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Biomedical subjects

A Mortara

Publications and source records attributed to A Mortara.

51 records · Page 3Linked to original sources
PubMed1994

[Assessment of the autonomic nervous system after infarction and its prognostic significance].

Recently there has been increased interest in the analysis of heart rate variability (HRV) and baroreflex sensitivity (BRS) for postinfarction risk stratification. HRV and BRS are decreased in patients following myocardial infarction and both a reduced HRV and a depressed BRS identify a subgroup at higher risk of cardiac mortality and arrhythmic events. In a large trial of post-myocardial infarction patients the relative risk of mortality was 5.3 times higher in the group with depressed HRV (standard deviation of normal RR intervals over 24 hour recordings < 50 ms) than in the group with preserved HRV. These findings were later confirmed by both time domain and power spectral analysis of HRV. The predictive value of depressed HRV was found to be independent of other established risk predictors including other Holter features and left ventricular ejection fraction. By testing reflex vagal activity, in a series of 78 patients recovering from a first myocardial infarction, the risk of death increased more than 15 times in the presence of a markedly depressed BRS (< or = 3 ms/mmHg). In a subsequent study BRS was found to be the most significant predictor of induction of sustained monomorphic ventricular tachycardia at programmed electrical stimulation. BRS seems to be more valuable than HRV in the prediction of arrhythmic events by providing a relative risk four times greater than HRV to accurately predict inducibility to ventricular tachycardia. Additional data have shown that BRS but not HRV did clearly separate postinfarction patients with aborted sudden death from similar patients without ventricular tachycardia or fibrillation.(ABSTRACT TRUNCATED AT 250 WORDS)

Autonomic Nervous System↗
PubMed1993

Is sympathetic neural hyperactivity in chronic heart failure affected by heart transplantation?

It has been suggested that immunosuppression with cyclosporine induces marked sympathetic neural hyperactivity in heart transplant recipients. In the present study, the resting level of sympathetic nerve activity was investigated with intraneural recording in nine patients with severe chronic heart failure (NYHA class III-IV despite ongoing therapy), in nine heart-transplanted patients with previous heart failure (NYHA class III-IV) receiving standard low-dose triple-drug immunosuppression and in six age-matched controls without cardiovascular disease. Compared to the control group, resting sympathetic nerve discharge was markedly increased in heart failure patients (92 +/- 2 vs 60 +/- 6 B/100 b, P < 0.01), sympathetic nerve activity was lower in the majority of heart failure patients after heart transplantation, and mean burst incidence was significantly lower than in the cardiac failure group (70 +/- 7, P < 0.01). The difference between transplanted patients and the control group was not statistically significant. Thus, heart transplant recipients may reduce the augmented central sympathetic drive associated with cardiac failure despite ongoing cyclosporine treatment.

Cyclosporine↗
PubMed1992

Circadian variation of spectral indices of heart rate variability after myocardial infarction.

The circadian variations of spectral indices of heart rate variability were analyzed in 20 patients 4 weeks after a first and uncomplicated myocardial infarction (MI) and in 20 control subjects. R-R interval and variance showed a characteristic day-night pattern with a significant reduction of the latter parameter in patients after MI (10,967 +/- 1109 msec2 vs 16,860 +/- 2132 msec2). Control subjects were characterized by a predominance of low-frequency (approximately 0.1 Hz) component during the day and of high-frequency (approximately 0.25 Hz) component during the night, which reflected the expected 24-hour pattern of variation of sympatho-vagal balance. A 24-hour elevation (64 +/- 3 normalized units [nu] vs 56 +/- 2 nu; p less than 0.05) of the low-frequency component and a smaller (23 +/- 2 nu vs 32 +/- 2 nu; p less than 0.05) high-frequency component during the night differentiated patients after MI from subjects. The difference between the two groups was even more evident when the 24-hour sympatho-vagal balance was assessed with the low frequency/high frequency ratio. Thus spectral analysis of heart rate variability indicates that in patients after MI there is an alteration of neural control mechanisms as indicated by the presence of signs of sympathetic activation and by the attenuation of the nocturnal increase in vagal tone.

Aged↗
PubMed1992

Three-dimensional NMR microscopy: improving SNR with temperature and microcoils.

It is widely held that the spatial resolution achievable by NMR microscopic imaging is limited in biological systems by diffusion to approximately 1-5 microns. However, these estimates were developed for specific imaging techniques and represent practical rather than fundamental limits. NMR imaging is limited by the signal-to-noise ratio (SNR). Diffusion effects on spatial resolution can be made arbitrarily small in principle by increasing the gradient strength. The exponential signal attenuation from random spin motion in a gradient, however, will reduce the signal far below the noise level when the voxel size is reduced much below 5 microns. Two factors can be optimized to improve the SNR: (1) the inductive linkage between microscopic samples and the detection apparatus and (2) the temperature of the rf probe. In this work, the filling factor was optimized using inductors with diameters less than 1 mm. It is furthermore shown that probe circuit cooling results in significant improvements in SNR, whereas cooling of the preamplifier is of little value when proper noise matching between the resonant circuit and preamplifier is accomplished. Using three-dimensional Fourier imaging techniques, we have obtained images of single-cell organisms with spatial resolution of approximately 6 microns. Practical limitations include mechanical stability of the apparatus, thermal shielding between the sample and probe, and the magnetic susceptibility of the sample.

Chlorophyta↗
PubMed1992

Autonomic nervous system adaptations to short-term exercise training.

Signs of sympathetic hyperactivity and low parasympathetic activity have been found during the acute and recovery phases of myocardial infarction and have been associated with an increased risk of cardiac mortality. Beneficial effects of physical training have been recently reported in post-myocardial infarction patients. We tested the hypothesis that physical training would be effective in improving the autonomic balance by studying 22 patients with a first and recent myocardial infarction who were randomly assigned to enter or not enter a 4-week in-hospital physical training program. Spectral indices of heart rate variability were analyzed at rest and during 70 degrees head-up tilt before and after the index training, not training period. As expected, physical training induced a significant increase in exercise duration (13.7 +/- 0.8 vs 17.1 +/- 0.1 min, p less than 0.001) and in the anaerobic threshold (9.5 +/- 0.7 vs 12.0 +/- 1.0 min, p less than 0.02) in trained patients, while no changes were observed in the untrained group. At entry, in both groups, spectral profile of heart rate variability was characterized by a predominant LF component and a smaller HF component with no further modification after head-up tilt. After 4 weeks, in resting conditions, no significant changes in spectral components were observed in both trained and untrained patients. After physical training, head-up tilt produced significant modifications in spectral profile with an increase in the LF component (84 +/- 3 vs 69 +/- 5 nu, p less than 0.01) and a decrease in the HF component (7 +/- 1 vs 19 +/- 4 nu, p less than 0.05) in trained patients, while no changes were observed in the untrained patients. Our data suggest that in postmyocardial infarction patients, 4 weeks of physical training may induce an improvement in the autonomic balance with a restoration toward normal in the reflex activity of the system.

Adaptation, Physiological↗
PubMed1992

Myocardial infarction and baroreflex sensitivity. Clinical studies.

Based on solid experimental evidence the concept has emerged that analysis of autonomic reflexes, and specifically of baroreceptive reflexes, might contribute to the identification of high risk subgroups in the post myocardial infarction phase. Accordingly, we brought this concept to clinical fruition and have performed the first clinical study to investigate the potential prognostic value of baroreflex sensitivity. The present article reviews those clinical results which indicate an almost 15 times greater risk for cardiac mortality among the patients with depressed baroreflex sensitivity. Baroreflex sensitivity has also been correlated with heart rate variability and it was found that the degree of correlation is relatively weak and such that it is not possible to predict one measure from the other. Thus, these two autonomic markers are not redundant. Among the various possibilities to induce favorable alterations in the autonomic balance, our group has selected and analyzed exercise training and the chronic administration of beta-blocking agents. Exercise training, examined in a case-control study involving 70 patients, was found to increase baroreflex sensitivity by 30%. Beta-blockers were found to augment baroreflex sensitivity in 40% of the patients tested. As a logical evolution of these studies we have initiated a large prospective collaborative study destined to enroll 1200 post myocardial infarction patients and to assess the prognostic value of baroreflex sensitivity, of heart rate variability, and of traditional markers such as left ventricular ejection fraction and late potentials.

Clinical Trials as Topic↗
PubMed1990

Simultaneous Doppler and thermodilution assessment of pulmonary artery flow during acute interventions in patients with chronic obstructive pulmonary disease.

Subcostal pulsed wave Doppler echocardiography of the right ventricular outflow tract was used to assess pulmonary arterial flow at basal conditions and during interventions in 20 patients with chronic obstructive pulmonary disease. The changes in the pulmonary flow induced by interventions ranged from -1.5 l/min to +4.18 l/min (73% to 183% of the basal value). When considered alone, heart rate changes induced by the interventions could explain 53% of the changes in pulmonary flow measured with thermodilution. When Doppler-assessed right ventricular stroke volume changes were also considered the coefficient of determination (R) increased to 77% (r = 0.88, p less than 0.001, SEE = 12%). Doppler echocardiography was less precise in predicting absolute basal values of pulmonary artery flow (r = 0.70, p less than 0.001, SEE = 1.00 l/min), probably indicating inaccurate assessment of the diameter of the right ventricular outflow tract.

Administration, Sublingual↗
PubMed1989

Acute and chronic effects of nicardipine on rest and exercise haemodynamics in post-myocardial infarction patients with latent cardiac failure.

The acute and chronic haemodynamic effects of nicardipine were studied, at rest and during exercise, in 10 post-myocardial infarction patients with latent cardiac failure and no signs of residual myocardial ischaemia. Intravenous administration of nicardipine (5 mg over 10 min) was associated with a significant increase in cardiac index and significant reductions in mean pulmonary artery pressure, mean pulmonary wedge pressure, total pulmonary resistance and systemic vascular resistance under conditions of rest and peak exercise. After 3 weeks of oral treatment (20 mg three times daily) cardiac index did not change, but the improvements in mean pulmonary artery pressure, mean pulmonary wedge pressure and total pulmonary resistance were sustained at rest and during exercise, at the same workload attained prior to medication. Chronic treatment with nicardipine significantly increased exercise tolerance, while mean pulmonary artery pressure, mean pulmonary wedge pressure and total pulmonary resistance were maintained below the control values. It is concluded that nicardipine improves both rest and exercise cardiac performance in post-myocardial infarction patients with latent cardiac failure, thus avoiding the risk of pulmonary congestion.

Clinical Trials as Topic↗
PubMed1988

Baroreflex sensitivity, clinical correlates, and cardiovascular mortality among patients with a first myocardial infarction. A prospective study.

Experimental studies have shown that among dogs with a healed myocardial infarction, depressed baroreflex sensitivity (BRS) identifies a subgroup at higher risk for sudden death. We have examined the relation among BRS, several clinical cardiovascular variables, and subsequent mortality in 78 patients below the age of 65 years who have had a first myocardial infarction. BRS was assessed by calculating the regression line relating phenylephrine-induced increases in systolic blood pressure to the attendant changes in the RR interval. A reduced BRS primarily reflects an impairment in the vagal efferent component of the baroreceptor reflexes. The BRS of the entire population was 7.8 +/- 4.9 msec/mm Hg. BRS was lower among patients with an inferior myocardial infarction (6.1 +/- 3.3 vs. 8.9 +/- 5.8 msec/mm Hg, p = 0.03), with a three- versus a one-vessel disease (4.8 +/- 2.7 vs. 7.1 +/- 3.1 msec/mm Hg, p = 0.04), and with episodes of ventricular tachycardia (5.1 +/- 3.0 vs. 8.3 +/- 5.1, p = 0.03). There was no correlation between BRS and left ventricular ejection fraction or with mean pulmonary capillary wedge pressure at peak exercise, but a correlation (r = 0.35, p less than 0.001) was present with exercise tolerance. During the 24 months mean follow-up period, there were six cardiovascular deaths (7.6%), and four were sudden.(ABSTRACT TRUNCATED AT 250 WORDS)

Blood Pressure↗
PubMed1982

[Benign gastric ulcer and ulcerated gastric carcinoma. Considerations on various clinico-endoscopic cases].

Clinical data, X-ray, findings, and the endoscopic and cytologic diagnosis of 94 patients admitted to hospital for gastric ulcer have been reviewed. The purpose of the study was to establish the frequency of malignancy and the reliability and comparative merits of clinical factors, radiology, endoscopy and multiple biopsies in arriving at exact diagnosis. The results show that endoscopy is the most accurate in differentiating benign from malignant gastric ulcers.

Adult↗
PubMedDate not supplied

Prognostic implications of autonomic nervous system analysis in chronic heart failure: role of heart rate variability and baroreflex sensitivity.

Increased sympathetic activity and plasma levels of norepinephrine (NE), parasympathetic withdrawal and impaired baroreflex gain have been reported in chronic heart failure (CHF). It is still debated whether, and if so, to what extent, the marked sympathetic activity influences the survival. Very little data is available on the prognostic implications of baroreflex sensitivity (BRS) and heart rate variability (HRV). Both BRS and HRV have been shown to be markedly reduced in CHF and significantly associated with the degree of ventricular dysfunction and with a further progression of the severity of the disease. Only small studies involving a limited number of patients have correlated these indices to an increased risk of death in CHF. We studied 119 consecutive sinus rhythm patients with mild to severe CHF. It was found that time and frequency parameters of HRV were not different between deceased and surviving patients, while BRS at univariate analysis was significantly associated with mortality; however, this prognostic information was not confirmed in a multivariate model. Although further analyses are necessary, our data and those of the literature do not confirm in CHF the important role which has been attributed to HRV and BRS in post-myocardial infarction risk stratification. In this paper some methodological limitations concerning the measure of these indices in CHF and possible different interpretative keys of the results are discussed to explain the discrepancies.

Journal Article↗
PubMedDate not supplied

Cardiovascular effects of TENS: heart rate variability and plethysmographic wave evaluation in a group of normal subjects.

Transcutaneous electrical nerve stimulation (TENS) is generally used in controlling pain. Side effects are not frequent, but sometimes do happen. Among these, automatic disturbances have been described. The purpose of the investigation was to study high frequency TENS effects on heart rate variability and the plethysmographic wave. Results showed no change in heart rate variability parameters (Standard Deviation, Mean Square Successive Difference) despite an increase in R-R interval, while a decrease in the amplitude of the plethysmographic wave was observed. This study seems to point out that high frequency TENS does not modify the neural control to the heart while a sympathominetic effect is shown on the peripheral plethysmographic wave.

Blood Circulation↗