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Biomedical subjects

C Longhini

Publications and source records attributed to C Longhini.

At least 19 recordsLinked to original sources
PubMed1992

A new, noninvasive method to monitor the aging of bioprosthetic valves in the mitral position.

Bioprosthetic valves undergo a tissue degeneration of unpredictable onset and amount. This process alters the structure and function of the valve and consequently shortens its lifespan. The echocardiographic technique usually used in the follow-up of these patients does not provide accurate information concerning the amount of prosthesis tissue degeneration. A new technique has been developed based on the spectral analysis of the first heart sound, which enables the evaluation of prosthetic leaflet stiffness. The Young's modulus (E) and stress (s) of the valve leaflets were derived as functions of the inner diameter of the heterograft and its primary vibration frequency, which can be obtained from the frequency spectrum of the first heart sound. Thirty-six patients with a mitral bioprosthetic valve were studied. Fifteen had thickening or calcification, or both, of the valvular leaflets at echocardiographic examination. In patients with a normal valve, E and s showed a good correlation with the duration of implantation (r = 0.909, p < 0.001; and r = 0.828, p < 0.001; respectively). Patients with abnormal leaflets had values of E and s that were greater than the theoretical values expected for their duration of implantation. The procedure is sensitive, accurate and easy to perform, and enables monitoring of the aging of the prosthetic valve and early identification of valve tissue degeneration. Together with echocardiography, this procedure yields a more complete evaluation of prosthetic valves for the follow-up of patients.

Aged↗
PubMed1992

Acute and chronic nitrendipine administration in essential hypertension: a chronobiologic study.

To evaluate the chronobiologic pattern of the hypotensive effect of nitrendipine, 10 patients with mild-to-moderate arterial hypertension were studied. They received a randomized single dose (20 mg) of nitrendipine and placebo, and 20 mg of nitrendipine daily for 2 months. Systolic and diastolic blood pressure (SBP and DBP, respectively) and heart rate (HR) were measured for 24 h using an automatic noninvasive device. The data were analyzed by single and mean cosinor methods and by ANOVA and Student's paired t test. Chronic administration of nitrendipine resulted in a more effective lowering of the SBP and DBP mesor, compared with placebo and acute administration, preserving the circadian rhythms. The preservation of the HR circadian rhythm agrees with the lack of interference of the drug with neurohormonal mechanisms.

Adult↗
PubMed1991

Circadian rhythm of blood pressure and calcium entry blockade: a chronobiologic study with nitrendipine in essential hypertension.

In order to evaluate the chronobiologic effect of nitrendipine, 27 patients with mild-to-moderate arterial essential hypertension were studied. After randomized administration of 20 mg of nitrendipine and placebo, systolic and diastolic blood pressure (SBP and DBP, respectively) and heart rate (HR) were measured for 24 h using an automatic noninvasive device. The data of the time series were statistically analyzed by single and mean cosinor methods (obtaining mesor, amplitude, and acrophase) and by ANOVA and Student's paired t test. Nitrendipine significantly reduced the SBP and DBP mesors without affecting the HR mesor, and reduced the SBP and DBP amplitudes while increasing the HR amplitude. After placebo, group circadian rhythms were observed for SBP, DBP, and HR and maintained after nitrendipine. In conclusion, a single-dose administration of nitrendipine is effective in lowering blood pressure. The increased HR amplitude is probably due to a tachycardic reaction. The preservation of the SBP, DBP, and HR group circadian rhythms agrees with the lack of interference of the drug with the neurohormonal mechanisms.

Adult↗
PubMed1979

The fast Fourier transform in the analysis of the normal phonocardiogram.

The present study is focused on spectrum analysis as a useful method of processing the PCG in order to obtain the frequency spectral distribution of normal heart sounds. Thirty normal subjects aged from 17 to 34 were studied. PCG was recorded on the fourth intercostal space at the left sternal border using a sound level meter coupled with a standard 6 ml cavity. The microphone had a linear response from 0.2 to 8,000 Hz. The signal was filtered with the standard B network according to the ANSI specifications and was registered on a four track FM tape recorder. A four channel analyzer with a microprocessor for off-line elaborations was used with 10 KHz sampling frequency. The PCG signal was triggered by a QRS detector on the R wave of the simultaneously recorded ECG. Fast Fourier transform was performed employing either a four channel analyzer with a microprocessor, or an A/D converter with a computer. Finally the results of the analysis were statistically elaborated. The described procedures permit to obtain a direct and exact tracing of the acoustic features of the heart, thus representing an attempt to come closer to the standardization and automatic analysis of the phonocardiographic technique.

Adolescent↗
PubMed1979

Diagnosis of mitral valve diseases using indirect (esophageal) left atrial pulse.

The diagnostic usefulness of the indirect (esophageal) left atrial pulse (ESO) has been analyzed in: 1) 25 patients (pts) with mitral insufficiency (MI), 2) 18 pts with mitral stenosis, 3) 29 pts with combined valvular disease, 4) 10 normal subjects. In addition, in 1) and 4), the ESO was recorded under the following dynamic conditions: a) during isometric exercise (handgrip), b) after inhalation of amyl nitrite, c) after intravenous infusion of methoxamine. The ESO tracing demonstrated estimates of the severity of the disease. Under dynamic conditions no modification from the resting morphology was obtained in the control group, whereas in MI the following modifications were observed: a) increased, progressive, positive elevation of the systolic phase of the ESO during the handgrip and the administration of the methoxamine; b) tendency to return to normal morphology after amyl nitrite.

Heart Atria↗
PubMed1979

[Technical and methodological aspects concerning the application of Fourier's analysis to phonocardiography (author's transl)].

The frequency spectrum analysis (Fourier's analysis) has recently been applied to phonocardiography. Using this mathematical approach instead of the current empirical analysis, it is possible to obtain -- on a less subjective basis -- more precise pathophysiological and diagnostic information from the acoustic cardiac phenomena. On the other hand, this refinement of the method of analysis stresses the need for better technical and methodological solutions, in order to reach the standardization of both the transduction and the recording of the acoustic signal at higher level of sensibility, fidelity and reproducibility. With this in mind, and on the basis of their experience, the Authors suggest the adoption of devices with specific technical characteristics, and propose a suitable method of application of Fourier's analysis to the phonocardiogram.

Fourier Analysis↗
PubMed1979

Cardiomechanical effect of k-strophanthoside administered to healthy volunteers by the rectal route.

Eight healthy volunteers were given k-strophanthoside (Strofopan) 1 mg rectally in order to evaluate changes in the cardiac function. Cardiomechanical measurements were performed by the polygraphic method before administering the drug and 1, 2, 3, 4, 5 and 6 h later. Three of the eight subjects continued to receive k-strophanthoside 1 mg daily for a further 6 days. Similar evaluations were made at the same times on day 3 and on day 7 of treatment. All indices considered varied to a statistically significant extent and showed the maximum effect at about the 4th h. The most evident changes were observed in the ICT and the PEP/LVET ratio. Here, the maximum variations were 46.3% and 29.5%, respectively, as compared with baseline values (P less than 0.01). When treatment was given for 7 days, the baseline values measured on day 3 and day 7 before administration showed a moderate and constant decrease in all parameters as compared with the first baseline value. This proves that k-strophanthoside administered rectally possesses steady-state activity with time. From a comparison of the changes in the same parameters as observed in a previous investigation after administering digoxin 0.50 mg orally there is reason to conclude that the effects obtained after administering k-strophanthoside 1 mg rectally were of the same magnitude.

Adult↗
PubMed1979

An improvement in digoxin bioavailability. Studies with soft gelatin capsules containing a solution of digoxin.

A study of relative bioavailability of two digoxin formulations was carried out on 28 healthy volunteer human subjects of both sexes. A commercial digoxin in tablet form was compared with a new commercial formulation which contains a solution of digoxin in soft gelatin capsules. The parameters investigated were: plasma levels, area under the plasma level-time curve, daily urinary excretion of digoxin and a series of polycardiographic measurements, all the parameters being evaluated in a steady-state condition (14 days of treatment). All the parameters investigated demonstrated better bioavailability in the capsules than in the tablets, the average improvement being 26.1%. The better bioavailability of digoxin capsules also resulted in more rapid and wider variations in the polycardiographic parameters.

Adult↗