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Biomedical subjects

A Masoni

Publications and source records attributed to A Masoni.

At least 55 records · Page 3Linked to original sources
PubMed1984

Clinical effects of digoxin on sinus node and atrioventricular node function after pharmacologic autonomic blockade.

The effects of digoxin on sinus node and atrioventricular (AV) node function were studied in 18 patients (mean age 53.6 years) with normal intrinsic heart rates. Electrophysiologic testing was performed both during basal state and after autonomic blockade with propranolol and atropine. Full digitalization was achieved by intravenous administration of digoxin (0.02 mg/kg) given in three divided doses over a 24-hour period. The following day, after a basal recording, autonomic blockade was again induced and the study was repeated. During basal state, digoxin significantly prolonged the sinus cycle length (SCL) (p less than 0.01) and the AH interval (p less than 0.01). However, when the intrinsic sinus node functions were compared (i.e., the values obtained after autonomic blockade), digoxin did not produce significant changes in intrinsic SCL, corrected sinus node recovery time, and sinoatrial conduction time. No significant changes were noted even in the intrinsic AH interval and AV nodal refractory periods. These findings suggest that: (1) intravenous administration of digoxin in therapeutic doses does not produce any depression of the intrinsic functions of the sinus node and AV node; and (2) the depressant effects induced by digoxin during basal state appear to be mediated through the autonomic nervous system.

Adult↗
PubMed1984

The role of the autonomic nervous system on sinus node function in patients with intermittent sinoatrial block.

Sinus node (SN) function was analyzed with and without autonomic blockade (AB) in 31 patients (mean age: 57.6 +/- 12.8) with intermittent sinoatrial block. Twenty-one patients had organic heart disease; in the remaining ten signs of underlying heart disease were not present. Nineteen patients had dizziness or syncope. Sinus cycle length, sinus rate, corrected sinus node recovery time (CSRT) and sinoatrial conduction time (SACT) were analyzed. After control measurements, AB was produced by i.v. propranolol (0.2 mg/Kg) and atropine (0.04 mg/Kg). Measurements of electrophysiological parameters were then repeated. After AB sinus rate and CSRT did not show statistically significant differences, whereas SACT decreased significantly (P less than 0.001). When intrinsic heart rate (IHR) was abnormal (11 cases), intrinsic CSRT was always abnormal, whereas when IHR was normal, intrinsic CSRT was normal in 11 patients and abnormal in nine. In several cases, when sinus rate increased after AB, CSRT decreased and vice-versa. The parameters of intrinsic SN function were normal in 80% of patients with a normal heart and only in 14.2% of patients with organic heart disease. These data indicate that: (1) during the control period SACT is mainly conditioned by the vagal tone; (2) abnormalities in control CSRT are not uniformly abolished after AB in patients with normal IHR; (3) AB has a differential effect on the two variables of SN automaticity; i.e. sinus rate and CSRT; and (4) in patients without underlying heart disease, the SN dysfunction is almost exclusively related to alterations of the autonomic nervous system.

Adult↗
PubMed1984

Latent abnormalities of sinus node function in patients with organic heart disease and normal sinus node on clinical basis.

Sinus node (SN) function was analyzed in 22 patients (mean age: 46.2 +/- 12.9 years) with organic heart disease and normal SN on clinical basis (group I) and in 20 normal subjects (mean age: 43.9 +/- 15.6 years), (control group). Sinus cycle length (SCL), corrected sinus node recovery time (CSRT) and sinoatrial conduction time (SACT) were analyzed. After the control study, autonomic blockade (AB) was induced by i.v. propranolol (0.2 mg/Kg) and atropine (0.04 mg/Kg). Measurements of SCL, CSRT and SACT were then repeated. The mean SCL values were very similar in the two groups during the control state and after AB. There were no significant differences in SACTs between the two groups during the control state or after AB. On the contrary, the CSRT of group I was significantly longer than that of control group during the control state (344.8 +/- 78.9 versus 262.2 +/- 46.3 msec, P less than 0.001) and after AB (238.9 +/- 72.8 versus 166.8 +/- 39.3 msec, P less than 0.001). The analysis of real depression of SN automaticity (CSRT minus SACT) in the two groups shows that prolongation of CSRT in group I during the control study and after AB is related to an intrinsic abnormality of SN automaticity; on the contrary, no dysfunctions of the autonomic nervous system appear. These data indicate that the intrinsic abnormality of SN automaticity represents the earliest involvement of the SN in subjects with organic heart disease and normal SN on clinical basis, although this conclusion is speculative and requires experimental verification.

Adolescent↗
PubMed1984

Slight middle slurring in V1-V2 without bundle branch block. An electrocardiographic and follow-up study.

A slight middle slurring in V1 and/or V2 with rS morphology (R less than S) in these leads, without right or left bundle branch block is a nearly ignored electrocardiographic finding. The purpose of this work is to provide a prospective and electrocardiographic analysis of this finding. We followed 200 subjects with middle slurring in V1 and/or V2, in the absence of bundle branch block (study group), (age: 41.5 +/- 19 years, follow-up period: 5.7 +/- 2.5 years) and 200 subjects with rS morphology in V1-V2 without the middle slurring (control group), (age: 39.8 +/- 20 years, follow-up period: 5.2 +/- 2 years). The age, sex, prevalence of organic heart disease, QRS duration and follow-up period did not show significant differences between the two group. In the study group there was a higher prevalence of vertical axis (P less than 0.001), of S1S2S3 morphology (P less than 0.001) and of terminal r wave in a VR (P less than 0.05) compared to control group. During the follow-up period, a right bundle branch block appeared in 19 subjects of study group (incomplete in 15 and complete in 4) and in 2 (complete) of control group (P less than 0.001). A left bundle branch block appeared only in one patient of study group and in one of control group. We conclude that the isolated slight middle slurring in V1-V2 expresses an initial involvement of the right bundle branch system and increases the likelihood of appearance of right bundle branch block.

Adolescent↗
PubMed1982

Multicenter evaluation of mepindolol and of mepindolol plus hydrochlorothiazide in essential hypertension.

The effect on systolic (SAP) and diastolic (DAP) arterial blood pressure of 5 mg mepindolol daily vs 12.5 mg hydrochlorothiazide daily vs 5 mg mepindolol plus 12.5 mg hydrochlorothiazide daily was evaluated in this multicenter study. After a 2-week washout period with placebo, 138 patients with mild to moderate essential hypertension (WHO Class I and II), homogeneous for age and blood pressure values, were randomly allocated to one of the three treatment groups. Arterial blood pressure and heart rate were obtained at the beginning and at the end of the washout placebo period, and after 2, 4, and 6 weeks of active treatment. At the beginning and at the end of the study, all patients underwent a thorough clinical and laboratory evaluation, including blood chemistry, electrocardiogram, and chest roentgenogram. A trend toward normalization of blood pressure was defined as a lowering of DAP to 90 mmHg or at least a 10-mmHg decrease from the control value. Statistical analysis was performed on all the data. After 6 weeks of treatment, SAP and DAP values were significantly reduced in 67% of the patients in all groups. In 71% of patients on mepindolol plus hydrochlorothiazide a particularly more marked decrease in DAP was observed. Mepindolol was well tolerated: side effects were generally mild and inconsequential. The results show that mepindolol, given as a single oral dose of 5 mg, is an effective agent in the treatment of mild to moderate essential hypertension. Because of its efficacy, the advantage of single daily administration, and lack of important side effects, it can increase compliance to therapy. Moreover the association of mepindolol plus hydrochlorothiazide appears to be safe and effective.

Blood Pressure↗
PubMed1982

[Verapamil in effort angina: a multi-centre study].

We have performed a multi-centre study with 47 outpatients in order to evaluate the efficacy of Verapamil (V) in the treatment of stable effort angina, and to compare the effect of two different doses of the drug (240 and 360 mg/die). The protocol consisted of a first period of Placebo, followed by the double-blind randomized cross-over administration of Placebo (P) and Verapamil (V) in doses of 240 and 360 mg/die. The symptomatology, the consumption of TNG, the ECG pattern at rest and during exercise, the maximum exercise tolerance during exercise and the rate of recovery were evaluated at the end of each 1 month period. V. provided a significant reduction of the number of angina attacks and of the consumption of TNG pills with improvement of symptomatology. The maximum exercise performance improved without changes in maximum rate pressure double product. A decrease of double product was observed at rest and during the recovery period. The higher dose of V. (360 mg/die) provides a better improvement in the number of angina attacks, in the symptomatology, in the double product at rest, and in the rate of recovery than the lower dose (240 mg/die). Thus these data indicate that V. provides anti-anginal efficacy by reducing myocardial oxygen demand, and increases exercise tolerance in effort angina patients.

Adult↗
PubMed1981

Active transport of urea across the skin of the euryhaline toad, Bufo viridis.

Urea is accumulated in considerable amounts (greater than 100 mM) in the blood of the euryhaline toad Bufo viridis, under conditions of adaptation to high salinities. Salt adaptation increases active transport of urea (inward direction) in the skin, which was measured in vitro. The active transport of urea is insensitive to ADH, and was inhibited nearly 50% by 0.5 mM phloretin. This transport system is different from the facilitated diffusion of urea which has been studied extensively in the toad urinary bladder, and may offer a simple model system for the study of active urea transport.

Animals↗
PubMed1981

Active urea transport through isolated skins of frog and toad.

Urea influxes (Ji) and effluxes (Je) were studied across the isolated skins of Rana esculenta, Bufo bufo, and B. viridis. Two symmetrical pieces of the same skin, bathed in Ringer + 2 mM urea, were used for the two fluxes. In R. esculenta the urea fluxes are passive when the animals are kept in running water but become active after dehydration in air or preadaptation in saline solutions. The ratio Ji/Je can vary between 3 and 27 and the Ji between 2 and 22 nmol . h-1 . cm-2 according to preadaptation. Only the active fluxes obey saturation kinetics. Urea absorption is always independent of sodium transport. In toads, active urea transport occurs even when hydrated. It is markedly stimulated by saline preadaptation. A correlation between the degree of active urea transport across the skin and the capacity of the species to endure dehydrating conditions would appear to exist. The physiological significance of this transport mechanism is discussed.

Animals↗
PubMed1981

[Therapeutical comparison between atenolol and nifedipine in effort angina (author's transl)].

In order to assess the therapeutical efficacy of atenolol in stable angina pectoris of effort, we studied 40 patients with a positive exercise stress test. Our double-blind study included a first group of 20 patients treated with atenolol, 100 mg once daily, and a second group of 20 subjects, treated with nifedipine (10 mg 3 times daily). The exercise test was performed before the treatment, after one month of placebo and after one month of therapy with nifedipine or atenolol. The variables examinated were the frequency of anginal chest pain, the quantity of nitroglycerin taken by the patients, the arterial pressure, the heart rate and the double product at the peak of the exercise testing. Differences between the results obtained in the two groups weren't statistically significant.

Adult↗
PubMed1981

[Antiarrhythmic treatment with mexiletine in acute myocardial infarction (author's transl)].

The effect of an introduced i.v. bolus of 250 mg of mexiletine was checked in cases of acute myocardial infarction with ventricular premature beats. On the 19 observed subjects 17 are male and 2 female: 18 cases with acute myocardial infarction and 1 with acute coronary failure. The introduction of the bolus was followed by an infusion of 0.75 mg/m for the successive four days. After 60 m' no significant changes in arterial pressure and in the heart rate were recorded. The Extrasistolies decrease from 11 +/- 3 to 3 +/- 2/m' (-71%, p less than 0.01); PQ and QT variations were not significant. After four days of infusion, systolic arterial pressure decrease from 135 +/- 4 to 121 +/- 3 (-10%; p less than 0.01), sinusal rate drops from 90 +/- 4 to 80 +/- 3 (-12%, p less than 0.05). The changes of diastolic arterial pressure, PQ and QT were not significant. Extrasistolies disappears entirely. A comparison between a mexiletine and a xilocaine i.v. bolus showed that mexiletine performs a higher antiarrhythmic activity.

Aged↗
PubMed1981

Double atrial tachycardia with functional atrial dissociation.

A 57-year-old man with hypertensive and coronary heart disease and bradycardia-tachycardia syndrome suffered from paroxysmal palpitations, during which ECG showed a low atrial tachycardia at a rate of 150-200 beats/min with Wenckebach A-V block. During electrophysiological study an episode of atrial tachycardia appeared, characterized by: - atrial potentials in the high atrial electrocardiogram with regular cycle length (500-530 msec); - atrial potentials in the His bundle electrocardiogram with cycle length (570-580 msec), interrupted by premature atrial beats with coupling interval of 420-480 msec and with an atriogram of identical morphology. A-V conduction showed Wenckebach A-V block. After the cycles of 570-580 msec the low atrial potentials were simultaneous or preceded or followed the high atrial potentials by 10-20 msec. After the cycles of 420-480 msec the low atrial potentials preceded the high ones by 40-70 msec. Then, high atrial tachycardia abruptly stopped and the low atrial tachycardia only persisted with the same cycle length (570-580 msec); the high atrium was captured by the low atrial impulses with a low atrium - high atrium interval of 70 msec. These findings suggest that during the first part of tachycardia a conduction neither from high to low atrium, nor from low to high atrium can be possible. It is therefore a particular case of double atrial tachycardia - to our knowledge never before described in literature - sustained a few seconds because of functional atrial dissociation, induced by refractoriness related to the impulses delivered by the two tachycardia foci. The double atrial tachycardia was not diagnosed in the surface ECG leads. The two foci both appear to be localized at atrial level. The electrophysiological mechanism and the differential diagnosis with tachycardias at different sites are discussed.

Bradycardia↗