RESUMEN
Minimal models are developed to examine the origin of large negative thermal expansion in underconstrained systems. The dynamics of these models reveals how underconstraint can organize a thermodynamically extensive manifold of low-energy modes which not only drives negative thermal expansion but extends across the Brillioun zone. Mixing of twist and translation in the eigenvectors of these modes, for which in ZrW2O8 there is evidence from infrared and neutron scattering measurements, emerges naturally in our model as a signature of the dynamics of underconstraint.
RESUMEN
Results are presented of single crystal structural, thermodynamic, and reflectivity measurements of the double-perovskite Ba2NaOsO6. These characterize the material as a 5d1 ferromagnetic Mott insulator with an ordered moment of approximately 0.2microB per formula unit and TC=6.8(3) K. The magnetic entropy associated with this phase transition is close to Rln2, indicating that the quartet ground state anticipated from consideration of the crystal structure is split, consistent with a scenario in which the ferromagnetism is associated with orbital ordering.
RESUMEN
We combine the results of terahertz time-domain spectroscopy with far-infrared transmission and reflectivity to obtain the conductivity of SrRuO3 over an unprecedented continuous range in frequency, allowing us to characterize the approach to zero frequency as a function of temperature. We show that the conductivity follows a simple phenomenological form, with an analytic structure fundamentally different from that predicted by the standard theory of metals.
RESUMEN
BACKGROUND AND AIMS: Nitrate therapy improves hemodynamics in patients with heart failure, but the chronic effects of oral nitrates on exercise performance and clinical status have not been well studied. METHODS: Oral isosorbide-5-mononitrate (ISMN) (50 mg once daily) or placebo was administered to 136 patients (NYHA Class 2-3) treated for heart failure, all receiving captopril and most also furosemide. Endpoints were treadmill exercise time at 12 weeks by modified Naughton protocol (primary), with an additional 12-week follow-up period. Secondary endpoints included left ventricular dimensions, ejection fraction, cardiothoracic ratio, functional class, quality of life, hospitalizations and plasma norepinephrine and atrial natriuretic peptide in a four-center substudy. RESULTS: Intention-to-treat analysis showed that mean change in treadmill exercise duration tended to be greater in patients receiving ISMN than placebo (treatment difference +42 s, 95% CI -5, +90 s at 12 weeks and +21 s, 95% CI -25, +74 s after 24 weeks) (NS). Treatment difference was greater in the prespecified subgroup with ejection fraction 31-40% (+55 s, 95% CI -11, +136 s at 12 weeks and +65 s, 95% CI +3, +147 s) (p = 0.035) at 24 weeks. No deleterious effects (i.e. hypotension) were observed with ISMN, although headache was reported in 19% of the active treatment group (p = 0.0001). CONCLUSIONS: ISMN added to captopril increased treadmill exercise time in patients with heart failure and a lesser reduction in baseline ejection fraction, although for the group as a whole, the increase in treadmill time was not significant.
Asunto(s)
Electrocardiografía/efectos de los fármacos , Prueba de Esfuerzo/efectos de los fármacos , Insuficiencia Cardíaca/tratamiento farmacológico , Dinitrato de Isosorbide/análogos & derivados , Vasodilatadores/administración & dosificación , Administración Oral , Adulto , Anciano , Inhibidores de la Enzima Convertidora de Angiotensina/administración & dosificación , Inhibidores de la Enzima Convertidora de Angiotensina/efectos adversos , Captopril/administración & dosificación , Captopril/efectos adversos , Diuréticos/administración & dosificación , Diuréticos/efectos adversos , Método Doble Ciego , Femenino , Furosemida/administración & dosificación , Furosemida/efectos adversos , Insuficiencia Cardíaca/fisiopatología , Hemodinámica/efectos de los fármacos , Humanos , Dinitrato de Isosorbide/administración & dosificación , Dinitrato de Isosorbide/efectos adversos , Masculino , Persona de Mediana Edad , Calidad de Vida , Vasodilatadores/efectos adversosRESUMEN
OBJECTIVE: The objective of this study was to evaluate the efficacy, tolerability, and safety of mibefradil, a new selective T-type calcium channel blocker, in patients with chronic stable angina pectoris receiving concomitant beta-blocker therapy. DESIGN: This was a multicenter, double-blind, placebo-controlled study. METHODS: Ninety-five patients receiving a stable dose of beta-blockers, which was not changed for the purpose of the study, were administered either 50 mg mibefradil once daily for 2 weeks, then 100 mg once daily for 2 weeks, or matching placebo. Efficacy was evaluated by treadmill exercise tolerance testing 24 hours after dose and by diary registration of anginal episodes and nitroglycerin consumption. RESULTS: Two weeks of treatment with 50 mg mibefradil resulted in a significant increase in symptom-limited exercise duration and a significant delay in the onset of persistent 1 mm ST-segment depression (placebo-corrected treatment effect: 23.2 and 51.7 seconds, respectively). Treatment with the 100 mg dose for 2 additional weeks resulted in a larger improvement in treadmill exercise tolerance testing duration and onset of ischemia (placebo-corrected treatment effect: 52.7 and 75.8 seconds, respectively). In addition, a significant decrease in weekly anginal episodes was observed with the 100 mg dose of mibefradil compared with the effect in the placebo group (-53% vs - 12%, p = 0.037). CONCLUSIONS: The combined treatment of mibefradil and beta-blockers was well tolerated, and the overall incidence of adverse events was no different from that with beta-blockers alone. The results indicate that adding mibefradil to chronic beta-blocker treatment is associated with significant improvement in efficacy, which is not achieved at the expense of tolerability.
Asunto(s)
Antagonistas Adrenérgicos beta/uso terapéutico , Angina de Pecho/tratamiento farmacológico , Bencimidazoles/uso terapéutico , Bloqueadores de los Canales de Calcio/uso terapéutico , Tetrahidronaftalenos/uso terapéutico , Antagonistas Adrenérgicos beta/administración & dosificación , Bencimidazoles/administración & dosificación , Bencimidazoles/efectos adversos , Bloqueadores de los Canales de Calcio/administración & dosificación , Bloqueadores de los Canales de Calcio/efectos adversos , Método Doble Ciego , Quimioterapia Combinada , Prueba de Esfuerzo , Femenino , Humanos , Masculino , Mibefradil , Persona de Mediana Edad , Tetrahidronaftalenos/administración & dosificación , Tetrahidronaftalenos/efectos adversos , Factores de TiempoRESUMEN
The value of transtelephonic transmission of ECG information is well established, and technological advances have continuously provided improved state-of-the-art equipment. Shahal Medical Services provides professional care to subscribers who call the medical center and describe their symptoms, whereupon therapeutic measures are decided upon. A new 12-lead patient controlled device for telephonically transmitting an ECG (GB-12L) has become available; the aim of this study was to evaluate its accuracy and practicability. Forty tracings (20 standard ECG tracings obtained under medical supervision in the physician's office and 20 by the patient in his home using the new CB-12L ECG device and transmitted by telephone to the center) from 20 subjects with various electrocardiographic pathologies were reviewed by 19 experienced physicians who were asked to interpret the results and identify the recording device. In 82% of the possibilities, the interpretation of the tracings was identical for both those recorded by the standard ECG recorder and the CB-12L ECG. An equal number of physicians could not identify the means by which device the tracings were taken. Proper placement of the electrodes did not prove to be a problem for the patient. Thus, the CB-12L ECG was found to be an easily operable and reliable tool which may be of value for early and prompt diagnosis of threatening cardiac situations in the prehospital setting.
Asunto(s)
Electrocardiografía , Telemetría/instrumentación , Teléfono , Electrocardiografía/instrumentación , Diseño de Equipo , Estudios de Evaluación como Asunto , Femenino , Humanos , MasculinoRESUMEN
We report on the experience accumulated by the subscribers of SHAHAL cardiac services who self-injected intramuscular lidocaine (using an automatic injector "LidoPen") for documented ventricular tachyarrhythmias which were not associated with an acute myocardial infarction. SHAHAL provides professional care to its subscribers who telephone a monitor center and describe their symptoms, whereupon therapeutic measures are decided upon. Patient data are stored in a central computer, and the center can dispatch mobile intensive care units. All subscribers carry a portable transtelephonic electrocardiographic transmitter and are provided with the LidoPen. Indications for self-injection were: transmission of a wide-QRS tachycardia (rate > 100 beats/min), symptomatic multiple or complex ventricular premature complexes in association with chest discomfort, and when the time of arrival of a medical team to the patient was estimated to be at least 8 to 10 minutes. Successful usage of the LidoPen was reported in 137 cases (123 patients). An additional 11 patients failed to use the injector properly. There was a success rate in abolishing rapid sustained ventricular tachycardia (27 of 76 patients) and nonsustained ventricular tachycardia and/or multiple and complex ventricular ectopic activity (8 of 30 patients) of 33% (total 35 of 106 patients). In another 9%, those arrhythmias were slowed markedly. The remaining 31 cases were eventually interpreted as being of supraventricular origin. No complications attributed to the use of the injector were reported and its use was found to be both feasible and effective in the prehospital setting.
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Antiarrítmicos/administración & dosificación , Primeros Auxilios , Lidocaína/administración & dosificación , Taquicardia Ventricular/tratamiento farmacológico , Adulto , Anciano , Anciano de 80 o más Años , Ambulancias , Angina de Pecho/tratamiento farmacológico , Cuidados Críticos , Electrocardiografía Ambulatoria , Servicio de Urgencia en Hospital , Estudios de Factibilidad , Femenino , Humanos , Inyecciones Intramusculares , Israel , Masculino , Persona de Mediana Edad , Infarto del Miocardio , Seguridad , Autoadministración , Taquicardia Supraventricular/tratamiento farmacológico , Resultado del Tratamiento , Complejos Prematuros Ventriculares/tratamiento farmacológicoRESUMEN
OBJECTIVES: This study sought to establish the risk ratio for mortality associated with calcium antagonists in a large population of patients with chronic coronary artery disease. BACKGROUND: Recent reports have suggested that the use of short-acting nifedipine may cause an increase in overall mortality in patients with coronary artery disease and that a similar effect may be produced by other calcium antagonists, in particular those of the dihydropyridine type. METHODS: Mortality data were obtained for 11,575 patients screened for the Bezafibrate Infarction Prevention study (5,843 with and 5,732 without calcium antagonists) after a mean follow-up period of 3.2 years. RESULTS: There were 495 deaths (8.5%) in the calcium antagonist group compared with 410 in the control group (7.2%). The age-adjusted risk ratio for mortality was 1.08 (95% confidence interval [CI] 0.95 to 1.24). After adjustment for the differences between the groups in age and gender and the prevalence of previous myocardial infarction, angina pectoris, hypertension, New York Heart Association functional class, peripheral vascular disease, chronic obstructive pulmonary disease, diabetes and current smoking, the adjusted risk ratio declined to 0.97 (95% CI 0.84 to 1.11). After further adjustment for concomitant medication, the risk ratio was estimated at 0.94 (95% CI 0.82 to 1.08). CONCLUSIONS: The current analysis does not support the claim that calcium antagonist therapy in patients with chronic coronary artery disease, whether myocardial infarction survivors or others harbors an increased risk of mortality.
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Bloqueadores de los Canales de Calcio/efectos adversos , Enfermedad Coronaria/mortalidad , Bloqueadores de los Canales de Calcio/farmacología , Bloqueadores de los Canales de Calcio/uso terapéutico , Estudios de Casos y Controles , Estudios de Cohortes , Enfermedad Coronaria/tratamiento farmacológico , Femenino , Estudios de Seguimiento , Humanos , Hipertensión/tratamiento farmacológico , Israel/epidemiología , Masculino , Persona de Mediana Edad , Oportunidad Relativa , Modelos de Riesgos Proporcionales , Factores de Riesgo , Factores de TiempoRESUMEN
Serum lipids were measured in children and their parents from 40 families in which the father had a myocardial infarction or coronary heart disease (CHD) before age 40 years. The relationship between physical activity and serum lipid concentrations in the children was also evaluated. Twenty six men had one or more abnormal lipid value (in mmol/l): total venous cholesterol (TVC) > 6.24, triglycerides < 2.55, low density lipoprotein cholesterol (LDL-C) > 4.42, or high density lipoprotein cholesterol (HDL-C) < 0.91. There were 15 spouses with significant hyperlipidaemia (values above). In the 107 children examined, TVC mean (SD) was 4.68 (1.17), triglycerides 1.4 (0.8), LDL-C 3.0 (1.0), and HDL-C 1.18 (0.28). Altogether 42% of the children had significant hyperlipidaemia. No significant correlation was found between the degree of physical activity of the children and their LDL-C and TVC concentrations. However, a significant positive correlation was found between the degree of physical activity and HDL-C and a significant negative one with triglyceride concentrations. It is concluded that screening the progeny of young CHD patients is highly productive in identifying young people at excessive risk for future CHD. The data also suggest that promoting high degrees of activity among these children may have a positive influence on risk factors for adult onset CHD.
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Enfermedad Coronaria/sangre , Padre , Lípidos/sangre , Adolescente , Adulto , Factores de Edad , Niño , Preescolar , Colesterol/sangre , HDL-Colesterol/sangre , LDL-Colesterol/sangre , Enfermedad Coronaria/diagnóstico , Ejercicio Físico/fisiología , Femenino , Humanos , Masculino , Factores de Riesgo , Triglicéridos/sangreRESUMEN
Restrictive ventricular filling pattern derived from Doppler echocardiography after anterior wall AMI may serve as an indicator of diastolic dysfunction due to initial myocardial stiffness and complications such as extension of the infarction, Dressler syndrome, septal rupture, or myocardial failure. Later changes, such as prolongation of deceleration time, may indicate remodeling process, healing of the complications of AMI, or improved revascularization.
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Ecocardiografía Doppler , Infarto del Miocardio/diagnóstico por imagen , Función Ventricular Izquierda , Anciano , Velocidad del Flujo Sanguíneo , Diástole , Femenino , Humanos , Masculino , Persona de Mediana Edad , Infarto del Miocardio/fisiopatologíaRESUMEN
PURPOSE: The purpose of this study was to report the prevalence and the clinical significance of clinically recognized chronic obstructive pulmonary disease (COPD) during acute myocardial infarction. PATIENTS AND METHODS: During 1981 to 1983, a secondary prevention study with nifedipine (SPRINT) was conducted in Israel among 2,276 survivors of acute myocardial infarction. During the study, demographic, historical, and medical data were collected on special forms for all patients with diagnosed acute myocardial infarction in 13 hospitals (the SPRINT Registry, n = 5,839). Mortality follow-up was completed for 99% of hospital survivors for a mean follow-up of 5.5 years (range: 4.5 to 7 years). RESULTS: The prevalence of COPD was 7% (406 of 5,839). The latter rate increased significantly in men (7.6%), smokers (9.7%), and older patients (70 years or older, 10.0%). Patients with COPD exhibited a complicated hospital course with an in-hospital mortality rate of 23.9%. Subsequent mortality rates in survivors at 1 and 5 years were 12.3% and 35.9%, respectively. Rates at the same time periods in patients without COPD were 17.2%, 9.2%, and 26.9% (p < 0.005 for in-hospital and 5 years). In a multivariate analysis that included age, gender, and history of myocardial infarction and congestive heart failure, COPD was not independently associated with either in-hospital or postdischarge excess fatality rates. CONCLUSION: In this large cohort of consecutive patients with myocardial infarction, the prevalence of COPD was 7% and higher among smokers, men, and elderly patients. Although in-hospital and postdischarge mortality rates were higher among patients with COPD, this condition did not independently increase either the risk of early death or the risk of long-term mortality among survivors of acute myocardial infarction.
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Enfermedades Pulmonares Obstructivas/epidemiología , Infarto del Miocardio/complicaciones , Análisis Actuarial , Factores de Edad , Anciano , Causas de Muerte , Comorbilidad , Unidades de Cuidados Coronarios , Femenino , Estudios de Seguimiento , Insuficiencia Cardíaca/complicaciones , Insuficiencia Cardíaca/epidemiología , Mortalidad Hospitalaria , Humanos , Israel/epidemiología , Enfermedades Pulmonares Obstructivas/complicaciones , Masculino , Tamizaje Masivo , Persona de Mediana Edad , Infarto del Miocardio/tratamiento farmacológico , Infarto del Miocardio/mortalidad , Prevalencia , Pronóstico , Sistema de Registros , Factores Sexuales , Fumar/efectos adversos , Fumar/epidemiología , Análisis de Supervivencia , Tasa de SupervivenciaRESUMEN
A 70-year-old man was treated with oral mexiletene because of ventricular premature beats due to ischemic heart disease. He developed a severe maculopapular rash which did not respond to antiallergic treatment, but disappeared after discontinuation of the drug. Adverse effects on the central nervous, cardiovascular and gastrointestinal systems have been described. A rash is rare, and in our case was of unusual severity.
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Erupciones por Medicamentos/etiología , Mexiletine/efectos adversos , Anciano , Complejos Cardíacos Prematuros/tratamiento farmacológico , Erupciones por Medicamentos/tratamiento farmacológico , Humanos , MasculinoAsunto(s)
Calcinosis/complicaciones , Cardiomiopatías/complicaciones , Cardiomiopatías/epidemiología , Enfermedades de las Válvulas Cardíacas/epidemiología , Anciano , Calcinosis/patología , Cardiomiopatías/diagnóstico por imagen , Cardiomiopatías/patología , Ecocardiografía Doppler , Femenino , Enfermedades de las Válvulas Cardíacas/diagnóstico por imagen , Humanos , MasculinoRESUMEN
Recent studies have demonstrated a trend toward improved survival in coronary artery disease. Contributing to this trend are advances in medical therapy. In order to evaluate the preventive effect of drugs in secondary prevention of coronary heart disease, many multi-centered trials were conducted. There is evidence that beta-adrenergic blocking agents may decrease mortality following myocardial infarction. Platelet-active drugs reduce the rate of reinfarctions and may have a beneficial effect on survival. In contrast lipid lowering agents, anticoagulants, antiarrhythmic drugs and calcium channel blockers have not shown convincing beneficial effect on the survival of patients following myocardial infarction, and further studies are required to determine the effect of the various modalities in different clinical settings.
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Enfermedad Coronaria/tratamiento farmacológico , Antiarrítmicos/uso terapéutico , Anticoagulantes/uso terapéutico , Bloqueadores de los Canales de Calcio/uso terapéutico , Humanos , Hipolipemiantes/uso terapéutico , Inhibidores de Agregación Plaquetaria/uso terapéuticoRESUMEN
Since the pacing threshold of artificial pacemakers sometimes increases and causes ineffective pacing, emergency restoration of cardiac pacing may occasionally be required. In such situations sympathomimetic agents, such as isoproterenol, increase excitability and lower threshold. A 83-year-old man with acute ineffective pacing and hemodynamic instability is reported. Intravenous administration of isoproterenol restored effective, artificial cardiac pacing.
Asunto(s)
Estimulación Cardíaca Artificial , Isoproterenol/administración & dosificación , Anciano , Humanos , Inyecciones Intravenosas , MasculinoRESUMEN
A case of a huge right atrial mass that developed 2 years after a permanent pacemaker implantation is described. The patient had a history of polycythemia vera, which is known to present a high tendency towards the development of thrombosis. In light of this fact, we suggest that in similar cases a full echocardiography follow-up should be performed, and long-term anticoagulant therapy should be considered in selected cases.