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Biomedical subjects

L Spinelli

Publications and source records attributed to L Spinelli.

At least 37 records · Page 2Linked to original sources
PubMed2000

Circulating levels of cytokines and their site of production in patients with mild to severe chronic heart failure.

BACKGROUND: Patients with chronic heart failure have elevated levels of proinflammatory cytokines; however, the mechanism for their increased expression and the site of their production are unknown. METHODS: Twenty-two patients with heart failure, New York Heart Association functional class II to IV, underwent hemodynamic evaluation and echocardiographic study. Blood samples for cytokine evaluation were performed in the ascending aorta, coronary sinus, inferior vena cava, and hepatic vein. Levels of tumor necrosis factor-alpha (TNF-alpha), its soluble receptors sTNF-RI and sTNF-RII, interleukin-6 (IL-6), IL-6 soluble receptor, soluble gp130, interleukin-2 soluble receptor, and soluble Fas were measured with enzyme-linked immunosorbent assay kits. RESULTS: IL-6 concentrations were higher in class IV patients than in class III patients, which in turn were higher than those in class II. TNF-alpha, sTNF-RI, and sTNF-RII were higher in class IV patients than in class III and II patients. Significant correlations were found between IL-6 concentrations and left ventricular end-systolic volume (r = 0.64; P <.001), pulmonary wedge pressure (r = 0.56; P <.01), and left ventricular ejection fraction (r = -0.56; P <.01). No correlation was found between TNF-alpha and its soluble receptors and left ventricular volumes or hemodynamic measures. Finally, no difference in cytokine concentrations was found among the different sample sites. CONCLUSIONS: Among inflammatory cytokines, IL-6 concentrations better reflect the hemodynamic derangement in patients with heart failure. No cardiac or gut production of cytokines occurs in patients with mild to severe heart failure.

Adult↗
PubMed2000

Effects of losartan treatment on cardiac autonomic control during volume loading in patients with DCM.

This study evaluated the effect of angiotensin II receptor blockade on cardiac autonomic control adaptation and urine output in response to acute isotonic volume load in patients with idiopathic dilated cardiomyopathy (DCM) and asymptomatic to mildly symptomatic heart failure. Left ventricular volumes and heart rate variability measurements were assessed at baseline and during intravenous saline load in 14 patients before and after 2 mo of losartan treatment. After losartan treatment, blood pressure values were lower, whereas left ventricular ejection fraction was higher (F = 79, P < 0.001), than before treatment. During saline load, ejection fraction decreased before losartan treatment (F = 5.6, P < 0.05) but did not change after treatment. Urinary volume, unchanged during saline load in untreated patients, increased after losartan (F = 9.38, P < 0. 001). Time-domain measurements that represent vagal modulation of heart rate (root-mean-square successive differences and percentage of differences between successive R-R intervals >50 ms) decreased during saline load in untreated patients (F = 3.1, P < 0.05 and F = 6.5, P < 0.01, respectively), but not after losartan. Similarly, a decrease in very low frequency (F = 3.2, P < 0.05), low-frequency (F = 2.9, P < 0.05), and high-frequency power (F = 6.1, P < 0.01) after saline load was observed only in untreated patients. In patients with DCM, losartan treatment improves the cardiac autonomic adaptation and increases urine output in response to volume overload.

Adult↗
PubMed2000

Cardiovascular effects of depot long-acting somatostatin analog Sandostatin LAR in acromegaly.

Cardiovascular disease is the most severe complication of acromegaly accounting for the increased mortality of these patients. Recently, the slow-release form of octreotide (OCT; Sandostatin LAR, OCT-LAR), for im injection every 28 days, was reported to induce suppression of GH levels below 7.5 mU/L (2.5 microg/L) in 39-75% of patients, and normalization of insulin-like growth factor (IGF)-I levels for age in 64-88% of patients, with an excellent patients' compliance. The aim of the present study was to investigate the early effect of OCT-LAR treatment on the left ventricular (LV) structure and performance in 15 somatostatin analog-naive patients with acromegaly (GH, 94.8 +/- 24.9 mU/L; IGF-I, 757.9 +/- 66.6 microg/L), focusing on the early effect of GH and IGF-I suppression on the heart. Cardiac structure was investigated by echocardiography, whereas LV performance was investigated by gated-blood-pool scintigraphy, before and after 3 and 6 months of treatment with OCT-LAR. OCT-LAR was initially administered im, at a dose of 20 mg every 28 days, for 3 months. In six patients, the dose was then increased to 30 mg every 28 days to achieve disease control, which was considered when fasting and/or glucose-suppressed GH values were below 7.5 and 3.0 mU/L, respectively, together with IGF-I values within the normal range for age. The treatment with OCT-LAR for 6 months induced a significant decrease of GH (to 12.9 +/- 3.0 mU/L) and IGF-I levels (to 340.3 +/- 40.2 microg/L) in all 15 patients. After 6 months of treatment, the percent IGF-I suppression was 52.8 +/- 4.4%, and serum GH/IGF-I levels were normalized in 9 patients. A significant decrease of LV mass index (LVMi), interventricular septum thickness, and LV posterior wall thickness was observed in all 15 patients after 3 and 6 months of OCT-LAR treatment: LVMi was decreased by 19.1 +/- 2.0% without any difference in patients with (19.9 +/- 2.7%) or without disease control (17.8 +/- 3.3%). Among the 11 patients with LV hypertrophy, 6 normalized their LVMi after treatment. At study entry, an inadequate LV ejection fraction (LVEF) at rest (<50%) was found in 5 patients (33.3%), whereas an impaired response of LVEF at peak exercise (<5% increase of basal value) was found in 9 patients (60%). A significant increase in LVEF, both at rest (from 51.6 +/- 2.6 to 58.1 +/- 1.7%, P < 0.01) and at peak exercise (from 51.6 +/- 2.3 to 60.2 +/- 2.4%, P < 0.001) was found in patients with (as compared with those without) disease control (from 55.2 +/- 3.8 to 58.0 +/- 4% and from 61.8 +/- 4.6 to 61.8 +/- 3.4%, respectively). Among the 5 patients with inadequate LVEF at rest, all but 1 regained a normal LVEF after 6 months of treatment; whereas, among the 9 patients with an impaired response of the LVEF at peak exercise, 3 patients normalized, 4 improved, and 2 impaired their responses after treatment. The percent of IGF-I suppression was significantly correlated with the percent increase of resting LVEF (r = 0.644, P < 0.01). Exercise duration (from 6.0 +/- 0.7 to 7.3 +/- 0.7 min) and capacity (from 69.0 +/- 8.2 to 80 +/- 7.8 watts) were increased in the 15 patients considered as a whole, but the improvement in the exercise response was significant only in patients with disease control (P < 0.01 and P < 0.05, respectively) who also had an increase in the peak ejection rate (P = 0.03). No change in hemodynamic parameters, either at rest or at peak exercise, was found after treatment with OCT-LAR in the 15 patients. In conclusion, the results of the present study demonstrate that OCT-LAR im injections every 28 days induces a sustained suppression of GH levels and IGF-I levels in all acromegalic patients, allowing achievement of disease control in 60% of patients after 6 months of treatment. The sustained suppression of IGF-I levels was followed by a significant reduction of LVMi in all patients already after 3 months of treatment, with recovery of LV hypertrophy in 6 of 11 patients. (ABSTRACT TRUN

Acromegaly↗
PubMed2000

Measuring the complexity of time series: an application to neurophysiological signals.

Measures of signal complexity can be used to distinguish neurophysiological activation from noise in those neuroimaging techniques where we record variations of brain activity with time, e.g., fMRI, EEG, ERP. In this paper we explore a recently developed approach to calculate a quantitative measure of deterministic signal complexity and information content: The Renyi number. The Renyi number is by definition an entropy, i.e., a classically used measure of disorder in physical systems, and is calculated in this paper over the basis of the time frequency representation (TFRs) of the measured signals. When calculated in this form, the Renyi entropy (RE) indirectly characterizes the complexity of a signal by providing an approximate counting of the number of separated elementary atoms that compose the time series in the time frequency plane. In this sense, this measure conforms closely to our visual notion of complexity since low complexity values are obtained for signals formed by a small number of "components". The most remarkable properties of this measure are twofold: 1) It does not rely on assumptions about the time series such as stationarity or gaussianity and 2) No model of the neural process under study is required, e.g., no hemodynamic response model for fMRI. The method is illustrated in this paper using fMRI, intracranial ERPs and intracranial potentials estimated from scalp recorded ERPs through an inverse solution (ELECTRA). The main theoretical and practical drawbacks of this measure, especially its dependence of the selected TFR, are discussed. Also the capability of this approach to produce, with less restrictive hypothesis, results comparable to those obtained with more standard methods but is emphasized.

Algorithms↗
PubMed1999

Visual activity in the human frontal eye field.

Although visual information processing in the monkey frontal eye field (FEF) has been well demonstrated, the contribution of its human homologue to vision is still unknown. Here we report a study of intracranial visual evoked potentials (VEPs) recorded from the human FEF which was identified by electrical cortical stimulation. Electrical stimulations and EEG recordings were carried out via subdural grid electrodes placed over the frontal cortex in three epileptic patients. Evoked eye movements were mainly horizontal and always directed to the hemispace contralateral to the stimulation site. Intracranial VEPs showed responses predominately to stimuli in the contralateral visual field. Our findings demonstrate a close relationship between the direction of the electrically elicited eye movements and the visual stimulus location which predominantly leads to neural responses in the FEF. These findings provide evidence for the functional role of the human FEF in the analysis of visual stimuli from the contralateral visual field as well as in the generation of eye movements towards these conspicuous targets.

Adolescent↗
PubMed1999

Wavelet transform analysis of heart rate variability during dipyridamole-induced myocardial ischemia: relation to angiographic severity and echocardiographic dyssynergy.

BACKGROUND: Analysis of heart rate variability (HRV) is a valuable noninvasive method for quantifying autonomic cardiac control in humans and has been utilized during dipyridamole echocardiographic test to differentiate positive from negative test results. HYPOTHESIS: We aimed to evaluate, by means of HRV analysis, the influence of the angiographic severity of coronary artery disease on cardiac autonomic control during dipyridamole-induced myocardial ischemia. METHODS: We analyzed RR interval variability changes during dipyridamole-induced myocardial ischemia in 31 selected patients (mean age 54 +/- 9 years) with available coronary angiography and positive dipyridamole echocardiographic test. Spectral components of HRV were assessed by means of wavelet transform analysis for the last 5 min before the beginning of the test (baseline) and for 5 min after the onset of ischemia-related events (peak dipyridamole effect). RESULTS: Patients were divided into three groups according to the number of coronary diseased vessels (Group A, single-vessel disease; Group B, double-vessel disease; Group C, triple-vessel disease). No difference was detectable at baseline among the three groups. After dipyridamole, low-frequency power, a measure of sympathetic modulation of heart rate, increased and echocardiographic wall motion score index worsened in all groups (p < 0.001). The increase in low-frequency power was more evident in Group C patients than in the other two groups (p < 0.005). Furthermore, after dipyridamole, a direct correlation was found between low-frequency power and wall motion score index (r = 0.59; p < 0.001). CONCLUSIONS: These data suggest that HRV analysis performed during dipyridamole echocardiographic test provides useful information to assess the severity of coronary artery disease.

Autonomic Nervous System↗
PubMed1999

Left temporal rhythmic electrical activity: a correlate for psychosis? A case report.

It is well recognized that epileptic patients are at higher risk for acute or chronic psychotic states than non-epileptic subjects. Here we present intracranial depth electrode recordings during a psychotic episode in a 20-year-old woman who was referred for presurgical evaluation. Unrelated to her seizures, she presented acoustic hallucinations and delusions and became agitated for a duration of 18-24 hours. During this period, a new unusual pattern of sharp slow waves was seen semi-rhythmically every 2-3 sec from left anterior neocortical temporal areas. Her condition responded well to a treatment with Haloperidol, but not with Benzodiazepines. Ictal and interictal scalp- and depth-EEG recordings outside the psychotic episode as well as MRI-based volumetry, PET, SPECT and neuropsychological testing gave evidence of bilateral temporal and frontal dysfunction. This case report suggests that psychosis in epileptic patients may be based on a bilateral cerebral dysfunction linked together in a pathological network, but with a focal (here: left temporal) driving mechanism.

Adult↗
PubMed1999

Spatiotemporal EEG analysis and distributed source estimation in presurgical epilepsy evaluation.

In the attempts to localize electric sources in the brain on the basis of multichannel EEG and/or MEG measurements, distributed source estimation procedures have become of increasing interest. Several commercial software packages offer such localization programs and results using these methods are seen more and more frequently in the literature. It is crucial that the users understand the similarities and differences of these methods and that they become aware of the advantages and limitations that are inherent to each approach. This review provides this information from a theoretical as well as from a practical point of view. The theoretical part gives the algorithmic basis of the electromagnetic inverse problem and shows how the different a priori assumptions are formally integrated in these equations. The authors restrict this formalism to the linear inverse solutions i.e., those solutions in which the inversion procedure can be represented as a matrix applied to the data. It will be shown that their properties can be best characterized by their resolution kernels and that methods with optimal resolution matrices can be designed. The authors also discuss the important problem of regularization strategies that are used to minimize the influence of noise. Finally, a new kind of inverse solution, termed ELECTRA (for ELECTRical Analysis), is presented that is based on constraining the source model on the basis of the currents that can actually be measured by the scalp recorded EEG. The practical part of the review illustrates the localization procedures with different clinical data sets. Three aspects become important when working with real data: 1) Clinical data is usually far from ideal (limited number of electrodes, noise, etc.). The behavior of inverse procedures in such unfortunate situations has to be evaluated. 2) The selection of the time points or time periods of interest is crucial, especially in the analysis of spontaneous EEG. 3) Additional information coming from other modalities is usually available and can be incorporated. The authors are illustrating these important points in the case of interictal and ictal epileptiform activity. Spike averaging, frequency domain source localization, and temporal segmentation based on electric field topographies will be discussed. Finally, the technique of EEG-triggered functional magnetic resonance imaging (fMRI) will be illustrated, where EEG is recorded in the magnet and is used to synchronize fMRI acquisition with interictal events. The analysis of both functional data, i.e. the EEG in terms of three-dimensional source localization and the EEG-triggered fMRI, combines the advantages of the two techniques: the temporal resolution of the EEG and the spatial resolution of the fMRI.

Adult↗
PubMed1999

Comparison of verapamil versus felodipine on heart rate variability in hypertensive patients.

OBJECTIVE: We evaluated the effect of two calcium channel blockers, verapamil and felodipine, on heart rate variability in hypertensive patients. DESIGN: Time and frequency domain measures of heart rate variability were obtained from 24 h Holter recording in 25 previously untreated hypertensive patients without left ventricular hypertrophy, before and after 3 months of verapamil slow-release treatment (240 mg once daily) or felodipine extended-release treatment (10 mg once daily). RESULTS: Blood pressure values decreased with both drugs. Measures of heart rate variability, comparable at baseline in the two groups, were unchanged after felodipine. After verapamil, the average RR interval, the square root of the mean of the squared differences between all adjacent normal RR intervals (r-MSSD) and the percentage of differences between all adjacent normal RR intervals > 50 ms (pNN50), measures of vagal modulation of heart rate, increased (from 735 +/- 67 to 827 +/- 84 ms, P < 0.001; from 30 +/- 10 to 44 +/- 15 ms, P < 0.001; and from 3 +/- 2 to 7 +/- 6%, P < 0.01, respectively) and were higher than after felodipine. The coefficient of variation, a measure that compensates for heart rate effects, increased only after verapamil (from 5.8 +/- 1.3% to 6.6 +/- 1.0%; P < 0.05). High frequency power and its coefficient of component variance, both representing the vagal modulation of heart rate, increased after verapamil (from 5.33 +/- 0.29 to 5.80 +/- 0.27 In units, P < 0.001 and from 1.9 +/- 0.3 to 2.2 +/- 0.25%; P < 0.05). Finally, the low to high frequency power ratio, an indicator of sympathovagal balance, with a high value suggesting a sympathetic predominance, decreased after verapamil (from 2.16 +/- 0.41 to 1.36 +/- 0.35; P < 0.001), confirming the improvement in vagal modulation of heart rate. CONCLUSION: In hypertensive patients, despite a comparable anti-hypertensive effect, verapamil, but not felodipine, has favourable effect on cardiac autonomic control.

Aged↗
PubMed1999

Topological aspects of geometrical signatures of phase transitions.

Certain geometric properties of submanifolds of configuration space are numerically investigated for classical phi(4) models in one and two dimensions. Peculiar behaviors of the computed geometric quantities are found only in the two-dimensional case, when a phase transition is present. The observed phenomenology strongly supports, though in an indirect way, a recently proposed topological conjecture about a topology change of the configuration space submanifolds as counterpart to a phase transition.

Journal Article↗
PubMed1999

Cardiac autonomic responses to volume overload in normal subjects and in patients with dilated cardiomyopathy.

This study evaluated the effects of acute isotonic volume expansion on heart rate variability (HRV) in 10 patients with dilated cardiomyopathy (DCM) and in 10 age- and sex-matched normal volunteers. Echocardiographic left ventricular volumes and HRV measurements by continuous Holter recording were assessed at baseline, at 60 and 120 min during intravenous saline load (0.9% NaCl, 0.25 ml. kg(-1). min(-1)), and 60 min after infusion was terminated. Data analysis was performed by repeated-measures ANOVA. After volume expansion, left ventricular ejection fraction increased (F = 9.8; P < 0.001) in normal subjects and decreased (F = 8.7; P < 0.001) in DCM patients. During volume expansion a significant difference was also detectable between the two groups in root-mean-square successive difference (F = 25.2; P < 0.001), percentage of differences between successive normal R-R intervals >50 ms (F = 97.6; P < 0.001), high-frequency power (F = 50.1; P < 0.001), and low-frequency power (F = 41.6; P < 0.001), all of which reflect parasympathetic modulation of heart rate; in fact, these measurements increased in normal subjects and decreased in DCM patients. In normal subjects, the increase in HRV measurements during volume expansion suggests a parasympathetic activation, mediated by stimulation of cardiopulmonary and arterial mechanoreceptors. On the contrary, in DCM patients the parasympathetic withdrawal, already detectable at baseline, increases during volume expansion.

Adult↗
PubMed1999

[Heart tomography with 99mTc sestamibi and echocardiography with dobutamine in the identification of reversible left ventricular dysfunction in patients with acute myocardial infarction].

INTRODUCTION: We investigated the role of technetium-99m (99mTc) sestamibi cardiac imaging and dobutamine echocardiography in detecting myocardial viability early after acute myocardial infarction. MATERIAL AND METHODS: Nineteen patients (mean age 52 +/- 10 years) underwent coronary angiography, low-dose dobutamine echocardiography and rest 99mTc sestamibi imaging within 10 days of myocardial infarction. All patients were revascularized. Resting echocardiogram was repeated 8 months later to evaluate segmental functional recovery. RESULTS: Sixty-one of 108 akinetic or dyskinetic segments at baseline showed functional recovery after revascularization. Sensitivity in predicting segmental functional recovery was 87% for sestamibi imaging and 66% for dobutamine echocardiography (p < 0.001), while specificity and accuracy were comparable. Sestamibi activity was the strongest predictor of segmental functional recovery (p < 0.001). CONCLUSIONS: Dobutamine echocardiography predicts functional recovery after myocardial infarction. However, sestamibi imaging is useful to identify patients with dysfunctional segments without contractile reserve which may benefit by revascularization.

Cardiotonic Agents↗
PubMed1999

Prediction of recovery of left ventricular dysfunction after acute myocardial infarction: comparison between 99mTc-sestamibi cardiac tomography and low-dose dobutamine echocardiography.

UNLABELLED: The aim of this study was to evaluate the role of 99mTc-sestamibi cardiac imaging and dobutamine echocardiography in detecting myocardial viability early after acute myocardial infarction. METHODS: Forty-nine patients (mean age 52 +/- 10 y) underwent coronary angiography, low-dose dobutamine echocardiography, radionuclide angiography and rest 99mTc-sestamibi imaging within 10 d after myocardial infarction. Of these patients, 19 were revascularized and 30 were treated medically. Resting echocardiogram and radionuclide angiography were repeated 8 mo later to evaluate segmental functional recovery and changes in left ventricular (LV) ejection fraction, respectively. RESULTS: In revascularized patients, 61 of 108 akinetic or dyskinetic segments showed functional recovery. In these patients, sensitivity in predicting segmental functional recovery was 87% for sestamibi imaging and 66% for dobutamine echocardiography (P < 0.001), whereas specificity and accuracy were comparable. Sestamibi activity (> or =55% of peak) was the strongest predictor of segmental functional recovery (P < 0.001) and of LV ejection fraction improvement > or =5% (P < 0.01) after revascularization. In medically treated patients, 60 of 149 akinetic or dyskinetic segments showed functional recovery. In these patients, the majority (94%) of segments with contractile reserve on dobutamine were viable on sestamibi imaging and 86% of them improved function at follow-up. Functional recovery was poor in segments without contractile reserve either with (38%) or without (62%) preserved sestamibi uptake. Inotropic response was the best predictor of segmental (P < 0.001) and global (P < 0.01) LV functional improvement in medically treated patients. CONCLUSION: Dobutamine echocardiography predicts spontaneous functional recovery after acute myocardial infarction. However, sestamibi imaging is useful to identify patients with dysfunctional myocardium without contractile reserve who may benefit from coronary revascularization.

Acute Disease↗
PubMed1997

From flow cytometric BrdUrd data to cell population growth and doubling time.

We describe a direct way to use flow cytometric data for measuring the growth curve of a cell population. The starting point is analysis of the intrinsic informative content of the time course, after bromodeoxyuridine (BrdUrd) labeling, of the percentages of cells detected within four windows of biparametric BrdUrd-DNA histograms. We did not introduce a particular cell cycle model or use the hypothesis of exponential growth. We obtained a simple formal proof of the existence of four independent formulae connecting the flow cytometric data and the relative growth curve of the cell population. The formulae were then challenged in a number of simulated kinetic scenarios, moving away from their expected limits of validity. The results suggest additional uses of the formulae and a way of estimating cell-cycle-phase durations. Considering exponential growth in the presence of cell loss, the formulae were used to estimate the potential doubling time from a single flow cytometric measure vs. other procedures that additionally require an estimate of the duration of the phase S. The theoretical precision of the procedures may differ depending on how cell loss occurs.

Antimetabolites↗
PubMed1997

May age onset be relevant in the occurrence of left ventricular hypertrophy in Friedreich's ataxia?

BACKGROUND: Although heart involvement has been widely reported in Friedreich's ataxia (FA), which is the most prevalent of the spino-cerebellar degenerative diseases, the reason that cardiac abnormalities develop has not been yet established. HYPOTHESIS: The investigation was undertaken to study the prevalence and characteristics of cardiac abnormalities in patients with FA and to evaluate whether the presence of left ventricular hypertrophy could be predicted. METHODS: In all, 75 patients with FA and 16 patients with late onset FA (LOFA) disease were investigated for cardiac abnormalities using noninvasive methods. RESULTS: A significant (p < 0.01) difference in the age onset (9.8 +/- 3.9 years) was found in 31 of the 75 patients with FA (41%) who showed left ventricular hypertrophy (LVH) at echocardiographic examination compared with the remaining 44 patients with FA without LVH (12.6 +/- 4.3 years). Moreover, none of the 16 patients with LOFA (age onset 26.5 +/- 4.2 years) showed abnormalities at echocardiographic examination. A significant (p < 0.01) concordance in the familial distribution of hypertrophy was also found. CONCLUSION: These data suggest that the earlier the disease develops the more frequently LVH occurs.

Adolescent↗
PubMed1997

Extracranial localization of intracranial interictal epileptiform activity using LORETA (low resolution electromagnetic tomography).

Besides the standard clinical methods of EEG waveshape analysis, mathematical models for reconstruction of dipolar sources from the digitized surface EEG have been introduced in epilepsy research. Although useful for localizing focal sources, these methods are inadequate for analyzing widespread epileptiform activity. A recently introduced alternative method called LORETA (low resolution electromagnetic tomography, Pascual-Marqui et al., 1994), directly computes the current distribution throughout the full brain volume, assuming that neighboring neuronal populations are simultaneously and synchronously activated. In mathematical terms the method selects the smoothest of all possible 3-dimensional current distributions, inherently introducing a certain amount of dispersion. In 7 patients, undergoing simultaneous EEG recording from 10 intracranial (subdural) and 22 extracranial electrodes, 111 subdural discharges (61 subtemporal and 50 lateral temporal) were identified. The exact time point of maximal intracranial activity was automatically identified, and the LORETA solution at that timepoint was computed from the surface EEG. Statistical comparison revealed significantly higher LORETA current density in the area corresponding to the subdurally recorded spike compared to other areas, and a more anterior and more medial LORETA location for subtemporal compared to lateral temporal spikes. This study indicates that the LORETA technique may become a useful method to localize electrical activity in the brain.

Adolescent↗
PubMed1995

Relation between diastolic perfusion time and coronary artery stenosis during stress-induced myocardial ischemia.

BACKGROUND: Experimental studies have demonstrated that during stress-induced myocardial ischemia, coronary obstruction and diastolic perfusion time are factors that limit subendocardial perfusion and correlate to degree of myocardial dysfunction. The relation between these two factors has not yet been investigated in humans. The aim of the present study was to assess the relation between diastolic perfusion time and degree of coronary stenosis during different types of stress tests. METHODS AND RESULTS: Nine patients with isolated and proximal stenosis of the left anterior descending coronary artery were selected. Patients underwent three different randomized stress tests (upright, supine bicycle stress test, and transesophageal atrial pacing). Diastolic perfusion time, heart rate (RR interval), and systolic and diastolic pressures were measured during the test and at the ischemic threshold (0.1-mV ST-segment depression). Angiographic measurements of coronary stenosis were evaluated by quantitative coronary angiography. At the ischemic threshold, significant differences among tests were found in heart rate (P < .05), systolic pressure (P < .001), and diastolic pressure (P < .05). In each stress test, diastolic perfusion time at the ischemic threshold was closely correlated with minimal stenosis diameter (r = .97; P < .001) and percent diameter stenosis (r = .92; P < .001) with no difference among the tests. In contrast, heart rate, rate-pressure product, and time to ischemic threshold were not significantly correlated with percent diameter stenosis and minimal stenosis diameter. No significant correlation was observed at the ischemic threshold between diastolic perfusion time and corresponding values of heart rate, despite the close correlation at rest (r = .95; P < .001). CONCLUSIONS: Despite differences in associated hemodynamic responses to various stress tests, a close relation exists between stenosis severity and diastolic perfusion time at the onset of stress-induced myocardial ischemia. Therefore, diastolic perfusion time at the ischemic threshold may be an indirect estimate of the hemodynamic significance of coronary stenosis.

Coronary Angiography↗