Viewing rate and reproducibility of papillary muscle areas in foetal atrioventricular valves using spatio-temporal image correlation in the rendering mode in congenital heart disease.

OBJECTIVE: To assess the viewing rate and reproducibility of areas of the papillary muscles (PMs) of foetal atrioventricular valves using spatio-temporal image correlation (STIC) in the rendering mode in congenital heart disease (CHD). METHODS: We retrospectively reviewed 40 4D-STIC volume datasets from different foetal CHD cases at a gestational age of 18w6d­35w6d. The following papillary muscles (PMs) were assessed: antero-lateral (MPAL) and postero-medial (MPPM) to the mitral valve and antero-superior (MPAS), inferior (MPI) and septal (MPS) to the tricuspid valve. To assess the valve viewing rate, percentages (%) were used. The concordance correlation coefficient (CCC) was used to assess inter-observer reliability. RESULTS: Two independent observers concluded that a complete examination of the PMs was impossible in 11 cases, yielding a viewing rate of 72.5%. The complete examination of the PMs of the tricuspid and mitral valves was possible by both examiners in 33/40 (82.5%) and 32/40 (80.0%) cases, respectively. We observed moderate to good inter-observer reliability with CCCs of 0.95, 0.92, 0.97, 0.96 and 0.97 for MPS, MPI, MPAS, MPAL and MPPM, respectively. CONCLUSION: The viewing rate of PM areas in different CHDs using STIC in the rendering mode was moderate. The inter-observer reproducibility was moderate to good for all PM areas.

Septomarginal trabecula and anterior papillary muscle in primate hearts: developmental issues.

The septomarginal trabecula is present in all human hearts as well as in the hearts of other primates. It usually connects the interventricular septum with the anterior papillary muscle, although there are many variations in how this is achieved. The object of the analyses was to estimate the bilateral topography of the septomarginal trabecula and the anterior papillary muscle in the context of the ontogeny and phylogeny of primates. A total of 138 hearts were examined from number of different non-human primates. The presence of the septomarginal trabecula was confirmed in 94.9% of cases, although not in the hearts of Lemur varius. Four configurations could be distinguished by defining the location of the septomarginal trabecula and its relation to the anterior papillary muscle.For the hearts of the Strepsirrhini and the majority of Platyrrhini neither structure was related, whereas in all examined representatives of Homino idea they had fused and created morphologically varying forms. On the basis of these results,a concept was developed for the sequence of changes which the topography of the septomarginal trabecula and the anterior papillary muscle undergo during ontogeny and phylogeny.

Intracellular localization of Cthrc1 characterizes differentiated smooth muscle.

OBJECTIVE: We recently reported expression of collagen triple helix repeat containing-1 (Cthrc1) in injured arteries and proteolytic cleavage of Cthrc1 in smooth muscle cells in vitro. The present study characterizes Cthrc1 processing and determines its biological significance. METHODS AND RESULTS: Domain-specific antibodies localized full-length Cthrc1 in the cytoplasm of vascular, gastrointestinal, and uterine smooth muscle as well as in some neurons. Unlike smooth muscle alpha-actin, Cthrc1 was not expressed in the embryonic myocardium. Intracellular localization of full-length Cthrc1 was sharply reduced in dedifferentiated smooth muscle of the developing neointima despite the previously shown increase in mRNA levels with accompanying extracellular Cthrc1 immunoreactivity. Immunoblotting suggested an apparent covalent association of monomeric full-length Cthrc1 with a cytoplasmic protein present in differentiated smooth muscle. Plasmin was identified as a protease that cleaved a putative propeptide generating an N-terminally truncated form of Cthrc1 with increased inhibitory activity of procollagen synthesis. CONCLUSIONS: Our data show that the differentiated smooth muscle cell phenotype is associated with the intracellular localization of noncleaved Cthrc1 despite the presence of a signal peptide. On arterial injury, increased Cthrc1 expression with apparent extracellular localization of N-terminally truncated Cthrc1 occurs. Removal of the propeptide correlated with increased activity of the molecule.

Contractile and Ca2+-handling properties of the right ventricular papillary muscle in the late-gestation sheep fetus.

The force-generating capacity of cardiomyocytes rapidly changes during gestation and early postnatal life coinciding with a transition in cardiomyocyte nucleation in both mice and rats. Changes in nucleation, in turn, appear to coincide with important changes in the excitation-contraction coupling architecture. However, it is not clear whether similar changes are observed in other mammals in which this transition occurs prenatally, such as sheep. Using small (70-300 microM diameter) chemically skinned cardiomyocyte bundles from the right ventricular papillary muscle of sheep fetuses at 126-132 and 137-140 days (d) gestational age (GA), we aimed to examine whether changes in cardiomyocyte nucleation during late gestation coincided with developmental changes in excitation-contraction coupling parameters (e.g., Ca(2+) uptake, Ca(2+) release, and force development). All experiments were conducted at room temperature (23 +/- 1 degrees C). We found that the proportion of mononucleate cardiomyocytes decreased significantly with GA (126-132 d, 45.7 +/- 4.7%, n = 7; 137-140 d, 32.8 +/- 1.6%, n = 6; P < 0.05). When we then examined force development between the two groups, there was no significant difference in either the maximal Ca(2+)-activated force (6.73 +/- 1.54 mN/mm(2), n = 14 vs. 6.55 +/- 1.25 mN/mm(2), n = 7, respectively) or the Ca(2+) sensitivity of the contractile apparatus (pCa at 50% maximum Ca(2+)-activated force: 126-132 d, 6.17 +/- 0.06, n = 14; 137-140 d, 6.24 +/- 0.08, n = 7). However, sarcoplasmic reticulum (SR) Ca(2+) uptake rates (but not Ca(2+) release) increased with GA (P < 0.05). These data reveal that during late gestation in sheep when there is a major transition in cardiomyocyte nucleation, SR Ca(2+) uptake rates increase, which would influence total SR Ca(2+) content and force production.

Effects of long-term high-altitude hypoxia and troponin I phosphorylation on cardiac myofilament calcium responses in fetal and nonpregnant sheep.

OBJECTIVE: We studied the effects of long-term high-altitude hypoxia and protein kinase A (PKA) phosphorylation on calcium (Ca2+) responses of skinned cardiac papillary muscles from fetal and adult sheep. METHODS: Fetal and nonpregnant adult sheep were exposed to high-altitude (3820 m), long-term (approximately 110 days) hypoxia. Papillary muscles were isolated and mounted in well-oxygenated, temperature-controlled baths. After the papillary muscles were stimulated electrically to establish the diastolic tension that produced the maximum active contraction, the electrical stimulation was stopped, and the muscles were skinned with 1% vol/vol Triton-X-100. In protocol 1, the skinned muscles were exposed to activating solutions containing different calcium concentrations (pCa; from pCa 8.0 to pCa 4.0), which were prepared by varying the Ca-EGTA/EGTA ratio, and the steady-state tension was measured at each pCa. In protocol 2, the skinned muscles were contracted with activating solution containing a pCa of 5.0. After equilibration, the solution in some baths was changed to activating solution at the same pCa of 5.0 but also containing the catalytic subunit of PKA. The other baths were exchanged with activating solution at a pCa of 5.0 containing no PKA. We then measured the degree of tension reduction caused by PKA until tension reached a new steady state. RESULTS: In the long-term hypoxic fetal heart, the maximum tension response of right, but not left, ventricular skinned papillary muscle to Ca2+ was significantly less than that in control muscles. In the long-term hypoxic adult heart, the left ventricle, but not the right ventricle, displayed an increased maximum tension response to Ca2+ compared with control. Phosphorylation of troponin I (TnI) with PKA reduced active tension in both fetal ventricles of the long-term hypoxic group more than in hearts from control fetuses. In the adult, phosphorylation with PKA resulted in a larger decrease in tension in the left ventricle and a smaller decrease in tension in the right ventricle in the long-term hypoxic group, although the differences were small. CONCLUSION: In the long-term hypoxic fetal right ventricle, the decreased maximum tension response to Ca2+ is consistent with the decrease in myofibrillar magnesium-activated adenosine triphosphatase activity observed previously. The larger decrease in tension after PKA phosphorylation of TnI in the long-term hypoxic fetal left ventricle indicates a larger reduction in Ca2+ binding to troponin C.

Isolated multiple bilateral echogenic papillary muscles: A unique sonographic feature of trisomy 13.

BACKGROUND: Echogenic papillary muscles are noted in 30% of fetuses with trisomy 13. All reported fetuses with trisomy 13 and echogenic papillary muscles have exhibited additional abnormal sonographic findings. CASE: A 21.7-week fetus demonstrated three papillary echogenicities in each cardiac ventricle during ultrasound examination. Chromosomal analysis of amniocytes showed the karyotype 47,XX,+13. CONCLUSION: Multiple bilateral papillary muscles may provide the only sonographic sign of fetal trisomy 13.

Influence of prenatal alcohol exposure on myocardial contractile function in adult rat hearts: role of intracellular calcium and apoptosis.

To assess the teratogenic action of ethanol on cardiac contractile function in offspring exposed to ethanol in utero, pregnant Sprague-Dawley rats were fed with ethanol during gestation. Left-ventricular papillary muscles and myocytes were isolated from the offspring of the ethanol-ingesting and control pregnant rats. Mechanical parameters measured were peak tension development (PTD, indicating the myocardial force-generating capacity), peak cell shortening (PS), time-to-PTD/PS (TPT/TPS), time-to-90% relaxation/re-lengthening (RT(90)/TR(90)), and maximal velocities of contraction/shortening and relaxation/re-lengthening (+/- VT and +/- dL/dt). Intracellular Ca(2+) levels and apoptosis were evaluated with fura-2 fluorescent dye and Caspase-3 activation assay, respectively. Offspring of the ethanol group displayed decreased heart weight associated with comparable body, liver and kidney weight, and papillary muscle weight/size, compared to the control group. However, prenatal ethanol exposure depressed myocardial PTD and +/- VT. The myocardium from the ethanol group also exhibited slightly but significantly shortened TPT, accompanied with normal RT(90). Muscles from both groups exhibited comparable responses to post-rest potentiation, increasing extracellular Ca(2+) concentration, noradrenaline and acute ethanol challenge. Ventricular myocytes from both the control and ethanol groups possessed similar PS, TPS, TR(90) and +/- dL/dt. Both resting and peak intracellular Ca(2+) levels were elevated in myocytes from the ethanol group. Additionally, acute ethanol application depressed caffeine-induced intracellular Ca(2+) rise in myocytes from both groups. Myocytes from the ethanol group displayed an enhanced Caspase-3 activation, compared to control myocytes. These results suggest that prenatal ethanol exposure alters myocardial contractile function and may contribute to the development of postnatal cardiac dysfunction through, in part, increased intracellular Ca(2+) loading and apoptosis.

Echogenic intracardiac focus in 2nd-trimester fetuses with trisomy 21: usefulness as a US marker.

PURPOSE: To determine whether there is a relationship between the presence of an echogenic intracardiac focus in 2nd-trimester fetuses and trisomy 21 (Down syndrome). MATERIALS AND METHODS: A complete genetic ultrasonographic (US) scan was obtained in 3,303 consecutive fetuses with an estimated gestational age of 14.0-24.0 weeks (mean +/- SD, 17.1 weeks +/- 1.75). US was performed in a prospective fashion without any knowledge of karyotype and included assessment of any potential echogenic intracardiac focus (ie, calcified papillary muscle). Karyotypes were obtained in all fetuses. Maternal ages ranged from 13.0 to 47.4 years (mean, 35.1 years +/- 5.1). The prevalence of Down syndrome in this population was 1.6% (53 of 3,303 fetuses). RESULTS: An echogenic intracardiac focus was seen in 147 of the 3,192 karyotypically normal fetuses (4.6%) and 16 of the 53 fetuses with trisomy 21 (30%). The positive predictive value (PPV) of an echogenic intracardiac focus in this high-risk population was 9.8%; sensitivity, 30%; specificity, 95%; likelihood ratio, 6.6; and relative risk (RR), 8.2 (P <.001). For a sonographically isolated echogenic intracardiac focus, the PPV was 3.7%; sensitivity, 19%; specificity, 95%; likelihood ratio, 4.2; and RR, 4.8 (P =.002). CONCLUSION: A sonographically isolated echogenic intracardiac focus (no other anomalies or markers noted on a complete genetic sonogram) was associated in our high-risk population with a 4.8-fold (95% CI: 1.8, 12.5) increase in RR for trisomy 21 (P =.002).

Myoblast cell grafting into heart muscle: cellular biology and potential applications.

This review surveys a wide range of cellular and molecular approaches to strengthening the injured or weakened heart, focusing on strategies to replace dysfunctional, necrotic, or apoptotic cardiomyocytes with new cells of mesodermal origin. A variety of cell types, including myogenic cell lines, adult skeletal myoblasts, immoratalized atrial cells, embryonic and adult cardiomyocytes, embryonic stem cells, tetratoma cells, genetically altered fibroblasts, smooth muscle cells, and bone marrow-derived cells have all been proposed as useful cells in cardiac repair and may have the capacity to perform cardiac work. We focus on the implantation of mesodermally derived cells, the best developed of the options. We review the developmental and cell biology that have stimulated these studies, examine the limitations of current knowledge, and identify challenges for the future, which we believe are considerable.

Expression, regulation and localisation of dystrophin isoforms in human foetal skeletal and cardiac muscle.

We characterised the expression, localisation and developmental regulation of the three major dystrophin isoforms in human foetal skeletal and cardiac muscles and in the corresponding cultures. Gene expression studies in foetal cardiac muscle-tissue and cultures showed that the Muscle- and the Brain- but not the Purkinje-transcripts were always co-expressed. In skeletal muscle the Muscle-isoform was already present at 11.8 weeks while the Brain-isoform was detected only after 13 weeks. Myoblast cultures showed a similar sequence of isoform transcription. The Purkinje-isoform was never detected. Localisation studies showed that in cardiac muscle dystrophin was seen discontinuously at the sarcolemma from 8.5 weeks, and evenly expressed by 15 weeks. Cardiomyocyte cultures expressed desmin but not dystrophin after 7 days. Protein studies in foetal skeletal muscle suggested that dystrophin is expressed in the cytoplasm from 8.5 weeks and at the sarcolemma only after 10.5 weeks. Similar results were obtained in cultured myoblasts. This study shows that in cardiac muscle both the Muscle- and Brain-isoforms are transcribed in parallel from the very early stages of development, while in skeletal muscle transcription of the Muscle-isoform occurs first, followed by the Brain-isoform.

Development of the papillary muscles of the mitral valve: morphogenetic background of parachute-like asymmetric mitral valves and other mitral valve anomalies.

OBJECTIVES: To understand papillary muscle malformations, such as in parachute mitral valves or parachute-like asymmetric mitral valves, we studied the development of papillary muscles. METHODS: Normal human hearts at between 5 and 19 weeks of development were studied with immunohistochemistry, three-dimensional reconstructions, and gross inspection. Scanning electron microscopy was used to study human and rat hearts. RESULTS: In embryonic hearts a prominent horseshoe-shaped myocardial ridge runs from the anterior wall through the apex to the posterior wall of the left ventricle. In the atrioventricular region this ridge is continuous with atrial myocardium and covered with cushion tissue. The anterior and posterior parts of the trabecular ridge enlarge and loosen their connections with the atrial myocardium. Their lateral sides gradually delaminate from the left ventricular wall, and the continuity between the two parts is incorporated in the apical trabecular network. In this way the anterior and posterior parts of the ridge transform into the anterolateral and the posteromedial papillary muscles, respectively. Simultaneously, the cushions remodel into valve leaflets and chordae. Only the chordal part of the cushions remains attached to the developing papillary muscles. CONCLUSIONS: Disturbed delamination of the anterior or posterior part of the trabecular ridge from the ventricular wall, combined with underdevelopment of chordae, seems to be the cause of asymmetric mitral valves. Parachute valves, however, develop when the connection between the posterior and anterior part of the ridge condenses to form one single papillary muscle. Thus parachute valves and parachute-like asymmetric mitral valves originate in different ways.

Oxygen dose-response curve of cardiac papillary muscle from fetal and nonpregnant adult sheep exposed to long-term, high-altitude hypoxemia.

OBJECTIVE: We tested the hypothesis that hearts of fetal and nonpregnant adult sheep exposed to long-term hypoxemia would be able to sustain higher contractile function during exposure to acute hypoxia than hearts from normoxic animals. METHODS: Pregnant and nonpregnant sheep were exposed to high altitude (3820 m) for 100 days. Right and left ventricular papillary muscle strips were obtained from fetuses and nonpregnant adults, mounted in an isolated bath system, stimulated electrically and subjected to acute hypoxia in a dose response manner. Measurements were made of maximum tension production (Tmax), maximum rate of tension development (+dT/dtmax), maximum rate of relaxation (-dT/dtmax), time to peak tension, and duration of contraction. Results were compared to papillary muscle from a normoxic group of animals. RESULTS: Baseline values (95% O2 + 5% CO2 bubbled in the bath) of Tmax and +/- dt/dtmax for each ventricle were greater in adults than fetuses in both normoxic and long-term hypoxemic groups. During hypoxia (at 40 and 20% O2) Tmax and +/- dT/dtmax, were all maintained at significantly higher values in papillary muscle from long-term hypoxemic fetuses than in papillary muscle from normoxic fetuses. Duration of contraction and time to peak tension did not differ between the normoxic and hypoxemic groups. In both ventricles of the long-term hypoxemic adult, Tmax and +/- dT/dtmax, as well as duration and time to peak tension, were significantly higher than in normoxic adults, but only at the lowest level of hypoxia (20% O2). CONCLUSIONS: Contrary to the original hypothesis, heart muscle from both fetal and adult sheep that had been exposed to long-term hypoxemia could maintain contractile function better during acute hypoxia. The responsible mechanisms are not clearly understood.

Cardiac beta-adrenergic receptor function in fetal sheep exposed to long-term high-altitude hypoxemia.

In this study, we hypothesized that a reduction in beta-adrenergic receptor number or a decrease in functional coupling of the receptor to the adenylate cyclase system may be responsible for the blunted inotropic response to isoproterenol observed in fetal sheep exposed to high altitude (3,820 m) from 30 to 138-142 days gestation. We measured the contractile response to increasing doses of isoproterenol and forskolin in papillary muscles from both ventricles, estimated beta-adrenergic receptor density (Bmax) and ligand affinity (Kd) using [125I]iodocyanopindolol, and measured adenosine 3',5'-cyclic monophosphate (cAMP) levels before and after maximally stimulating doses of isoproterenol and forskolin. Left ventricular wet weight was unchanged, but right ventricular weight was 20% lower than controls. At the highest concentration of isoproterenol (10 microM), maximum active tension was 32 and 20% lower than controls in hypoxemic left and right ventricles, respectively. The contractile response to forskolin was severely attenuated in both hypoxemic ventricles. Bmax was unchanged in the left ventricle, but increased by 55% in the hypoxemic right ventricle. Kd was not different from controls in either ventricle. Basal cAMP levels were not different from controls, but isoproterenol-stimulated and forskolin-stimulated cAMP levels were 1.4- to 2-fold higher than controls in both hypoxemic ventricles. The results suggest mechanisms downstream from cAMP in the beta-adrenergic receptor pathway are responsible for the attenuated contractile responses to isoproterenol.

Three-dimensional magnetic resonance imaging of the postmortem fetal heart.

Five postmortem fetuses were scanned by magnetic resonance (MR) imaging. Of eight three-dimensional (3D) data sets reconstructed on an MGI workstation, five sets demonstrated detailed 3D fetal cardiac structures, and one depicted clear information regarding the disposition and compression of the heart and lungs in diaphragmatic hernia. This study has shown the potential of 3D MR imaging in support of postmortem examination and for interactive visual teaching of the fetal cardiac structures. The new technique may eventually be of significance in prenatal detection of cardiac abnormalities with the development of fast real-time MR imaging.

Regional myocardial glucose utilization by developing fetal and maternal hearts.

Regional glucose utilization of the developing fetal feline heart was assessed during three stages of gestation and compared with the maternal heart and non-pregnant controls. The specific aims were to determine: 1) if glucose utilization by the whole heart changes from early to late gestation; 2) if there are differences in glucose utilization by specific regions of the heart; 3) if these regional differences in glucose utilization are consistent throughout gestation. Regional myocardial glucose utilization was measured using the [14C] 2-deoxyglucose high spatial resolution autoradiographic technique. Eleven fetal and 16 adult hearts were studied. Two of the fetuses were at 49 days of gestation, three were at 35 days, and six were at 25 days of gestation. This was the first study to assess regional myocardial glucose utilization in the developing fetus. Glucose utilization by the fetal heart was greater than that seen in the normal control adult or maternal heart, and was highest during early gestation. The posterior wall of the left ventricle had glucose utilization twice that measured for the anterior wall. Other regions were not significantly different. This information indicates that availability of glucose to the fetus is important for normal cardiac metabolism and development.

The electrophysiologic effects of bupivacaine on adult, neonatal, and fetal guinea pig papillary muscles.

The authors used standard microelectrode techniques to study developmental changes in the effects of bupivacaine on the transmembrane potentials of adult, neonatal, and fetal guinea pig papillary muscles. Bupivacaine hyperpolarized membrane potential in the adult and neonatal muscles but not the fetal muscles. In all three age groups, action potential overshoot and the maximum rate of increase of phase 0 (Vmax) were significantly reduced by bupivacaine greater than or equal to 1.0 microgram/ml. Bupivacaine 1.5 micrograms/ml reduced action potential duration at both 50% and 100% repolarization in the fetal tissues, but not in adult or neonatal tissues. Tonic block was not induced by bupivacaine in any of the three groups. Use-dependent block was variable at bupivacaine 0.2 micrograms/ml in all three groups and was consistent and equivalent at higher concentrations. The onset and offset of use-dependent block were the same in all three groups, with onset occurring between 6.0 and 6.7 beats and the time constant for recovery being 1.9-2.3 s. The authors conclude there is an age-related bupivacaine effect on action potential duration but no age-related change in bupivacaine-induced use-dependent block.

Abnormalities in position of left ventricular papillary muscles in congenital aortic stenosis.

Subclinical structural abnormalities may accompany some congenital cardiovascular abnormalities. Echocardiographic observations led us to hypothesize that the positions of the left ventricular papillary muscles are abnormal in hearts with aortic valvar stenosis. To test this hypothesis, we examined 6 normal heart specimens and hearts with congenital cardiovascular malformations, including 5 with pulmonary atresia and an intact ventricular septum, 6 with tetralogy of Fallot and 5 with aortic valvar stenosis. We marked the papillary muscles and the mitral commissures, X-rayed the hearts, and measured the angular positions of the papillary muscles using the midpoint of a chord drawn between the mitral commissures as a reference point. The direction from the midpoint to the lateral commissure was designated as 0 degrees. The data (mean +/- SEM) were analyzed using a computer program (ANOVA). In normal hearts, the anterolateral and posteromedial papillary muscles were positioned, respectively, at 43 +/- 19 degrees and 126 +/- 26 degrees. The positions of the papillary muscles were similar to normal in the hearts with pulmonary atresia (62 +/- 38 degrees and 128 +/- 27 degrees) and tetralogy of Fallot (40 +/- 13 degrees and 130 +/- 37 degrees). In aortic stenosis, the locations of the papillary muscles (-76 +/- 42 degrees and 71 +/- 25 degrees) were significantly different from normal (P less than 0.05). The arc between the papillary muscles was 83 +/- 16 degrees in normals and 147 +/- 45 degrees in aortic stenosis (P less than 0.05). The length of the arc was similar to normal in other heart specimens. Thus, the papillary muscles were abnormally positioned in aortic stenosis.(ABSTRACT TRUNCATED AT 250 WORDS)

Atrioventricular valves development in human heart: the Paris embryological collection revisited.

29 human embryos staging from stage 15 to stage 23 (post-somitic period, collection of the UER Biomedicale des Saints-Péres, Université René Descartes Paris V) have been studied. The most important morphological events of the atrioventricular valves development have been reinvestigated and photographed. This is a complementary information about cardiac development analysing this french collection of human embryos (Mandarim-de-Lacerda, in press). At stage 15, we can observe the gelatinous reticulum well organized when cardiac valves will become established; progressively the fused endocardial cushions and right and left lateral cushions encircle the atrioventricular channels indicating the site of the tricuspid valves. These cushions, however, have a temporary influence being replaced gradually by atrial and ventricular myocardium. At stage 23, the heart presents a complete atrioventricular valvular structure.

The medial papillary complex.

The anatomy of the papillary muscle of the conus, also known as Lancisi's muscle, was studied in 100 normal hearts from pathological collections and in 8 embryonic and fetal hearts. Wide morphological variations were observed and because of this the name medial papillary complex is proposed. It is concluded that the value of this complex as an anatomical landmark in the right ventricle is a very restricted one. The development of the medial papillary complex is described.