Measurement of tissue oxygenation in isolated rat hearts using near infrared spectroscopy

New techniques involving Near Infrared Spectroscopy (NIRS) and imaging are rapidly evolving for a large number of new clinical applications. These techniques, based upon nearinfrared light transmission through biological tissue, aim to monitor the hemoglobin and myoglobin concentration changes due to particular physiological state. Clinical applications regard, for instance, the monitoring of muscles and cerebral oxygenation, functional brain activation studies and heart perfusion research. Recently, some works presented tissue oxygenation studies in beating or arrested isolated porcine hearts. In our work we present the design and realization of a dedicated NIRS system for the myocardial perfusion analysis of isolated, saline solution perfused beating rat hearts; in this case the absence of blood allows for unambiguous measurement of tissue myoglobin oxygenation. The presented prototype is portable, low cost, battery operated and permits the measurement of both oxy and deoxy myoglobin concentration changes during imposed regional or global ischemia and reperfusion

EFFECTS OF OXIDISED LDL ON NITRIC OXIDE AND ENDOTHELIN-1 PRODUCTION IN HUMAN MICROVASCULAR ENDOTHELIUM: ROLE OF THROMBOXANE A2 RECEPTOR

LDL particles modulate the release of NO and endothelin-1 by the endothelium. To what extent these effects depend on LDL concentration and degree of oxidation and eventually what is the role of tromboxane A2 receptor is unknown. HMEC-1 were exposed for 24-h to a) 3 concentrations (50, 100 and 200 ?g/ml) of either native, low- or medium-oxidised LDL, b) 8-epi-PGF2? (F2?IP, 10-11, 10-10, 10-9, and 10-8 M) either alone or with TXA2 receptor blocker SQ 29.548 (10-6 M), c) native, low- and medium-oxidised LDL either alone or with SQ 29.548 (10-6 M). In all experiments intracellular eNOS, and NO2/NO3, endothelin-1 and interleukin-6 concentration in the medium were measured. Both native and oxidised LDL induced a NO2/NO3 accumulation with dose and degree of oxidation acting synergistically; eNOS was stimulated only by oxidised LDL. F2?IP, NO2/NO3 and eNOS with SQ 29.548 completely preventing these effects but only partially the effect of LDL. IL-6 was also synergistically stimulated by LDL dose and degree of oxidation but not by direct exposure to F2?IP nor was affected by SQ 29.548. Both native and oxidised LDL stimulated endothelin-1 production independently of dose or degree of oxidation. F2?IP had a modest stimulatory effect while the effect of SQ 29.548 was evident only with oxidised LDL. In HMEC-1 LDL dose and degree of oxidation synergistically stimulate NO and IL-6 production and the effect on NO is largely mediated through the TXA2 receptor. LDL simultaneously facilitate endothelin-1 production independently of the dose and degree of oxidation

Potential role of low kV ex vivo micro-CT for 3D morphometry of paraffin embedded coronary vessels before histology

Purpose: Micro CT is an established tool for non destructive 3D inspection of small specimens. Aim of the study was to demonstrate that despite its limitations in differentiation of soft materials, micro CT can reliably display coronary vessel structure and surrounding tissues after paraffin embedding. Data were obtained from coronary specimens of pig, physical phantoms and numerical simulations. Preliminary images with dual-energy techniques are also shown. Methods: A micro CT scanner built by our group was used for the experiments. The x-ray tube was set up in the range of 20-50 kV; the voxel size was set to 21 μm. A phantom composed of formalin fixed fat and myocardium of rat, dehydrated and paraffin embedded, was used to measure the contrast of different tissues with respect to background. Similar acquisitions were simulated numerically. Real samples of pig excised coronary arteries were processed in the same way and acquired with the same settings; resulting images were compared to those obtained by histology. Results: In phantom, the myocardium contrast vs. paraffin varied from 40% at 20 kV to 29% at 50 kV. The fat contrast vs. background was 2% at 20 kV, whereas it was indistinguishable from the background at 50 kV; all the contrasts in phantom appeared lower than those expected from simulations, probably because of tissue shrinkage. In the samples from pig (see Figure), the vessel wall contrast was 25% greater than the myocardium contrast; the pericardium and a balloon induced stenosis were clearly distinguished. All micro CT scans were shorter than 1 hour. Conclusion: Micro CT is a useful complementary tool for the 3D morphometry of coronary vessels after paraffin embedding, and it can help for the preliminary identification of features of interest for subsequent histological analysis

Gas embolization of the liver in a rat model of rapid decompression

Occurrence of liver gas embolism after rapid decompression was assessed in 31 female rats that were decompressed in 12 min after 42 min of compression at 7 ATA (protocol A). Sixteen rats died after decompression (group I). Of the surviving rats, seven were killed at 3 h (group II), and eight at 24 h (group III). In group I, bubbles were visible in the right heart, aortic arch, liver, and mesenteric veins and on the intestinal surface. Histology showed perilobular microcavities in sinusoids, interstitial spaces, and hepatocytes. In group II, liver gas was visible in two rats. Perilobular vacuolization and significant plasma aminotransferase increase were present. In group III, liver edema was evident at gross examination in all cases. Histology showed perilobular cell swelling, vacuolization, or hydropic degeneration. Compared with basal, enzymatic markers of liver damage increased significantly. An additional 14 rats were decompressed twice (protocol B). Overall mortality was 93%. In addition to diffuse hydropic degeneration, centrilobular necrosis was frequently observed after the second decompression. Additionally, 10 rats were exposed to three decompression sessions (protocol C) with doubled decompression time. Their mortality rate decreased to 20%, but enzymatic markers still increased in surviving rats compared with predecompression, and perilobular cell swelling and vacuolization were present in five rats. Study challenges were 1) liver is not part of the pathophysiology of decompression in the existing paradigm, and 2) although significant cellular necrosis was observed in few animals, zonal or diffuse hepatocellular damage associated with liver dysfunction was frequently demonstrated. Liver participation in human decompression sickness should be looked for and clinically evaluated

Myocardial structural, perfusion and metabolic correlates of left bundle branch block mechanical derangement in patient with dilated cardiomyopathy

Background-Left bundle branch block (LBBB) influences upon regional left ventricular (LV) structure, perfusion and metabolism were not thoroughly investigated in dilated cardiomyopathy (DCM) patients. Methods and Results-Eleven DCM patients with LBBB (69?11 years, LV ejection fraction[EF]: 35?8%) and 7 DMC patients without LBBB (58?9 years, LV EF: 37?10%) were studied by cardiac magnetic resonance (CMR) and positron emission tomography (PET). Left ventricle was divided in 3 regions: septum, adjacent (anterior-inferior) and lateral. Regional midwall circumferential strain, maximum shortening (&#1013;peak) and strain rate were obtained from tagged CMR. Systolic stretch index (SSI) was calculated as positive strain rate (stretching) divided by total strain rate. Myocardial metabolic rate of glucose (MMRG), resting and hyperemic myocardial blood flow (MBF) were quantitated using 2-[18F]fluoro-2-deoxyglucose and [13N]ammonia PET, respectively. Conversely from non LBBB patients, LBBB patients showed highly inhomogeneous systolic deformation pattern which changed gradually moving from discoordinate [(SSI: 0.485 (0.284)] and poorly contracting (&#1013;peak: -1.14?0.96%) septum to coordinate [SSI: 0.002 (0.168)] and strongly contracting (&#1013;peak: -13.63?2.58%) lateral region (both P<0.0001). This pattern was closely matched to MMRG distribution disclosing lowest, intermediate and highest values respectively in the septum, adjacent and lateral regions (P<0.0001). Septal-to-lateral thickness ratio was lower in LBBB than non LBBB patients (P=0.03). In both groups, LV distribution of resting and hyperemic MBF and MBF reserve did not differ significantly. Conclusions-In DCM patients, the extensive LV contraction abnormalities induced by LBBB caused regional myocardial metabolic and structural remodeling without consistent changes in blood flows.-

Adiponectin and cardiometabolic risk factor: effect on myocardial blood flow in patients with dilated cardiomyopathy

Purpose: Adiponectin (ADN) is an insulin-sensitizing, anti-atherogenic and anti-inflammatory adipocytokine, with endothelial protective effects. In patients with dilated cardiomyopathy (DCM), absolute myocardial blood flow (MBF) is frequently impaired because of coronary microvascular/endothelial dysfunction. We aimed at evaluating whether the potential effects of ADN on MBF in DCM are modulated by cardiometabolic risk factors. Methods: Sixty-one consecutive patients (46 males, age 59?10 yrs) with LV dysfunction (LV ejection fraction 38?9%, range 19-54%) and angiographically normal coronary arteries were studied. Absolute MBF was measured by positron emission tomography, using 13N-Ammonia as flow tracer, both at rest and during dipyridamole infusion (0.56 mg/kg I.V. over 4 min). Abnormal MBF was defined for resting MBF<0.65 ml/min/g and dipyridamole MBF<1.36 ml/min/g. Plasma adiponectin was measured by a specific ELISA (Linco Research). Cardiometabolic risk factors including age, sex, insulin resistance, lipid profile and obesity were entered into a multivariate linear regression analysis to assess independent determinants of adiponectin and, in turn, their effect on myocardial and microvascular damage. Results: Abnormal MBF was present in 34/61 patients, in 13/31 (42%) with ADN higher than median value and in 21/30 (70%) with ADN levels lower than median value (p<0.05). Among cardiometabolic risk factors, only HDL-cholesterol and obesity were independent determinants of ADN [0.34 (0.13), -0.34 (0.14), &#946;-coefficient (SE), respectively, p<0.05] at multivariate analysis. After correction for HDL-cholesterol and obesity the positive association between ADN and MBF remained significant (p<0.05). Conclusion: ADN is a determinant of MBF in DCM patients and is related with low HDL-cholesterol and obesity

Neutrophil-to-Lymphocyte Ratio Predicts Prognosis in Patients with Chronic Coronary Heart Disease

Purpose: A relationship between blood cell count and survival has been observed both in healthy individuals and in patients with stable angina, unstable angina, myocardial infarction or heart failure. We tested the hypothesis that a complete blood count with subfraction concentrations would provide prognostic information in patients with chronic coronary heart disease (CHD), and that this information is additive to a standard diagnostic work-up. Methods: We prospectively examined 2370 consecutive patients with chronic CHD, defined by a > 50% stenosis at coronary angiography and/or history of myocardial infarction (MI). We examined the association between complete blood count, clinical variables and future cardiac events (cardiac death and non-fatal MI). Results: During follow-up (median 46 months), 147 patients (6.2%) died of cardiac causes and 81 (3.4%) experienced a non-fatal MI. Using univariate analysis, reduced hematocrit (< 36% if male and < 40% if female) and a neutrophil-to-lymphocyte (N/L) ratio > 2.42, but not white blood cell count and platelet count, were significantly associated with a reduced cardiac event-free survival (P < 0.001 and P <0.0001, respectively). The impact of anemia and high N/L ratio on survival persisted after adjustment for age, diabetes mellitus, left ventricular ejection fraction and angiographic extent of coronary atherosclerosis. The negative prognostic impact of a high N/L ratio persisted even after adjustment for both clinical variables and other routine laboratory variables (risk ratio: 1.57, 95% confidence interval: 1.19 to 2.08, p = 0.0014). Conclusion: An elevated N/L ratio is a significant predictor of adverse prognosis in patients with chronic CHD

Mind-body relationships in elite apnea divers during breath holding: a study of autonomic responses to acute hypoxemia

The mental control of ventilation with all associated phenomena, from relaxation to modulation of emotions, from cardiovascular to metabolic adaptations, constitutes a psychophysiological condition characterizing voluntary breath-holding (BH). BH induces several autonomic responses, involving both autonomic cardiovascular and cutaneous pathways, whose characterization is the main aim of this study. Electrocardiogram and skin conductance (SC) recordings were collected from 14 elite divers during three conditions: free breathing (FB), normoxic phase of BH (NPBH) and hypoxic phase of BH (HPBH). Thus, we compared a set of features describing signal dynamics between the three experimental conditions: from heart rate variability (HRV) features (in time and frequency-domains and by using nonlinear methods) to rate and shape of spontaneous SC responses (SCRs). The main result of the study rises by applying a Factor Analysis to the subset of features significantly changed in the two BH phases. Indeed, the Factor Analysis allowed to uncover the structure of latent factors which modeled the autonomic response: a factor describing the autonomic balance (AB), one the information increase rate (IIR), and a latter the central nervous system driver (CNSD). The BH did not disrupt the FB factorial structure, and only few features moved among factors. Factor Analysis indicates that during BH (1) only the SC described the emotional output, (2) the sympathetic tone on heart did not change, (3) the dynamics of interbeats intervals showed an increase of long-range correlation that anticipates the HPBH, followed by a drop to a random behavior. In conclusion, data show that the autonomic control on heart rate and SC are differentially modulated during BH, which could be related to a more pronounced effect on emotional control induced by the mental training to BH

Myocardial perfusion in chronic diabetic mice by the up-regulation of pLKB1 and AMPK signaling

Previous studies related impaired myocardial microcirculation in diabetes to oxidative stress and endothelial dysfunction. Thus, this study was aimed to determine the effect of up-regulating pAMPK-pAKT signaling on coronary microvascular reactivity in the isolated heart of diabetic mice. We measured coronary resistance in wild-type and streptozotocin (STZ)-treated mice, during perfusion pressure changes. Glucose, insulin, and adiponectin levels in plasma and superoxide formation, NOx levels and heme oxygenase (HO) activity in myocardial tissue were determined. In addition, the expression of HO-1, 3-nitrotyrosine, pLKB1, pAMPK, pAKT, and peNOS proteins in control and diabetic hearts were measured. Coronary response to changes in perfusion pressure diverged from control in a time-dependent manner following STZ administration. The responses observed at 28 weeks of diabetes (the maximum time examined) were mimicked by L-NAME administration to control animals and were associated with a decrease in serum adiponectin and myocardial pLKB1, pAMPK, pAKT, and pGSK-3 expression. Cobalt protoporphyrin treatment to induce HO-1 expression reversed the microvascular reactivity seen in diabetes towards that of controls. Up-regulation of HO-1 was associated with an increase in adiponectin, pLKB1, pAKT, pAMPK, pGSK-3, and peNOS levels and a decrease in myocardial superoxide and 3-nitrotyrosine levels. In the present study we describe the time course of microvascular functional changes during the development of diabetes and the existence of a unique relationship between the levels of serum adiponectin, pLKB1, pAKT, and pAMPK activation in diabetic hearts. The restoration of microvascular function suggests a new therapeutic approach to even advanced cardiac microvascular derangement in diabetes