether diffusive O2 supply is adequate to support the resting metabolism. Resting metabolism of left ventricular papillary muscles was measured in vitro (27 degrees C) using the myothermic technique. The rate of resting metabolism declined exponentially with time towards a steady value, with a time constant of 18+/-2 min (n=13). There was no alteration in isometric force output during this time. The magnitude of the resting metabolism, which depended inversely on muscle mass, more than doubled following a change in substrate from glucose to pyruvate and was increased 2.5-fold when the osmolarity of the bathing solution was increased by addition of 300 mM sucrose. Addition of 30 mM 2, 3-butanedione monoxime affected neither the time course of the decline in metabolic rate nor the eventual steady value. Analysis of the diffusive oxygen supply to the isolated preparation indicated that small papillary muscles (mass <1 mg), which have a very high resting metabolic rate early in an experiment, are unlikely to be adequately oxygenated.

Animals↗
PubMed1979

Augmented aftercontractions in papillary muscles from rats with cardiac hypertrophy.

Paired-pulse stimulation induced larger aftercontractions in papillary muscles from spontaneously hypertensive rats (SHR) than from normotensive Wistar-Kyoto rats (WKY). To determine whether aftercontraction exaggeration is a general characteristic of hypertrophied cardiac muscle, three models were examined: SHRs, deoxycorticosterone acetate (DOCA)-treated rats, and aorta-constricted rats. Responses of pipillary muscles from hypertrophied hearts tested under conditions conducive to aftercontraction generation were compared to pipillary muscles from WKY or sham-treated controls, respectively. Field-stimulated papillary muscles mounted in an oxygenated temperature-controlled physiologic salt solution were exposed to calcium concentrations of 2.5 and 5.0 mM, and temperatures of 27 degrees C and 17 degrees C. Although testing conditions influenced the contractile responses to single stimuli, there was no difference in active tension, time to peak tension, or one-half relaxation time between the three experimental groups and their respective controls. Paired-pulse stimulation induced aftercontractions that were enhanced in high-calcium and low-temperature solutions. Under these conditions, papillary muscles from hypertrophied hearts developed larger aftercontractions than did their respective controls.

Animals↗
PubMed1978

The pathogenesis of papillary muscle rupture complicating myocardial infarction: hemorrhage accompanying contraction band necrosis.

Although frank rupture of the papillary muscle complicating myocardial infarction is gaining widespread interest as its incidence continues to rise, the mechanism of rupture remains unclear. Of all patients who died with myocardial infarction and who came to autopsy at this institution over the past 21 years, 13 were found to have papillary muscle rupture. Twelve of these 13 had severe contraction band necrosis with interstitial hemorrhage in the areas surrounding the site of rupture. The hemorrhages infiltrated the interstitium and appeared to have dissected both longitudinally and transversely through the myocardium. In contrast, those patients with papillary muscle infarction without rupture were found to have coagulation necrosis. These findings suggest that the interstitial hemorrhages occurring with contraction band necrosis may act as dissecting masses of blood, thereby causing the rupture.

Adult↗
PubMed2006

Epithelial cyst of the cardiac papillary muscle: case report and review of the literature.

BACKGROUND: Reports of endodermal heterotopia (previously known as inclusion cysts) in cardiac atria are rare and there is only a single previous case report of endodermal heterotopia in a cardiac papillary muscle. AIM AND METHODS: A cyst in a cardiac papillary muscle was identified during the autopsy of an 87-year-old man who had died from an unrelated myocardial infarction. The cyst was examined histologically and mucin staining and immunostaining were carried out. RESULTS: We report a unilocular cyst in a cardiac papillary muscle, which is lined by low cuboidal, pseudostratified and occasionally ciliated respiratory-type epithelium, surrounded by a layer of smooth muscle. The immunohistochemical features (MNF116+, cytokeratin (CK)7+, CK8+, CK18+, CK19+, epithelial membrane antigen positive, scattered cells positive for neuroendocrine markers) suggest that this is an endodermal heterotopia. Immunostaining of positive thyroid transcription factor-1 provides evidence for bronchogenic differentiation. DISCUSSION: The differential diagnoses of cystic structures in cardiac papillary muscle and the origin and importance of endodermal heterotopias are discussed.

Aged, 80 and over↗
PubMed2000

Effects of aging on the work output and efficiency of rat papillary muscle.

OBJECTIVES: This study aimed to investigate the effect of aging on the work output and efficiency of rat papillary muscle. METHODS: The mechanical and energetic properties of left ventricular papillary muscle preparations isolated from 6-, 15-, and 27- to 32-month-old Sprague-Dawley rats were measured in myothermic experiments at 27 degrees C at a stimulus frequency of 0.167 Hz. RESULTS: We found that the basal metabolism measured in quiescent papillary muscles was significantly reduced in the 27- to 32-month-old group (4.9 mWg(-1) compared to 7.7 and 7.0 mWg(-1) in the 6- and 15-month groups). In isotonic experiments, the work output (at a range of afterloads) was significantly depressed for the 27- to 32-month group being only 52% of the work output of the 6-month group. This outcome was due to a decrease in both the extent of muscle shortening only, 66% of 6- and 15-month data, and in the maximum force developed. The reduced work was accompanied by a parallel decrease in energy consumption (enthalpy) and hence, the net mechanical efficiency (work/active enthalpyx100%) was not altered. A force-length- area (FLA) analysis was applied to the isotonic data and an energy: FLA regression line was obtained for each preparation. We found that there were no significant differences in either the intercept or slope of the energy: FLA relation with age. Contractile efficiency (39+/-3%) in the 27- to 32-month group was not significantly different to that found in the 6-month (43+/-4%) or 15-month (40+/-3% group). CONCLUSION: There are no changes in the mechanical performance or efficiency of cardiac muscle from young (6-month-old) or adult (15-month-old) rats but in the aged and senescent rats (27-32-month-old) there is a pronounced decline in stress development and shortening ability leading to a fall in work output. Mechanical and contractile efficiency however remain unchanged in old age and the data resembles that obtained in pressure overload hypertrophy.

Aging↗
PubMed1981

[Two-dimensional echocardiographic observation of ruptured chordae tendineae of the mitral valve: Its localization and uneven development of papillary muscles (author's transl)].

Twenty-three cases with ruptured chordae tendineae (RCT) of the mitral valve and 9 normal control cases were studied by two-dimensional echocardiography. Mitral valve replacement (MVR) was performed in 13 of the 23 cases. The preoperative diagnosis of RCT was proven accurately at operation in all except 2 cases with bacterial endocarditis. Whether RCT occurred in the antero-lateral or in the postero-medial commissural side could be determined perfectly. RCT was observed in the postero-medial side more often than in the anterolateral side, i.e., postero-medial side in 16 (9 operated) and antero-lateral side in 5 (2 operated). This tendency has also been noted in other Japanese reports regardless of the cause of RCT. In the short axis view at the level of the papillary muscles, the area of the posterior papillary muscles was smaller than the area of the anterior papillary muscles in the RCT cases. It is speculated that the smaller size of the posterior papillary muscles has a certain relation with the more frequent RCT in the postero-medial commissural side.

Adolescent↗
PubMed1979

[False aneurysm associated with mitral insufficiency due to rupture of the heart at the point of insertion of the anterior papillary muscle. A successfully operated case].

Although rupture of a mitral papillary muscle during myocardial infarction is well known, and post-infarction transmural ruptures causing false aneurysms occasionally reported, the association of rupture of the anterior papillary muscle and a underlying transmural parietal rupture giving rise to a false aneurysm is quite exceptional, and, to the best of our knowledge, has not previously been reported. Despite the serious nature of the disease, surgical cure of the aneurysm with mitral valve replacement was successful, due to the limitation of the anatomical disruption by early pericardial symphysis.

Aneurysm↗
PubMed1989

The effect of acoustic cavitation on the contraction force and membrane potential of rat papillary muscle.

In experiments on isolated rat papillary muscles an acoustic cavitation induced by continuous wave focused ultrasound (543 kHz with intensity up to 3 W/cm2) was found to result in reversible membrane depolarization by 54.0 +/- 1.4 mV (n = 5), loss of excitability and rise in resting tension up to 53.1 +/- 4.3% (n = 15) of contractile response in the control. It was supposed that the rapid recovery of excitability (69.3 +/- 10.3 s, n = 15) might be a result of Ca2+ pump activation and/or alterations of intercellular coupling when cavitation ends.

Animals↗
PubMed1992

Transesophageal echocardiographic findings in partial and complete papillary muscle rupture complicating acute myocardial infarction.

Papillary muscle rupture occurred in two patients with recent inferior myocardial infarction. In one case with partial rupture transesophageal echocardiography in the standard four-chamber view did not visualize the rupture and in the second case with complete rupture it provided incomplete diagnostic information. A not previously described transgastric longitudinal scanning of the left ventricle provided complete delineation of the lesion and it was of great value in the diagnosis and management of this potentially lethal complication. Both patients were operated upon and had a favourable outcome.

Echocardiography↗