Topic modeling to mind illegal compensation for occupational injuries

Background

Accurate reports of occupational injuries are important to monitor workplace safety and health initiatives. In South Korea, media reports, experts, and workers have been constantly raising the issue of underreporting. Supposedly it is because employers have strong market “incentives” by underreporting their employees’ injuries. A critical way to underreport or cover-up is illegal compensation (in Korean called “gong-sang”). Unfortunately, “gong-sang” is not counted as official occupational injury statistics. The aim of this study was to analyze the social media data using topic modeling and to explore issues surrounding “gong-sang”.

Methods

We used web scraping technology and collected 2,210 social media data from Web search engines. Data was processed to transform unstructured textual documents into structured data using the Python and applied Latent Dirichlet allocation (LDA) in the Python library, Gensim, for topic modeling.

Results

Based on the LDA method from “gong-sang”- related documentation, 10 topics were identified. Topic 1 was the greatest concern (60.5%), with keywords implying the choice between illegal compensation (“gong-sang”) and legal insurance claims. The next concern was Topic 2 including keywords associated with claims for industrial accident insurance benefits. The rest topics (topic 3-10) showed the monetary issue, precarious employment, and vulnerable body parts to “gong-sang”.

Conclusions

We explored web-based data and identified the salient issues surrounding “gong-sang”. LDA topics may be helpful to ensure efficient occupational health and safety scheme to protect vulnerable employees from “gong-sang” practices.

Key messages

The topics formulated by LDA included queries about legal insurance claims. Legal insurance claims including private or social insurance, monetary compensation, injured body parts, and the type of jobs vulnerable to “gong-sang”.

Effect of goal-directed haemodynamic therapy in free flap reconstruction for head and neck cancer

BACKGROUND

In free flap reconstruction for head and neck cancer, achieving a haemodynamic target using excessive fluid infusion is associated with decreased flap survival rates and extended hospital stays. We hypothesized that goal-directed haemodynamic therapy would improve flap survival rates and shorten hospitalization periods.

METHODS

Patients scheduled for free flap reconstruction were randomly assigned to a goal-directed haemodynamic therapy group (n = 31) or a conventional haemodynamic therapy control group (n = 31). The control group received extra bolus fluid and ephedrine or norepinephrine to maintain a mean arterial pressure ≥ 65 mmHg. The goal-directed haemodynamic therapy group received a colloid solution as the extra bolus fluid to maintain a stroke volume variation < 12%; dobutamine, ephedrine, or norepinephrine was administered to maintain a cardiac index ≥ 2.5 l/min/m² and mean arterial pressure ≥ 65 mmHg. Enhanced recovery after surgery protocols were not used except for fluid therapy. An otolaryngologist blinded to group assignments assessed flap outcomes and classified them as 'survival,' 'at risk' or 'failure.'

RESULTS

The hospitalization period was not significantly different between the groups. The goal-directed haemodynamic therapy group had significantly shorter intensive care unit stays and a higher flap survival rate. The crystalloid volume was significantly lower in goal-directed haemodynamic therapy group. Reoperation rates, post-operative complications, and laboratory data including inflammatory markers were similar between the groups.

CONCLUSION

Compared to conventional haemodynamic therapy, goal-directed haemodynamic therapy does not reduce hospitalization periods; it may, however, reduce the length of intensive care unit stays and increase flap survival rates. Further studies including multi-centre trials with larger sample sizes are warranted.

Adequate interval for the monitoring of vital signs during endotracheal intubation

Background

In the perioperative period, it may be inappropriate to monitor vital signs during endotracheal intubation using the same interval as during a hemodynamically stable period. The aim of the present study was to determine whether it is appropriate to use the same intervals used during the endotracheal intubation and stable periods to monitor vital signs of patients under general anesthesia.

Methods

The mean arterial pressure (MAP) and heart rate (HR) were continuously measured during endotracheal intubation (15 min after intubation) and hemodynamically stable (15 min before skin incision) periods in 24 general anesthesia patients. Data was considered “unrecognized” when continuously measured values were 30% more or less than the monitored value measured at 5- or 2.5-min intervals. The incidence of unrecognized data during endotracheal intubation was compared to that during the hemodynamically stable period.

Result

There were significantly more unrecognized MAP data measured at 5-min intervals during endotracheal intubation than during the hemodynamically stable period (p value <0.05). However, there was no difference in the incidence of unrecognized MAP data at 2.5 min intervals or HR data at 5 or 2.5 min intervals between during the endotracheal intubation and hemodynamically stable periods.

Conclusion

A 5-min interval throughout the operation period was not appropriate for monitoring vital signs. Therefore, , a 2.5-min interval is recommended for monitoring the MAP during endotracheal intubation.

CD14 Receptor Gene Promoter Polymorphism: Awakening Maternal Immunity during Pregnancy

We investigated whether monocyte CD14 receptor gene promoter polymorphisms were associated with the development and severity of pre-eclampsia. We genotyped the CD14-260 C/T polymorphism in 36 preeclamptic patients and 52 healthy pregnant controls. A total of 30.6% and 69.4% of pre-eclamptic patients had the C and T alleles, respectively, and 48.0% and 52.0% of the controls, respectively. More pre-eclamptic patients were TT homozygotes compared with controls (50.0% versus 13.5%). In pre-eclamptic patients, the TT homozygotes exhibited a significantly higher mean systolic blood pressure compared with the non-TT homozygotes (173 ± 28 mmHg versus 153 ± 22 mmHg). We also noted a tendency towards increased proteinuria and placental abruption in the TT homozygotes compared with the non-TT homozygotes. We conclude that CD14 gene promoter polymorphisms appear to be a risk factor for pre-eclampsia. With further research, these findings might form the basis of a prognostic tool for pre-eclampsia.

Evaluation of inferior turbinate outfracture outcomes using computed tomography

BACKGROUND

Outfracture of the inferior turbinate (IT) presents numerous advantages, but it is generally believed that the lateralized IT will resume its original position. The purpose of this study was to evaluate the outcome of IT outfracture objectively using computed tomography (CT).

METHODOLOGY

Fifteen patients who underwent bilateral IT outfracture for the removal of pituitary adenomas by the endonasal approach were enrolled. The angles between the lateral wall of the nasal cavity (NC) and IT on both sides were measured from CT scans before and at least 6 months after operation. In addition, we evaluated the effects of variables including age, thickness of IT attachment site and width of the nasal floor, on the angles.

RESULTS

Regardless of the side where a Hardy retractor was placed, the angle between the lateral wall of the NC and IT decreased significantly within 6 months after the outfracture compared to preoperative values on both sides. Other variables showed no significant correlations with the angle between the IT and the lateral wall of the NC.

CONCLUSION

The outfracture procedure effectively lateralized the IT and it maintained that position for at least 6 months after the operation.

Relationship between chewing ability and depressive symptoms

OBJECTIVE

Depression, as one of the most common mental health problems, has many related factors. Recent studies have suggested chewing difficulties as a risk factor for depression in the elderly. This study seeks to investigate whether chewing ability is associated with depressive symptoms in a Korean population.

METHODS

This study used data from the Fifth Korean National Health and Nutrition Examination Survey (KNHANES V) conducted in 2010. Self-reported questionnaires assessed depressive symptoms and chewing ability for the purposes of this study. A total of 6,255 subjects aged over 19 years were included for this study (2,704 males and 3,551 females).

RESULTS

Comparing depressive symptoms with chewing ability (i.e., very poor, poor, moderate, good, and very good), the adjusted odds ratios (ORs) and confidence intervals (CI) were 1.05 (95% CI: 0.84-1.32) for good vs. very good (as a reference), 1.31 (95% CI: 1.00-1.73) for moderate vs. very good, 1.41 (95% CI: 1.12-1.78) for poor vs. very good, and 1.76 (95% CI: 1.16-2.76) for very poor vs. very good.

CONCLUSION

This study suggests that subjects with reduced chewing ability were more susceptible to having depressive symptoms.

The Sparing Effect of Low-Dose Esmolol on Sevoflurane during Laparoscopic Gynaecological Surgery

This double-blind, randomized, placebocontrolled study evaluated the sparing effect of esmolol on sevoflurane during laparoscopic gynaecological surgery in 54 patients between December 2009 and May 2010. The concentration of sevoflurane required to maintain adequate anaesthesia was determined. Patients received either a 0.5 mg/kg esmolol intravenous loading dose followed by infusion of 30 μg/kg per min or an identical volume of normal saline (placebo). During surgery the input concentration of sevoflurane was adjusted every 5 min to maintain systolic blood pressure within 15% of baseline and bispectral index at 50–60. Infusion of esmolol resulted in an 18.2% decrease in mean sevoflurane input concentration. Patients receiving esmolol had an earlier discharge from the postanaesthetic care unit and a lower mean fentanyl dose. In conclusion, intraoperative esmolol infusion decreased both the requirement for sevoflurane and postoperative administration of fentanyl.

In-utero development of the fetal anal sphincter

OBJECTIVE

To investigate the in-utero development of the fetal anal sphincter using transabdominal ultrasound.

METHODS

This was a cross-sectional study in which the diameter of the fetal anal sphincter was measured sonographically once in 631 well-dated, non-anomalous fetuses scanned between 19 and 38 weeks of gestation. Visualization rates were determined. Regression analysis was used to assess the relationship between the diameter of the fetal anal sphincter and gestational age (GA), and reference values including the mean and 95% reference interval were calculated for each GA.

RESULTS

The sonographic visualization rate of the fetal anal sphincter increased with gestational age, plateauing at 90-100% between 23-34 weeks of gestation. There was a significant positive relationship between fetal anal sphincter diameter and GA, which was best described by the equation: anal sphincter diameter (mm) = - 0.014 x GA(2) + 1.107 x GA - 11.664 (R(2) = 0.62).

CONCLUSION

We have provided reference values for the in-utero development of the fetal anal sphincter throughout gestation.

Serum anti-amyloid-beta antibodies and Alzheimer's disease in elderly Korean patients

Alzheimer's disease (AD) is characterized by the deposition of senile plaques and neurofibrillary tangles in the brain. The presence of the amyloid-beta (Abeta) peptide in senile plaques seems to play a central role in the neuropathology of AD. Diagnosis of AD involves neuropsychological examinations or magnetic resonance imaging and, to date, a specific diagnostic marker indicating AD has not been found. This study analysed anti-Abeta antibodies from the serum of 153 patients with AD using an enzyme-linked immunosorbent assay method. The levels of anti-Abeta antibody from patients in the control group (n=193) were compared with those of patients with AD. Our results showed a significantly lower anti-Abeta antibody level in patients with AD than in the control group. These results showed that the anti-Abeta antibody level in serum could potentially be used to diagnose the presence of AD.

Diameter of the normal fetal thymus on ultrasound

OBJECTIVE

To present the normative data of the transverse diameter of the developing fetal thymus.

METHODS

In this prospective study, the maximum transverse diameter of the thymus was measured by one sonologist in 376 normal fetuses between 19 and 38 weeks of gestation. We assessed the relationship of the transverse thymic diameter with gestational age (GA), biparietal diameter, femur length and abdominal circumference using general linear regression modeling. The predicted mean and 95% reference range of thymic diameter at each GA were calculated from the regression equation.

RESULTS

Measurements of the transverse diameter were possible in 352 of the 376 (94%) fetuses. The transverse diameter of the fetal thymus increased with increasing GA and fetal size parameters in a linear manner. The regression equation for transverse diameter of the thymus as a function of GA was: thymic diameter (cm) = 0.15 x GA (weeks) - 1.59 (r(2) = 0.86, P < 0.001).

CONCLUSION

The transverse diameter of the fetal thymus is easy to measure; this study presents normative data.

Staurosporin induces neurite outgrowth through ROS generation in HN33 hippocampal cell lines

Staurosporin, a specific inhibitor of PKC, is widely used in studies of signal transduction pathways. Previous studies have shown that staurosporin induces neurite outgrowth, but the underlying mechanisms remain unclear. Here we report that staurosporin induces neurite outgrowth in HN33 hippocampal cells. Two other PKC inhibitors, Go 6976 (specific for alpha- and beta-isoforms) and rotterlin (a selective inhibitor of PKC delta), have no neuritogenic effect. In addition, staurosporin specifically increases ROS generation. NAC, which inhibits the generation of ROS, suppresses the staurosporin-induced neurite outgrowth in HN33 cells. Further, H(2)O(2) causes neurite outgrowth. Taken together, these results confirm a neuritogenic effect of staurosporin and point to ROS as the signal mediator of staurosporin-induced neurite outgrowth in HN33 hippocampal cells. Theme: Development and regeneration Topic: Neurotrophic factors: receptors and cellular mechanisms.

Rapid in vitro adventitious shoot propagation of Scopolia parviflora through rhizome cultures for enhanced production of tropane alkaloids

A rapid micropropagation system for Scopolia parviflora Nakai (Solanaceae), a rare medicinal plant native to Korea, was established using rhizome cultures. Shoots that originated from adventitious shoots of the rhizome were multiplied when the rhizomes were cultured on half-strength B5 liquid medium supplemented with various growth regulators. Optimum shoot multiplication was observed in half-strength B5 medium containing 3% (w/v) sucrose and 5.77 microM gibberellic acid (GA(3)). Each rhizome gave rise to an average of 12 shoots. Shoot elongation and root induction from multiple shoots occurred on growth regulator-free half-strength B5 solid medium. Healthy plantlets were transferred to a peat moss:vermiculite mixture for acclimatization, which was successful. The concentrations of tropane alkaloids, hyoscyamine and scopolamine were determined in different tissues of native growing plants, in vitro-propagated plants and acclimatized plants by high-performance liquid chromatography. The analysis revealed that the levels of hyoscyamine and scopolamine were higher in in vitro-propagated plants than in the native growing plants. When the rhizome was cut into segments and transferred to optimal culture conditions for multiple shoot propagation, only 12 weeks were required to produce a mature plant. We conclude that in vitro propagation techniques through rhizome cultures provide an efficient and rapid method for shoot propagation of S. parviflora.

Normal pericardial fluid in the fetus: color and spectral Doppler analysis

OBJECTIVES

To estimate the incidence of sonographic identification of pericardial fluid in normal fetuses and to evaluate the flow pattern of pericardial fluid by using color and spectral Doppler techniques.

METHODS

We evaluated 27 normal fetuses for the presence of pericardial fluid by using gray-scale two-dimensional and M-mode ultrasound, and color and spectral Doppler techniques.

RESULTS

Pericardial fluid was detected in 52% of cases by two-dimensional and M-mode ultrasound and in 81% of cases by color Doppler. The pericardial fluid moved towards the ventricles during systole and towards the atria during diastole. In 9 of 22 fetuses with pericardial fluid identified by color Doppler, spectral waveforms were obtained. The waveforms confirmed the bidirectional flow pattern identified at color Doppler. In six cases there was monophasic systolic and biphasic diastolic flow. In the remaining three cases, the flow was monophasic during both systole and diastole.

CONCLUSIONS

Pericardial fluid can be identified with color Doppler in the majority of normal fetuses. It characteristically shows bidirectional flow as it moves with ventricular systole and diastole. Spectral waveforms can be obtained from the pericardial fluid. The presence of pericardial fluid per se should not be considered as abnormal. Color-coded pericardial fluid should not be mistaken for coronary artery blood flow.

Metoprolol attenuates postischemic depressed myocardial function in papillary muscles isolated from normal and postinfarction rat hearts

The present study was designed to test the hypothesis that metoprolol treatment may enhance tolerance to ischemia in normal and postinfarction rat myocardium. Myocardial infarction was induced by permanent ligation of the left coronary artery in adult rats. Animals were divided into sham-operated and infarction groups with or without metoprolol treatment. Metoprolol treatment (60 mg/kg/day via gastric gavage) was started on the second day after surgery and continued until sacrifice at 6 weeks after myocardial infarction. Isometric force and intracellular Ca(2+) ([Ca(2+)](i)) transients were simultaneously recorded in isolated left ventricular papillary muscles. Ischemia was simulated by immersing the muscles into fluorocarbon with hypoxia. Metoprolol treatment induced a significant improvement of isometric force and ameliorated diastolic [Ca(2+)](i) overload in postinfarction rat myocardium at baseline. Metoprolol treatment also reduced diastolic [Ca(2+)](i), ameliorated the depression of developed tension during ischemia, and enhanced recovery of postischemic depressed myocardial function in sham-operated and postinfarction rat papillary muscles. Protein levels of the sarcoplasmic reticulum Ca(2+) ATPase of left ventricles and postischemic papillary muscles from metoprolol-treated rats were higher than those in placebo-treated animals. We concluded, therefore, that metoprolol treatment produced appreciable improvement of intracellular Ca(2+) handling during ischemia-reoxygenation cycles, and enhanced recovery of postischemic depressed myocardial function in both normal and postinfarction rat myocardium.

Arrangement of the systemic and pulmonary venous components of the atrial chambers in hearts with isomeric atrial appendages

BACKGROUND

The morphological definition of atrial chambers, and the determination of atrial laterality, are based on analysis of the structure of the atrial appendages. The systemic and pulmonary venous connections to the heart, nonetheless, are important in the management of patients having isomeric appendages. In this study, therefore, we analysed the morphology of the postero-superior walls of the atrial chambers so as to provide evidence concerning the morphogenetic background of those hearts, and to improve operative management.

METHODS

We reviewed 15 autopsied specimens with isomeric right appendages, and 10 with isomeric left appendages, paying particular attention to the morphology of the systemic and pulmonary venous connections. The postero-superior walls of the atrial chambers can be made up of the atrial body, the systemic venous components, or the pulmonary venous component. We analysed the contributions made by each of these components.

RESULTS

The postero-superior walls of the atrial chambers were markedly variable, but could be grouped into five patterns. Bilaterally well-developed systemic venous components and absence of the pulmonary venous component within the hypoplastic atrial body were present in 9 hearts with extracardiac pulmonary venous connections in the setting of right isomerism. Bilaterally well-developed systemic venous components, and a hypoplastic pulmonary venous component within the hypoplastic atrial body, were present in 5 hearts with intracardiac pulmonary venous connections in right isomerism. Bilaterally well-developed systemic venous components, and a hypoplastic pulmonary venous component within the sizable atrial body, were present in 1 heart with an intracardiac pulmonary venous connection in right isomerism. A well-developed pulmonary venous component within the atrial body, and hypoplasia of one systemic venous component, were present in 7 hearts with left isomerism. A well-developed pulmonary venous component within the atrial body, and hypoplasia of bilateral systemic venous components, were present in 3 hearts with left isomerism.

CONCLUSIONS

The postero-superior walls of the atrial chambers in hearts with isomeric atrial appendages can be analysed on the basis of a compound structure made of bilateral systemic venous components, a central pulmonary venous component, and the body of the atrium. Hearts with isomeric right appendages have absence or hypoplasia of the pulmonary venous component, while hearts with isomeric left appendages have hypoplastic systemic venous components.

Depressed tolerance to fluorocarbon-simulated ischemia in failing myocardium due to impaired [Ca(2+)](i) modulation

The aim of this study was to investigate the tolerance of failing myocardium from postinfarction rats to simulated ischemia. Myocardial infarction (MI) was induced by ligation of the left coronary artery in male Wistar rats. Isometric force and free intracellular Ca(2+) concentration ([Ca(2+)](i)) were measured in isolated left ventricular papillary muscles from sham-operated and post-MI animals 6 wk after surgery. Ischemia was simulated by using fluorocarbon immersion with hypoxia. Results showed that mechanical performance was depressed during the period of hypoxia in physiological salt solution (44 +/- 7% of baseline in sham vs. 30 +/- 6% of baseline in MI, P < 0.05) or ischemia (16 +/- 2% of baseline in sham vs. 9 +/- 1% of baseline in MI, P < 0.01) accompanied by no corresponding decrease of peak [Ca(2+)](i) (hypoxia: 51 +/- 8% of baseline in sham vs. 46 +/- 7% of baseline in MI, P = NS; ischemia: 47 +/- 5% of baseline in sham, 39 +/- 7% of baseline in MI, P = NS). After reoxygenation, [Ca(2+)](i) rapidly returned to near preischemic basal levels, whereas developed tension in fluorocarbon remained significantly lower. This dissociation between peak [Ca(2+)](i) and isometric contractility was more pronounced in the failing myocardium from postinfarction rats. In conclusion, more severe impairment of [Ca(2+)](i) homeostasis in the failing myocardium from postinfarction rats increases susceptibility to ischemia-reperfusion injury.

Differential effects of mibefradil, verapamil, and amlodipine on myocardial function and intracellular Ca(2+) handling in rats with chronic myocardial infarction

Mibefradil is a selective T-type Ca(2+) channel blocker that exerts a potent vasodilating but weak inotropic action. The present study compared mibefradil with traditional L-type Ca(2+) channel blockers in regard to the effects of chronic oral administration on hemodynamics, contractility, and intracellular Ca(2+) handling in failing myocardium from postinfarction rats. Male Wistar rats with ligation-induced myocardial infarction were assigned to placebo or treatment with mibefradil (10 mg/kg/day), verapamil (8 mg/kg/day), or amlodipine (4 mg/kg/day) by oral gavage starting 7 days before the induction of myocardial infarction. Six weeks after myocardial infarction, hemodynamic measurements were performed in conscious animals. In addition, isometric force and free [Ca(2+)](i) were determined in isolated left ventricular papillary muscles. Placebo-treated rats exhibited a decreased mean atrial pressure, an increased left ventricular end-diastolic pressure, and a reduced rate of pressure rise compared with sham-operated animals. Mibefradil treatment significantly improved all of these parameters, whereas both amlodipine and verapamil exerted only minor effects. beta-Adrenergic stimulation with isoproterenol (ISO) enhanced contractility and Ca(2+) availability in papillary muscles from sham-operated rats, whereas the ISO-induced inotropic effect in muscles from placebo-treated rats was severely blunted. Chronic mibefradil treatment significantly improved the inotropic response to ISO stimulation, although the Ca(2+)(i) availability appeared to be less than in muscles from placebo-treated animals. In contrast, both verapamil and amlodipine did not restore the inotropic and Ca(2+)(i) modulating effect of ISO in remodeled myocardium. Thus, T-type Ca(2+) current appears to be of pathophysiological relevance in postischemic reperfused myocardium.

Effects of the calcium channel antagonist mibefradil on haemodynamic parameters and myocardial Ca(2+)-handling in infarct-induced heart failure in rats

OBJECTIVE

Abnormal intracellular Ca(2+)-handling has been implicated in the pathogenesis of contractile dysfunction and arrhythmias in failing hearts. Calcium channel antagonists (CCA) have been proposed for the prevention of cardiac events after myocardial infarction (MI). Recent studies suggest that the blockade of T-type Ca(2+)-channels induced a heart rate reduction without negative inotropic effects. We investigated the effects of the preferentially T-channel blocking CCA, mibefradil, on haemodynamic parameters and intramyocardial Ca(2+)-handling and contractility in the early and late period after MI.

METHODS

MI was induced by permanent ligation of the left coronary artery in male normotensive Wistar rats. Animals were divided in sham-operated and placebo- or mibefradil-treated MI rats. Placebo or Mibefradil treatment (10 mg/kg/d via gastric gavage) was started 7 days prior to MI-induction. Haemodynamic and intramyocardial Ca2+ measurements were performed 1, 3, 7 and 42 days after surgery. At these time points, mean arterial blood pressure (MAP), heart rate (HR), left ventricular enddiastolic pressure (LVEDP) and cardiac contractility (dP/dtmax) were measured in conscious rats. After haemodynamic measurements, the left ventricular papillary muscle was separated to determine developed tension (DT), time to peak tension (TPT) and systolic and diastolic free intracellular Ca2+ concentrations ([Ca2+]i) using the Ca2+ indicator aequorin. Dose-response curves after extracellular isoproterenol- or Ca(2+)-stimulation were recorded.

RESULTS

In the early (1-3 days) period after MI, MAP and dP/dtmax were decreased and LVEDP and HR were increased in placebo-treated MI rats. Mibefradil treatment increased MAP and dP/dtmax and decreased LVEDP and HR in infarcted rats. In the papillary muscle of placebo-treated rats, MI induced a decrease in DT and an increase in TPT and in diastolic and systolic [Ca2+]i. DT of placebo-treated MI rats showed a reduced reactivity after isoproterenol- or Ca(2+)-stimulation. After mibefradil treatment DT was increased and TPT was reduced in the late period (7-42 days) after MI, and diastolic and systolic [Ca2+]i were decreased in the early period after MI (1-3 days). The inotropic response to beta-adrenergic or extracellular Ca(2+)-stimulation was markedly improved by mibefradil 7 and 42 days after MI.

CONCLUSION

We conclude, that mibefradil improves cardiac function, protects the myocardium against ischemia-induced Ca(2+)-overload and increases beta-adrenergic responsiveness in chronically failing rat hearts.

Dantrolene sodium improves the force-frequency relationship and beta-adregenic responsiveness in failing human myocardium

BACKGROUND

Failing human myocardium is characterized by a negative force-frequency relationship and impaired beta-adrenergic responsiveness which have been related to alterations of the intracellular Ca2+ homeostasis. Dantrolene sodium is a clinically used drug that modulates myocardial [Ca2+]i handling in animal models. This study investigated the effects of dantrolene sodium on intracellular Ca2+ handling and contractile function in failing human myocardium.

METHODS AND RESULTS

Twenty-three muscle strips from human left ventricular trabeculae were obtained from patients undergoing heart transplantation for end-stage heart failure caused by idiopathic dilated cardiomyopathy (n = 15). Isometric contraction and intracellular Ca2+ transients (Ca2+ indicator: aequorin) were recorded simultaneously. The experiments were performed in three separate groups exposed to control condition (n = 8), addition of dantrolene (10 micromol/l; n = 8), or addition of verapamil (1 micromol/l; n = 7). Isoproterenol induced a moderate positive inotropic effect in the control group with a maximal increase of developed tension from 10.8 +/- 2.9 to 23.4 +/- 4.7 mN/mm2 and a parallel rise in peak systolic [Ca2+]i to a maximum of 1.36 +/- 0.20 micromol/l. Dantrolene significantly improved (10.2 +/- 3.8 to 32.4 +/- 0.9 mN/mm2) and verapamil blunted (8.3 +/- 2.8 to 17.1 +/- 4.3 mN/mm2) the inotropic response to isoproterenol. The diastolic and systolic [Ca2+]i during isoproterenol stimulation were slightly lower in the dantrolene group but significantly depressed in the verapamil group as compared to the control group. Similarly, analyses of force-frequency relationships revealed an improvement of developed tension in dantrolene-treated as compared to control preparations whereas the peak systolic [Ca2+]i was almost identical.

CONCLUSION

Dantrolene improves the negative force-frequency relationship and beta-adrenergic responsiveness in failing human myocardium. These effects are not accompanied by an additional increase in intracellular [Ca2+]i but might be related to modifications of the diastolic [Ca2+]i homeostasis.

Effects of angiotensin II on inotropy and intracellular Ca2+ handling in normal and hypertrophied rat myocardium

The direct inotropic effect of angiotensin II on the myocardium is still controversial and little information exists as to its potential modification by heart disorders. Therefore, this study performed simultaneous measurements of isometric force and intracellular Ca2+ concentrations ([Ca2+]i) in left ventricular papillary muscles from sham-operated and aortic-banded rats at 10 weeks post-surgery. Angiotensin II (10(-6) M) induced a reduction of peak systolic [Ca2+]i (0.56 +/- 0.03 to 0.48 +/- 0.04 microM; P<0.05) and a parallel but insignificant diminution of developed tension (10.5 +/- 1.3 to 9.6 +/- 0.8 mN/mm2) in normal papillary muscles from sham-operated animals. Hypertrophied papillary muscles from aortic-banded rats demonstrated a significant decline in both peak systolic [Ca2+]i (0.51 +/- 0.02 to 0.44 +/- 0.01 microM; P<0.05) and developed tension (8.4 +/- 1.1 to 6.8 +/- 1.7 mN/mm2; P<0.05) after addition of angiotensin II. The time courses of the mechanical contraction and the intracellular Ca2+ signal were prolonged by angiotension II in both groups. Isoproterenol dose-dependently increased developed tension and peak systolic [Ca2+]i in papillary muscles from sham-operated rats. In contrast, the positive inotropic response to isoproterenol was markedly reduced in hypertrophied muscles despite a seemingly unimpaired increase in peak systolic [Ca2+]i. Pretreatment with angiotensin II (10(-6) M) resulted in a significant attenuation of the systolic [Ca2+]i response to isoproterenol stimulation in both normal and hypertrophied papillary muscles. Neither the bradykinin B2 antagonist icatibent (10(-6) M) nor the nitric oxide (NO) inhibitor L-NMMA (10(-6) M) abolished the depressant effects of angiotension II. Thus, ANG II induces a parallel decline of the mechanical performance and Ca2+ availability in rat myocardium. These effects are more distinct in hypertrophied than in normal muscle and become accentuated during beta-adrenergic stimulation. The underlying mechanism is not associated with the NO pathway but might involve a negative functional coupling between the angiotensin and beta-adrenergic-receptor complex.

Heterogeneity of noninvasive arrhythmic risk indicators in patients with ischemic cardiomyopathy

Noninvasive electrocardiographic variables for arrhythmic risk stratification in chronic heart failure are of great clinical interest but remain highly controversial. This study analyzed repolarization dispersion, heart rate variability, ventricular ectopic activity, and hemodynamic parameters in 30 patients with ischemic heart failure and in 20 normal control subjects. The values for all parameters were distinctly separated between the failure and control group. Left ventricular ejection fraction had a strong relation to ventricular ectopic activity (r = .54), a weak association with repolarization dispersion (r = .29), and seemingly no parallels with heart rate variability (r = .12). However, no linear association could be detected between any of the arrhythmic risk indicators (r = .10-.22), whereas a number of linearly related angiographic-hemodynamic variables readily defined the mechanical risk profile. Thus, alterations of noninvasive arrhythmic risk indicators in heart failure are not uniform, which confounds approaches for a composite ECG risk score in individual patients.