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Biomedical subjects

J A Marin-Neto

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

At least 55 records · Page 3Linked to original sources
PubMed1991

High output failure in patients with peripartum cardiomyopathy: a comparative study with dilated cardiomyopathy.

Although few studies have reported on relatively preserved ventricular function in patient with peripartum cardiomyopathy, the condition is usually believed to have the typical low-output congestive hemodynamic pattern of the dilated congestive cardiomyopathies. Two groups of patients, 14 with peripartum cardiomyopathy and 12 with dilated congestive cardiomyopathy who were matched for gender and age, were studied. They had normal blood pressure and similar New York Heart Association functional class, nutritional status, thyroid function and routine laboratory evaluation. All patients were catheterized during stable in-hospital compensation of heart failure, which was achieved by bed rest, sodium restriction, and administration of digoxin and diuretics long (more than 3 months) after delivery. Significant differences (p less than 0.05) between patients with peripartum cardiomyopathy and those with dilated congestive cardiomyopathy were observed in regard to: (1) cardiac index: 3.34 +/- 1.36 L/min/m2 versus 2.24 +/- 0.72 L/min/m2, (2) systemic vascular resistance: 1713 +/- 567 dynes.sec.cm-5 versus 2194 +/- 603 dynes.sec.cm-5, (3) right ventricular stroke work index: 8.6 +/- 4.2 g.M/m2 versus 14.8 +/- 8.2 g.M/m2 in the peripartum cardiomyopathy and the dilated congestive cardiomyopathy groups, respectively. Three of the patients with peripartum cardiomyopathy had resting cardiac index values that were even higher than the normal upper limit for our laboratory (4.5 L/min/m2): 4.80, 5.70, and 5.63 L/min/m2. They also had nearly normal left ventricular ejection fractions: 0.68, 0.41, and 0.51, respectively. These results indicate that, unlike the common dilated cardiomyopathy, the hemodynamic pattern in patients with peripartum cardiomyopathy is not homogeneous, and some patients have high-output failure and near normal left ventricular function.

Adult↗
PubMed1991

Acquired aorto-coronary vein fistula after bypass graft surgery: report of two cases with long-term follow-up.

Two patients who underwent bypass surgery with saphenous grafts had a fistula resulting from inadvertent grafting of the cardiac vein correspondent to a targeted diagonal artery. Hemodynamic effects at rest were restricted to moderate elevation of the pulmonary blood flow, by 23 and 13% respectively, at 5 and 12 months postoperatively. No objective signs of ischemia could be elicited in either patient, in the fistula related region, and left ventricular function remained within normal limits in both cases throughout the follow-up period (36 and 24 months, respectively).

Aged↗
PubMed1990

[Hemodynamic study of peripartum cardiopathy following compensation of heart failure].

PURPOSE: To assess hemodynamic characteristics of patients with peripartum cardiomyopathy under standardized conditions of clinical compensation of heart failure, and more than 3 months after the end of the gravidic period. PATIENTS AND METHODS: Fourteen patients with peripartum cardiomyopathy underwent left and right cardiac catheterization, under rest condition. Cardiac output was measured by the Fick method, left ventricular ejection fraction determined by contrast ventriculography, and the coronary circulation was studied angiographically. RESULTS: The hemodynamic pattern observed was variable, with 28% of the cases showing low right and left ventricular filling pressures, normal LV ejection fraction, and normal or even elevated cardiac output, with low pulmonary and systemic vascular resistance. CONCLUSION: Although the mechanisms responsible for such peculiar hemodynamic characteristics, have not been elucidated, it is likely that they are associated with more benign prognosis, as compared to other patients with peripartum cardiomyopathy, who show the low-output failure commonly seen in cases of dilated cardiomyopathy.

Adolescent↗
PubMed1990

Depressed respiratory sinus arrhythmia: additional evidence for impairment of vagal activity in human hyperthyroidism.

The efferent activity of the parasympathetic component of the autonomic nervous system was evaluated by measuring the magnitude of the respiratory sinus arrhythmia in 3 female patients with hyperthyroidism (Basedow-Graves' disease) before and after treatment. The heart rate variations induced by the test increased in all patients after treatment of thyrotoxicosis (from 15 +/- 2.9 to 28.3 +/- 6.6 beats/min; mean +/- SEM) with propylthiouracil (600 mg/day). This result confirms our previous observations indicating an important and reversible impairment of the efferent vagal activity in human hyperthyroidism.

Arrhythmia, Sinus↗
PubMed1989

Evaluation of the autonomic nervous system of the heart in male patients with mitral valve prolapse syndrome using respiratory sinus arrhythmia and dynamic exercise.

The autonomic nervous system of the heart was evaluated in two male groups composed of 11 patients with mitral valve prolapse and of 10 normal subjects, using the heart rate response in two types of tests: respiratory sinus arrhythmia at rest and dynamic exercise. Sinus arrhythmia was of higher magnitude in patients with mitral valve prolapse when compared to the control group; however, the differences reached statistical significance only at a respiratory frequency of 7 cycles/min. With respect to dynamic exercise (25, 50, 100, 150 W during 4 min), the heart rate response, either in terms of the early, vagus-dependent fast tachycardia (first 10 s), or the late, sympathetic-dependent tachycardia (1-4 min) was normal in both groups studied, the same occurring with aerobic exercise capacity evaluated by measurement of the anaerobic threshold. Thus, our results show that in the group of male patients with mitral valve prolapse studied here, the parasympathetic abnormalities, if present, are of questionable physiological significance and do not affect the sympathetic and parasympathetic control of heart rate during dynamic exercise.

Adult↗
PubMed1989

Sympathetic and parasympathetic changes in heart rate control during dynamic exercise induced by endurance training in man.

1. Seven healthy young men of sedentary habits were submitted to a 10-week period of endurance physical training on a cycle ergometer. The training program caused a 15% increase in maximal oxygen consumption (VO2max) and a 16% reduction in resting heart rate (HR). Before and after training, these volunteers performed dynamic exercise (DE) on a cycle ergometer at loads of 25, 50, 75, 100 and 150 w for 4 min at each level. The same exercise protocol was applied to 13 sedentary individuals and to 7 athletes (medium distance runners) who showed a VO2max of 39.4 and 53.8 ml/kg, respectively. HR was continuously monitored throughout the period of effort at each workload. 2. During the first 10 s of DE, a period when tachycardia is mediated almost exclusively by vagal withdrawal, the athletes presented a more rapid increase in HR than sedentary subjects. The same tendency was observed in the sedentary individuals after the training period, although of a lesser magnitude. 3. During the DE phase in which sympathetic mediation plays an important role (between 30 s and 4 min), the athletes presented a lower HR increase than the sedentary individuals, and the same response pattern was observed in the group submitted to physical training. Total HR increase (from 0 to 4 min) induced by DE was lower in athletes than in sedentary subjects and was not changed by training of the sedentary subjects. 4. These results suggest that aerobic training decreases the slow sympathetic and increases the fast parasympathetic contribution to HR during dynamic exercise at the same absolute workloads. 5. These functional changes in the autonomic control of HR may or may not be associated with modifications of absolute HR values which increase from rest to the end of exercise. In contrast to what happens in athletes, the autonomic adaptations observed after short-term aerobic training may occur during DE without changes in the total HR response.

Adaptation, Physiological↗
PubMed1989

[Ventricular function in mitral valve prolapse: effects of beta adrenergic blockers with and without intrinsic sympathomimetic activity].

A corollary of the "cardiomyopathy therapy" implies that mitral valve prolapse may cause intrinsic myocardial depression. The impairment of ventricular function may not be detected in basal conditions, but could be unmasked by superimposing depressant factors. The use of beta-blockers constitutes the first choice treatment for the symptomatic management of patients with mitral valve prolapse. Therefore, we tested the hypothesis that myocardial depression could be shown during beta-blockade in the uncomplicated primary form of mitral valve prolapse. The results of echocardiographic and radionuclide angiographic evaluation of left ventricular function during basal conditions, as well as under beta-blockade with propranolol and pindolol, do not lend support to the cardiomyopathy hypothesis of the pathogenesis of primary mitral valve prolapse. However, significant decreases of heart rate, left ventricular ejection fraction and peak velocity of left ventricular systolic emptying were seen with propranolol, but not with pindolol. Beta-blockade with intrinsic sympathomimetic activity may be preferable therapeutic option for patients with mitral valve prolapse.

Adolescent↗
PubMed1989

Leg endurance training has no effect on the autonomic control of heart rate during isometric exercise.

1. Heart rate (HR) response to isometric exercise (handgrip) was investigated in 7 normal males of sedentary habits before and after endurance training involving the muscles of the lower limbs. Thirteen additional sedentary individuals and 7 middle-distance runners were also studied. Isometric exercise was performed at 100, 75 and 50% of maximum voluntary contraction (MVC) during 10, 20 and 40 s, respectively. Training produced a 15.6 +/- 1.4% (mean +/- SEM) increase in VO2max and a reduction in resting HR from 69 +/- 1.9 to 58 +/- 1.7 bpm. HR was monitored throughout each period of isometric exercise. 2. The pattern of HR response to static effort performed by untrained muscles was comparable before and after training as well as in athletes and sedentary individuals during the first 10 s of contraction, a period during which tachycardia is mainly mediated by vagal release. After the first 10 s, when the sympathetic influence on tachycardia becomes evident, athletes and trained individuals showed a slight but nonsignificant tendency toward lower HR increases. 3. These results do not demonstrate any appreciable alteration in the efferent activity of autonomic components induced by aerobic training of the leg muscles when isometric exercise is performed with untrained muscles.

Adaptation, Physiological↗
PubMed1988

Cardiovascular effects of berberine in patients with severe congestive heart failure.

Berberine, an alkaloid of the protoberberine family, has been shown to have strong positive inotropic and peripheral resistance-lowering effects in dogs with and without heart failure. To determine the acute cardiovascular effects of berberine in humans, 12 patients with refractory congestive heart failure were studied before and during berberine intravenous infusion at rates of 0.02 and 0.2 mg/kg per min for 30 minutes. The lower infusion dose produced no significant circulatory changes, apart from a reduction in heart rate (14%). The 0.2 mg/kg per min dose elicited several significant changes: (a) Decreases in systemic (48%, p less than 0.01) and pulmonary vascular resistance (41%, p less than 0.01), and in right atrium (28%, p less than 0.05) and left ventricular end-diastolic pressures (32%, p less than 0.01). (b) Increases in cardiac index (45%, p less than 0.01), stroke index (45%, p less than 0.01), and LV ejection fraction measured by contrast angiography (56%, p less than 0.01). (c) Increases in hemodynamic and echocardiographic indices of LV performance: peak measured velocity of shortening (45%, p less than 0.01), peak shortening velocity at zero load (41%, p less than 0.01), rate of development of pressure at developed isovolumic pressure of 40 mmHg (20%, p less than 0.01), percent fractional shortening (50%, p less than 0.01), and the mean velocity of circumferential fiber shortening (54%, p less than 0.01). (d) Decrease of arteriovenous oxygen difference (28%, p less than 0.05) with no changes in total body oxygen uptake, arterial oxygen tension, or hemoglobin dissociation properties.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

The use of isometric exercise as a means of evaluating the parasympathetic contribution to the tachycardia induced by dynamic exercise in normal man.

Fourteen normal subjects were submitted to isometric exercise (IE), dynamic exercise (DE) and a combination of the two (IE + DE). The main purpose of the present study was to use IE as a means of evaluating the mechanism of the heart rate (HR) increase induced by DE. To this end, the magnitude of the IE (handgrip) was standardized so as to cause an elevation of HR almost exclusively by vagal withdrawal: IE was performed using a dynamometer strain-gauge system with a linear response at 75% of maximum voluntary contraction (MVC) for 10 s, repeated at 1 min intervals. The change in HR evoked by IE under control conditions was compared with that evoked during DE, and during the corresponding recovery period. DE was performed by the legs, with the subject in the seated position for 4 min, at workloads of 55 and 105 watts, separated by a rest period. In the combined protocol, IE was performed at the beginning of DE, as well as at 1, 2 and 3 min during DE, and at 0, 1, 2, 3 and 5 min during recovery period. The following results were obtained: (1) IE associated with DE always induced smaller increase in heart rate than IE alone, and this effect was more marked at 105 than at 55 W; this finding suggested a workload-dependent vagal withdrawal at the very beginning of DE that was sustained until the end of effort.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1988

Inadequacy of first and second order models to characterize the heart rate response induced by dynamic exercise.

Six normal subjects were submitted to dynamic exercise at workloads of 25, 50, 100 and 150 w for 4 min, intercalated by periods of rest, before and after an aerobic training period of 10 weeks. The heart rate response was fitted to 2 mathematical models, a 1st-order model and a 2nd-order model. The results indicate that these 2 models were not adequate to characterize the physiological response of heart rate induced by dynamic exercise.

Exercise Test↗