RESUMO
The medical records of ten pediatric patients with a clinical diagnosis of tetanus were reviewed retrospectively. The heart rate and blood pressure of all tetanus patients were measured noninvasively every hour during the first two weeks of hospitalization. Six of ten tetanus patients presented clinical evidence of sympathetic hyperactivity (group A) and were compared with a control group consisting of four children who required mechanical ventilation for diseases other than tetanus (group B). Heart rate and blood pressure simultaneously and progressively increased to a maximum by day 7. The increase over baseline was 43.70 +/- 11.77 bpm (mean +/- SD) for heart rate (P<0.01) and 38.60 +/- 26.40 mmHg for blood pressure (P<0.01). These values were higher and significantly different from those of the control group (group B) at day 6, which had an average heart rate increase over baseline of 19.35 +/- 12.26 bpm (P<0.05) and blood pressure of 10.24 +/- 13.30 mmHg (P<0.05). By the end of the second week of hospitalization, in group A the increase of systolic blood pressure over baseline had diminished to 9.60 +/- 15.37 mmHg (P<0.05), but the heart rate continued to be elevated (27.80 +/- 33.92 bpm, P = NS), when compared to day 7 maximal values. The dissociation of these two cardiovascular variables at the end of the second week of hospitalization suggests the presence of asymmetric cardiac and vascular sympathetic control. One possible explanation for these observations is a selective and delayed action of tetanus toxin on the inhibitory neurons which control sympathetic outflow to the heart.
Assuntos
Sistema Nervoso Autônomo/fisiopatologia , Pressão Sanguínea , Frequência Cardíaca , Tétano/fisiopatologia , Adolescente , Estudos de Casos e Controles , Criança , Pré-Escolar , Feminino , Humanos , Hipertensão/etiologia , Masculino , Estudos Retrospectivos , Índice de Gravidade de Doença , Taquicardia/etiologia , Tétano/complicaçõesRESUMO
The medical records of ten pediatric patients with a clinical diagnosis of tetanus were reviewed retrospectively. The heart rate and blood pressure of all tetanus patients were measured noninvasively every hour during the first two weeks of hospitalization. Six of ten tetanus patients presented clinical evidence of sympathetic hyperactivity (group A) and were compared with a control group consisting of four children who required mechanical ventilation for diseases other than tetanus (group B). Heart rate and blood pressure simultaneously and progressively increased to a maximum by day 7. The increase over baseline was 43.70 + or - 11.77 bpm (mean + or - SD) for heart rate (P<0.01) and 38.60 + or - 26.40 mmHg for blood pressure (P<0.01). These values were higher and significantly different from those of the control group (group B) at day 6, which had an average heart rate increase over baseline of 19.35 + or - bpm (P<0.05) and blood pressure of 10.24 + or - mmHg (P<0.05). By the end of the second week of hospitalization, in group A the increase of systolic blood pressure over baseline had diminished to 9.60 + or - mmHg (P<0.05), but the heart rate continued to be elevated (27.80 + or - 0 bpm, P = NS), when compared to day 7 maximal values. The dissociation of these two cardiovascular variables at the end of the second week of hospitalization suggests the presence of asymmetric cardiac and vascular sympathetic control. One possible explanation for these observations is a selective and delayed action of tetanus toxin on the inhibitory neurons which control sympathetic outflow to the heart
Assuntos
Humanos , Masculino , Feminino , Criança , Pré-Escolar , Sistema Nervoso Autônomo , Tétano , Pressão Sanguínea , Estudos de Casos e Controles , Frequência Cardíaca , Estudos Retrospectivos , Índice de Gravidade de Doença , TétanoRESUMO
We administered arecoline to rats, with experimentally induced chagasic myocarditis, in order to study the sinus node sensitivity to a muscarinic agonist. Sixteen month old rats were inoculated with 200,000 T. cruzi parasites ("Y" strain). Between days 18 and 21 (acute stage), 8 infected rats and 8 age-matched controls received intravenous arecoline as a bolus injection at the following doses: 5. 0, 10.0, 20.0, 40.0, and 80.0 microg/kg. Heart rate was recorded before, during and after each dose of arecoline. The remaining 8 infected animals and 8 controls were subjected to the same experimental procedure during the subacute stage, i.e., days 60 to 70 after inoculation. The baseline heart rate, of the animals studied during the acute stage (349 +/- 68 bpm, mean +/- SD), was higher than that of the controls (250 +/- 50 bpm, p < 0.005). The heart rate changes were expressed as percentage changes over baseline values. A dose-response curve was constructed for each group of animals. Log scales were used to plot the systematically doubled doses of arecoline and the induced-heart rate changes. The slope of the regression line for the acutely infected animals (r = - 0.99, b =1.78) was not different from that for the control animals (r = - 0.97, b = 1.61). The infected animals studied during the subacute stage (r = - 0.99, b = 1.81) were also not different from the age-matched controls (r = - 0.99, b = 1.26, NS). Consequently, our results show no pharmacological evidence of postjunctional hypersensitivity to the muscarinic agonist arecoline. Therefore, these results indirectly suggest that the postganglionic parasympathetic innervation, of the sinus node of rats with autopsy proved chagasic myocarditis, is not irreversibly damaged by Trypanosoma cruzi.
Assuntos
Arecolina/farmacologia , Cardiomiopatia Chagásica/fisiopatologia , Frequência Cardíaca/efeitos dos fármacos , Agonistas Muscarínicos/farmacologia , Nó Sinoatrial/efeitos dos fármacos , Doença Aguda , Animais , Cardiomiopatia Chagásica/tratamento farmacológico , Sistema Nervoso Parassimpático/efeitos dos fármacos , Sistema Nervoso Parassimpático/parasitologia , Ratos , Ratos Wistar , Nó Sinoatrial/inervaçãoRESUMO
Cardiac chambers have afferent connections to the brainstem and to the spinal cord. Vagal afferents mediate depressor responses and become activated by volume expansion, increased myocardial contractility and atrial natriuretic factor. Sympathetic afferents, on the contrary, are activated by metabolic mediators, myocardial ischemia and cardiac enlargement. These opposite behaviors may lead to activation or suppression of the sympathetic nervous system and of the renin-angiotensin-aldosterone system. As cardiac diseases progress, the heart dilates, plasma norepinephrine increases, atrial natriuretic factor is released and the renin-angiotensin-aldosterone system is suppressed to maintain water and sodium excretion. This dissociation of the neurohormonal profile of cardiac patients, may be explained by coactivation of sympathetic afferents, by cardiac dilatation, and of vagal afferents by atrial natriuretic factor. In more advanced stages, atrial natriuretic factor suppression of the renin-angiotensin-aldosterone system is overridden by overt sympathetic activation and sodium and water retention ensues. Digitalis, angiotensin-converting enzyme inhibitors and beta-blockers selectively decrease cardiac adrenergic drive. A common mechanism of action, to all three groups of drugs, would be attenuation of sympathetic afferents and partial normalization of vagal afferents. Consequently, heart size and cardiac afferents emerge as the key factors to understand the pathophysiology and treatment of the syndrome of congestive heart failure.
Assuntos
Vias Aferentes/fisiopatologia , Insuficiência Cardíaca/fisiopatologia , Nervo Vago/fisiopatologia , Vias Aferentes/fisiologia , Animais , Fator Natriurético Atrial/fisiologia , Tronco Encefálico/fisiologia , Tronco Encefálico/fisiopatologia , Humanos , Modelos Cardiovasculares , Modelos Neurológicos , Contração Miocárdica , Norepinefrina/fisiologia , Sistema Renina-Angiotensina , Medula Espinal/fisiologia , Medula Espinal/fisiopatologia , Nervo Vago/fisiologiaRESUMO
UNLABELLED: The cardiac effects of experimentally induced myocarditis, when the parasite is obtained from mouse blood, are well known. However, the consequences of the infection when the parasites are obtained from bug faeces are less well defined. In the present investigation, we have used the "Y" strain of Trypanosoma cruzi, which was maintained in Rhodnius prolixus by repeated passages in mice. The faeces of 30 infected bugs were collected, the number of parasites counted and 4,000 parasites inoculated by the conjunctival route in 60 rats. Twenty-nine other rats received faeces from noninfected bugs (sham-inoculated controls) and 40 were used as normal controls. The heart rate of the three groups of animals was recorded under general anesthesia with ether. The heart rate, at day 0 pre-inoculation, was similar in the three groups of animals ( CONTROLS: 379 +/- 27 beats/min Mean +/- SD; Sham-inoculated: 366 +/- 31; Infected: 351 +/- 29) (p> 0.05). In the infected animals, the mean heart rate began to increase significantly by day 12 following infection (375 +/- 31), reaching the highest values between days 18 (390 +/- 33) and 21 (403 +/- 33) and returned to baseline by day 30 (359 +/- 28) (p< 0.05). The heart rate changes were statistically different from those observed in the sham-inoculated controls and in the control animals. Therefore, these heart rate changes were provoked by the Trypanosoma cruzi-induced infection. Thus, it appears that irrespective of the source of the parasite and route of inoculation, Trypanosoma cruziacute infection provokes a transient sinus tachycardia.
Assuntos
Frequência Cardíaca , Trypanosoma cruzi , Animais , Túnica Conjuntiva , Fezes , Feminino , RatosRESUMO
The autonomic nervous system is abnormal in patients with advanced Chagas' heart disease. Most researchers consider these autonomic abnormalities as primary, specific and irreversible. However, when and why these abnormalities appear in the natural history of Chagas' disease, is still the subject of intense controversy. Recent morphological and functional studies strongly suggest that the sympathetic and the parasympathetic abnormalities are preceded by myocardial damage and left ventricular dysfunction. Moreover, chagasic patients with cardiac failure benefit from drugs which antagonize neurohumoral activation. Consequently, the abnormalities of the autonomic nervous system of chagasic patients are very likely secondary and partially reversible.
Assuntos
Sistema Nervoso Autônomo/fisiopatologia , Cardiomiopatia Chagásica/fisiopatologia , Progressão da Doença , Humanos , Sistema Nervoso Simpático/fisiopatologia , Disfunção Ventricular Esquerda/fisiopatologiaRESUMO
This study involves a review of the records of 64 children referred to the University of los Andes Hospital with the diagnosis of scorpion envenomation. The patients were divided into group 1 (local manifestations, 42.4%) and group 2 (systemic manifestations, 7.8%). Seven of these patients had severe cardiorespiratory complications, came from distinct geographical zones and received antivenin. Our results indicate that poisonous and extremely dangerous scorpions predominate in certain geographical zones within the state of Merida, Venezuela.
Assuntos
Venenos de Escorpião/toxicidade , Adolescente , Criança , Pré-Escolar , Humanos , Lactente , Estudos RetrospectivosRESUMO
To determine the possible relationship between left ventricular dilatation and heart rate changes provoked by the Valsalva maneuver (Valsava ratio), we studied 9 patients with isolated chronic aortic insufficiency. Left ventricular systolic function was assessed by two dimensional echocardiography and cardiac catheterization. All patients were asymptomatic (functional class I of the New York Heart Association). The left ventricular internal diameters and volumes were significantly increased in all patients. The asymptomatic patients had either normal or slightly depressed ejection fraction (EF>0.40). The Valsalva ratio of these asymptomatic patients showed no significant correlation with the left ventricular volumes or with the left ventricular ejection fraction. In other words, parasympathetic heart rate control, as expressed by the Valsalva ratio, was normal in the asymptomatic patients with left ventricular dilatation and preserved left ventricular ejection fraction. Therefore, left ventricular dilatation may not be the major mechanism responsible for the abnormal parasympathetic heart rate control of patients with acquired heart disease.
Assuntos
Adulto , Feminino , Humanos , Adolescente , Insuficiência da Valva Aórtica/fisiopatologia , Frequência Cardíaca , Manobra de Valsalva , Função Ventricular EsquerdaRESUMO
To determine the possible relationship between left ventricular dilatation and heart rate changes provoked by the Valsalva maneuver (Valsalva ratio), we studied 9 patients with isolated chronic aortic insufficiency. Left ventricular systolic function was assessed by two-dimensional echocardiography and cardiac catheterization. All patients were asymptomatic (functional class I of the New York Heart Association). The left ventricular internal diameters and volumes were significantly increased in all patients. The asymptomatic patients had either normal or slightly depressed ejection fraction (EF > 0.40). The Valsalva ratio of these asymptomatic patients showed no significant correlation with the left ventricular volumes or with the left ventricular ejection fraction. In other words, parasympathetic heart rate control, as expressed by the Valsalva ratio, was normal in the asymptomatic patients with left ventricular dilatation and preserved left ventricular ejection fraction. Therefore, left ventricular dilatation may not be the major mechanism responsible for the abnormal parasympathetic heart rate control of patients with acquired heart disease.
Assuntos
Insuficiência da Valva Aórtica/fisiopatologia , Frequência Cardíaca , Manobra de Valsalva , Adolescente , Adulto , Feminino , Humanos , Masculino , Função Ventricular EsquerdaRESUMO
Chagasic patients with congestive heart failure are usually treated with digitalis and converting enzyme inhibitors. According to the neurogenic and dysautonomic theories, chagasic patients would not benefit from these drugs. To clarify this controversial issue, we have studied patients with congestive heart failure and suspected Chagas' heart disease. All patients received intravenous methyl-digoxin for 24 h and oral enalapril for 96 h. Blood samples for plasma norepinephrine, aldosterone and renin were taken at baseline, after acute digitalization and following enalapril. Based on the serology for Chagas' disease, the patients were divided into non-chagasic and chagasic patients. In the chagasic group three patients were in functional class III and 3 were in functional class IV. In the non-chagasic group five patients were in functional class III and 2 were in functional class IV. Both groups had a marked and quantitatively similar degree of neurohormonal activation. All patients improved at least one functional class and lost more than 5 kg of body weight with treatment. The chagasic patients had a statistically significant reduction in plasma norepinephrine (2262 +/- 1407 to 865 +/- 390, P < 0.008, pg/ml, M +/- S.D.), plasma aldosterone (330 +/- 168 to 155 +/- 75, P < 0.01, pg/ml, M +/- S.D.) and plasma renin activity (14 +/- 13 to 2 +/- 1.6 ng/ml per h, M +/- S.D., P < 0.05), with digitalis. Following enalapril, norepinephrine and aldosterone there was a further but non-significant reduction, when compared to postdigitalis values. These results indicated that chagasic patients do benefit from digitalis and enalapril. Furthermore, the prominent and significant reduction in all three neurohormones suggest that the parasympathetic and sympathetic systems of these chagasic and non-chagasic patients, are responding to the neuromodulatory effects of digitalis and enalapril.