PubMed Health⌕ Search

Biomedical subjects

G Brevetti

Publications and source records attributed to G Brevetti.

At least 19 recordsLinked to original sources
PubMed1992

Superiority of L-propionylcarnitine vs L-carnitine in improving walking capacity in patients with peripheral vascular disease: an acute, intravenous, double-blind, cross-over study.

The effects of L-propionylcarnitine on walking capacity were assessed in a group of patients with peripheral vascular disease. In 12 patients, 300 mg of L-propionylcarnitine, given intravenously as a single bolus did not affect walking capacity, while 600 mg increased both initial claudication distance from the placebo value of 179 +/- 114 to 245 +/- 129 m (P less than 0.05), and maximal walking distance from 245 +/- 124 to 349 +/- 155 m (P less than 0.05). Once the efficacious dose of L-propionylcarnitine was assessed, its effect was compared to that of an equimolar dose of L-carnitine (500 mg i.v.) according to a double-blind, double-dummy, cross-over design. In 14 patients, both treatments improved walking capacity; however, the analysis of variance showed that the increase in maximal walking distance with L-propionylcarnitine was greater than that with L-carnitine (P less than 0.05). Finally, in seven additional patients, the effects of L-propionylcarnitine and L-carnitine on the haemodynamics of the affected limb were assessed by an ultrasonic duplex system. Results indicated that both drugs did not affect the blood velocity and the blood flow rate in the ischaemic leg, thus suggesting that the beneficial effect on walking capacity was dependent on a metabolic effect. In conclusion, L-propionylcarnitine improves walking capacity in patients with peripheral vascular disease, probably acting through a metabolic mechanism. On a molar basis, this beneficial effect is greater than that observed with L-carnitine and, thus, the findings of the present study may have clinical relevance in terms of treatment cost and patient compliance.

Arterial Occlusive Diseases↗
PubMed1992

Beta-adrenoceptor modulation in a case of pure autonomic failure.

In a patient with pure autonomic failure, exercise did not modify beta-adrenoceptor density, probably due to an insufficient increase in plasma catecholamines. Isoproterenol infusion increased the number of beta-adrenoceptor by only 17%. Since in control subjects an increased beta-adrenoceptor level was found, following both physical stress and isoproterenol infusion, we suggest that the lack of increased beta-adrenoceptor levels may contribute to the poor circulatory adjustments observed in autonomic dysfunction during activities involving the sympathetic nervous system.

Autonomic Nervous System Diseases↗
PubMed1991

Muscle carnitine deficiency in patients with severe peripheral vascular disease.

BACKGROUND: This study was designed to evaluate the effect of severe peripheral arterial insufficiency on carnitine concentrations and carnitine acetyltransferase and palmitoyltransferase activities in the ischemic skeletal muscles of patients with severe peripheral vascular disease. METHODS AND RESULTS: Nine biopsy specimens of ischemic muscles were obtained from five patients undergoing reconstructive vascular surgery. Biopsies from 35 normal subjects served as controls. Ischemic muscles showed a significant reduction in total carnitine from the control value of 20.9 +/- 5.2 to 11.6 +/- 6.2 nmol/mg noncollagen protein (p less than 0.01). A significantly lower free carnitine and acylcarnitine content contributed to this reduction. Similarly, carnitine acetyltransferase activity was reduced in the ischemic muscles from the control value of 102.1 +/- 41.2 to 52.9 +/- 22.1 nmol/min/mg noncollagen protein (p less than 0.01). On the contrary, carnitine palmitoyltransferase activity did not show any change (0.29 +/- 0.05 nmol/min/mg noncollagen protein in the ischemic muscles and 0.28 +/- 0.07 nmol/min/mg noncollagen protein in controls). Carnitine, acylcarnitines, and enzyme activities were also measured in the ischemic muscles in four additional patients 2 days after intravenous administration of L-propionylcarnitine (1.5 g as a single bolus followed by an infusion of 1 mg/kg/min for 30 minutes). Treatment restored normal levels of carnitine and its esters in the ischemic muscles but did not affect enzyme activities. CONCLUSIONS: Demonstration of carnitine deficiency in severe peripheral vascular disease substantiates previous findings showing the efficacy of carnitine supplementation to ischemic muscles. Furthermore, the feasibility of restoring carnitine homeostasis with L-propionylcarnitine provides the basis for clinical trials aimed at assessing the efficacy of this carnitine ester in the treatment of peripheral vascular disease.

Aged↗
PubMed1990

Parkinson's disease and hypotension: 24-hour blood pressure recording in ambulant patients.

Continuous intra-arterial blood pressure was recorded in 5 ambulatory patients with Parkinson's disease and in 5 control subjects. The 24-h mean systolic blood pressure was 135 +/- 7.6 mmHg in controls and 123.8 +/- 8.1 mmHg (p less than 0.01) in the parkinsonian group. Similarly, diastolic blood pressure was 89 +/- 8.1 mmHg in the control group while in the parkinsonian patients it was lower, 69.4 +/- 5.8 (p less than 0.01). Averages were also calculated for 8-h periods, the results of which indicate that both systolic and diastolic blood pressure were significantly lower in patients than in controls in all three 8-h periods of the day. We normalized the blood pressure curve to mealtimes and arousal times and did not observe any difference between parkinsonian patients and controls. This first study reporting continuous intra-arterial blood pressure measurements in ambulant parkinsonian patients demonstrates that blood pressure in such patients is lower than the mean for their age group. This finding may be of direct relevance in the management of idiopathic parkinsonism.

Adult↗
PubMed1990

[Increase in the lymphocyte beta-adrenergic receptor population during physical exercise].

The risk of cardiac arrhythmias during exercise and the recovery period may be enhanced by sympathetic activity. Accordingly, lymphocyte beta-adrenoceptor density was measured in 5 healthy men, aged between 25 and 32 years, at rest, at peak exercise and during the recovery period. Exercise increased 3H-dihydroalprenolol binding from 125 +/- 58 to 234 +/- 70 fmol/mg protein (p less than 0.02). During recovery, beta-adrenoceptor density was still higher than at rest, being 192 +/- 36 fmol/mg protein (p less than 0.02). No significant difference was found between exercise and recovery values (Tab. I). Results did not change when binding data were standardized to lymphocyte number, thus demonstrating that increases in binding were independent of exercise-induced lymphocytosis. Kd did not change significantly during the study. Since lymphocytic beta-adrenoceptor density may parallel myocardial beta-adrenoceptor density, this study suggests the myocardium may be more sensitive to the arrhythmogenic properties of catecholamines during exercise.

Adult↗
PubMed1989

Effect of L-carnitine on the reactive hyperemia in patients affected by peripheral vascular disease: a double-blind, crossover study.

A double-blind, crossover study was designed to evaluate the effect of L-carnitine on the reactive hyperemia in patients with peripheral vascular disease. After drug washout, 18 patients were randomly assigned to receive placebo or L-carnitine, 3 g IV as a bolus, followed by continuous intravenous infusion of 2 mg/kg/min for thirty minutes. Blood flow in the affected limb was measured by impedance plethysmography, under resting conditions and every two minutes for ten minutes after a five-minute ischemia induced in the affected limb. As compared with placebo, L-carnitine did not modify blood flow at rest. On the contrary, the hyperemic response with carnitine was higher than that observed with placebo. A significant increase in blood flow was found two, four, and six minutes after the release of ischemia with placebo, whereas the blood perfusion to the affected limb rose significantly at all times of recording after carnitine administration. Moreover, the values of the blood flow at two and ten minutes with carnitine were significantly higher than those recorded after placebo at the same times of recording. After the release of ischemia, the mean maximum value of blood flow observed after carnitine was 3.1 +/- 1.4 mL/min/100 mL, a value significantly higher than that recorded after placebo, which was 2.7 +/- 1.3 mL/min/100 mL (p less than 0.05). In conclusion, this study demonstrates that L-carnitine, although not affecting blood flow and ankle/arm systolic blood pressure ratio under resting conditions, improves the functional circulatory reserve in patients with peripheral vascular disease.

Carnitine↗
PubMed1989

Beneficial effect of a new prostacyclin derivative on the walking capacity in patients with peripheral arterial insufficiency.

The efficacy, tolerance and safety of iloprost, a stable analogue of carbaprostacyclin, were evaluated in 7 patients with peripheral arterial insufficiency at stage II of Fontaine's classification. After washout, placebo was infused intravenously for seven days, then iloprost was given by a six-hour intravenous infusion of 1 ng/kg/min over the next seven days. At the end of each period, the initial (ICD) and the absolute (ACD) claudication distance were measured by treadmill. The ankle/arm systolic blood pressure ratio (WI) was also assessed, at rest and ten minutes after exercise. As compared with placebo, ICD increased from 98 +/- 60 to 137 +/- 91 meters (p less than 0.05) and ACD from 151 +/- 76 to 210 +/- 95 meters (p less than 0.05). Similarly, WI rose from 0.44 +/- 0.14 to 0.52 +/- 0.18 (p less than 0.05) at rest and from 0.40 +/- 0.13 to 0.48 +/- 0.20 (p less than 0.05) ten minutes after treadmill exercise. Owing to the spontaneous fluctuation in walking distance experienced by such patients, an increase in ACD greater than or equal to 50% was considered as clinically relevant. In 3 patients, who experienced such an improvement, iloprost continued to be infused at the same dosage as before, for an additional seven days. In the remaining 4 patients (nonresponders), the dose was increased to 2 ng/kg/min.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1988

Increases in walking distance in patients with peripheral vascular disease treated with L-carnitine: a double-blind, cross-over study.

A double-blind, cross-over study was designed to evaluate the effects of L-carnitine in patients with peripheral vascular disease. After drug washout, 20 patients were randomly assigned to receive placebo or L-carnitine (2 g bid, orally) for a period of 3 weeks and were then crossed over to the other treatment for an additional 3 weeks. The effect on walking distance at the end of each treatment period was measured by treadmill test. Absolute walking distance rose from 174 +/- 63 m with placebo to 306 +/- 122 m (p less than .01) with carnitine. Biopsy of the ischemic muscle, carried out before and after 15 days of L-carnitine administration in four additional patients, showed that treatment significantly increased total carnitine levels. An additional goal of this study was to ascertain the effects of L-carnitine on the metabolic changes induced by exercise in the affected limb. In six patients under control conditions, arterial and popliteal venous lactate and pyruvate concentrations were determined at rest, when the maximal walking distance was reached, and 5 min after the walking test. Twenty-four hours later, L-carnitine was administered intravenously (3 g as a bolus followed by an infusion of 2 mg/kg/min for 30 min) and metabolic assessments were repeated. Five minutes after the walking test, popliteal venous lactate concentration increased by 107 +/- 16% before treatment and by only 54 +/- 32% (p less than .01) after carnitine. Furthermore, carnitine induced a more rapid recovery to the resting value of the lactate/pyruvate ratio.(ABSTRACT TRUNCATED AT 250 WORDS)

Carnitine↗
PubMed1985

24-hour blood pressure recording in patients with orthostatic hypotension.

Continuous intra-arterial blood pressure measurement and electrocardiograms were obtained in two ambulatory patients with orthostatic hypotension due to autonomic dysfunction. Systolic and diastolic arterial pressure presented marked variations which took place mainly during the day and were related to several physical activities; however, marked falls in blood pressure were also observed during sleep and at the moment of arousal. A peak incidence of hypotensive events was found in the afternoon, mainly in the hours following the afternoon meal. Recording was repeated after 3 weeks of treatment with propranolol, 40 mg t.i.d. In patient 1, beta blockade drastically reduced the number and severity of hypotensive episodes, while propranolol failed to control blood pressure in patient 2, who experienced a higher number of hypotensive events during treatment. Findings of this study may be relevant to the management of patients with orthostatic hypotension and should contribute to a more accurate characterization of blood pressure profile in autonomic dysfunction.

Blood Pressure↗
PubMed1980

Three hundred and fifty-three consecutive patients with permanent transvenous pacemakers.

The safety and convenience of the transvenous approach to long-term endocardial pacing are well established, but its principal drawback is electrode displacement. The reported incidence of this complication varies between 3.0% to 36.7%, and is highest in the early post-implantation period before endocardial fixation of the electrode tip. Recently Brewster and Evans determined that the electrode displacement rate in 21 published series averaged 14.3%. However, the Inter Society Committee on Heart Diseases (ICHD) report on pacemakers states that a rate of early displacement greater than 5% calls for a critical review of results. The training and expertise of the persons inserting the pacemaker electrodes undoubtedly are major factors which determine the proper transvenous placement of permanent cardiac electrodes. This paper deals with our clinical experience of 353 patients who received permanent transvenous pacemakers during the period September 1, 1974 through March 1, 1979, with emphasis on problems and complications encountered and overall results.

Adolescent↗
PubMed1979

Effects of propranolol in a case of orthostatic hypotension.

In a hypertensive patient with orthostatic hypotension, the changes in several haemodynamic indices with respect to posture were evaluated. In the upright position, systemic blood pressure was reduced as compared with the supine position, and peripheral vasodilation was present, as shown by an increase in Jantsch's index of the impedance plethysmographic tracings. Systolic time intervals remained unchanged with changes in posture. Propranolol 10 mg intravenously brought the response to normal. In fact, after beta-blockade in the standing position the blood pressure remained unchanged and normal peripheral vasoconstriction was observed. Similar results were seen during atrial pacing at a constant heart rate of 130 beats/minute. In this patient, propranolol appears to normalise the response to the posture change, by restoring normal vasoconstriction in the upright position.

Blood Pressure↗
PubMed1979

Protective effects of propranolol on the exercise-induced reduction of blood flow in arteriopathic patients.

The vascular steal phenomenow, that is, the shunting of blood from ischemic to normally perfused areas, is commonly observed during exercise in the affected limbs of patients with peripheral arterial insufficiency. Propranolol was administered to 18 arteriopathic patients before the exercise to ascertain whether the reverse situation can be induced. The results indicate that before propranolol administration, Jantsch's index (used to quantify the plethysmographic waves) decreased from 0.53 +/- 0.05 to 0.33 +/- 0.04 (P less than 0.001) at 1 minute, and to 0.38 +/- 0.04 (P less than 0.001) at 5 minutes after the end of the exercise. When the exercise was repeated after propranolol, Jantsch's index did not change. These findings indicate that propranolol can inhibit exercise-induced vascular steal.

Arterial Occlusive Diseases↗
PubMed1977

Reduction of blood flow following ischemia in arteriopathic patients: reversion of the phenomenon induced by propranolol.

In most arteriopathic patients, the release of a transitory ischemia in the affected limb reduces blood flow, instead of increasing it as in normal subjects. In this study the effects of propranolol administration on this paradoxical response have been investigated. After rheographic tracings were recorded in 14 arteriopathic patients in the basal condition and in the postischemic period, 10 mg of propranolol was administered IV and the protocol was then repeated. The blood flow in the affected area, measured as Jantsch's index of the rheographic tracings, was 0.63 +/- 0.04 in the basal condition and was reduced to 0.51 +/- 0.05 (P less than 0.001) in the postischemic period. When the ischemia was repeated after propranolol administration, Jantsch's index rose from 0.57 +/- 0.04 to 0.85 +/- 0.09 (P less than 0.01). The reversion of the paradoxical response to the ischemia induced by propranolol administration suggests that the beta-adrenergic blockade can increase blood flow to the ischemic area, probably through a constrictive action on arterovenous connections.

Arteriosclerosis↗