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Biomedical subjects

P Rizzon

Publications and source records attributed to P Rizzon.

At least 163 records · Page 9Linked to original sources
PubMed1989

High doses of L-carnitine in acute myocardial infarction: metabolic and antiarrhythmic effects.

Fatty acids accumulate in the muscle cells in some carnitine deficiency syndromes due to a variety of genetic defects in intermediary metabolism. L-Carnitine administration may relieve this excess by transporting acyl compounds out of the cell as acylcarnitine. Similar fatty acid accumulation occurs during myocardial ischaemia because of the decreased rate of beta-oxidation, and this has been put forward as a cause of ventricular arrhythmias. This study was carried out to investigate whether administration of high doses of i.v. L-carnitine in patients with acute myocardial infarction could increase urinary excretion of acylcarnitine and reduce early ventricular arrhythmias. Fifty-six patients suffering from acute myocardial infarction, admitted to the Coronary Unit between 3 and 12 h after the onset of symptoms, were included in the study. The design of the study was double blind, parallel and placebo controlled. Allocation of treatment to patients was done randomly after stratification (time from onset of pain and site of infarction). The first group (28 patients) received intravenous L-carnitine at a dose of 100 mg kg-1 b.w. every 12 h for 36 h while the second group (28 patients) received placebo intravenously. Immediately before starting treatment two blood samples were taken (at 5-min intervals) and a further 16 samples were taken at regular intervals over the following 48 h. Patients' urine was collected over the same period of time. Concentrations of free carnitine, short chain acylcarnitine esters and long chain acylcarnitine esters in serum and urine were measured.(ABSTRACT TRUNCATED AT 250 WORDS)

Aged↗
PubMed1989

[Effect of intracoronary and intravenous administration of propranolol on coronary vasomotility at rest and during exercise].

The effect of intracoronary and intravenous propranolol on coronary vasomotion was evaluated in 30 patients with coronary artery disease. Luminal area of a normal and a stenotic coronary segment was determined at rest, during supine bicycle exercise and 5 min after 1.6 mg sublingual nitroglycerin administered at the end of the exercise test using biplane quantitative coronary arteriography. Patients were divided into 3 groups: Group I (n = 12) served as control Group II consisted of 10 patients with intracoronary administration of 1 mg propranolol and Group III of 8 patients with intravenous administration of 0.1 mg/kg propranolol prior to the exercise test. In the control Group there was coronary vasodilation (+23%, p less than 0.01) of the normal and coronary vasoconstriction (-29%, p less than 0.001) of the stenotic vessel segment during bicycle exercise. After sublingual administration of 1.6 mg nitroglycerin there was vasodilation of both normal (+40%, p less than 0.001 vs rest) and stenotic (+12%, NS vs rest) segments. In Group II intracoronary propranolol was not accompanied by a change in coronary area but both normal (+13%, p less than 0.05) and stenotic (+22%, p less than 0.05) segments showed coronary vasodilation during bicycle exercise. After sublingual nitroglycerin there was further vasodilation of both normal (+31%, p less than 0.001 vs rest) and stenotic (+45%, p less than 0.01 vs rest) arteries. In Group III intravenous administration of propranolol was associated with a decrease in coronary luminal area of both normal (-24%, p less than 0.001) and stenotic (-41%, p less than 0.001) segments. During dynamic exercise there was coronary vasodilation of both segments when compared to the data after intravenous injection of propranolol but there was no change in luminal area (normal vessel-2%, NS vs rest; stenotic vessel-3%, NS vs rest) when compared to the resting data. After sublingual administration of 1.6 mg nitroglycerin both normal (+21%, p less than 0.001) and stenotic (+46%, p less than 0.001) segments showed coronary vasodilation. It is concluded that supine bicycle exercise in patients with coronary artery disease is associated with vasodilation of the normal and vasoconstriction of the stenotic coronary arteries. Intravenous administration of propranolol is followed by coronary vasoconstriction of both normal and stenotic coronary arteries probably due to secondary mechanisms (reduction in heart rate and contractility) because it is not observed after intracoronary injection of propranolol and it is overridden by bicycle exercise and sublingual nitroglycerin.

Adult↗
PubMed1989

[Efficacy and length of action of a slow-release formulation of isosorbide-5-mononitrate in stable effort angina].

This double-blind randomized placebo-controlled study was designed to evaluate the acute effects of orally administered slow-release isosorbide-5-mononitrate (SR IS-5-MN) in 12 patients with chronic stable angina. After a prestudy screening to assess the reproducibility of exercise response, the patients entered the study lasting 5 days. On the first and fourth day of the trial, each patient underwent a bicycle exercise test 4, 8 and 24 hours after acute administration of SR IS-5-MN 50 mg or placebo. Statistic analysis of the results was performed using a 2-way analysis of variance for cross-over design. Compared to placebo, 4 hours after administration, SR IS-5-MN prolonged the exercise time from 525 +/- 162 s to 685 +/- 207 s (p less than 0.05; 30%) and - 1mm time from 437 +/- 147 s to 562 +/- 219 (p less than 0.05; 29%). After 8 hours SR IS-5-MN prolonged the exercise time from 510 +/- 145 s to 615 +/- 189 s (p:ns; 21%), and - 1mm time from 415 +/- 128 s to 522 +/- 205 s (p less than 0.05; 26%). No significant changes were observed 24 hours after SR IS-5-MN administration. The maximal rate-pressure product was significantly increased by SR IS-5-MN 4 hours after administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Doppler velocimetry of the internal mammary artery anastomosed to the anterior descendent coronary artery: a noninvasive analysis of coronary circulation].

This study analyses the static and dynamic characteristics of the flow curves obtained by continuous wave Doppler flow velocity analysis in the internal mammary artery (IM) under normal conditions and after left anterior descending coronary artery by-pass. The IM flow velocity curve has the characteristics of a muscular artery both in basal conditions and during hyperventilation and Valsalva manoeuvre. On the other hand, the by-passed IM shows a typically phasic flow velocity curve, the diastolic flow prevailing over the systolic as is commonly the case in the coronary circulation. This curve also shows variations characteristic of the coronary circulation during Valsalva manoeuvre, whereas it is not affected by the alterations induced by hyperventilation in the area of the respiratory muscles. Continuous wave Doppler flow analysis of the by-passed IM can therefore be considered a reliable method for evaluating coronary flow in man. The fact that this method is non-invasive makes it obviously advantageous and widens its field of application not only to strictly diagnostic evaluations but also to physiopathological and therapeutical ones.

Anastomosis, Surgical↗
PubMed1989

[Acute effects of propionyl-L-carnitine on anomalies of parietal kinetics of the left ventricle induced by atrial pacing in patients with ischemic heart disease. A bidimensional echocardiographic study].

This double-blind randomized placebo (PL) controlled study was undertaken to evaluate, by 2D echo transesophageal atrial pacing (TAP), the effects of acute iv administration of a new compound propionyl-L-carnitine (PLC) on atrial pacing (AP) induced left ventricular wall motion abnormalities. Twelve male patients with coronary artery disease and normal regional motion at rest, after a preliminary 2D echo-TAP, on the eight and thirteenth day of trial were subjected to 2D echo-TAP 30 min after iv administration of 15 mg/Kg PLC or PL. For analysis, the left ventricle was divided into 11 segments. A wall motion score (WMS), evaluated at 130 b/min and at 150 b/min, was derived by adding together the scores assigned to each segment. Wall motion was graded +2 (normokinetic), +1 (hypokinetic), 0 (akinetic), -1 (dyskinetic). Left ventricular ejection fraction (EF) was evaluated at rest and at 150 b/min. Statistical analysis of the results was performed using a 2-way analysis of variance. The WMS at 130 b/min improved significantly after PLC vs PL from 18.66 +/- 2.46 to 19.50 +/- 2.77 (p less than 0.02). The WMS at 150 b/min improved significantly after PLC vs PL from 16.00 +/- 2.95 to 16.91 +/- 3.47 (p less than 0.01). The EF at rest was not significantly unchanged after PLC. The EF at 150 b/min was significantly different after PLC vs PL, from 53.6 +/- 7.36 to 55.6 +/- 6.45 (p less than 0.05). The blood pressure and the double product at rest and at 150 b/min were not unchanged after PLC.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1989

[Abnormal coronary vasomotility in subjects with normal coronary arteries and reduced reserve of coronary flow].

A reduced coronary flow reserve has been reported in patients with ischemia-like symptoms and normal coronary arteries. In 13 such subjects both coronary vasomotion and flow reserve were studied. The luminal area of the proximal and distal third of the left anterior descending and left circumflex artery were determined by biplane quantitative coronary arteriography using a computer-assisted system. Subjects were studied at rest, during submaximal supine bicycle exercise (4.0 min, 116 W) and 5 min after sublingual administration of 1.6 mg nitroglycerin. Heart rate, mean pulmonary and aortic pressure as well as the percent change of both proximal and distal luminal area were determined. In 10 of the 13 subjects, coronary sinus blood flow was measured by coronary sinus thermodilution technique at rest and after dipyridamole infusion (0.5 mg/Kg in 15 min) 10 +/- 5 days after quantitative coronary arteriography. Coronary flow ratio (dipyridamole/rest) and coronary resistance ratio (rest/dipyridamole) were determined in these subjects. Subjects were divided into 2 groups according to the behaviour of the coronary vessels during exercise (vasodilation = Group 1, vasoconstriction = Group 2). Coronary vasodilation of the proximal (luminal area + 26%; p less than 0.001) and distal (+ 45%; p less than 0.001) artery was observed in 7 subjects (Group 1) during exercise and after sublingual nitroglycerin (+46%; p less than 0.001 and +99%; p less than 0.001, respectively). In Group 2 (n = 6), however, there was coronary vasoconstriction of the distal vessel segments (-24%; p less than 0.001) during exercise, whereas the proximal coronary artery showed vasodilation (+ 26%; p less than 0.001) during exercise. Following sublingual nitroglycerin, both vessel segments elicited vasodilation (distal coronary + 44%; p less than 0.001, proximal coronary artery +47%; p less than 0.001). Coronary flow ratio amounted to 2.5 in Group 1 and to 1.2 in Group 2 (p less than 0.05) and coronary resistance ratio to 2.7 in Group 1 and to 1.2 in Group 2 (p less than 0.05), respectively. Thus, among subjects with ischemia-like symptoms and normal coronary arteries there is a subgroup of patients (Group 2) with an abnormal dilator response of the distal coronary arteries to the physiologic dilator stimulus of exercise and a reduced dilator capacity of the resistance vessels after dipyridamole (= abnormal coronary vasodilator syndrome). The nature of this exercise-induced distal coronary vasoconstriction is not clear but might be due to an abnormal neurohumoral tone which may cause or contribute to the blunted vascular response during exercise.

Adult↗
PubMed1988

Effects of acute intrathoracic pressure changes on left ventricular geometry and filling.

Acute changes in intrathoracic pressure (ITP) affect left ventricular (LV) function. It has been suggested that this functional impairment could be the result of an alteration in LV filling caused by a reduction in LV compliance induced by the rearrangement of biventricular geometry that occurs under these conditions. Therefore, to evaluate the effects of an acute increase or decrease in ITP on LV geometry and filling, we used two-dimensional and Doppler echocardiography to study 25 normal volunteers both during the Müller maneuver (acute decrease in ITP induced by a forced inspiration against a closed airway) and during continuous positive airway pressure breathing. During both maneuvers LV geometry was altered as demonstrated by the significant increase in the normalized curvature radius of the interventricular septum and the unchanged curvature radius of the LV free wall. LV filling was altered during both maneuvers as demonstrated by significant decreases in early peak flow velocity, early-to-late peak flow velocity ratio, and early deceleration rate. Thus, during maneuvers that acutely decrease or increase ITP, alterations in LV geometry occur. These acute distortions of LV geometry may be one of the mechanisms responsible for alterations in LV filling.

Adult↗
PubMed1988

Doppler echocardiographic evaluation of the effect of atrial pacing-induced ischemia on left ventricular filling in patients with coronary artery disease.

Very little is known about the effects of acute myocardial ischemia on left ventricular filling. Previous studies of these effects have been of limited value because they were performed with 1) imaging techniques that, like cineventriculography or radionuclide ventriculography, do not allow beat to beat monitoring of left ventricular filling throughout the entire ischemic attack; and 2) exercise, which, even if effective in inducing myocardial ischemia in patients with coronary artery disease, also considerably shortens cycle length, thus leading to additional nonischemic filling alterations. To overcome these limitations, left ventricular filling was studied by means of Doppler echocardiographic evaluation of transmitral flow velocities before and immediately after rapid atrial pacing in 17 patients. Eight patients had coronary artery disease but did not develop ischemia (ST depression greater than or equal to 1.5 mm) during atrial pacing (Group 1) whereas nine had coronary artery disease and developed ischemia during atrial pacing (Group 2). No differences were observed from rest to postpacing in any of the filling variables considered in Group 1 patients. In contrast, a significant rearrangement of left ventricular filling occurred during ischemia in Group 2 patients.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Incidence of 'dual A-V nodal pathways' in first- and second-degree type I supra-His A-V block.

The incidence of 'dual A-V nodal pathways', diagnosed on the basis of spontaneous or induced modifications in the PR interval, has been assessed in a group of 168 consecutive patients with first- (77) and second-degree (91) type I supra-His block. 'Dual A-V nodal pathways' were found in 12 cases (16%) with first-degree and in 7 cases (7.7%) with second-degree type I supra-His A-V block. His bundle recording confirmed the hypothesis that PR interval variations observed in these cases are due to modifications in the AH interval and thus to changes in A-V nodal conduction velocity. The electrophysiologic study also showed that the phenomenon was easily reproduced by atrial stimulation. The frequent association between 'dual A-V nodal pathways' and supra-His blocks suggests that the block mechanism should be studied in depth as it could have prognostic and therapeutic implications.

Adolescent↗
PubMed1987

Prediction of the extent of coronary artery disease with the evaluation of left ventricular wall motion abnormalities during atrial pacing. A cross-sectional echocardiographic study.

UNLABELLED: In patients with coronary artery disease, left ventricular performance during stress is affected by the degree of coronary stenosis. In order to verify whether there exists a relationship between the extent of wall motion abnormalities detectable during atrial pacing and the degree of coronary obstruction, 76 patients, without previous myocardial infarction, were studied. Each patient underwent cross-sectional echocardiography during transesophageal atrial pacing and exercise electrocardiography before coronary angiography. Of the 76 patients, 46 had significant coronary artery disease (stenosis greater than or equal to 75% of at least one major coronary vessel), while 30 had normal coronaries or a stenosis of less than 75%. Eighteen patients had single-, 14 had two- and 14 had three-vessel disease. For each patient a coronary score was obtained: the score used took into consideration the site, number and severity of the stenosis. This score was then correlated with the wall motion score, obtained from the analysis of 9 segments of the left ventricle. A weak correlation was obtained between wall motion score at rest and coronary score (r = -0.42), while the correlation between coronary score and the difference between wall motion score at rest and during transesophageal atrial pacing was slightly better (r = 0.53); this correlation further improved if wall motion score during pacing was considered (r = -0.63). If the patients with discordant diagnostic tests (echocardiography during transesophageal atrial pacing and exercise electrocardiography) were excluded, the correlation coefficient between coronary score and wall motion score during pacing increased even more (r = -0.77). IN CONCLUSION: (1) analysis of wall motion of the left ventricle during atrial pacing is useful for the non-invasive evaluation of the severity of coronary disease; (2) cross-sectional echocardiography during atrial pacing, apart from being a useful diagnostic tool, is also a help in judging the degree of severity of coronary artery disease.

Adult↗
PubMed1987

Role of QT prolongation secondary to a postextrasystolic pause as a possible mechanism for the induction of ventricular fibrillation. Report of two cases.

Two patients developed ventricular fibrillation (VF) while undergoing continuous electrocardiographic monitoring. Analysis showed that VF appeared only when a particular combination of circumstances occurred: a postextrasystolic pause, QT prolongation of the subsequent beat and a premature ventricular beat that did not have a short coupling interval. The relevance of this sequence as a trigger mechanism of VF is discussed.

Aged↗