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Biomedical subjects

J A Marin-Neto

Publications and source records attributed to J A Marin-Neto.

At least 73 records · Page 4Linked to original sources
PubMed1987

Effects of intravenous atropine on static P-V curves of the lung in normal man.

In eight normal subjects we studied the effects of intravenous (i.v.) injection of 2 mg atropine sulfate on the static lung recoil pressure-volume (PV) curves, plethysmographic airway resistance (Raw), and maximum expiratory flow rates (Vmax). In addition, we determined the influence of atropine injection in esophageal elastance (Ees) by measuring the esophageal pressure with an esophageal balloon containing five different volumes (0.5 to 4 ml) of air and by calculating the change in esophageal pressure per unit change in balloon volume (delta Pes/delta Vb). This procedure allowed us to obtain static lung recoil pressure (Pst(1] at a balloon volume extrapolated to zero, thus avoiding the interference of changes in esophageal tone following atropine administration with the measurement of Pst(1). After vagal blockade with atropine, Pst(1) significantly decreased with a shift to the left of PV curves, Raw decreased, and Vmax increased mainly at lower lung volumes. Ees also decreased with parasympathetic blockade. We interpret these findings to indicate that inhibition of vagal tone results in dilatation of large and small airways, and also in the relaxation of smooth muscle in terminal lung units.

Adult↗
PubMed1987

Use of isometric exercise to demonstrate cardiac parasympathetic impairment in the digestive form of Chagas' disease.

Standardized handgrip at 100% of maximal voluntary capacity was used to study heart rate responses to isometric exercise in patients with the digestive form of Chagas' disease. The chronotropic responses of the group were significantly lower (P less than 0.001) than those exhibited by control subjects, and comparable to those observed in a group of cardiac chagasic patients. These results show that severe impairment of autonomic control of the heart may occur in chagasic patients apparently having only digestive tract involvement.

Blood Pressure↗
PubMed1986

The evolution of experimental Trypanosoma cruzi cardiomyopathy in rabbits: further parasitological, morphological and functional studies.

Young rabbits (1-2 months of age) inoculated with trypomastigote forms of the Colombia strain of Trypanosoma cruzi have been shown to develop cardiac pathological changes (together with parasitological and immunological alterations) which are very similar to those observed in the acute and chronic phases of Chagas' disease in man. The cardiac alterations in the acute phase are characterized grossly by slight cardiomegaly with dilatation of the right-sided chambers. Microscopically they are characterized by mild focal myocarditis. The chronic phase is characterized by moderate to marked cardiomegaly with hypertrophy and dilatation of both ventricular chambers. There is thinning of the apical region (apical aneurysm), particularly of the left ventricle. Focal myocarditis is seen microscopically with areas of myocytolytic necrosis, atrophic and hypertrophic myofibers, an inflammatory response predominantly composed of mononuclear cells and interstitial fibrosis. Cineventriculography in the left ventricle of rabbits during the chronic phase disclosed regional myocardial dysfunction, with typical apical systolic bulging. The pathogenesis of Chagasic cardiomyopathy is briefly discussed in the light of these findings. Our investigation has further shown that this animal model is particularly suitable for studies on on the mechanisms, pathology and treatment of Chagas' heart disease.

Actin Cytoskeleton↗
PubMed1986

Effect of parasympathetic impairment on the haemodynamic response to handgrip in Chagas's heart disease.

Haemodynamic responses to sustained isometric exercise (handgrip at 30% of maximum voluntary capacity) were studied in 10 patients with Chagas's cardiopathy without previous or current heart failure. Five of the patients (group 1) had profound impairment of parasympathetic control of heart rate. They had no tachycardia in response to intravenous administration of atropine and no bradycardia during phase IV of the Valsalva manoeuvre. The other five (group 2) showed normal vagal regulation of heart rate, as judged by chronotropic responses to these tests. The heart rate change (mean (SD] elicited by the handgrip test was significantly lower in group 1 (from 93.0 (14.1) to 95.0 (16.7) beats/min) than in group 2 (from 78.2 (15.8) to 92.8 (18.1) beats/min). Pressor responses to handgrip were of similar magnitude (from 91.6 (7.8) to 109.0 (8.0) mm Hg in group 1 and from 88.6 (11.9) to 106.8 (20.9) mm Hg in group 2). In both groups no significant change in stroke index was detected during handgrip. Cardiac index increased during handgrip from 4.0 (1.2) to 4.8 (1.3) 1/min/m2 in group 2, but there was no significant change in group 1 (from 4.9 (0.7) to 4.8 (1.1) 1/min/m2). Changes in calculated systemic vascular resistance were significantly higher in group 1 (from 934 (175) to 1176 (383) dyn s cm-5) than in group 2 (from 1109 (404) to 1112 (424). This study shows that parasympathetic impairment adversely influences the haemodynamic pattern of response to isometric exercise in patients with Chagas's heart disease. In such conditions, the pressor response to handgrip is predominantly mediated by an increase in systemic vascular resistance rather than an increase in cardiac output.

Adult↗
PubMed1985

Late surgical repair of ventricular septal defect due to nonpenetrating chest trauma: review and report of two contrasting cases.

Traumatic rupture of the interventricular septum is a rare condition usually presenting in infancy and childhood. This report describes two cases: a 3-year-old boy operated on soon after the diagnosis was made, and a 15-year-old girl operated on 12 years following the causative accident. Both patients had the diagnosis confirmed by cardiac catheterization. The typical appearance of a traumatic ventricular septal defect (VSD) was seen during surgical repair that was successfully carried out in both patients. The protracted clinical course of the second patient, eventually requiring corrective intervention, contributes to the understanding of natural history of traumatic VSD.

Child, Preschool↗
PubMed1985

Evaluation of severe ventricular arrhythmias in chronic Chagas' heart disease by effort test and Holter monitoring.

The objective of the present study was to evaluate the ability of the gradual effort test (GET) to detect ventricular extrasystoles (VE), and, in particular, to identify patients with high arrhythmic risk in Chagas' heart disease, as well as to compare the results to those obtained by 24 h ambulatory electrocardiographic monitoring (Holter monitoring). A total of 103 Chagasic patients aged 20 to 55 years who exhibited no clinical signs of heart failure or complex arrhythmias under resting conditions were submitted to 24 h Holter monitoring and to a GET with discontinuous loads first applied to reach 120 bpm and then submaximal or maximal heart rate. The results of 24 h ambulatory electrocardiographic monitoring demonstrated that 52.4% of patients had no VE, 20.4% had few isolated VE (Grade I), 1.9% had frequent monomorphic VE (grade II), 4.8% very frequent polymorphic VE (grade III), and the remaining 20.4% had repetitive forms (doubles or bursts of 3 or more) classified as grade IV. In 68% of these patients, the GET did not detect VE. These were the patients who showed no arrhythmias or isolated VE during the Holter test. The 32% of patients who exhibited VE when submitted to the GET included all patients shown to have grade III and grade IV arrhythmia (27 cases) and 5 patients shown to have grade I arrhythmia by the Holter test. The GET showed 100% sensitivity in the detection of pathological (greater than 100 VE daily) and high-risk arrhythmias (greater than 1000 VE per 24 h, polymorphism or repetitive forms), with a specificity of 93 and 92%, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1985

Subtle cardiac autonomic impairment in Chagas' disease detected by baroreflex sensitivity testing.

The sensitivity of baroreflex bradycardia and tachycardia was determined in fourteen patients with Chagas' disease who seemed to be normal with respect to cardiac autonomic control evaluated in terms of heart rate responses to the conventional atropinization and Valsalva maneuver tests. Eleven normal subjects were studied for comparison. Baroreflex sensitivity was determined by relating the beat-to-beat pulse intervals to systolic pressure values during transient phenylephrine- and amyl nitrite-induced changes in arterial pressure. Chagasic patients showed mean bradycardia sensitivity (10.1 +/- 1.3 ms/mmHg) which was significantly lower than that obtained for the control group (16.7 +/- 2.1 ms/mmHg). When only the subgroup of ten patients with overt disease (cardiac and/or digestive form) was considered, the value fell to 8.6 +/- 1.4 ms/mmHg. The lowest individual values were exhibited by the majority of patients with exclusive cardiac or associated cardiac and digestive disease. Patients with only digestive disease or without overt disease (indeterminate form) had values within the normal range. Tachycardia sensitivity (6.3 +/- 0.8 ms/mmHg) was similar to that obtained for the control group (6.6 +/- 1.0 ms/mmHg). Only one patient with associated disease presented a reduced value. These data show that the estimation of baroreflex sensitivity can be used to identify impaired cardiac autonomic control in chronic Chagas' disease not detectable by conventional tests. The reduced baroreflex sensitivity appears to be due to the subtle impairment of the parasympathetic influence on the heart. Furthermore, there is a relationship between the degree of baroreflex sensitivity and the clinical form of organic involvement in Chagas' disease.

Adult↗
PubMed1985

Efficacy of pharmacological blockade of the cardiac parasympathetic system with atropine in normal men.

The effect of parasympathetic blockade with intravenously administered atropine (0.04 mg/kg body weight) on the heart rate (HR) of 11 normal males was evaluated using a standardized isometric exercise (handgrip). This type of exercise, when maintained for 10 s at the maximum intensity tolerated by the volunteer, causes tachycardia mediated almost exclusively by parasympathetic withdrawal. The test was performed under baseline conditions and at 20 +/- 3, 33 +/- 3, 42 +/- 3, 52 +/- 3 and 61 +/- 3 min after atropine infusion. The heart rate of the subjects at rest in the supine position (mean +/- SEM) was 70 +/- 2 bpm, reaching values of 119 +/- 3 bpm after atropine. Under control conditions (sitting position), the increase in HR induced by isometric exercise was 22 +/- 1.8 bpm. After blockade, the increase was 4 +/- 0.8, 4 +/- 0.7, 5 +/- 0.6, 4 +/- 1.0 and 4 +/- 0.8 bpm, respectively, at each repetition of the test. These results suggest that the blockade induced by this dose of atropine is effective for at least 1 h. They also indicate the need for a more rigorous definition of the functional half-life of atropine in the heart, when considering physiological tests that either stimulate or withdraw parasympathetic activity upon the heart.

Adult↗
PubMed1983

Impairment of baroreflex control of the sinoatrial node after cardiac operations with extracorporeal circulation in man.

The sensitivity of the baroreceptor reflex to transient hypertension was determined in 13 patients before (control) and after (72 hours) open cardiac operations with extracorporeal circulation (ECC). In all patients early postoperative values were appreciably decreased (p less than 0.01) as compared to the preoperative values. This decrease suggested severe impairment of baroreflex control of the sinoatrial node. These changes were not correlated with concurrent alterations in heart rate or systemic arterial, left atrial, or right atrial pressures. In addition, respiratory sinus node arrhythmia was absent in all subjects. In four patients, subsequent studies 4, 8, 10, and 12 months, respectively, after the operation revealed good recovery of baroreflex sensitivity and respiratory influences on beat-to-beat variation. No similar effects were observed in two patients studied before and after cardiac operations without ECC. It is possible that direct trauma to the nervous supply of the sinoatrial node is a major factor in that reversible dysfunction; in fact, in three patients evidence was obtained that while sinoatrial node responses were impaired, the reflex control of the atrioventricular region remained unaltered. These findings point to further impairment of the fine control of heart rate imposed by the conditions of cardiac operations with ECC in patients with previously curtailed cardiac reserve.

Adolescent↗
PubMed1979

Effects of heparin and protamine on left ventricular performance in the dog.

The effects of protamine on left ventricular (LV) function were measured under conditions of controlled heart rate and proximal aortic pressure in eight anaesthetized, heparinised dogs. Protamine 3 mg.kg-1 produced a 21% decrease in LV dP/dt max, a 43% decrease in cardiac output, a 47% decrease in stroke work and decreases in systolic and diastolic pressures (-16%, -19% respectively). Protamine 6 mg.kg-1 resulted in a 17% decrease in LV dP/dt max, a 26% decrease in cardiac output, a 50% decrease in LV stroke work and 25 and 30% decreases in systolic and diastolic pressures. These results show that an impairment of LV function plays an important part in the circulatory depression produced by protamine.

Animals↗
PubMedDate not supplied

Functional pulmonary atresia in a newborn with normal intracardiac anatomy.

Functional pulmonary atresia is a relatively rare clinical condition usually associated with Ebstein's malformation, tricuspid valve dysplasia, Uhl's anomaly, or transient myocardial ischemia with severe tricuspid regurgitation. The occurrence of functional pulmonary atresia associated with transient tricuspid regurgitation in a newborn with an anatomically normal heart is even more uncommon. We describe a case in which color Doppler flow mapping played an essential role in diagnosis and follow-up of this clinical condition in a newborn who had normal intracardiac anatomy.

Diagnosis, Differential↗
PubMedDate not supplied

Cardiac tamponade: an unusual complication of pericardial cyst.

Pericardial cysts are not common and rarely cause symptoms. We report a unique case of a 15-year-old male patient with cardiac tamponade clinically diagnosed who was referred for echocardiography. Transthoracic echocardiography revealed, in addition to a large pericardial effusion associated with echocardiographic signs of cardiac tamponade, an 8 x 5 cm echofree image suggesting a pericardial cyst adjacent to the right atrium. Immediately after pericardiocentesis, yielding a serosanguinous liquid, the patient showed striking clinical improvement and echocardiography demonstrated minimal pericardial effusion with persistence of the cystic image. At surgery a pericardial cyst containing a sanguinous fluid was found and the pathologic findings were consistent with hematic pericardial cyst. Thus echocardiography played a fundamental role for the diagnosis and treatment of the rare complication of a pericardial cyst documented in this patient.

Adolescent↗
PubMedDate not supplied

Ventricular function in Chagas' heart disease.

Invasive and noninvasive methods used to evaluate ventricular function in Chagas's disease are reviewed. The traditional indices of overall ventricular performance reflect the interaction of preload, contractility, afterload and heart rate. Therefore, they are unable to distinguish changes in contractility from modifications of loading conditions. The role of ventricular function as a predictor of mortality in chronic Chagas' heart disease is discussed. Ventricular function abnormalities in patients with indeterminate and digestive forms of Chagas' disease are especially emphasized. Finally, the evidence of early impairment of diastolic performance in digestive forms of Chagas' disease are especially emphasized. Finally, the evidence of early impairment of diastolic performance in patients with Chagas' disease is presented.

Chagas Cardiomyopathy↗
PubMedDate not supplied

Studies of the coronary circulation in Chagas' heart disease.

Pathogenesis of chronic Chagas' heart disease may include various disturbances in the coronary circulation, that could be responsible for the myocardial lesions seen in human hearts and in experimental models of the disease. In this paper we critically reviewed the anatomical and functional abnormalities described in chronic chagasic patients, pertaining to the so-called vascular pathogenetic theory of Chagas' disease. The epicardial coronary arteries are usually free of significant obstructive disease in nonselected groups of chagasic patients examined at autopsy or by coronary angiography. However, chagasic patients who were studied after an episode of acute myocardial infarction, show the same patterns of atherosclerotic coronary artery disease seen in the general nonchagasic population. Studies of chagasic patients with angiographically normal coronary arteries, by several scintigraphy methods, revealed myocardial perfusion abnormalities which may be caused by the microcirculatory derangements described in animals experimentally infected with the T. cruzi. Since hypoperfusion has been detected in regions with normal or mildly impaired wall motion, it is likely that the microvascular disturbances precede and may be causative mechanism for the subsequent myocardial damage. We speculate that hibernating ventricular areas may occur in chagasic patients, on the basis of the evidence gathered from these studies. Recent investigations of chronic patients with Chagas' disease and chest pain showed attenuation of the vasomotor responses to physiological and pharmacological stimuli, in the epicardial coronary arteries.

Animals↗
PubMedDate not supplied

Radionuclide angiographic evidence for early predominant right ventricular involvement in patients with Chagas' disease.

Radionuclide angiography was used to study biventricular function in 11 noncardiac (group 1) and eight chronic cardiac chagasic patients (group 2). Results in chagasic patients were compared to those obtained in 10 normal subjects. Global ejection fraction and the standard deviation of peak (SDP) phase histogram were determined for each ventricle and qualitative evaluation of regional wall motion in both anterior and left anterior oblique projections was performed. Left ventricular dysfunction was markedly predominant in group 2, mean +/- SD ejection fraction 39.7 +/- 13.1% and SDP 29.8 +/- 15.6 degrees, as compared to group 1, in which these values were 56.7 +/- 9.9% (P less than 0.01) and 18.3 +/- 7.1 degrees (P less than 0.05), respectively. In contrast, severe right ventricular impairment was found equally in both groups: ejection fraction averaged 31.8 +/- 12.7 and 31.0 +/- 9.1%, and the mean SDP was 29.3 +/- 8.6 and 23.7 +/- 6.7 degrees, in groups 2 and 1, respectively. The qualitative analysis of segmental wall motion also showed apical and/or free-wall right dysynergy in all patients of group 1, while the same abnormalities were detected in six out of eight patients in group 2. These findings indicate that severe functional impairment of right ventricular performance is by far the most significant abnormality detected by radionuclide angiography in chagasic patients who are asymptomatic and have no other clinical sign of heart disease.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗