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Biomedical subjects

S Ghiringhelli

Publications and source records attributed to S Ghiringhelli.

At least 19 recordsLinked to original sources
PubMed2001

Structure and dynamics of high molecular weight glutenin subunits of durum wheat (Triticum durum) in water and alcohol solutions studied by electron paramagnetic resonance and circular dichroism spectroscopies.

Complementary information on the structure and dynamics of high molecular weight glutenin subunits (HMW-GS) of durum wheat (Triticum durum) was obtained by means of two spectroscopic techniques. Electron paramagnetic resonance was used to investigate the dynamics of the HMW-GS hydrated with two 2-propanol/water mixtures at temperatures between 268 and 308 K by specific spin labeling of their cysteine residues. Spectra were of a composite type, resulting from two populations of spin labels differing in molecular mobility, both undergoing isotropic rotational diffusion. Diffusional coefficients and populations of the fast- and slow-moving spin labels, determined by an accurate spectral line shape analysis, are discussed as a function of temperature and water content in the solvent systems. Far-UV circular dichroism was employed to provide information on the secondary structure of the HMW-GS in three different solvents [aqueous 50% (v/v) 2-propanol, aqueous 0.1% (v/v) trifluoroacetic acid, and trifluoroethanol]. For the first one, the influence of temperature on HMW-GS structure was also investigated.

2-Propanol↗
PubMed2001

[New methods of functional assessment in the catheterization room. Pressure wire, Doppler flow wire and echocontrastomyography].

Although coronary angiography has been used for many years in the evaluation of coronary artery disease the limitations of this technique are well known. The functional significance of individual coronary artery stenoses may not be easily determined particularly in patients with intermediate stenoses, lesions with irregular and complex morphology and in subjects with multivessel diffuse disease and/or prior myocardial infarction. In selected patients, the role of abnormalities of vasomotion and function at the microcirculatory level cannot be assessed with lone coronary angiography. The functional evaluation of the results of percutaneous coronary interventions usually requires adjunctive non-invasive testing. New techniques for physiological evaluation of coronary artery disease are now available in the catheterization laboratory. The intracoronary pressure wires and Doppler flow wires may provide for an accurate evaluation of the functional significance of the individual stenosis and of the vasodilatory capacity of the coronary bed. Disease of the coronary microcirculation and vasomotion abnormalities may be recognized. Several studies have indicated that these techniques may be helpful in the clinical decision-making process. The strategy of deferring or performing percutaneous coronary interventions may be guided by on-line functional evaluation of the target stenosis and the result of interventions may be evaluated. In addition, new imaging modalities such as myocardial contrast echocardiography with new sonicated agents for intracoronary use may represent a novel approach to the direct evaluation of regional myocardial perfusion and microvascular integrity. The application of these techniques is safe, useful and cost-effective. Unfortunately, physiologic evaluation of the coronary artery disease by means of these techniques still remains confined to few catheterization laboratories.

Cardiac Catheterization↗
PubMed1996

Clinical evaluation of algorithms for ST measurement during exercise test.

HYPOTHESIS: Computer processing of the exercise electrocardiogram (ECG) has many advantages, but the reliability of the analysis algorithms is not easily evaluable. No standard annotated database, nor recommended practice for testing and reporting performance results is available: thus, performance evaluation of such devices can be accomplished only by using a set of unannotated recordings, obtained in clinical practice. We evaluated the accuracy of an original microcomputer-based exercise test analyzer comparing the ST computer output with the measurements obtained by two experienced cardiologists. METHODS: Six hundred ECG strips were randomly selected from the exercise test recordings of 60 patients. The ST shift (at J + 80 ms) was blindly assessed by two observers (with the aid of a calibrated lens) and compared with computer measurements. Correlation coefficients, linear regression equations, percent of discrepant measurements, and 95% confidence limits of the mean error were calculated for all leads, peripheral leads, precordial leads, and "stress-test" leads (II, III, aVF, V4, V5, V6). RESULTS: The computer did not analyze five samples on a total of 600 (0.83%) ECG strips because of excessive noise or signal loss, while 51 (8.5%) were considered unreadable by both observers and 67 (11.2%) were rejected by at least one observer. Correlation between the measurements taken by computer and observer(s) measurements was statistically significant (p < 0.001 for all lead groups), no systematic measurement bias was found, and the mean difference was lower than human eye resolution. CONCLUSIONS: Our algorithms provide results as good as those provided by trained cardiologists in measuring ST changes occurring during exercise test. However, this study did not evaluate whether computer improvement of the signal-to-noise ratio would allow accurate measurements even on cardiologists' uninterpretable ECG. This potential advantage of computer-assisted analysis could be assessed only by using a dedicated exercise test database, in which different patterns of noise are superimposed on noise-free recordings previously annotated for ST level.

Adult↗
PubMed1996

Assessment of heart rate variability changes during dipyridamole infusion and dipyridamole-induced myocardial ischemia: a time variant spectral approach.

OBJECTIVES: We sought to evaluate changes in RR interval variability during dipyridamole infusion and dipyridamole-induced myocardial ischemia. BACKGROUND: Myocardial ischemia and the autonomic nervous system can be mutually interdependent. Spectral analysis of RR interval variability is a useful tool in assessing autonomic tone. METHODS: We used a time variant autoregressive spectral estimation algorithm that could extract spectral variables even in the presence of nonstationary signals. Two groups were considered: group A (patients with ischemia, n = 15) with effort or mixed angina, angiographically assessed coronary artery disease and positive exercise and dipyridamole echocardiographic test results, and group B (control subjects, n = 10) with normal exercise and dipyridamole echocardiographic test results. We investigated the following variables: RR interval mean and variance, low frequency (LF) and high frequency (HF) power in normalized units, LF ratio (LF/LFbasal power), HF ratio (HF/HFbasal power) and LF/HF ratio. For each test epoch, we calculated for group A and group B the mean value +/- SE of all indexes considered. Differences due to an effect either of group (ischemic vs. control) or of time (including both drug and ischemia effects) were analyzed by using analysis of variance for repeated measurements. RESULTS: Dipyridamole injection was characterized by a reduction of all spectral components in negative test. The LF ratio was the only variable able to discriminate patients with ischemia from control subjects (p < 0.05), whereas a time effect was evident for both mean RR interval and high frequency power in normalized units (p < 0.05). The LF ratio decreased in group B from 1 +/- 0.00 (basal) to 0.31 +/- 0.22 (peak), and increased in group A from 1 +/- 0.00 to 15.41 +/- 6.59, respectively. Results of an unpaired t test comparing the peak values of the two groups were also statistically significant (p < 0.01). CONCLUSIONS: Our data show that time variant analysis of heart rate variability evidences an increase in the low frequency ratio that allows differentiation of positive from negative test results, suggesting that the electrocardiogram may contain ischemia information unrelated to ST-T variations, even if their enhancement requires a more complex data processing procedure.

Aged↗
PubMed1992

Mechanocardiographic effects of an elevated central venous pressure.

Since 1985 we demonstrated that the increase of left ventricular mean diastolic pressure shortens the interval existing between the onset of the electrocardiographic P-wave and the onset of the left apexcardiographic "a"-wave (Aubert et al., 1981; Mortarino et al., 1985). In particular we showed that left P-"a" time interval shortens below 100 msec when left ventricular mean diastolic pressure rises above 12 mmHg. Our results thus substantiated the previous reports related to the P-4th heart sound shortening and 4th heart sound--1st heart sound increase occurring in patients with left ventricular failure (Shapira et al., 1982). In that same period, Kesteloot and collaborators showed a direct relationship between the velocity of appearance of the right internal jugular pulse (JVP) waves and the value of central venous pressure (CVP) (Minten et al., 1985). Moreover the range of variability of the right P-"a" interval (which is the time elapsing between the onset of the electrocardiographic P-wave and the onset of the "a"-wave on the JVP tracing) is, in adult subjects, of similar magnitude of the left P-"a" interval (respectively 60-140 msec (Fishleder, 1968) and 80-160 msec (Mortarino et al., 1985) suggesting a symmetric effect of an elevation of diastolic pressure on left and right P-"a" intervals. We therefore decided to test this hypothesis in a group of patients.

Adult↗
PubMed1991

Intra- and paraprosthetic valve regurgitation. A color Doppler echocardiographic study.

We prospectively followed a cohort of 64 patients bearing an aortic or mitral prosthetic valve (mean follow-up 5.2 +/- 3.2 months) in order to evaluate if color-coded two-dimensional Doppler echocardiography (CFD) could provide some major advantages with respect to pulsed (PW) and continuous wave (CW) Doppler in the diagnostic accuracy of detection of intra-, and paraprosthetic leaks. During follow-up 4 cases of pathologic prosthetic regurgitation ensued and were all correctly and easily identified by CFD while one of them was missed both by PW and CW Doppler. Based on our results we conclude that CFD is the best noninvasive tool actually available for the correct identification of prosthetic valvular regurgitation because it can provide useful accessory information difficult to obtain with other echocardiographic techniques.

Adult↗
PubMed1991

Reliability of standard apexcardiography for the measurement of sudden variations in mean pulmonary capillary wedge pressure.

We simultaneously registered the left apexcardiogram together with the left intraventricular pressure curve immediately before and after ventricular angiography in order to evaluate whether the relation existing between apexcardiographic protodiastolic filling period duration (cR interval) and left ventricular mean diastolic pressure (LVMDP) was maintained even in the presence of sudden variations of LVMDP. Administration of contrast media resulted in a significant increase of LVMDP (from 11.8 to 23.9 mm Hg) and in a simultaneous decrease of the cR interval (from 108.5 to 71.0 msec) and noninvasive LVMDP calculated as 36-0.24* cR closely correlated with the invasive values both before and after angiography (overall correlation r = 0.94). Apexcardiography thus confirms to be the only highly reliable noninvasive technique which can be used by the clinical cardiologist to measure LVMDP and/or mean pulmonary capillary wedge pressure.

Adult↗
PubMed1990

Evaluation of noninvasive alternatives to right heart catheterization.

We mechanocardiographically evaluated 50 patients with acute myocardial infarction, invasively monitored by Swan-Ganz catheters, in order to assess if mechanocardiography could provide reliable hemodynamic informations. The last 25 subjects were also studied by pulsed Doppler echocardiography. Our results confirm the high precision of apexcardiography in assessing mean pulmonary capillary wedge pressure (r = 0.91) while Doppler echocardiography proved itself better than mechanocardiography in assessing cardiac output (r = 0.82 vs r = 0.78). Moreover, Doppler echocardiography allowed a good estimation of mean pulmonary artery pressure (r = 0.81) which cannot be assessed by other noninvasive methods. However, we could not find any clinically useful relationship between Doppler mitralic flow characteristics and mean pulmonary capillary wedge pressure. Therefore noninvasive methods could represent a valid alternative to right heart catheterization provided that an integrated Doppler echocardiographic and mechanocardiographic approach is used.

Blood Pressure↗
PubMed1990

Mechanocardiographic effects of ACE-inhibitors.

Twenty-one subjects who suffered a recent medium sized anterior myocardial infarction conditioning a mild congestive heart failure were randomly allocated to treatment with captopril (25 mg b.i.d., 10 pts) or placebo (11 pts). After 2 months of therapy the group on the active treatment showed a significant increase of apexcardiographic protodiastolic filling period duration reflecting a clear cut decrease of mean pulmonary capillary wedge pressure (from 14 +/- 2 to 7 +/- 3 mm Hg) while patients on placebo did not show any difference in respect to baseline. Neither treatment significantly modified the PEP/LVET ratio despite a significant increase of left ventricular ejection fraction in patients receiving captopril (from 37 +/- 4% to 43 +/- 5%). Cardiac response to ACE-inhibitors can thus be noninvasively monitored by apexcardiography.

Captopril↗
PubMed1988

Hemodynamic effects of celiprolol at rest and during exercise; a comparison with enalapril.

The antihypertensive effects of once-daily administration of celiprolol 400 mg were compared with those of once-daily enalapril 20 mg in 20 mild to moderate essential hypertensives in a single-blind study in which the subjects were randomized to 2 weeks' treatment with either drug, preceded by 2 weeks of placebo administration. Supine and standing systolic blood pressure (SBP), diastolic pressure (DBP), and heart rate (HR) were measured at rest and during exercise (exercise bicycle with increasing work loads up to 100 watts) at the end of either period, 20 to 24 hr after drug or placebo administration. Compared to placebo, both celiprolol and enalapril reduced resting supine and standing SBP and DBP to a marked and similar extent; resting HR was unaffected by enalapril, while celiprolol produced modest reductions. During exercise, however, celiprolol significantly attenuated rises in SBP and HR, while enalapril did not. Indexes of cardiac function at rest obtained by echocardiography and systolic time intervals were unaffected by either drug. Thus, despite similar reductions by both drugs in resting blood pressures, celiprolol produced better antihypertensive effects during exercise than enalapril.

Adrenergic beta-Antagonists↗
PubMed1988

Comparison of the antihypertensive effects of celiprolol and enalapril.

Muscular exercise is the most common stress imposed on the cardiovascular system and, in hypertensive patients, it causes an exaggerated increase in the already elevated blood pressure. The evaluation of any antihypertensive drug must, therefore, include an investigation of its effects on the haemodynamic response to exercise. For this reason the effects of celiprolol and enalapril were studied in hypertensive patients, both at rest and during an exercise stress test performed on a bicycle ergometer. The haemodynamic changes observed were very similar at rest: both drugs consistently reduced blood pressure without impairing either myocardial geometry or function. The only between drug difference found at rest was slight bradycardia with celiprolol, whereas heart rate was unaffected by enalapril. By contrast, there was a marked difference in the effect on the blood pressure increase caused by muscular exercise: 24 h after dosing, celiprolol continued to attenuate the hypertensive response to exercise while enalapril failed to show any significant antihypertensive effect possibly because after this time there was a reduction in angiotensin converting enzyme inhibiting activity. Thus, celiprolol and enalapril are both effective once-a-day antihypertensive agents, but celiprolol provides a longer lasting protection from hypertensive peaks caused by exercise.

Adrenergic beta-Antagonists↗