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Biomedical subjects

M G Trivella

Publications and source records attributed to M G Trivella.

At least 19 recordsLinked to original sources
PubMed1999

A new technique for total hepatectomy in the pig for testing liver support devices.

BACKGROUND: A large animal model of total hepatectomy is suitable to test the efficacy of any system designed to support patients in hepatic coma. The models previously described in the pig entail a significant degree of surgical trauma, which might alter the evolution of the ensuring hepatic failure and compromise the reproducibility of the model. METHODS: Twenty-eight pigs underwent a total hepatectomy according to a new technique. A model was considered satisfactory when it required no blood transfusions and when hematologic and hemodynamic parameters determined before, during, and until 4 hours after hepatectomy showed no significant variations. Moreover, to revive the pattern of hepatic coma produced in the anhepatic model, 7 pigs were monitored until brain death occurred. RESULTS: Twenty-five pigs (89%) underwent a smooth total hepatectomy with minimal variations of the selected parameters. They constituted a highly homogeneous group. Survival of the 7 pigs, followed up until brain death occurred, ranged from 625 to 1595 minutes (mean 1013.57 minutes). The animals remained stable until a few hours before brain death, an event heralded by a final sharp increase of the serum ammonia level and by a well-evident decline of both arterial pressure and liver-dependent clotting factors. CONCLUSIONS: This technique of total hepatectomy allows the construction of a reproducible model of anhepaty suitable to test the efficacy of any system conceived to temporarily replace hepatic functions.

Anastomosis, Surgical↗
PubMed1998

Detection of perfusion defects during coronary occlusion and myocardial reperfusion after thrombolysis by intravenous administration of the echo-enhancing agent BR1.

The purpose of this study was to detect myocardial perfusion defects as a result of coronary occlusion and myocardial reperfusion after thrombolysis with intravenous (i.v.) administration of the echo contrast agent BR1 (Bracco Research, Switzerland), which consists of microbubbles (median diameter 2.5 microm) containing sulfur exafluoride in a phospholipidic shell. To generate a coronary thrombosis, a copper coil was advanced into the left circumflex coronary artery in eight anesthetized dogs with opened chest cavities. Coronary occlusion occurred 18 +/- 10 minutes after the insertion of the coil and was documented both by an electromagnetic flow meter (as zero blood flow) and by radiolabeled microspheres (as myocardial perfusion defect). After 2 hours of occlusion, streptokinase was infused i.v.; reperfusion was documented by both the flow-meter and microspheres. Left ventricular cavity enhancement was apparent after all contrast injections. Peak cavity intensity did not increase with dose and was not affected by signal processing (suggesting signal saturation), whereas the duration of contrast effect significantly increased with the dose (from 26 +/- 16 to 147 +/- 74 seconds). Myocardial contrast intensity also increased after contrast (from 15 +/- 12 to 21 +/- 18 gray level/pixel, p < 0.001). Contrast echo detected myocardial perfusion defects (corresponding to 17% +/- 11% of LV cross-sectional area) in all the injections performed during coronary occlusion and detected myocardial reperfusion with a sensitivity of 50% versus microspheres. The extent of perfusion defects by contrast echo showed a good correlation with microspheres (r = 0.73). Myocardial reperfusion was not detected by changes in heart rate, aortic pressure, pulmonary arterial pressure, cardiac output, left ventricular fractional area change, or wall-motion score index. Hemodynamic parameters were not affected by contrast injections. Thus, the i.v. administration of BR1 allows us to accurately detect myocardial perfusion defects during coronary occlusion and, to a lesser extent, myocardial reperfusion after thrombolysis.

Animals↗
PubMed1996

Cattell's 16 PF and PSY inventory: relationship between personality traits and behavioral responses in patients with acute myocardial infarction.

The aim of this study was to investigate the relationships between personality and behavioral responses in patients with acute myocardial infarction. In a first step, a new instrument (PSY Inventory) for assessment of six behavioral characteristics (Sense of Responsibility, Energy and Competitiveness, Obsessive Behavior, Anger and Hostility, Stress-related Disturbances, Time Urgency) was developed by using factor analysis on intercorrelations of responses from 524 subjects of the general population. Internal consistency reliability for each of the PSY subscales was estimated by Cronbach alpha coefficients. In a second step, the PSY Inventory was administered with the Cattell 16 PF Questionnaire to 838 patients affected by acute myocardial infarction. Significant correlations although relatively low in magnitude for PSY Inventory subscales and certain scales of the Cattell 16 PF were found. With factor analysis on 22 variables (including the six PSY Inventory subscales and the 16 scales of the Cattell 16 PF), five second-order factors were identified, namely, Extraversion, Neurotic Anxiety, Superego Strength, Pathemia, and Neurotic Hostility. While a Pathemia Factor (characterized by sensitivity, imagination, and self-sufficiency) was factorially independent of scales of the PSY Inventory, Extraversion, Neurotic Anxiety, Superego Strength, and Neurotic Hostility Factors were composed of the PSY Inventory scales and Cattell 16 PF scales combined. These relationships would reflect the concordance of internal constructs for behavioral measures of the PSY Inventory and those of personality traits of the 16 PF Questionnaire in patients with acute myocardial infarction.

Adaptation, Psychological↗
PubMed1996

Surgical research in orthotopic liver transplantation: experiences in the pig model.

Since the very beginning of liver transplantation in humans, research in animals has had close relationship with clinical practice. Results obtained in animals have been transferred to the clinics and problems borne in the clinics have been addressed again in animals for to be answered clearly. In this review the authors report their experience of transplantation in the pig model and discuss the significance of a team cooperation in the laboratory as a preparatory step for clinical practice.

Anesthesia↗
PubMed1995

The new nitroderivative ITF 296 improves collateral blood flow in a canine model of coronary thrombosis.

The actions of ITF 296 and isosorbide dinitrate (ISDN), 20, 70, and 200 g/kg/min, on myocardial transmural blood flow distribution during acute thrombotic occlusion of the left circumflex coronary artery (LCX) have been evaluated in seven and three anesthetized open-chest dogs, respectively, and compared with four animals receiving vehicle. Occlusion of LCX was achieved in 14 +/- 2 min by the insertion of a copper coil. This caused transmural myocardial ischemia in the LCX area, while leaving blood flow in the left anterior descending coronary artery (control area) unaffected. Infusion of ITF 296 (200 g/kg/min) increased transmural coronary flow in the border zone and in the control area without affecting blood flow in the central ischemic area. ISDN, given in the same dose, reduced systemic blood pressure but did not affect LCX blood flow. In three dogs with residual perfusion in the LCX central area ITF 296 also increased blood flow. These results confirm that ITF 296 promotes an increase of flow to the border zone, thus possibly reducing the area of myocardial infarction.

Anesthesia↗
PubMed1994

The second-order factor structure of Cattell's 16 PF in patients with coronary heart disease.

The second-order factor structure of the 16 Personality Factor Questionnaire (16 PF) was validated on a sample of 940 patients hospitalized for coronary heart disease. The purpose of this investigation was the evaluation of second-order factor structure, already confirmed for normal subjects, of a selected pathological population. With factor analyses, oblique promax rotation, five second-order factors were identified, namely, Anxiety, Extraversion, Pathemia, Control, and an unidentified factor. These results were compared with those of Cattell's and Krug's studies. As a high congruence coefficient was shown, a good replication of Cattell's originally published second-order factors was achieved.

Adult↗
PubMed1994

[Personality and acute myocardial infarction: distinctive traits].

AIM OF THE STUDY: Aim of this study is to evaluate the presence of peculiar personality traits in patients with acute myocardial infarction as compared with normal subjects. METHODS: The Sixteen Personality Factor Questionnaire (16 PF) by Cattell (D form) is administered to 654 patients (558 males, 96 females) hospitalized for acute myocardial infarction in 16 coronary care units and to 398 normal subjects (261 males, 137 females). The diagnosis of myocardial infarction is made according to the presence of at least two of the following criteria: prolonged chest pain, elevation of CPK and CPKMB (twice the upper normal values), Q wave on the electrocardiogram. The normality of the control group is assured by specific exclusion criteria (cardiac or psychiatric disease, metabolic and endocrine disease, continued therapeutic treatment for any organic disease, or continued assumption of hypnotic and/or anxiolytic drugs). RESULTS: In comparison with the control group, infarcted males result significantly different for factors C, N, Q1, Q4 (p < 0.001), for factors B, O (p < 0.01) and A, H, I (p < 0.05). Females with myocardial infarction differ significantly for factors C, O and I (p < 0.05). Four second-order factors is obtained from Cattell's 16 PF by factorial analysis: QI (anxiety), QII (extroversion), QIII (sensitivity), QIV (superego strength). The infarcted population shows statistically significant differences compared with controls: infarcted males show higher QI (p < 0.001) and lower QII and QIII (p < 0.05) while infarcted females have higher QI (p < 0.05). CONCLUSIONS: These differences confirm that peculiar personality traits can be found in patients with acute myocardial infarction. In particular, infarcted males are emotionally unstable, anxious, rigid and depressed, and have problems in communication with others; infarcted females differ from the normal population for being emotionally unstable, anxious and for having a less flexible mental disposition. The higher anxiety level in patients with acute myocardial infarction may be related to the neuroticism that, in other studies, has been often found to be associated with cardiovascular disease. In conclusion, with respect to the normal population, patients with acute myocardial infarction appear to be anxious introverts, with conflictual personality.

Adult↗
PubMed1993

Intracoronary air-filled albumin microspheres for myocardial blood flow measurement.

OBJECTIVES: The aim of this study was to explore the possibility of quantifying coronary blood flow by myocardial contrast echocardiography with air-filled serum albumin microspheres (Albunex). BACKGROUND: Air-filled albumin microspheres have been proposed as an intravascular tracer for the study of myocardial perfusion by contrast echocardiography. METHODS: In six anesthetized open chest dogs, the left circumflex coronary artery was cannulated and perfused by a roller pump with blood from the femoral artery. Both air-filled albumin microspheres (0.4 ml, 2 x 10(8) spheres/ml) and technetium-99m-labeled albumin were injected as a bolus into the coronary cannula at baseline and after treatment with dipyridamole (0.56 mg/kg body weight intravenously for 4 min). Two-dimensional echographic images of the left ventricular short axis were digitized to generate myocardial time-intensity curves; myocardial radioactivity was measured by an external detector to generate radionuclide time-activity curves. RESULTS: After dipyridamole, left circumflex coronary artery blood flow (as measured by both the pump and an electromagnetic flow meter) significantly increased (from 1.06 +/- 0.28 to 3.61 +/- 1.43 ml/min per g of myocardium). Peak intensity and rise time of contrast echo curves were able to differentiate baseline myocardial perfusion from coronary hyperemia but did not show any significant correlation with coronary blood flow. A weak inverse correlation with coronary blood flow was provided by myocardial mean transit time of air-filled albumin microspheres (r = 0.33). Conversely, a close inverse correlation with coronary blood flow was obtained by myocardial mean transit time of technetium-99m-labeled albumin (r = 0.95). Myocardial transit time of air-filled albumin microspheres (1.95 +/- 0.60 s) was also markedly shorter than that of labeled albumin (5.35 +/- 3.43 s, p < 0.001) and the measurements were less reproducible. CONCLUSIONS: In this experimental study, coronary blood flow was not adequately quantified by myocardial contrast echocardiography with intracoronary injection of air-filled albumin microspheres.

Albumins↗
PubMed1993

Effects of coronary blood flow on myocardial grey level amplitude in two dimensional echocardiography: an experimental study.

OBJECTIVE: The aims were: (1) to evaluate whether differences in absolute and cyclic echocardiographic image amplitude exist in different layers (subendocardium and subepicardium) and regions (septal, anterior, lateral, inferior wall) of the canine left ventricle; (2) to assess the dependence of these variables upon local variations of coronary blood flow. METHODS: In six anaesthetised open chest dogs the circumflex coronary artery was cannulated and perfused by a roller pump with blood from their own femoral artery. Maximum coronary vasodilatation was obtained by continuous adenosine infusion. The absolute values and the transmural distribution of coronary blood flow were measured by radionuclide labelled microspheres. Echo images were obtained in short axis view by a commercially available electronic sector scanner with a 5.0 MHz transducer directly placed on the epicardial surface of the right ventricle, and digitised off-line into a matrix of 256 x 256 pixels with 25% grey level per pixel. The average grey level was calculated for each region of interest. RESULTS: In 32 different conditions, circumflex flow ranged from 0.80 to 12.89 ml.min-1.g-1 and the endocardial/epicardial ratio of flow from 0.53 to 1.73. In the circumflex region (subjected to flow changes) segmental amplitude varied from 76(SD 20) (end diastole) to 56(18) (end systole), p < 0.001. In all regions, a consistent cyclic variation was found, ranging from 9(14) to 28(16)%. For all levels of flow, subendocardial and subepicardial regions showed similar values of both absolute amplitude and cyclic variation. No significant relationship was found between transmural distribution of blood flow and either segmental amplitude (r = 0.26) or cyclic variation (r = 0.04). CONCLUSIONS: (1) a consistent cyclic grey level variation is present in all regions of the canine left ventricle, but subendocardial and subepicardial layers show similar values of both absolute amplitude and cyclic variation; (2) in the absence of severe underperfusion and echocardiographically detectable dyssynergy, absolute amplitude and cyclic variation are totally unrelated to changes in coronary blood flow.

Animals↗
PubMed1993

Myocardial washout of sonicated iopamidol does not reflect the transmural distribution of coronary blood flow.

It has been shown in previous studies that myocardial contrast echocardiography provides quantitative information on coronary blood flow. However, the ability of contrast echo to assess the transmural (endo/epicardial) distribution of blood flow is still debated. To test this hypothesis, the left circumflex coronary arteries of six anaesthetized open-chested dogs were cannulated and perfused with blood from the femoral artery. At different rates of coronary blood flow, during adenosine-induced coronary vasodilation, sonicated iopamidol and radionuclide labelled microspheres were injected into the coronary cannula, immediately proximal to a mixing chamber. Two-D echo images were digitized and myocardial time-intensity curves were obtained for the endocardial, mid- and epicardial layers. A good correlation existed between contrast washout of the entire ventricular wall and coronary flow (r = 0.85). However, the washout rate from the endo-, mid- and epicardial layers showed weak correlations with corresponding regional blood flows measured by microspheres (r = 0.56, 0.71 and 0.58, respectively). No significant relationship was found between the endo/epicardial washout ratio and the corresponding flow ratio by microspheres. Thus, measurement of the transmural distribution of coronary blood flow by myocardial contrast echocardiography remains an elusive goal.

Animals↗
PubMed1992

Myocardial washout of sonicated iopamidol reflects coronary blood flow in the absence of autoregulation.

OBJECTIVES: The aim of the study was to evaluate the relation between measurements derived from myocardial contrast echocardiography and coronary blood flow. BACKGROUND: Contrast echocardiography has the potential for measuring blood flow. METHODS: In six open chest anesthetized dogs, the left circumflex coronary artery was cannulated and perfused with blood drawn from the left femoral artery. While adenosine was infused into the circuit, circumflex flow was generated by a calibrated roller pump to the point of abolishing coronary autoregulation. At each of 25 levels of coronary blood flow, paired bolus injections of sonicated iopamidol were performed proximal to a mixing chamber. The perfused area of the left circumflex coronary artery was labeled by radioactive microspheres injected into the perfusion line. Two-dimensional echocardiographic images of the left ventricular short axis were digitized off-line, and myocardial videodensity was measured in the area perfused by the left circumflex coronary artery to generate time-intensity curves. RESULTS: The washout slope of curves showed a good correlation with coronary blood flow, ranging from 0.5 to 12.5 ml/min per g of tissue. This correlation was good both in individual dogs (correlation coefficient [r] ranging from 0.78 to 0.96) and in the group of animals as a whole (r = 0.85). Washout slope also showed a good correlation with coronary diastolic pressure (r = 0.80), which ranged from 23 to 114 mm Hg, suggesting a possible primary effect of pressure on contrast washout. However, coronary blood flow appeared to be a stronger predictor of washout slope (partial F = 26.5, p < 0.001) than did perfusion pressure (partial F = 5.9, p < 0.05 by multiple regression). The injection to injection variability in myocardial washout slope appeared to be high (24%). The gamma variate fitting of curves did not improve the correlation with coronary flow (r = 0.78). CONCLUSIONS: Myocardial washout of sonicated iopamidol reflects coronary blood flow in a model in which coronary autoregulation is abolished.

Adenosine↗
PubMed1992

Regional myocardial deoxyglucose uptake following electrical stimulation of canine efferent sympathetic cardiopulmonary nerves.

OBJECTIVE: The aim was to study the effect of stimulating individual acutely decentralised cardiopulmonary nerves on myocardial uptake of deoxyglucose. METHODS: In 17 open chest anaesthetised dogs the efferent axons of individual decentralised cardiopulmonary nerves were stimulated intermittently throughout 1 h while haemodynamic variables were measured. Tritiated 2-deoxyglucose was injected intravenously at the beginning of stimulation. Atropine was given when a cardiopulmonary nerve with efferent parasympathetic axons was studied. Distribution of label was detected using a multiwire proportional chamber. It was compared to blood concentration of deoxyglucose to permit quantitative mapping of regional myocardial uptake during the stimulation of each nerve. RESULTS: Neural stimulation of most of sympathetic efferent cardiopulmonary nerves increased deoxyglucose uptake in all myocardial tissue. Uptake was greatest in the left ventricle, less in the right ventricle, and least in the left and right atria. Regional myocardial uptake was also observed following individual cardiopulmonary nerve stimulation. Some nerves caused greater uptake than others. Cardiopulmonary nerves which are known to enhance inotropism when stimulated induced little increase of deoxyglucose uptake, whereas other nerves known to exert little positive inotropic effect induced considerable uptake. There was no correlation between haemodynamic changes and deoxyglucose uptake. CONCLUSIONS: It appears that (1) efferent sympathetic axons in one cardiopulmonary nerve can preferentially increase deoxyglucose uptake in specific regions of the myocardium and (2) the mechanisms responsible for enhancement of glucose uptake may differ from those responsible for inotropic responses.

Animals↗
PubMed1992

[A mathematical model of the vascular architecture and of the distribution of resistances in the coronary tree].

The architecture and resistance distribution of the coronary arteriolar tree downstream 100 mu diameter vessels are still largely unknown, due to technical difficulties in direct visualization. In this study we propose a mathematical model of the architecture and the single vessel resistance distribution of terminal arteriolar vasculature in the beating dog heart, based on the analysis of embolization-induced changes of total coronary resistance. Coronary embolization was performed by injecting several boluses of 15 mu (6 cases) and 25 mu (6 cases) plastic microspheres into the maximally vasodilated (adenosine infusion) left circumflex artery of the open chest dog. The relation between the number of plastic beads progressively injected to embolize 15 mu and 25 mu vessels and the resulting increase in total coronary resistance (occlusion function) was obtained in each experiment. If we consider a binary symmetric vascular tree with i) equal resistance for vessels of the same branching order and ii) optimal ratio between resistance of parent and daughter vessels at all branching sites, the simulation of embolization in such a system shows that the occlusion function of the terminal vessels N in the linear portion between 0 and N/2 occluded vessels has a slope S' which is 5.6 times lower than the slope S" between N/2 and 3/4 N occluded vessels and 3.6 times lower than the S' of the occlusion function of the preterminal vessels. The occlusion function in our experiments has a ratio S"/S' close to that predicted by the model and a ratio between the S' of the 25 mu and that of 15 mu experiments equal to 4.(ABSTRACT TRUNCATED AT 250 WORDS)

Animals↗
PubMed1990

Transmural redistribution of coronary resistance during embolization: a clue to intramyocardial small artery architecture.

The aim of this study is to assess vascular architecture and the single vessel resistance distribution of the subepicardial (epi) and subendocardial (endo) layers of the left ventricular wall. For this purpose, coronary embolization was performed by injecting three boluses of 25 microns plastic microspheres into the maximally vasodilated left circumflex artery of six dogs; transmural blood flow was assessed by 15-microns radioactive microspheres. A branching tree model of the intramyocardial small artery system--whose general characteristics were described in a previous study (Pelosi et al., 1987, Microvasc. Res. 34, 318-335)--was developed and its parameters were tested against the increase in epi and endo coronary resistance observed during embolization. Embolization produced a significantly greater increase in epi resistance after each bolus injection (from 10.3 +/- 1.1 to 195.6 +/- 32.5 mm Hg/ml/min/g after the last bolus, P less than 0.001) as compared to endo resistance (from 10.3 +/- 2.0 to 56.5 +/- 8.2 mm Hg/ml/min/g after the last bolus, P less than 0.001); as a consequence, the epi/endo resistance ratio increased from 1.09 +/- 0.11 to 1.50 +/- 0.13, 2.48 +/- 0.51, and 3.66 +/- 0.42 (P less than 0.05 for all embolizing injections). The experimental relation (occlusion function) between the number of embolizing beads injected and the epi and endo resistance values was used to define the parameters of the epi and endo branching tree model. Assuming that the embolizing microspheres lodge in vessels of similar resistance (that is similar diameter and length) in the two layers, the experimental results indicate that the intramyocardial small artery system can be depicted as a symmetric dichotomous branching tree with twofold more terminal vessels in the endo than in the epi.

Animals↗