Elizabeth Roth

What is the adequate sampling interval of the ECG signal for heart rate variability analysis in the time domain

Heart rate variability (HRV) analysis is considered a simple method for investigating neurocardiac regulation. However, measures of HRV may be corrupted by technical artifacts. In order to investigate the consequences of digitization errors on the time domain parameters, HRV measures from model tachograms resampled at different rates were compared. Two 375-element tachograms from human ECG tracings were shifted to a mean of 800 ms and stretched to standard deviations (SD) of 5-120 ms in 5 ms steps. All were resampled at 1-10 ms in 1 ms steps, 10 times repetitively at each interval. The mean, SD, relative accuracy error (RAE) and relative precision error (RPE) were calculated from the mean RR-interval, SD (SDNN), root mean square of successive RR-differences (RMSSD) and the percentage of consecutive RR-interval differences greater than 50 ms (pNN50). The RAE and RPE of the mean heart rate were below 0.1%. In the series with 5 ms SD, the SDNN-RAE exceeded 30% at 10 ms SI, its RPE was lower than 2% all through. Resampling the 15 ms SD tachogram at 1, 2, 4, or 10 ms resulted in RMSSD-RAE of 0.7%, 2.5%, 7.8% and 45.1%, respectively, while its RPE remained below 5%. The pNN50 shows poor accuracy and precision. An ECG sampling interval of 1 ms is recommended for HRV analysis without interpolation in order to get accurate time domain measures even in seriously reduced-variability samples. However, a lower sampling rate may be satisfactory in cases where higher variability is expected.

Burn trauma induces early HMGB1 release in patients: Its correlation with cytokines

High-mobility group box protein 1 (HMGB1) is a nuclear protein that may be released actively from monocytes and macrophages or passively from necrotic or damaged cells. Several experimental data suggest that burn injury is accompanied by elevated plasma HMGB, but there are only few data available about its changes in burned patients. The aim of this study was to follow the time course and the prognostic value of plasma HMGB1 and cytokine changes in patients with severe burn injury affecting more than 10% of body surface area (n = 26). Blood samples were taken on admission and on the following 5 days. Plasma HMGB1 concentration was measured by the enzyme-linked immunosorbent assay method, whereas IL-6, IL-8, and IL-10 were assayed by the cytometric bead array kit. The HMGB1 and IL-10 concentrations were elevated on admission and gradually decreased thereafter. Significant differences were observed between survivors and nonsurvivors in HMGB1 (P < 0.01) and IL-10 (P < 0.001) concentrations on admission with higher levels in nonsurvivors. IL-6 and IL-8 started to increase markedly from day 2. Positive correlation (r = 0.669, P < 0.01) was found between burned body surface and HMGB1 on admission. Receiver operating characteristic analysis of data on admission showed that at a level of 16 ng/mL, HMGB1 indicated lethality, with 75.0% sensitivity and 85.7% specificity. Using the cutoff level of 14 pg/mL, IL-10 predicted intensive care unit mortality, with 85.7% sensitivity and 84.2% specificity. Very early HMGB1 and IL-10 release may have an important impact on the immune function of patients after burn trauma.

Effect of acetylsalicylic acid on nuclear factor-kappaB activation and on late preconditioning against infarction in the myocardium.

Nuclear factor-κB (NF-κB) plays an essential role in the intracellular signal transduction of the second window of protection (SWOP). Acetylsalicylic acid (ASA) blocks NF-κB-dependent gene activation in leukocytes and endothelial cells through preventing phosphorylation and subsequent degradation of the inhibitor IκB-α. This study investigated the effect of ASA on the late phase of ischemic preconditioning (PC) against myocardial infarction and on the activation of NF-κB in the preconditioned myocardium. Conscious rabbits were subjected to 4 cycles of 5 minutes of coronary occlusion and 5 minutes of reperfusion together with 3 different doses of ASA (5 mg/kg; 25 mg/kg; 130 mg/kg). After 30 minutes of reperfusion we determined the activation of NF-κB with an electrophoretic mobility shift assay (EMSA). Twenty-four hours later, after 30 minutes of test ischemia, we performed infarct size analysis using triphenyltetrazolium-chloride (TTC) staining. Neither 5 mg/kg (antithrombotic dose) nor 25 mg/kg (analgesic/antipyretic dose) of ASA interfered with the NF-κB activation and the protective effect of late preconditioning against myocardial infarction. In contrast, NF-kB activation and late PC effect were completely abrogated by 130 mg/kg of ASA. Our results suggest that nonselective doses of NSAIDs should be used with caution in patients with atherosclerotic cardiovascular disease because they may deprive the heart of its innate defensive response.

Effects of fluid resuscitation methods on burn trauma-induced oxidative stress.

The aim of the study was to analyze the oxidative stress response after severe burn injury. We studied the effect of two methods of fluid resuscitation regimes on the oxidative stress reaction. Sixteen patients were involved in the study. Inclusion criteria were the presence of flame burn injury affecting >20% of BSA and in-hospital fluid resuscitation started within 3 hours after injury. Patients were randomly assigned into two groups. In the first group (n = 8), the fluid resuscitation was guided by the hourly urine output and in the second (n = 8), by the intrathoracic blood volume index. Blood sample was taken from the patients at admission and on the following five mornings. White blood cell count normalized by the third day in both groups, but the relative number of granulocytes and lymphocytes significantly (P < .05) diverged between hourly urine output and intrathoracic blood volume index groups from the fourth day of trauma. Plasma malondialdehyde level (P < .05 vs control population), reactive oxygen species production in whole blood (P < .05 vs control population), and catalase activity were elevated, whereas glutathione, plasma sulfhydryl groups level (P < .05 vs control population), and superoxide dismutase enzyme activity lowered in both groups. Our results confirmed that burn injury induces pronounced oxidative stress. The main finding is that fluid resuscitation regimes have different impact on prooxidant status, mainly on the granulocyte function but not on the changes in endogenous antioxidants in burned patients.

Activated PMNs lead to oxidative stress on chondrocytes: A study of swine knees

Using an in vitro model, based on primary cultured chondrocytes, we examined possible oxidative injury caused by activated polymorphonuclear neutrophil granulocytes (PMNs), which are thought to be part of the pathomechanism of hemarthrosis. Chondrocytes were isolated from swine knee joints and divided into three groups. Pure chondrocytes acted as the control population (group I). PMNs from the systemic circulation, and hydrogen peroxide (as an artificial source of reactive oxygen species (ROS)) were added to groups II and III, respectively. All cultures were incubated for 6 hours. After the experiment, lipid membrane degradation by ROS was assessed by monitoring changes in the levels of malondialdehyde (MDA) and 4-hydroxyalkenal contents of the chondrocyte specimens. Changes in the endogenous scavenger status of the chondrocytes were characterized by measuring of reductions in glutathione (GSH) concentration and superoxide dismutase (SOD) activity. Significant increases in MDA/4-hydroxyalkenal levels and SOD activity as well as an expressive reduction in intracellular GSH content were highlighted by comparing the control to the PMN- or H2O2-treated cell populations. These findings confirm previous suggestions that PMN-derived ROS contribute to degradation of cartilage in hemarthrosis.

Cardioprotective action of urocortin in early pre- and postconditioning

Abstract:  Pre‐ and postconditioning are powerful endogenous adaptive phenomenon of the organism whereby different stimuli enhance the tolerance against various types of stress. Urocortin (Ucn), member of the corticotropin‐releasing factor (CRF) family has potent effects on the cardiovascular system. The aim of this article was to investigate the action of Ucn on cultured cardiomyocytes in the process of pre‐ and postconditioning. Isolated neonatal rat ventricular myocytes were preconditioned with adenosine, simulated ischemia, and Ucn (10‐min treatment followed by 10‐min reperfusion/recovery). For detecting the effect of alternative types of preconditioning, necrosis enzyme (lactate dehydrogenase [LDH]) release, vital staining (trypan blue), and ratio of apoptosis/necrosis were examined after cardiac cells were exposed to 3‐h sustained ischemia and 2‐h reperfusion. Same parameters were measured in the postconditioned groups (30‐ or 60‐min ischemia followed by postconditioning with 10‐min ischemic stimulus or Ucn and 2‐h reperfusion). Cells exposed to 3‐h ischemia followed by 2‐h reperfusion were shown as control. Our results show that LDH release a number of trypan blue‐stained dead cells and the ratio of apoptotized and necrotized cells was decreased in all preconditioned groups compared with control group. In postconditioned groups LDH content of culture medium, trypan blue‐positive cardiomyocytes, and the rate of apoptotic/necrotic cells was reduced contrasted with non‐postconditioned group. We can conclude that preconditioning with Ucn induced such a powerful cell protective effect as adenosine and ischemia. Furthermore, postconditioning with Ucn after 60‐min ischemia was more cardioprotective than ischemic postconditioning.

Effects of fluid resuscitation methods on the pro- and anti-inflammatory cytokines and expression of adhesion molecules after burn injury.

Fluid resuscitation management can influence inflammatory response after burn injury. The aim of this study was to analyze the effects of two fluid resuscitation methods on the cytokine production and on the expression of the leukocyte surface markers. Thirty patients were included in this prospective randomized study with burn injury affecting more than 20% of the body surface area. Fluid resuscitation was guided by hourly urine output (HUO, n = 15) or by intrathoracic blood volume index (ITBVI, n = 15). Blood samples were taken on admission and on the next five consecutive mornings. Concentrations of interleukin (IL)-1β, IL-6, IL-8, IL-10, IL-12p70, and tumor necrosis factor-α were measured in phorbol myristate acetate-stimulated and -nonstimulated samples. Leukocyte surface marker expressions (CD11a, CD11b, CD14, CD18, CD49d, and CD97) were also determined. In the ITBVI group, IL-6 levels on days 2 to 3 and IL-6/IL-10 ratios on days 2 to 3, and the IL-8/IL-10 ratios on days 3 to 5 were significantly higher than those in HUO group (P < .05). In the HUO group, IL-10 levels were significantly higher (P < .05) on days 4 and 5. Granulocyte CD11a levels on day 2, CD11b levels on days 4 to 6, lymphocyte CD11a on days 5 to 6, CD11b on days 3 to 6, CD49d on days 2 to 6, CD97 on day 6, monocyte CD11a, CD11b, CD18 levels on days 4 to 6, and CD14 levels on days 3 to 5 were significantly higher in the HUO group (P < .05). Our study suggests that ITBVI-guided fluid resuscitation of burned patients suppresses the shift toward anti-inflammatory imbalance and the expression of leukocyte surface markers more than HUO-guided resuscitation.

Seromuscular gastrocystoplasty in dogs

Introduction: The aim of this study was to investigate the feasibility of seromuscular gastrocystoplasty (SGCP) in an animal model and to compare it to conventional gastrocystoplasty (CGCP). Materials and Methods: CGCP and SGCP (using gastric segments without mucosa) were each performed in 6 dogs. In both procedures, two-thirds of the dome of the bladder were excised and the gastric segment anastomosed to the bladder remnant. Cystography, cystomanometry, measurements of urine pH, and gross and microscopic pathological studies were carried out preoperatively, and postoperatively, at 6 and 12 weeks. Results: All seromuscular gastric segments proved viable, and 6 weeks after the operation they were covered by a thin layer of transitional epithelium, which had gradually thickened by the end of the 12-week follow-up. There was no difference in bladder capacity and compliance between the two groups, however, fasting urinary pH values were higher (less acidic) in the SGCP group. Conclusions: Stripping off the mucosa of the gastric segment appears to stop hydrochloric acid secretion, thereby lessening the possible risk of ulceration, perforation, dysuria-haematuria, metaplasia and malignancy. The uroepithelium overgrowth of the seromuscular gastric segments might provide a more physiological neo-bladder than when using full-thickness gastrocystoplasty.

Long Term Follow-Up of Leukocyte Function during Myocardial Reperfusion Injury

Granulocyte activation and adhesion molecule expression are causal factors in microcirculatory disorders during myocardial reperfusion. While the dynamics of these processes have been well defined during acute reperfusion, there is very little data regarding long lasting reperfusion. The aim of this study was to investigate leukocyte adhesion molecule expression during myocardial ischemia followed by 4 weeks of reperfusion. The left descending coronary artery (LAD) was occluded in dogs for 1 hour and 3 hours followed by 4 weeks of reperfusion. Sham operated animals served as control. Leukocyte expression of CD11a was measured by flow cytometry in peripheral blood samples. Granulocyte CD11a expression started to increase at the second day of reperfusion with the maximal elevation (p < 0.05) by the third postoperative day in ischemic animals. The similar elevation in sham operated animals normalised within the first postoperative week, however, CD11a expression was elevated in both groups of ischemic animals even after 4 weeks reperfusion. The increased CD11a expression during first postoperative week may reflect the effect of surgical trauma, but the elevated leukocyte function during later reperfusion may indicate the activated state of cells and the prolonged healing of injured myocardium.

Prolonged adhesion molecule expression during repair of myocardial infarction

Release and actrvation of matrix metallcprotelnases (MMPs) significantly contributes to myocardial stunning injury immediately after ischemia and npetfusion. however, their role in preconditlonlng mmalns unknown. We themfore examined the effeUs of preconditioning and subsequent ischemia/mperfusion on MMP actMty In Isolated nt hearta. Hearh were subjected to a precondllbnbg protocol (three 5 min intermittent pedods of gbbal ischemia interspersed wllh 5 min of mperfwion) followed by 30 min ischemia and 5 min reperfusion. In order to measure MMP release, coronary efluent was co(leded: a) upon equitlbration. b) followlng each preconditioning Ischemia. and c) during the final reperfuslon following test Ischamia. 75. 72. and 62 kDa MMP-2 aciivities could be detectad by gelatin zymography in (he ventricles and coronary efnuent samples from the perfused hearts. The levels of each were markedly Inmased fdlowtng test ischemla in efluent fhxn control hearts without precondltbning. This was aaxmpanied by a decrease in corresponding tissue MMP activii. During pmwnditloning. MMP-2 release was non-slgnlflcentiy elevated durino the first oariod of ischemia/moerfusion and returned to basetne levels ’ after the third isdhemialreperfusion period. Preconditioning signiffcantly decreased the MMP-2 activity in the coronary effluent fallowing test ischemi8/repsriusion and preserved the MMP-2 protein content and atiity in Ihe myocardium Our results demonstrate that classic preccndihoning inhibits ischemia/mperfusion induced release and adivatiin of MMP-2 This mechanism may be involved in Ihe cardioprotedive effect of pmconditloning.