Wim Th. Hermens

C-Reactive Protein as a Cardiovascular Risk Factor More Than an Epiphenomenon?

BACKGROUND Circulating levels of C-reactive protein (CRP) may constitute an independent risk factor for cardiovascular disease. How CRP as a risk factor is involved in cardiovascular disease is still unclear. METHODS AND RESULTS By reviewing available studies, we discuss explanations for the associations between CRP and cardiovascular disease. CRP levels within the upper quartile/quintile of the normal range constitute an increased risk for cardiovascular events, both in apparently healthy persons and in persons with preexisting angina pectoris. High CRP responses after acute myocardial infarction indicate an unfavorable outcome, even after correction for other risk factors. This link between CRP and cardiovascular disease has been considered to reflect the response of the body to the inflammatory reactions in the atherosclerotic (coronary) vessels and adjacent myocardium. However, because CRP localizes in infarcted myocardium (with colocalization of activated complement), we hypothesize that CRP may directly interact with atherosclerotic vessels or ischemic myocardium by activation of the complement system, thereby promoting inflammation and thrombosis. CONCLUSIONS CRP constitutes an independent cardiovascular risk factor. Unraveling the molecular background of this association may provide new directions for prevention of cardiovascular events.

Impaired Renal Clearance Explains Elevated Troponin T Fragments in Hemodialysis Patients

Background—Patients with severe renal dysfunction often have unexplained elevated serum concentrations of cardiac troponin T (cTnT). We investigated whether in vivo fragmentation of cTnT could explain these increases. Methods and Results—cTnT, creatine kinase isoenzyme MB, and myoglobin serum concentrations were measured in all 63 dialysis patients of our in-hospital dialysis department. A highly sensitive immunoprecipitation assay, followed by electrophoresis and Western blotting, was used to extract and concentrate cTnT and its possible fragments from serum of these 63 hemodialysis patients. Although creatine kinase isoenzyme MB values excluded recent ischemic myocardial events in 55 of the 63 cases, cTnT fragments ranging in size from 8 to 25 kDa were present in the serum samples of all dialysis patients. Conclusions—cTnT is fragmented into molecules small enough to be cleared by the kidneys of healthy subjects. Impaired renal function causes accumulation of these cTnT fragments and is very likely the cause of the unexplained elevations of serum cTnT found in patients with severe renal failure.

Discrimination Between Myocardial and Skeletal Muscle Injury by Assessment of the Plasma Ratio of Myoglobin Over Fatty Acid–Binding Protein

BACKGROUND Myoglobin and fatty acid-binding protein (FABP) each are useful as early biochemical markers of muscle injury. We studied whether the ratio of myoglobin over FABP in plasma can be used to distinguish myocardial from skeletal muscle injury. METHODS AND RESULTS Myoglobin and FABP were assayed immunochemically in tissue samples of human heart and skeletal muscle and in serial plasma samples from 22 patients with acute myocardial infarction (AMI), from 9 patients undergoing aortic surgery (causing injury of skeletal muscles), and from 10 patients undergoing cardiac surgery. In human heart tissue, the myoglobin/FABP ratio was 4.5 and in skeletal muscles varied from 21 to 73. After AMI, the plasma concentrations of both proteins were elevated between approximately 1 and 15 to 20 hours after the onset of symptoms. In this period, the myoglobin/FABP ratio was constant both in subgroups of patients receiving and those not receiving thrombolytics and amounted to 5.3 +/- 1.2 (SD). In serum from aortic surgery patients, both proteins were elevated between 6 and 24 hours after surgery; the myoglobin/FABP ratio was 45 +/- 22 (SD), which is significantly different from plasma values in AMI patients (P < .001). In patients with cardiac surgery, the ratio increased from 11.3 +/- 4.7 to 32.1 +/- 13.6 (SD) during 24 hours after surgery, indicating more rapid release of protein from injured myocardium than from skeletal muscles. CONCLUSIONS The ratio of the concentrations of myoglobin over FABP in plasma from patients with muscle injury reflects the ratio found in the affected tissue. Since this ratio is different between heart (4.5) and skeletal muscle (20 to 70), its assessment in plasma allows the discrimination between myocardial and skeletal muscle injury in humans.

Intestinal-type and liver-type fatty acid-binding protein in the intestine. Tissue distribution and clinical utility.

OBJECTIVES Intestinal-type fatty acid-binding protein (I-FABP) has been proposed as plasma marker for the detection of acute intestinal injury. However, intestinal mucosa also expresses liver-type FABP (L-FABP). We have investigated the tissue distribution of I-FABP and L-FABP in segments of the human intestine along the duodenal to colonal axis and the potential of both proteins to serve as plasma marker for the diagnosis of intestinal injury. DESIGN AND METHODS I-FABP and L-FABP were measured with specific immunoassays in autopsy samples of the intestine (duodenum, jejunum, ileum and colon) of 23 subjects and in plasma samples from patients (n = 51) with intestinal and/or hepatic disease. Plasma reference values were established in normal healthy individuals (n = 92). RESULTS The I-FABP tissue contents in duodenum, jejunum, ileum, proximal colon and distal colon amounted to 2.22, 4.79, 1.04, 0.27 and 0.25 mug/g ww, respectively. L-FABP tissue contents were markedly higher, amounting to 124 and 198 mug/g ww in duodenum and jejunum, and to 58, 26 and 44 mug/g ww in ileum, proximal colon and distal colon, respectively. Elevated plasma levels of both I-FABP and L-FABP were found in patients suffering from intestinal diseases, while only L-FABP was increased in cases of purely hepatocellular injury. CONCLUSIONS I-FABP and L-FABP show a similar pattern of tissue distribution along the duodenal to colonal axis with highest tissue contents found in the jejunum but in each intestinal segment a >40-fold higher content of L-FABP than of I-FABP. Accordingly, besides I-FABP, also L-FABP is a useful plasma marker for the detection of intestinal injury, especially in patients undergoing intestinal surgery.

Fatty-acid-binding protein as a plasma marker for the estimation of myocardial infarct size in humans.

BACKGROUND--There are substantial amounts of cytoplasmic heart-type fatty-acid-binding protein (FABP) (15 kDa) in myocardial tissue. The rapid release of FABP into plasma during ischaemia indicates the possibility of using this protein as a biochemical marker for ischaemic myocardial injury. OBJECTIVE--To study the completeness of the release of FABP from damaged tissue in patients with acute myocardial infarction (AMI) and the suitability of serial plasma FABP concentrations for estimation of myocardial infarct size. METHODS--Immunochemically assayed FABP and enzymatically assayed creatine kinase isoenzyme MB (CK-MB) and alpha-hydroxybutyrate dehydrogenase (HBDH) were determined serially in plasma samples from 49 patients with AMI who had been treated with thrombolytic agents within six hours after the onset of AMI. Previously validated circulatory models and a value of 2.6 h-1 for the fractional clearance rate of FABP from plasma were used to calculate cumulative protein release into plasma. RESULTS--Release of FABP was completed earlier (24-36 h) after AMI than that of CK-MB (50-70 h) and that of HBDH (> 70 h). However, infarct size estimated from the cumulative release of the proteins and expressed as gram equivalents of healthy myocardium per litre of plasma yielded a comparable value of 4-6 for both FABP and the two enzymes. CONCLUSION--The data indicate that FABP released from the heart after AMI is quantitatively recovered in plasma and that FABP is a useful biochemical plasma marker for the estimation of myocardial infarct size in humans.

Fatty acid-binding protein and the early detection of acute myocardial infarction

Fatty acid-binding protein (FABP) is a newly introduced plasma marker of acute myocardial infarction (AMI). The plasma kinetics of FABP (15 kD) closely resemble those of myoglobin (18 kD) in that elevated plasma concentrations are found within 3 h after AMI and return to normal generally within 12 to 24 h. This makes both myoglobin and FABP useful biochemical markers for the early assessment or exclusion of AMI. The myocardial tissue content of FABP (0.5 mg/g) is about five-fold lower than that of myoglobin (2.5 mg/g), but the reference plasma concentration of FABP (ca. 2 microg/l) is about 15-fold lower than that of myoglobin (ca. 32 microg/l), together suggesting a superior performance of FABP for the early detection of AMI. Indeed, in a study including blood samples from 83 patients with confirmed AMI, taken immediately upon admission to the hospital (< 6 h after AMI), the diagnostic sensitivity was significantly greater for FABP (78%, confidence interval 67-87%) than for myoglobin (53%, CI 40-64%) (P < 0.05). In addition, the differences in contents of myoglobin and FABP in heart and skeletal muscles and their simultaneous release upon muscle injury allow the plasma ratio of myoglobin/FABP to be applied for discrimination of myocardial (ratio 4-5) from skeletal muscle injury (ratio 20-70). Rapid and sensitive immunochemical assay systems for FABP in plasma are now being developed and soon will enable the introduction of this marker in clinical practice.

Relation between infarct size and left ventricular performance assessed in patients with first acute myocardial infarction randomized to intracoronary thrombolytic therapy or to conventional treatment

Reperfusion of ischemic myocardium has been reported to increase the cumulative creatine kinase activity in plasma per gram of infarcted myocardium as assessed with the method of Shell et al. In an attempt to find out whether infarct size assessment using the method of Witteveen et al was affected by reperfusion, the relation between enzymatic infarct size was analyzed using Witteveens method and left ventricular (LV) function parameters in 266 patients with first acute myocardial infarction randomized to intracoronary thrombolysis (n = 134) or conventional therapy (n = 132). Compared with patients allocated to conventional therapy, patients allocated to intracoronary thrombolysis had smaller enzymatic infarct size by 29% (p less than 0.001), smaller LV end-diastolic and end-systolic volume indexes by 10% (p less than 0.05) and 20% (p less than 0.005), respectively, and higher LV ejection fraction (55 +/- 1% vs 49 +/- 1%; p less than 0.001). The beneficial effects of thrombolytic therapy on LV performance were closely associated with thrombolysis-induced limitation of infarct size. The dependence from infarct size of LV end-diastolic volume, LV end-systolic volume, and ejection fraction was not different in the 2 therapy groups. It was concluded that Witteveens method of infarct size assessment is not influenced by the presence of reperfusion. Therefore, this method was recommended for trials on recanalization in patients with acute myocardial infarction.

Value of admission electrocardiogram in predicting outcome of thrombolytic therapy in acute myocardial infarction: a randomized trial conducted by the Netherlands interuniversity cardiology institute

To determine the value of the admission 12-lead electrocardiogram to predict infarct size limitation by thrombolytic therapy, data were analyzed in 488 of 533 patients with acute myocardial infarction (AMI) from a randomized multicenter study. All patients had typical electrocardiographic changes diagnostic for an AMI and were admitted within 4 hours after the onset of chest pain; 245 patients were allocated to thrombolytic treatment and 243 to conventional treatment. Cumulative 72-hour release into plasma of myocardial alpha-hydroxybutyrate dehydrogenase (HBDH) was used as a measure of infarct size. In general, the amount of infarct limitation due to thrombolytic therapy was proportional to the size of the area at risk. Patients with new Q waves, high QRS score and high ST-segment elevation or depression had the largest enzymatic infarct size in both treatment groups, irrespective of location of the AMI. Compared with conventionally treated patients, patients with anterior AMI treated with streptokinase had significant infarct size limitation (480 U/liter HBDH, 37%), and limitation was most prominent in those with Q waves (820 U/liter HBDH) or high ST elevation (750 U/liter HBDH). Infarct size limitation in inferior AMI was less impressive (330 U/liter HBDH, 33%) and patients with high ST-segment elevation (460 U/liter HBDH) or marked contralateral ST-segment depression (430 U/liter HBDH) had the most notable infarct limitation.(ABSTRACT TRUNCATED AT 250 WORDS)

Value of admission electrocardiogram in predicting outcome of thrombolytic therapy in acute myocardial infarction

To determine the value of the admission 12-lead electrocardiogram to predict infarct size limitation by thrombolytic therapy, data were analyzed in 488 of 533 patients with acute myocardial infarction (AMI) from a randomized multicenter study. All patients had typical electrocardiographic changes diagnostic for an AMI and were admitted within 4 hours after the onset of chest pain; 245 patients were allocated to thrombolytic treatment and 243 to conventional treatment. Cumulative 72-hour release into plasma of myocardial alpha-hydroxybutyrate dehydrogenase (HBDH) was used as a measure of infarct size. In general, the amount of infarct limitation due to thrombolytic therapy was proportional to the size of the area at risk. Patients with new Q waves, high QRS score and high ST-segment elevation or depression had the largest enzymatic infarct size in both treatment groups, irrespective of location of the AMI. Compared with conventionally treated patients, patients with anterior AMI treated with streptokinase had significant infarct size limitation (480 U/liter HBDH, 37%), and limitation was most prominent in those with Q waves (820 U/liter HBDH) or high ST elevation (750 U/liter HBDH). Infarct size limitation in inferior AMI was less impressive (330 U/liter HBDH, 33%) and patients with high ST-segment elevation (460 U/liter HBDH) or marked contralateral ST-segment depression (430 U/liter HBDH) had the most notable infarct limitation.(ABSTRACT TRUNCATED AT 250 WORDS)

The role of intrinsic binding rate and transport rate in the adsorption of prothrombin, albumin, and fibrinogen to phospholipid bilayers

Abstract The rates of adsorption and desorption of prothrombin, albumin, and fibrinogen are studied by means of ellipsometry. The adsorbing surface consists of a chromium slide covered with a bilayer of negatively charged phospholipid (dioleoylphosphatidylserine) in a stirred buffer solution. Using an unstirred layer model, a simple graphical representation of the results is presented which allows detection of a transport limitation in sorption kinetics and also allows direct estimation of the thickness δ of the unstirred layer. Values of δ ranged from 2.5 to 10 μm, depending on the rate of stirring. The initial rate of prothrombin adsorption is transport-limited under all conditions studied. Adsorption of fibrinogen is much slower and determined by the intrinsic rate of protein binding. However, the adsorption becomes faster after lowering the pH and ionic strength of the buffer solution and eventually becomes transport-limited. Adsorption of albumin is slow and determined by the intrinsic binding rate for all conditions studied. Reversible adsorption is demonstrated for prothrombin, while the adsorption of fibrinogen and albumin was apparently irreversible.