Thomas Scheffold

Diagnostic efficiency of troponin T measurements in acute myocardial infarction.

BackgroundThe present study was designed to evaluate the effliciency of a newly developed troponin T enzyme immunoassay for the detection of acute myocardial infarction. Methods and ResultsThe study comprised 388 patients admitted with chest pain and suspected myocardial infarction and 101 patients with skeletal muscle damage and additional suspected myocardial cell damage. Troponin T was elevated to more than twice the analytical sensitivity of the assay (0.5 μg/l) in all patients with non-Q wave (range, 1.2-5 μg/l) and Q wave infarction (range, 3-220 μg/l). Troponin T appeared in serum as early as 3 hours after onset of pain in 50% of the patients and remained elevated in all patients for more than 130 hours, revealing release kinetics of both free cytosolic and structurally bound molecules. The diagnostic efficiency of troponin T was superior to that of creatine kinase-MB (98% versus 97%) and remained at 98% until 5.5 days after admission, if patients with unstable angina were excluded from analysis. In the 79 patients with unstable angina, troponin T was elevated (range, 0.55-3.1 μg/l) in at least one blood sample from each of 37 patients (56%). Circulating troponin T was correlated to the presence of reversible ST segment or T wave changes on the electrocardiogram (p<0.005) and to the frequency of in-hospital complications. In the 101 patients with skeletal muscle damage and suspected additional cardiac muscle damage, troponin T was the most useful test; its efficiency was 89% or 94% (depending on the discriminator value used) as compared with 63% for creatine kinase-MB. ConclusionsThus, the data of the study indicate that the newly developed troponin T test improves the efficiency of serodiagnostic tools for the detection of myocardial cell necrosis as compared with conventionally used cardiac enzymes. (Circulation 1991;83:902–912)

Intracellular compartmentation of cardiac troponin T and its release kinetics in patients with reperfused and nonreperfused myocardial infarction

In a previous study on the diagnostic efficiency of troponin T measurements in patients with suspected acute myocardial infarction (AMI), the authors found a high variability of troponin T serum concentration changes on day 1 in patients with AMI who underwent thrombolytic treatment. Therefore, the aims of the present study were to investigate the intracellular compartmentation of troponin T and to analyze the effects of AMI reperfusion on the appearance kinetics of cardiac troponin T in serum. Cardiac troponin T was measured with a newly developed bideterminant sandwich assay using cardiospecific, affinity-purified polyclonal antibodies and peroxidase-labeled monoclonal antibody. An unbound cytosolic troponin T pool was found in ultracentrifuged homogenates of myocardial tissue of different species ranging from 0.013 to 0.036 mg/g wet weight. The soluble troponin T molecule had electrophoretic properties identical to troponin T compartmented in the myofibrils. The clinical study group comprised 57 patients with AMI undergoing thrombolytic treatment. Blood flow to the infarct zone and point of time of reperfusion were tested by immediate and late angiography. The appearance of troponin T in serum on day 1 after the onset of AMI depended strongly on reperfusion and on duration of ischemia before reperfusion. Thus, in patients with early reperfused AMI, a marked peak in troponin T serum concentrations was found at 14 hours after the onset of pain. This early troponin T peak was absent in patients with AMI reperfusion occurring greater than 5.5 hours after the onset of pain and in patients with nonreperfused AMI. By contrast, the kinetics of troponin T release after the first day after AMI were unaffected by reperfusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Enzyme linked immuno assay of cardiac troponin T for the detection of acute myocardial infarction in patients

For the diagnosis of acute myocardial infarction (AMI) in patients circulating constituents of the contractile apparatus may be measured instead of cytosolic cardiac enzymes. The potential advantages of the use of myofibrillar cardiac proteins as marker proteins for AMI results from their expression as cardio-specific isoforms, their high intracellular concentration, and their continuous release from infarcting myocardium. While analyzing the specificity of polyclonal goat anti-human cardiac myosin light chains antisera a cardio-specific antibody fraction was identified which is directed against cardiac troponin T contaminations of the myosin light chains antigen. Using this antibody fraction a standardized enzyme immuno-assay for circulating troponin T was developed to detect AMI in patients. In this assay troponin T is bound on different epitopes by affinity purified goat anti-cardiac troponin T antibodies immobilized on polyvinyl chloride test tubes as well as horse raddish peroxidase labeled monoclonal anti-troponin T antibody in liquid phase. The assay procedure can be completed semiautomatically in 90 min with a detection limit of the assay of 0.5 ng/ml human or bovine cardiac troponin T. There is 1% crossreactivity with skeletal troponin T. In 26 healthy volunteers no cardiac troponin T was detectable in serum of 25 persons, while in 1 further volunteer 1 ng/ml troponin T was found. In the sera of all 50 patients with transmural AMI troponin T was elevated ranging from 7.2 to 110 ng/ml. In the mean troponin T remained elevated from three until 300 hours after onset of ischemic pain showing a biphasic serum concentration curve.(ABSTRACT TRUNCATED AT 250 WORDS)

Noncompaction of the Ventricular Myocardium Is Associated with a De Novo Mutation in the β-Myosin Heavy Chain Gene

Noncompaction of the ventricular myocardium (NVM) is the morphological hallmark of a rare familial or sporadic unclassified heart disease of heterogeneous origin. NVM results presumably from a congenital developmental error and has been traced back to single point mutations in various genes. The objective of this study was to determine the underlying genetic defect in a large German family suffering from NVM. Twenty four family members were clinically assessed using advanced imaging techniques. For molecular characterization, a genome-wide linkage analysis was undertaken and the disease locus was mapped to chromosome 14ptel-14q12. Subsequently, two genes of the disease interval, MYH6 and MYH7 (encoding the α- and β-myosin heavy chain, respectively) were sequenced, leading to the identification of a previously unknown de novo missense mutation, c.842G>C, in the gene MYH7. The mutation affects a highly conserved amino acid in the myosin subfragment-1 (R281T). In silico simulations suggest that the mutation R281T prevents the formation of a salt bridge between residues R281 and D325, thereby destabilizing the myosin head. The mutation was exclusively present in morphologically affected family members. A few members of the family displayed NVM in combination with other heart defects, such as dislocation of the tricuspid valve (Ebsteins anomaly, EA) and atrial septal defect (ASD). A high degree of clinical variability was observed, ranging from the absence of symptoms in childhood to cardiac death in the third decade of life. The data presented in this report provide first evidence that a mutation in a sarcomeric protein can cause noncompaction of the ventricular myocardium.

Intracellular compartmentation of troponin T: Release kinetics after global ischemia and calcium paradox in the isolated perfused rat heart

The marked differences in troponin T serum concentrations observed in patients with reperfused and non-reperfused myocardial infarction may be due to a perfusion dependent wash-out of an unbound fraction of cardiac troponin T. To test the release kinetics of troponin T experimentally, the isolated rat heart (Langendorff preparation) was damaged either by the calcium paradox or by no-flow ischemia. Following membrane damage by the calcium paradox troponin T (TNT) showed the same release kinetics in the coronary effluent as the cytosolic markers creatine kinase (CK) or lactate dehydrogenase (LDH). Peak levels of troponin T (282 +/- 58 micrograms/l), CK (6754 +/- 1642 U/l), and LDH (5817 +/- 1730 U/l) occurred 5 min after onset of reperfusion with calcium containing buffers and returned to 9.9%, 1.3%, and 1% of their respective peak levels within 55 min of reperfusion. During reperfusion after no-flow ischemia different release kinetics were found for cytosolic enzymes and troponin T. After 60 min of ischemia, troponin T levels in the coronary effluent increased over the entire reperfusion period of 55 min, almost doubling the 5 min value (191%). In contrast, cardiac enzymes rapidly declined to 18% (CK) and 23% (LDH) of their respective 5 min values at the end of reperfusion. Light microscopy after reperfusion with carbon black revealed a complete and homogeneous reperfusion of Langendorff hearts after no-flow ischemia. Immunoblot analysis confirmed the release of an undegraded 39 kDa troponin T molecule, both after global ischemia and the calcium paradox. These data indicate that prolonged ischemia induces a continuous liberation of cardiac troponin T, most probably from disintegrating myofibres, whereas membrane damage leads almost exclusively to leakage of a functionally unbound troponin T pool. These findings may explain the biphasic serum concentration changes of cardiac troponin T in patients with reperfused myocardial infarction.

Development and Characterization of a Rapid Assay for Bedside Determinations of Cardiac Troponin T

BACKGROUND The appearance of cardiac proteins in blood is the most specific and sensitive indicator of acute myocardial cell necrosis. The measurement of cardiac markers, however, is time consuming and requires sophisticated equipment. To facilitate the biochemical detection for acute myocardial cell necrosis, a whole-blood rapid assay device for cardiac troponin T detection was developed that provides a test result within 20 minutes. METHODS AND RESULTS Monoclonal antibody M7 is labeled with gold particles, and antibody 1B10 is labeled with biotin. Both antibodies, as well as buffer substances and detergents, are adsorbed onto paper fleeces mounted below an application well. Heparinized blood (160 microL) applied to this well solubilizes the dry chemistry reagents. Blood cells are separated from plasma via a glass-fiber fleece. The immunocomplexes formed are concentrated within the reading zone by binding of the biotin-labeled antibody with streptavidine immobilized to the test device. Troponin T bound to the test device serves as a control. The detection limit of this assay is 0.18 microgram/L with a cross-reactivity with skeletal troponin T of 0.5%. In clinical analyses involving 25 healthy volunteers, 62 patients with chest pain but without myocardial ischemia, 35 patients with acute myocardial infarction, 24 patients with minor myocardial cell damage due to radiofrequency ablation, and 35 patients with unstable angina, the rapid assay was comparable to the troponin T enzyme immunoassay in regard to sensitivity and specificity. CONCLUSIONS This newly developed assay allows accurate, rapid, and convenient diagnosis of acute myocardial cell necrosis.

Elevated plasma levels of TNF-alpha and interleukin-6 in patients with diastolic dysfunction and glucose metabolism disorders.

BackgroundDiabetes mellitus (DM) has reached epidemic proportions and is an important risk factor for heart failure (HF). Left ventricular diastolic dysfunction (LVDD) is recognized as the earliest manifestation of DM-induced LV dysfunction, but its pathophysiology remains incompletely understood. We sought to evaluate the relationship between proinflammatory cytokine levels (TNF-alpha, IL-6) and tissue Doppler derived indices of LVDD in patients with stable coronary artery disease.MethodsWe enrolled 41 consecutive patients (mean age 65+/-10 years) submitted for coronary angiography. Echocardiographic assessment was performed in all patients. Pulsed tissue Doppler imaging was performed at the mitral annulus and was characterized by the diastolic early relaxation velocity Em. Conventional transmitral flow was measured with pw-doppler. Early (E) transmitral flow velocity was measured. LVDD was defined as E/Em ratio ≥ 15, E/Em 8-14 was classified as borderline. Plasma levels of TNF-alpha and IL-6 were determined in all patients. A standardized oral glucose tolerance test was performed in subjects without diabetes.ResultsPatients with E/Em ratio ≥ 15, classified as LVDD and those with E/Em ratio 8-14 (classified as borderline) had significantly higher IL-6 (P = 0,001), TNF-alpha (P < 0,001) and NT-pro- BNP (P = 0,001) plasma levels compared to those with normal diastolic function. TNF-alpha and IL-6 levels remains significantly elevated after adjustment for sex, age, left ventricular ejection function, body mass index, coronary heart disease, smoking, hypertension and diabetes mellitus with linear regression analysis. Furthermore, in subjects LVDD or borderline LV diastolic function, 75% had diabetes or IGT, respectively. When subjects without diabetes were excluded, both IL-6 (P = 0,006) and TNF-alpha (P = 0,002) remained significantly elevated in subjects with E/Em ratio ≥ 15.ConclusionThis study reveals that increased plasma levels of IL-6 and TNF-alpha were associated with LVDD. These findings suggest a link between low-grade inflammation and the presence of LVDD. An active proinflammatory process may be of importance in the pathogenesis of diastolic dysfunction.

Influence of reperfusion on serum concentrations of cytosolic creatine kinase and structural myosin light chains in acute myocardial infarction.

The kinetics of cytosolic and structural marker protein release from myocardium were studied in 44 patients with acute myocardial infarction. After intracoronary infusion of streptokinase, there was early recanalization of the infarct-related artery in 8 patients and late recanalization in 18. In 18 patients the infarct-related artery remained occluded. Creatine kinase (CK) level peaked and normalized significantly earlier in patients with early reperfusion than in patients with late reperfusion, and in patients with late reperfusion earlier than in patients with permanent occlusion. Thus, the interval of absolute diagnostic sensitivity of CK depends on early infarct perfusion. In contrast, release of myosin light chains was not significantly changed by recanalization of the infarct-related artery compared with that in nonreperfused myocardial infarction. Thus, in patients with acute myocardial infarction, myosin light chains may be superior to CK as a diagnostic means and for estimation of infarct size.

C/T polymorphism of the intercellular adhesion molecule-1 gene (exon 6, codon 469). A risk factor for coronary heart disease and myocardial infarction

BACKGROUND The intercellular adhesion molecule-1 (ICAM-1) mediates the interaction of activated endothelial cells with leukocytes and plays a fundamental role in the pathogenesis of coronary atherosclerosis. ICAM-1 single-base C/T polymorphism, which determines an amino acid substitution in the ICAM-1 protein in exon 6 codon 469, has been described. Our purpose was to determine whether this C/T polymorphism influences the risk of coronary heart disease (CHD) and myocardial infarction (MI) in humans. METHODS AND RESULTS We enrolled 349 patients with angiographically documented CHD, including a sub-group of 179 patients with acute or chronic MI. The control group consisted of 213 patients with normal left ventricular function and no documented evidence of CHD. All patients and controls were Germans genotyped by polymerase chain reaction and allele-specific oligonucleotide techniques for the ICAM-1 polymorphism. In the patients with CHD and MI the frequencies of the T genotype (TT+TC) were significantly higher than the CC genotype compared to the control subjects (P<0.001). With the additional use of multivariable logistic regression analysis for CHD (TT+TC versus CC; P=0.011, odds ratio 2.21, 95% CI 1.20-4.07), we found a significant association between CHD and MI and the TT and TC genotype of the ICAM-1 gene polymorphism. CONCLUSIONS These results suggest that the TT and TC genotype of the ICAM-1 gene polymorphism in codon 469 is a genetic factor that may determine an individuals susceptibility for CHD and MI.

Novel correlations between the genotype and the phenotype of hypertrophic and dilated cardiomyopathy: results from the German Competence Network Heart Failure

Hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) can both be due to mutations in the genes encoding β‐myosin heavy chain (MYH7) or cardiac myosin‐binding protein C (MYBPC3). The aim of the present study was to determine the prevalence and spectrum of mutations in both genes in German HCM and DCM patients and to establish novel genotype‐to‐phenotype correlations.