Effects of acetate-free double-chamber hemodiafiltration and standard dialysis on systemic hemodynamics and troponin T levels

Using acetate as a buffer during hemodialysis is recognized to predispose to intradialytic hypotension; however, bicarbonate-based dialysis is not acetate free. Paired hemodiafiltration (PHF) is a novel online acetate-free technique. We investigated whether PHF is capable of abrogating the changes in systemic hemodynamics and troponin T (cTnT) seen with conventional hemodialysis. Twelve patients entered a randomized crossover study. Blood pressure (BP) and a full range of hemodynamic variables were measured throughout PHF and standard dialysis using continuous pulse wave analysis. We also measured predialysis cTnT in 54 stable and unstable dialysis patients. BP was lower during PHF but without increased instability. Stoke volume and cardiac output declined progressively during both treatments but to a much lesser extent during PHF (p = 0.003, p < 0.0001 respectively), whereas peripheral resistance rose to a larger degree during hemodialysis (p < 0.0001). cTnT levels were lower before PHF as compared with hemodialysis (p = 0.023), with levels falling after PHF and rising after hemodialysis (p < 0.0001). In the supplementary patient group, predialysis median serum cTnT was higher in the unstable patients (p = 0.0001). This study demonstrates that PHF (without exposure to acetate) is associated with less deterioration in systemic hemodynamics, maintenance of BP, and less suppression of myocardial contractility as compared with bicarbonate dialysis.

Porcine cardiac myocyte power output is increased after chronic exercise training

Chronic exercise training increases the functional capacity of the heart, perhaps by increased myocyte contractile function, as has been observed in rodent exercise models. We examined whether cardiac myocyte function is enhanced after chronic exercise training in Yucatan miniature swine, whose heart characteristics are similar to humans. Animals were designated as either sedentary (Sed), i.e., cage confined, or exercise trained (Ex), i.e., underwent 16-20 wk of progressive treadmill training. Exercise training efficacy was shown with significantly increased heart weight-to-body weight ratios, skeletal muscle citrate synthase activity, and exercise tolerance. Force-velocity properties were measured by attaching skinned cardiac myocytes between a force transducer and position motor, and shortening velocities were measured over a range of loads during maximal Ca2+ activation. Myocytes (n = 9) from nine Ex pigs had comparable force production but a approximately 30% increase in peak power output compared with myocytes (n = 8) from eight Sed. Interestingly, Ex myofibrillar samples also had higher baseline PKA-induced phosphorylation levels of cardiac troponin I, which may contribute to the increase in power. Overall, these results suggest that enhanced power-generating capacity of porcine cardiac myofibrils contributes to improved cardiac function after chronic exercise training.

Troponin as a marker of myocardiac damage in drug-induced cardiotoxicity

Cardiac troponins T and I (cTnT and cTnI) are becoming the serum biomarkers of choice for monitoring potential drug-induced myocardial injury in both clinical and preclinical studies. The utility of cardiac troponins has been mainly demonstrated following the administration of antineoplastic drugs and beta-sympathomimetics, although the routine use of these markers in the monitoring in patients who received anthracyclines therapy is far from settled. Unlike the previous markers, which suffered from numerous shortages, the main advantages of cardiac troponins are their high specificity and sensitivity, wide diagnostic window and the possibility to use commercially available assays in clinical settings as well as in a broad range of laboratory animals. Nevertheless, in spite of vigorous research in this area, a number of questions are still unanswered and these are discussed in this review. The main problems seem to be the lack of standardisation of variety of troponin immunoassays, the assessment of suitable cutoff for drug-induced cardiotoxicity and determination of critical diagnostic window related to the optimal timing of sample collection, which may be drug-dependent.

Myocardial protective effect of warm blood, tepid blood, and cold crystalloid cardioplegia in coronary artery bypass grafting surgery

AIM

To compare the myocardial effects of cardioplegia by warm blood, tepid blood, and cold crystalloid during coronary artery bypass grafting (CABG).

METHODS

Patients undergoing CABG surgery at Kaunas University Hospital between 2000 and 2004 were randomized into three groups (n=156), receiving a different method of cardioplegia. Intermittent antegrade warm blood cardioplegia was used in 51 patients, tepid blood cardioplegia in 50 patients, and cold crystalloid cardioplegia in 55 patients. Mitochondrial function, myocardial ultrastructure, troponin T, and hemodynamic and clinical data were analyzed after surgery.

RESULTS

All cardioplegic methods similarly affected structural and functional properties of mitochondria and coupling of oxidative phosphorylation, and all lowered the capacity of mitochondria to synthesize ATP. Ultrastructure of myocytes showed slight to moderate injury in the cold crystalloid cardioplegia group. The concentration of troponin T was significantly lower in the warm blood cardioplegia group than in the tepid blood cardioplegia and cold crystalloid cardioplegia groups at 12 hours (0.8+/-0.1 ng/mL, 1.9+/-0.2 ng/mL, and 2.8+/-0.3 ng/mL, respectively; P<0.001) and 24 hours after surgery (1.0+/-0.1 ng/mL, 2.2+/-0.3 ng/mL, and 2.5+/-0.3 ng/mL, respectively; P<0.001). Echocardiographic examination after surgery revealed that the changes in the left ventricle diastolic function were similar in all groups, and that systolic function did not change. The warm blood cardioplegia group showed shorter duration of intubation and hospitalization. There were no differences in the need of catecholamine administration, incidence of complications, and duration of stay in the intensive care unit.

CONCLUSIONS

Intermittent antegrade warm blood cardioplegia provides better myocardial protection during CABG surgery, as assessed by the lower release of troponin T, lower fluid balance, shorter duration of tracheal intubation and hospital stay.

Diagnostic utility of new immunoassays for the cardiac markers cTnI, myoglobin and CK-MB mass

OBJECTIVES

We investigated the diagnostic value of a new system, the Innotrac Aio! immunoassays for troponin, myoglobin and CK-MB, in 270 samples from patients with ACS, after bypass surgery (CABG) or with stable heart failure in comparison to the respective Roche assays.

RESULTS

The values of the cardiac markers assessed by the respective assays correlated (cTnT/cTnI Rho = 0.94, myoglobin Rho = 0.87, CK-MB Rho = 0.84). If values were dichotomised, we found a high concordance of test positive and negative classified patients by troponins with the respective assays.

CONCLUSION

There is strong evidence that the Innotrac Aio! system for cTnI measurement can be used reliably.

Amniotic fluid cardiac troponin T in pathological pregnancies with evidence of chronic fetal hypoxia

AIM

To determine if prenatally measured cardiac troponin T in the amniotic fluid (Am-TnT) could be used as a marker of fetal myocardial hypoxia and necrosis in pathological pregnancy characterized by increased concentration of amniotic fluid erythropoietin (Am-EPO) as a sign of chronic fetal hypoxia.

METHOD

We measured Am-TnT and Am-EPO in 29 pathological and 5 uncomplicated pregnancies. Samples of amniotic fluid were collected prospectively during elective amniocentesis (n=15), cesarean sections (n=17), and before elective induction of labor in two pregnancies with stillbirth. Am-TnT and Am-EPO were determined by chemiluminescent immunological method.

RESULTS

Am-TnT was undetectable in normal pregnancies, but it was detectable in 9 of 29 amniotic fluid samples from pathological pregnancies, with a median value of 0.030 microg/L (range, 0.010-111.6 microg/L). Am-EPO values were above normal values (>11 U/L) in all pathological pregnancies. Am-EPO concentration showed positive correlation with the Am-TnT concentration (r=0.526, P=0.003). Median concentration of Am-EPO in 9 pregnancies with detectable Am-TnT was 198 U/L (range, 16-3,378 U/L). In 20 pathologic pregnancies with undetectable Am-TnT, the median concentration of Am-EPO was 39 U/L (range, 12-293 U/L). There was no statistically significant difference between the groups (P=0.051).

CONCLUSION

Am-TnT is measurable in some pathological pregnancies with signs of fetal chronic hypoxia and myocardial involvement and could be potentially used as a biochemical marker of fetal myocardial injury.

Profound hypotension and associated electrocardiographic changes during prolonged cord occlusion in the near term fetal sheep

OBJECTIVE

To determine whether the onset of fetal hypotension during profound asphyxia is reflected by alterations in the ratio between the T height, measured from the level of the PQ interval, and the QRS amplitude (T/QRS ratio) and ST waveform.

STUDY DESIGN

Chronically instrumented near-term fetal sheep received complete occlusion of the umbilical cord for either 8 (n=6) or 15-min (n=9).

RESULTS

Cord occlusion led to sustained bradycardia and severe acidosis. Mean arterial blood pressure initially rose and then fell to a nadir of 32.6 +/- 2.6 mm Hg in the 8-min group and 9.3 +/- 1.0 mm Hg in the 15-min group (P < .001). The T/QRS ratio rose initially in parallel with mean arterial blood pressure and then reduced as mean arterial blood pressure fell but remained significantly above baseline. Biphasic ST waveforms during occlusion occurred in only 2 fetuses, but biphasic and negative waveforms occurred during reperfusion in the 15-min group, with a significant rise in troponin T levels (0.58 +/- 0.46 versus 0.02 +/- 0.01 ng/mL at 6 h, P < .01).

CONCLUSION

Elevation of the T/QRS ratio does not identify fetal hypotension during severe hypoxia, but abnormal waveforms in the recovery phase may indicate developing cardiac injury.

The ECG in acute coronary syndromes: new tricks from an old dog

The ECG remains the pre-eminent test for myocardial ischaemia, directing therapeutic management and prognostic stratification.

Biochemical analysis and immunohistochemical determination of cardiac troponin for the postmortem diagnosis of myocardial damage

Cardiac disease is the most common cause of sudden death in Western nations. In forensic practice there is a need for more sensitive diagnostic methods for the postmortem diagnosis of myocardial damage. The aim of this study was to analyse the diagnostic efficacy of biochemical markers in cadaver fluids in conjunction with histological studies and the immunohistochemical determination of cardiac troponin C (cTnC) and cardiac troponin T (cTnT) levels in myocardial tissue fixed in formol and included in paraffin. We studied 50 cadavers (43 males and 7 females) with a mean age of 47.5 years (SD 19.2; range 12 to 87 years). Cases were chosen according to the postmortem interval, cause of death, and circumstances of death. Pericardial fluid and serum were tested in duplicate for cardiac troponin I (cTn I), myoglobin and CKMB by immunoassay system using commercial kits. In myocardial tissue, histological studies were performed with hematoxylin and eosin (HE), Masson's trichrome staining and immunohistochemical techniques involving streptavidin-biotin-peroxidase were performed. The results pointed to statistically significant differences for all the biochemical markers in pericardial fluid. The highest levels were obtained in the group of cadavers who had died from myocardial infarction. The immunohistochemical expression of cTnC was detected in 86% of cases; it was strongly positive and usually diffuse. The expression of cTnT, was much less frequent (46% of cases) and less intense. It was concluded that the immunohistochemical determination of cTnC and cTnT levels in myocardial tissue may be used as an index of myocardium damage.

On-line Hemodiafiltration Does Not Induce Inflammatory Response in End-stage Renal Disease Patients: Results From a Multicenter Cross-over Study

BACKGROUND

On-line hemodiafiltration (HDF) represents the supreme blood purification modality for end-stage renal disease (ESRD) patients. Large-volume infusion of on-line prepared substitution fluid may, however, expose patients to inflammatory contaminants. As a result, on-line HDF might aggravate chronic inflammation, which correlates with malnutrition, cardiovascular disease, and mortality among ESRD patients.

METHODS

In a multicenter cross-over study, 27 ESRD patients were randomly assigned to treatment with on-line HDF and low-flux hemodialysis (HD). After 6 months, patients were crossed to the other treatment modality, and treatment continued for another 6 months. Both on-line HDF and low-flux HD were conducted with polysulfone membranes and ultrapure dialysis fluid. Samples were drawn at the end of each treatment period.

RESULTS

Inflammatory parameters were elevated in the study population when compared to healthy controls. Induction of interleukin-1 receptor antagonist (IL-1Ra) and tumor necrosis factor alpha (TNF-alpha) was comparable for on-line HDF and low-flux HD, and there was no intradialytic increase in cytokine production. As a result, interleukin-6 (IL-6) plasma levels did not differ significantly between the two treatment modalities. Similarly, no difference between on-line HDF and low-flux HD was observed for C-reactive protein (CRP) and albumin. Markers of endothelial cell activation (soluble intercellular and vascular cell adhesion molecules sICAM-1 and sVCAM-1) as well as the cardiovascular risk marker cardiac troponin T (cTnT) remained elevated compared to healthy subjects, but showed no difference between the two treatment modalities.

CONCLUSIONS

On-line HDF, as the most effective renal replacement therapy, does not provoke inflammatory response and is both safe and highly biocompatible.

Survival among hospital in-patients with troponin T elevation below levels defining myocardial infarction

BACKGROUND

Cardiac troponin T (cTnT) has an accepted place in the management of patients presenting with suspected acute coronary syndrome (ACS). Uncertainty remains about the significance and interpretation of elevated cTnT below the cut-off levels defining myocardial infarction (0.1 microg/l).

AIM

To compare the mortality risks for elevation of cTnT in the ranges 0.01-0.029 microg/l, 0.03-0.099 microg/l and <0.01 microg/l.

DESIGN

Retrospective record study in three hospitals.

METHODS

All cTnT measurements with values in the range >0.01-0.099 microg/l analysed during January 2002 were extracted from clinical biochemistry laboratory databases. Following agreed exclusion criteria, 179 patients with cTnT in the range 0.01-0.099 microg/l and 60 patients <0.01 microg/l were selected at random from across the three sites. Six-month follow-up was completed by review of case notes and contact with the patients' GP.

RESULTS

There was a graded increase in mortality with increasing cTnT, although only achieving statistical significance for patients in the 0.03-0.099 microg/l range. The graded increase in relative risk with cTnT was weaker after adjustment for potential confounding factors

DISCUSSION

We found a trend for worse survival with increasing cTnT within the range 0.01-0.099 microg/l in unselected patient populations presenting with possible acute coronary syndrome. This suggests that the combined effects of assay imprecision and co-morbidity should be taken into account when interpreting borderline elevation of cTnT. The use of a cut-off based on current standards of assay precision should be used to define the sensitivity of cTnT as biochemical evidence of ischaemic cardiac damage and as an indicator of mortality risk. This level is likely to be between 0.03 and 0.1 microg/l.

Role of "Ischemia modified albumin", a new biochemical marker of myocardial ischaemia, in the early diagnosis of acute coronary syndromes

BACKGROUND

Diagnosis of cardiac ischaemia in patients attending emergency departments (ED) with symptoms of acute coronary syndromes is often difficult. Cardiac troponin (cTn) is sensitive and specific for the detection of myocardial damage but may not rise during reversible myocardial ischaemia. Ischemia Modified Albumin (IMA) has recently been shown to be a sensitive and early biochemical marker of ischaemia.

METHODS AND RESULTS

This study evaluated IMA in conjunction with ECG and cTn in 208 patients presenting to the ED within three hours of acute chest pain. At presentation, a 12-lead ECG was recorded and blood taken for IMA and cardiac troponin T (cTnT). Patients underwent standardised triage, diagnostic procedures, and treatment. Results of IMA, ECG, and cTnT, alone and in combination, were correlated with final diagnoses of non-ischaemic chest pain, unstable angina, ST segment elevation, and non-ST segment elevation myocardial infarction. In the whole patient group, sensitivity of IMA at presentation for an ischaemic origin of chest pain was 82%, compared with 45% of ECG and 20% of cTnT. IMA used together with cTnT or ECG, had a sensitivity of 90% and 92%, respectively. All three tests combined identified 95% of patients whose chest pain was attributable to ischaemic heart disease. In patients with unstable angina, sensitivity of IMA used alone was equivalent to that of IMA and ECG combined.

CONCLUSIONS

IMA is highly sensitive for the diagnosis of myocardial ischaemia in patients presenting with symptoms of acute chest pain.

Both Cell Fusion and Transdifferentiation Account for the Transformation of Human Peripheral Blood CD34-Positive Cells Into Cardiomyocytes In Vivo

Background— Adult human peripheral blood CD34-positive (CD34 + ) cells appear to transform into cardiomyocytes in the injured hearts of severe combined immunodeficient mice. It remains unclear, however, whether the apparent transformation is the result of transdifferentiation of the donor stem cells or of fusion of the donor cell with the cardiomyocyte of the recipients.

Methods and Results— We performed flow cytometry analyses of cells isolated from the hearts of mice that received human CD34 + cells. Human HLA-ABC antigen and cardiac troponin T or Nkx2.5 were used as markers for cardiomyocytes derived from human CD34 + cells, and HLA-ABC and VE-cadherin were used to identify the transformed endothelial cells. The double-positive cells were collected and interphase fluorescence in situ hybridization was used to detect the expression of human and mouse X chromosomes in these cells. We found that 73.3% of nuclei derived from HLA + and troponin T + or Nkx2.5 + cardiomyocytes contain both human and mouse X chromosomes and 23.7% contain only human X chromosome. In contrast, the nuclei of HLA − , troponin T + cells contain only mouse X chromosomes. Furthermore, 97.3% of endothelial cells derived from CD34 + cells contained human X chromosome only.

Conclusions— Thus, both cell fusion and transdifferentiation may account for the transformation of peripheral blood CD34 + cells into cardiomyocytes in vivo.

[A rare cause of non-Q myocardial infarction--acute carbon monoxide poisoning]

Myocardial infarction is a rarely reported complication of acute carbon monoxide (CO) poisoning. We report the case of a 77 years old woman who presented to our emergency department with altered consciousness as a consequence of exposure to CO. The patient didn't experience any chest pain, but the electrocardiogram showed a non-Q-wave antero-septal acute myocardial infarction, with typical elevation in troponin T and creatine-phosphokinase MB levels. The patient recovered completely after specific treatment of poisoning with no major cardiac complication. We consider that careful electrocardiographic and enzymatic monitoring of all patients, especially elderly patients, in the first hours after CO exposure is important for early diagnosis and treatment of this rare complication of CO poisoning, and can improve the outcome of these patients.

Troponin I and T levels in renal failure patients without acute coronary syndrome: a systematic review of the literature

BACKGROUND

Debate surrounds the interpretation of troponin assays for the diagnosis and prognosis of cardiac disease in patients with renal failure.

OBJECTIVES

To systematically review the diagnostic and prognostic test characteristics of quantitative serum cardiac troponin I (cTnI) and T (cTnT) in renal failure patients without acute coronary syndrome (ACS) symptoms.

METHODS

English-language literature was identified through searching MEDLINE from 1966 to August 2003 and reviewing reference lists. Studies were excluded if they did not meet research objectives, had fewer than 10 patients or focused primarily on nonrenal patients. Of 119 potential studies, 39 articles with over 349 patients with chronic kidney disease (CKD) and 3899 hemodialysis patients were selected for abstraction.

RESULTS

Among CKD and hemodialysis patients without ACS symptoms, cTnI had a mean specificity of 97% (95% CI 93% to 99%) and 96% (95% CI 94% to 98%), respectively, using the myocardial infarction cut-off threshold. The mean specificity of cTnT compared less favourably at 85% (95% CI 75% to 93%) and 71% (95% CI 64% to 77%) for CKD and hemodialysis patients, respectively. In hemodialysis patients without ACS symptoms, positive and negative likelihood ratios for all-cause mortality over 12 to 24 months for cTnT were 4.5 (95% CI 2.9 to 7.1) and 0.6 (95% CI 0.4 to 0.8), and for cTnI were 1.6 (95% CI 0.9 to 2.9) and 1.0 (95% CI 0.9 to 1.1), respectively.

CONCLUSIONS

In CKD and hemodialysis patients without ACS symptoms, troponin I, at the myocardial infarction cut-off threshold, is unlikely to be falsely elevated. Among hemodialysis patients without ACS symptoms, a positive troponin T helps predict all-cause mortality.

Prehospital 80-LAD mapping: Does it add significantly to the diagnosis of acute coronary syndromes?

Early detection of acute myocardial infarction (MI) is vital in the management of acute coronary syndromes (ACS). Hence we compared the diagnostic capability of the standard 12-lead electrocardiogram (ECG) with the 80-lead ECG body surface map (BSM) prehospital.

METHODS

Consecutive patients (n = 294) presenting prehospital with ischemic type chest pain were included. All had an ECG and BSM pretreatment and a baseline and 12-hour cardiac troponin-T or I (cTnT or cTnI). Acute MI was defined as cTnT > 0.09 or cTnI > 0.1 ng/mL. Acute MI on the BSM was defined as ST elevation measured at the J-point, > or = 1 mm inferior/right ventricular/high right anterior/lateral regions, > or = 2 mm anterior region, > or = 0.5 mm posterior region.

RESULTS

Acute MI occurred in 182/294 (62%) based on cTnT or I. ST elevation on the standard ECG predicted acute MI in 103 (sensitivity 57%, specificity 94%; c-statistic 0.73). The optimal model for the standard ECG included ST elevation, summed ST depression and past history of MI (c-statistic 0.82; Chi-square (Wald) 120.7, 3df). The BSM predicted acute MI in 146 (sensitivity 80%, specificity 92%; c-statistic 0.86). The optimal model for the BSM included BSM criteria for acute MI and past history of MI (c-statistic 0.91; Chi-square (Wald) 180.3, 2df).

CONCLUSION

The 80-lead BSM is superior to the standard 12-lead ECG in predicting acute MI prehospital.

Effect of hemolysis on cardiac troponin T determination by the Elecsys® 2010 immunoanalyzer

OBJECTIVE

To evaluate the effect of hemolysis on the measurement of cardiac troponin T (cTnT) using the Elecsys 2010 immunoanalyzer.

METHODS

cTnT concentrations were measured using the Elecsys 2010. Interference studies were conducted by mixing serum of known cTnT concentration with either hemolysates or serum to which purified hemoglobin (Hgb) had been added. Hemolysates were prepared by mechanical disruption. PROBIT analysis was conducted to determine the probability of a cTnT result of >0.1 microg/l being decreased to <0.1 microg/l due to hemoglobin interference.

RESULTS

Purified hemoglobin as well as serum-hemolysates mediated a concentration-dependent inhibition of cTnT determination with the Elecsys 2010. With every 1 g/l increase in hemoglobin, the probability of cTnT >0.1 is decreased by 2.5%.

CONCLUSIONS

A concentration-dependent negative bias in the measurement of cTnT is associated with increasing hemoglobin concentrations in serum.

Stunned peri-infarct canine myocardium is characterized by degradation of troponin T, not troponin I

OBJECTIVE

Degradation of cardiac troponin I (cTnI) has been proposed to represent the underlying molecular mechanism responsible for post-ischemic contractile dysfunction of viable but 'stunned' myocardium. However, this concept is largely derived from models of brief, sublethal ischemia essentially devoid of necrosis, and there is speculation that defects in cTnI may be model-dependent. Accordingly, our primary aim was to evaluate the integrity of cardiac troponins-i.e., cTnI, as well as cTnT and cTnC-in viable but stunned peri-infarct tissue. In addition, we addressed the as-yet unexplored issue of whether the profound reduction of infarct size evoked by brief preconditioning ischemia (PC) was accompanied by a favorable attenuation in ischemia/reperfusion-induced degradation of cTnI, cTnT or cTnC in the remaining viable subepicardium.

METHODS

Anesthetized open-chest dogs received 10 min of PC ischemia or a comparable control period, followed by 1 h of sustained coronary occlusion and 3 h of reperfusion. Subepicardial biopsies from the center of the soon-to-be ischemic territory were obtained at baseline and at 30 min and 3 h post-reflow, and myofilament protein integrity (intact cTnI, cTnT and cTnC, as well as degradation bands and covalent complexes) were assessed by Western immunoblotting. In addition, in all dogs, wall thickening was measured by echocardiography, collateral blood flow was assessed during sustained occlusion by injection of radiolabeled microspheres, and infarct size was delineated by tetrazolium staining.

RESULTS

Although PC was, as expected, cardioprotective (infarct size of 2 +/- 1% of the risk region vs. 17 +/- 6% in controls; p < 0.05), both control and PC groups exhibited profound and comparable contractile dysfunction following reflow (mean wall thickening reduced to 20-22% of baseline values). There was, however, no significant degradation of cTnI in the viable but stunned, peri-infarct tissue. We did observe degradation of cTnT in the stunned subepicardium, an effect that was attenuated in dogs that received antecedent PC ischemia. However, there was no correlation between post-ischemic wall thickening and the immunoreactivity of the intact cTnT band, or wall thickening and the intensity of the cTnT degradation products.

CONCLUSIONS

Our results suggest cTnI degradation is not a universal determinant of post-ischemic myocardial stunning. Moreover, the dissociation between cTnT degradation and wall thickening argue against a direct 'cause-and-effect' relationship between proteolysis of cTnT and acute, post-ischemic contractile dysfunction of stunned peri-infarct myocardium.

Cardiac Troponin T levels and myocardial involvement in children with severe respiratory syncytial virus lung disease

AIMS

To determine the prevalence of myocardial damage in severe respiratory syncytial virus (RSV) disease as evident from elevated cardiac Troponin T (cTnT) levels. To assess the nature of the myocardial involvement as manifested in electro- and echocardiographic abnormalities. To compare severity of disease with and without myocardial involvement as evident from duration of ventilation, inotrope requirements and death.

METHODS

This was a prospective observational cohort study of children with RSV infection admitted to the paediatric intensive care unit at the Royal Liverpool Children's Hospital during the winter season 2002/2003. cTnT concentrations were measured using a third generation monoclonal sandwich immunoassay (Roche Diagnostics).

RESULTS

34 children were included in our study. 12 (35%) had elevated cTnT levels. The levels measured after admission had a median [interquartile range (IQR)] of 50 pg/ml (37.5-67.5). There was no significant difference (p > 0.05) between patients with and without elevated cTnT levels with regards to gender, gestational age at birth, history of neonatal intensive care, presence of congenital heart disease, chronic lung disease, inotrope requirements, duration of ventilation, death, fractional shortening on echocardiogram or arrhythmias. Children with elevated cTnT levels were significantly younger [median (IQR): 1.4 months (0.8-2.0)] than children without [median (IQR): 4.0 months (1.7-6.6)] (p = 0.04). The systolic blood pressure on admission was lower in children with increased cTnT compared to those with undetectable cTnT (p = 0.01).

CONCLUSIONS

Myocardial involvement is common in infants with severe RSV lung disease without congenital heart disease. cTnT level elevation was associated with hypotension.

Type-selective muscular degeneration promotes infiltrative growth of intramuscular lipoma

Background

Intramuscular lipoma is a relatively common benign neoplasm that is occasionally described as an infiltrating lipoma. Typical benign tumors show a clear margin, however, the infiltrative growth pattern of this lipoma mimics that of a malignant tumor. Although its growth has an effect on muscle bundles and it is known to never metastasize, the mechanism of infiltrative growth is not well understood. Previously, little attention has been paid to pathogenic features of muscle fibers around an intramuscular lipoma.

Methods

In the present study, we focused on pathologic changes of the surrounding skeletal muscles especially to the degenerative features of involving muscular types, and evaluate the role of type-selective muscular degeneration for the infiltrative growth of intramuscular lipomas. Following a review of the medical records in our institute, 17 lesions containing muscle tissues in their specimens (15 infiltrating lipomas, 2 well-circumscribed lipomas) were analyzed immunohistochemically. The tumor from the most recent case was also subjected to ultrastructural analysis. Two cases of the traumatic muscle damage were also evaluated as the control experiments.

Results

These analyses revealed type-selective muscle involution in 11 of 17 intramuscular lipomas and in 10 of 11 of the infiltrative type, with an involving pattern that resembled that of a neurogenic or myogenic disorder. Immunoreactivity to cathepsin-D, a lysosomal catabolic enzyme, was increased in the involved muscle fibers. Subsarcolemmal vacuoles in the muscle fibers of the peripheral areas were also positive for cathepsin-D, while degenerative findings were not visually apparent in these areas. Ultrastructural analysis revealed degenerative changes in those fibers. Neither positive staining for cathepsin-D nor type-selective atrophy was detected in the sections of traumatic muscle damage.

Conclusions

Our findings suggest that type-selective muscular degeneration and endomysial fatty growth as a result of atrophy may modulate the infiltrating growth characteristic of intramuscular lipoma.

Cardiac troponin T content in heart and skeletal muscle and in blood samples from ApoE/LDL receptor double knockout mice

BACKGROUND

The isolated perfused mouse heart is a useful experimental model, and cardiac troponin T (cTnT) in coronary effluent may be a sensitive marker of myocardial damage. In recent years, the apolipoprotein E/low-density lipoprotein receptor double knockout (apoE/LDLr KO) mice have become valuable tools in atherosclerosis research. The aim of the study was to validate measurements of cTnT in heart, skeletal muscle, and serum of apoE/LDLr KO mice.

METHODS

Wild-type C57BL/6J mice were fed with standard diet, and apoE/LDLr KO mice were fed an atherogenic diet. Blood was sampled from the jugular vein or the thoracic cavity. Heart and femoral skeletal muscle were sampled and homogenized. cTnT was measured with the third-generation cTnT assay (Troponin T STAT) on Elecsys 2010 immunoassay analyser (Roche Diagnostics).

RESULTS

Median serum cTnT in samples from the thoracic cavity of C57BL/6J mice was about 20-90 times higher, and from ApoE/LDLr KO mice about 30 times higher than serum cTnT in samples from the external jugular vein. There was no difference in cTnT content (microg cTnT/g heart muscle) in hearts from C57BL/6J and apoE/LDLr KO mice. The median cTnT content in skeletal muscle was less than 0.1% of the cTnT content in heart muscle.

CONCLUSION

There is no difference in cTnT content of heart muscle comparing C57BL/6J and ApoE/LDLr KO mice, which have larger hearts. Sampling from the thoracic cavity causes unacceptably high cTnT levels. Serum cTnT in samples from the jugular vein is only slightly elevated. Elevated baseline levels of cTnT in mice are not caused by troponin T from skeletal muscle.