RESUMEN
In the present work, PANI (polyaniline) emeraldine salt (doped) and base (dedoped) were used as the sensitive layer of a silicon microcantilever, and the mechanical response (deflection) of the bimaterial (coated microcantilever) was investigated under the influence of humidity. PANI in the emeraldine base oxidation state was obtained by interfacial synthesis and was deposited on the microcantilever surface by spin-coating (dedoped). Next, the conducting polymer was doped with 1 M HCl (hydrochloric acid). A four-quadrant AFM head with an integrated laser and a position-sensitive detector (AFM Veeco Dimension V) was used to measure the optical deflection of the coated microcantilever. The deflection of the coated (doped and undoped PANI) and uncoated microcantilever was measured under different humidities (in triplicate) at room pressure and temperature in a closed chamber to evaluate the sensor's sensitivity. The relative humidity (RH) in the chamber was varied from 20% to 70% using dry nitrogen as a carrier gas, which was passed through a bubbler containing water to generate humidity. The results showed that microcantilevers coated with sensitive layers of doped and undoped PANI films were sensitive (12,717 ± 6% and 6,939 ± 8%, respectively) and provided good repeatability (98.6 ± 0.015% and 99 ± 0.01%, respectively) after several cycles of exposure to RH. The microcantilever sensor without a PANI coating (uncoated) was not sensitive to humidity. The strong effect of doping on the sensitivity of the sensor was attributed to an increased adsorption of water molecules dissociated at imine nitrogen centers, which improves the performance of the coated microcantilever sensor. Moreover, microcantilever sensors coated with a sensitive layer provided good results in several cycles of exposure to RH (%).
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Compuestos de Anilina/química , Materiales Biocompatibles Revestidos , Humedad , Vapor/análisis , Fenómenos Mecánicos , Sensibilidad y EspecificidadRESUMEN
This paper describes a silicon cantilever sensor coated with a conducting polymer layer. The mechanical response (deflection) of the bimaterial (the coated microcantilever) was investigated under the influence of several volatile compounds-methanol, ethanol, acetone, propanol, dichloroethane, toluene and benzene. The variations in the deflection of the coated and uncoated microcantilevers when exposed to volatile organic compounds were evaluated, and the results indicated that the highest sensitivity was obtained with the coated microcantilever and methanol. The uncoated microcantilever was not sensitive to the volatile organic compounds. An increase in the concentration of the volatile organic compound resulted in higher deflections of the microcantilever sensor. The sensor responses were reversible, sensible, rapid and proportional to the volatile concentration.
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Compuestos de Anilina/química , Técnicas Biosensibles/instrumentación , Compuestos Orgánicos Volátiles/análisis , Técnicas Biosensibles/métodos , Sensibilidad y Especificidad , Compuestos Orgánicos Volátiles/químicaRESUMEN
AIMS: The transversal distribution of coronary atherosclerotic plaques (AP) (myocardial vs pericardial) affects vessel remodelling. The aim of this study was to define the impact of transversal lesion distribution on vessel remodelling in proximal and distal coronary segments using a 3D intravascular ultrasound (IVUS) reconstruction. METHODS: The study group included 70 lesions located in the left anterior descending artery within 5mm of the septal take-off, and imaged using 3D-IVUS. The take-off of the septal branch was used to divide the plaque into a myocardial and pericardial surface. The IVUS index of vessel remodelling was calculated as: [narrowest external elastic membrane (EEM) site cross-sectional area (CSA)-reference EEM CSA)/reference EEM CSAx100]. The lesions with an intermediate vessel remodelling index (between -25% and +15%) were excluded from analysis. RESULTS: Of the 38 APs with a pericardial distribution, 34 (89%) showed positive remodelling (P<0.001). The distal lesions had a positive vessel remodelling index regardless of transversal plaque distribution. At multivariate analysis, pericardial distribution and the distal location of AP were the only independent variables predictive of positive remodelling. CONCLUSIONS: The transversal distribution of atherosclerotic plaque affects vessel remodelling in left anterior descending coronary lesions, probably because of an extravascular splinting effect. Distal lesions usually show positive remodelling regardless of transversal plaque distribution.
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Tejido Adiposo/fisiología , Enfermedad de la Arteria Coronaria/patología , Vasos Coronarios/patología , Anciano , Arterias , Enfermedad de la Arteria Coronaria/diagnóstico por imagen , Vasos Coronarios/diagnóstico por imagen , Ecocardiografía Tridimensional/métodos , Endosonografía , Femenino , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Persona de Mediana Edad , PericardioRESUMEN
AIMS: To investigate the prevalence of the G20210A prothrombin and G1691A factor V gene variants in patients with acute coronary syndrome stratified according to risk factor profile and to extent of coronary disease, in comparison with matched healthy controls. METHODS AND RESULTS: The 20210 prothrombin and the 1691 factor V loci were genotyped in 247 patients < or =65 years of age (190 myocardial infarction and 57 unstable angina as first presentation of disease) and in 247 healthy age- and sex-matched controls. The prevalence of the 1691A factor V allele was similar in cases and controls. The frequency of heterozygotes for the 20210A prothrombin allele was 6.5% among patients and 2.8% among controls (OR 2.4, 95% CI 1.0-5.9), increasing to 8.7% in patients with a family history of myocardial infarction (OR 3.3, 95% CI 1.2-9.1), to 9.9% in patients (n=81) with < or =1 vessel disease (OR 3.8, 95% CI 1.3-10.8), and to 13.0% in patients who were normocholesterolaemic, non-diabetic, normotensive and non-smokers (OR 5.1, 95% CI 1.2-21.4). CONCLUSIONS: These findings suggest that the 20210A prothrombin allele represents an inherited risk factor for acute coronary syndrome among patients who have limited extent of coronary disease at angiography or who lack major metabolic and acquired risk factors.
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Enfermedad Coronaria/genética , Protrombina/genética , Enfermedad Aguda , Anciano , Alelos , Angiografía Coronaria , Enfermedad Coronaria/diagnóstico por imagen , Factor V/análisis , Femenino , Variación Genética , Humanos , Italia/epidemiología , Masculino , Persona de Mediana Edad , Infarto del Miocardio/diagnóstico por imagen , Infarto del Miocardio/genética , Prevalencia , Factores de Riesgo , SíndromeRESUMEN
Statins (3-hydroxy-3-methylglutaryl-coenzyme A reductase inhibitors) are widely used for the treatment of hypercholesterolemia. They reduce LDL levels more than other lipid-lowering drugs. Moreover, they are effective in raising HDL and even in reducing triglyceride levels. Statins have an excellent tolerability and safety. Clinical trials in patients with and without ischemic heart disease and with and without high cholesterol levels have demonstrated that statins significantly reduce the relative risk of major coronary events and of total mortality. Other mechanisms independent of LDL lowering may play an important role in the clinical benefits conferred by these drugs and may broaden their therapeutic indications from lipid-lowering to antiatherogenic agents.
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Anticolesterolemiantes/uso terapéutico , Arteriosclerosis/tratamiento farmacológico , Arteriosclerosis/prevención & control , Hipolipemiantes/uso terapéutico , Ensayos Clínicos como Asunto , Predicción , HumanosRESUMEN
PURPOSE: Apoptosis is considered a common pathological feature in acute myocardial infarction (MI) and heart failure; however its role in the later phases post MI has not been characterized. The goal of our study was to investigate by pathological examination human hearts at 20 to 30 days post MI and identify signs of ongoing cell apoptosis. MATERIALS AND METHODS: Two hearts were collected at autopsy from patients who died 20 to 30 days from the onset of MI (Cases 1 and 2). Gross anatomy and light microscopy examination of the hearts was performed to define the infarcted area and the infarct-related artery. The in situ end-labeling of DNA fragmentation (TUNEL) was performed to identify apoptotic cells and the apoptotic rate (AR) was calculated. RESULTS: There were no signs of acute necrosis in any of the specimens examined. A high number of myocardiocyte were positive at TUNEL examination in specimens obtained at sites of infarction, mean AR = 44%, but not in specimens derived from the same patients at regions remote from the MI, AR = 0. CONCLUSIONS: High grade apoptosis is present at sites of infarction and not in regions remote from the infarcted area in the later phases post MI. These data support persistent myocardiocyte loss and identify a possible explanation of progressive left ventricular dysfunction in the subacute phases of MI.
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Apoptosis , Infarto del Miocardio/patología , Anciano , Autopsia , Humanos , Etiquetado Corte-Fin in Situ , Persona de Mediana Edad , Infarto del Miocardio/complicaciones , Infarto del Miocardio/fisiopatología , Disfunción Ventricular Izquierda/etiología , Disfunción Ventricular Izquierda/patología , Disfunción Ventricular Izquierda/fisiopatologíaRESUMEN
Glycoprotein IIb-IIIa receptor inhibitors are the newest anti-platelets drugs currently used in patients with coronary artery disease. We examined mechanisms of their action and different pharmacokinetic and pharmacodynamic characteristics of the four glycoprotein IIb-IIIa antagonists evaluated in randomized, controlled and multicenter trials. We reviewed results of these trials in the settings of percutaneous revascularizations procedures or unstable coronary syndromes. Platelet glycoprotein IIb-IIIa receptor inhibitors reduced incidence of cardiac death and myocardial infarction during the short- and midterm, and benefit was greater in: a) patients undergoing coronary angioplasty with or without stent implantation, particularly in the presence of unstable angina, diabetes or complex and diffuse coronary artery disease; b) as a direct therapy of unstable coronary syndromes, particularly in patients with refractory angina, diabetes and elevated Troponin; more recently they have been used as adjuvant therapy in acute myocardial infarction. Infusion of these drugs was not associated with higher rates of major bleedings.
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Fibrinolíticos/uso terapéutico , Isquemia Miocárdica/tratamiento farmacológico , Inhibidores de Agregación Plaquetaria/uso terapéutico , Complejo GPIIb-IIIa de Glicoproteína Plaquetaria/antagonistas & inhibidores , Complejo GPIIb-IIIa de Glicoproteína Plaquetaria/metabolismo , Tirosina/análogos & derivados , Abciximab , Acetatos/uso terapéutico , Angioplastia Coronaria con Balón , Anticuerpos Monoclonales/uso terapéutico , Complicaciones de la Diabetes , Eptifibatida , Fibrinolíticos/efectos adversos , Humanos , Fragmentos Fab de Inmunoglobulinas/uso terapéutico , Estudios Multicéntricos como Asunto , Isquemia Miocárdica/sangre , Isquemia Miocárdica/complicaciones , Isquemia Miocárdica/mortalidad , Péptidos/uso terapéutico , Inhibidores de Agregación Plaquetaria/efectos adversos , Ensayos Clínicos Controlados Aleatorios como Asunto , Stents , Análisis de Supervivencia , Síndrome , Tirofibán , Resultado del Tratamiento , Troponina/sangre , Tirosina/uso terapéuticoRESUMEN
Diffuse coronary artery disease (CAD) is considered unfavorable for interventional procedures; however, the results of stenting of diffuse CAD have not been completely characterized. We performed stenting in 100 consecutive patients with diffuse CAD, defined as significant stenosis >20 mm (n = 59 patients), multiple significant stenoses in the same artery (n = 23 patients), or significant narrowing involving the whole length of the coronary artery (n = 18 patients). Angiographic success was achieved in 103 arteries (100%) and clinical success was obtained in all 100 patients. There were no deaths; no patient had stent closure, acute myocardial infarction, or required emergency coronary artery bypass surgery. All 100 patients had >6 months follow-up (mean 18 +/- 7 months, range 7 to 31); 77 (77%) remained asymptomatic, and 5 (5%) had acute myocardial infarction, of whom 2 died (2%). In-stent restenosis was observed in 12 patients (12%) and repeat angioplasty was performed in 10. Including those patients who underwent repeat angioplasty, 89 (89%) maintained clinical improvement and 95 (95%) were alive and free of bypass surgery during follow-up. Life-table analysis showed 86% freedom from death, myocardial infarction, and target lesion revascularization at 28 months. Thus, selected patients with diffuse CAD may be treated with satisfactory acute and long-term results by stent implantation.
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Angioplastia Coronaria con Balón/métodos , Enfermedad Coronaria/terapia , Stents , Angiografía Coronaria , Enfermedad Coronaria/diagnóstico por imagen , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , Estudios Prospectivos , Recurrencia , Índice de Severidad de la EnfermedadRESUMEN
The importance of genetics to the pathogenesis of myocardial infarction is suggested by the frequent familial clustering of premature disease. Yet, studies associating myocardial infarction with gene polymorphisms of vascular proteins (angiotensinogen, angiotensin converting enzyme, angiotensin II type 1 receptor, endothelial nitric oxide synthase) and haemostatic factors (fibrinogen, coagulation factors II, V, VII and XIII, plasminogen activator inhibitor-1, tissue-type plasminogen activator, platelet glycoproteins IIb/IIIa, Ia/IIa and Ib-IX-V, or methylenetetrahydrofolate reductase) have revealed conflicting results. This is hardly surprising, given: 1) the multigenic nature of myocardial infarction, whereby single polymorphisms are bound to play at best only a limited role in the global risk of disease; 2) the multiple pathogenetic mechanisms of infarction (e.g., atheromatous obstruction, plaque rupture, thrombosis, vasospasm), each of which is likely influenced by a number of genes and by several environmental factors. The simultaneous investigation of a set of polymorphisms--and of their interactions with environmental factors--in extremely homogeneous sets of patients should offer a better understanding of the contribution of specific genes to the risk of myocardial infarction.
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Factores de Coagulación Sanguínea/genética , Infarto del Miocardio/genética , Polimorfismo Genético , Angiotensinógeno/genética , Plaquetas/fisiología , Factor VII/genética , Fibrinógeno/genética , Fibrinólisis/fisiología , Humanos , Óxido Nítrico Sintasa/genética , Óxido Nítrico Sintasa de Tipo III , Peptidil-Dipeptidasa A/genética , Glicoproteínas de Membrana Plaquetaria/genética , Receptores de Angiotensina/genéticaRESUMEN
This pictorial introduction to homocysteine illustrates at a glance the nature of homocysteine and its role in cardiovascular disease by means of eight simple figures and an essential bibliography. Homocysteine is a sulfur-containing metabolite of methionine. Conversion back to methionine or transsulfuration to cysteine are the two major metabolic pathways that reduce total homocysteine (tHcy) concentrations in cells and blood. B vitamins are essential cofactors in homocysteine metabolism. Median fasting total homocysteine levels in adult males are approximately 10 micromol/L. Increased plasma tHcy concentrations are found with methionine-rich diets, low vitamin B intake, male gender, age, impaired renal function, and genetically determined defects of the enzymes involved in homocysteine metabolism. An inverse relation exists between plasma tHcy and circulating folate or vitamin B(6) concentrations, and folic acid supplements of 0.5 mg/d can reduce tHcy levels by approximately 25%. Homocystinuric patients, who have severe hyperhomocysteinemia, die prematurely of atherothrombotic disease. Many (but not all) cross-sectional and prospective studies indicate, on average, that plasma tHcy levels <.10 micromol/L are associated with, or predict the development of, coronary, cerebral, and peripheral vascular disease. The risk conferred by hyperhomocysteinemia is graded and is independent of traditional risk factors, with an estimated odds ratio for ischemic heart disease of 1.4 for every 5 micromol/L increase in plasma tHcy. In vitro and in vivo, tHcy has been found to impair endothelial function. It is now well established that tHcy represents a marker of current or subsequent ischemic vascular disease. However, irrefutable proof that hyperhomocysteinemia actually causes atherothrombosis will come only if interventions to lower plasma tHcy will produce concomitant reductions in cardiovascular events.
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Enfermedades Cardiovasculares/epidemiología , Enfermedades Cardiovasculares/etiología , Homocisteína/sangre , Homocisteína/fisiología , Arteriosclerosis/sangre , Arteriosclerosis/etiología , Biomarcadores/sangre , Enfermedades Cardiovasculares/sangre , Homocisteína/metabolismo , Humanos , Hiperhomocisteinemia/sangre , Hiperhomocisteinemia/complicaciones , Factores de Riesgo , Trombosis/sangre , Trombosis/etiologíaRESUMEN
BACKGROUND: One of the most potent pro-inflammatory mediators is the early-acting cytokine interleukin (IL)-1, whose actions are regulated by the structurally related IL-1 receptor antagonist (IL-1 Ra). IL-1 Ra is a competitive IL-1 inhibitor and a powerful anti-inflammatory agent. Several autoimmune and inflammatory diseases have been associated with an allelic polymorphism of the IL-1 Ra gene. METHODS: We investigated the frequency of allele 2 of an intron 2 polymorphism of the IL-1 Ra gene in 115 consecutive patients with ischemic heart disease -74 of which had a previous myocardial infarction (48 +/- 11 years), 21 chronic stable angina (54 +/- 10 years), and 20 unstable angina (54 +/- 9 years)--and in 80 healthy controls, matched for age and sex to patients with myocardial infarction (47 +/- 10 years). An 86 base pair variable tandem repeat in intron 2 of the IL-1 Ra gene was determined by a polymerase chain reaction-based method. RESULTS: The frequency of allele 2 was 15% in controls (carriage rate 25%) and 17% in ischemic heart disease patients (carriage rate 28%; p = 0.70). The allele 2 frequency did not differ significantly among the three patient groups. Among patients with myocardial infarction, the allele 2 frequency tended to be higher in patients with myocardial infarction < 40 years compared to those > or = 40 years (20 vs 11%, p = 0.20, OR 1.85, 95% CI 0.70-4.90), and in patients with C-reactive protein levels > or = 3 mg/l compared to those with values < 3 mg/l (31 vs 16%, p = 0.15, OR 2.38, 95% CI 0.64-9.25). CONCLUSIONS: These data do not show a clear-cut association between the allele 2 of this IL-1 Ra gene polymorphism and ischemic heart disease. Among patients with myocardial infarction, the increased allele 2 frequency in those of younger age and with higher levels of C-reactive protein merits further investigation.
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Alelos , Isquemia Miocárdica/genética , Polimorfismo Genético/genética , Receptores de Interleucina-1/antagonistas & inhibidores , Sialoglicoproteínas/genética , Adulto , Angina de Pecho/genética , Angina Inestable/genética , Enfermedad Crónica , Femenino , Frecuencia de los Genes/genética , Humanos , Proteína Antagonista del Receptor de Interleucina 1 , Masculino , Persona de Mediana Edad , Infarto del Miocardio/genética , Receptores de Interleucina-1/genética , Factores de RiesgoRESUMEN
We report one case in which chronic native competitive flow from an almost normal target coronary artery did not influence IMA graft patency. This patient underwent control postoperative angiography 11 months after surgery and the mammary artery-left anterior descending graft was found to be normofunctioning despite the fact that the coronary artery showed no residual stenosis.
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Enfermedad Coronaria/cirugía , Revascularización Miocárdica , Complicaciones Posoperatorias/diagnóstico por imagen , Grado de Desobstrucción Vascular/fisiología , Angiografía Coronaria , Circulación Coronaria/fisiología , Enfermedad Coronaria/diagnóstico por imagen , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Venas/trasplanteRESUMEN
Many cross-sectional and prospective studies have shown that raised serum/plasma levels of total homocysteine increase the risk of coronary, cerebral, and peripheral artery disease. The risk associated with hyperhomocysteinemia appears to be concentration-dependent and not attributable to traditional risk factors. The odds ratio for ischemic heart disease has been estimated to be 1.4 for every 5 mumol/l increase of total plasma homocysteine. Median fasting total plasma homocysteine in adult males is approximately 10 mumol/l. Mild hyperhomocysteinemia is estimated to occur in 5-10% of the general population. Plasma concentrations are increased as a result of age, male gender, impaired renal function, low vitamin B intake, and genetically-determined defects of the enzymes involved in homocysteine metabolism. Folate supplements can reduce total homocysteine levels by approximately 25%. Studies in vitro and in vivo indicate that homocysteine can impair endothelial function. Despite increasing recognition of hyperhomocysteinemia as a risk factor for arterial occlusive disease, irrefutable proof that mild hyperhomocysteinemia contributes directly to the pathogenesis of atherothrombosis will come if interventions to lower total homocysteine reduce cardiovascular events. Family studies may also provide evidence of causality if genetic causes of hyperhomocysteinemia are found to segregate with disease.
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Arteriopatías Oclusivas/etiología , Hiperhomocisteinemia/complicaciones , Biomarcadores/sangre , Dieta/efectos adversos , Homocisteína/metabolismo , Humanos , Hiperhomocisteinemia/etiología , Valores de Referencia , Factores de RiesgoRESUMEN
In patients with coronary bypass which utilizes left (LIMA) or right internal mammary artery (RIMA), recurrent ischemia is often due to stenosis of the distal anastomoses of the grafts. However, occasionally, ischemia may be due to extracoronary causes, such as subclavian disease proximal to the internal mammary artery origins. This case report describes such clinical situation emphasizing the need for careful patient evaluation, and discusses therapeutic interventional options, in particular, safety and effectiveness of self expanding subclavian stent implantation. A review of the literature is also presented.
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Isquemia Miocárdica/cirugía , Revascularización Miocárdica , Stents , Arteria Subclavia/cirugía , Humanos , Masculino , Persona de Mediana Edad , Isquemia Miocárdica/diagnóstico , Radiografía , Recurrencia , Arteria Subclavia/diagnóstico por imagenAsunto(s)
Infarto del Miocardio/diagnóstico , Complicaciones Cardiovasculares del Embarazo/diagnóstico , Trastornos Puerperales/diagnóstico , Cateterismo Cardíaco , Angiografía Coronaria , Ecocardiografía , Electrocardiografía , Femenino , Humanos , Edad Materna , Persona de Mediana Edad , Infarto del Miocardio/tratamiento farmacológico , Infarto del Miocardio/epidemiología , Infarto del Miocardio/etiología , Embarazo , Complicaciones Cardiovasculares del Embarazo/tratamiento farmacológico , Complicaciones Cardiovasculares del Embarazo/epidemiología , Complicaciones Cardiovasculares del Embarazo/etiología , Embarazo de Alto Riesgo , Trastornos Puerperales/tratamiento farmacológico , Trastornos Puerperales/epidemiología , Trastornos Puerperales/etiologíaRESUMEN
To evaluate whether Holter electrocardiographic monitoring may improve the detection of ST-segment depression in patients with anginal chest pain and normal coronary arteries, we performed symptom-limited exercise testing and 24-hour Holter monitoring in a group of 38 such patients (27 women, age 54 +/- 8 years). Patients were divided into 2 groups:group X1 included 28 patients with and group X2 10 patients without significant ST-segment depression during exercise testing. There were no significant differences between the 2 groups in age, gender, characteristics of chest pain, exercise duration, heart rate (HR), and blood pressure at peak exercise, but anginal pain during exercise testing was reported by 10 patients of group X1 (36%) and 9 of group X2 (90%) (p <0.01). Episodes of ST-segment depression on Holter monitoring were found in 17 patients of group X1 (61%) and in 5 patients of group X2 (50%) (p = NS). There were no differences between the 2 groups in daily number of ST episodes (3.6 +/- 4 vs 2.8 +/- 5 episodes per patient), symptomatic episodes (8% vs 18%), and duration of the episodes. On average, HR increased significantly, in a similar way, from 15 minutes before ST-segment depression to 1-mm ST in both groups, and its value at the onset of ischemia was similar in the 2 groups (102 +/- 22 vs 109 +/- 18 beats/min, p = NS). Finally, HR at 1-mm ST during Holter monitoring was significantly lower than that observed at 1-mm ST during exercise testing (127 +/- 16 beats/min, p < or = 0.01) in group X1, and it was also lower than that observed at peak exercise (136 +/- 22 beats/min, p < or = 0.01) in group X2. In conclusion, Holter monitoring can significantly increase the detection of ST-segment depression in patients with anginal pain and normal coronary arteries, indicating a cardiac, although not necessarily ischemic, origin of the pain. Indeed, 50% of our patients with negative symptom-limited exercise testing showed spontaneous ST changes, compatible with transient myocardial ischemia, during daily activities. Differences in the response of coronary microvascular tone to exercise testing and to stimuli operating during daily life are likely to play a significant role in determining these findings.
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Angina de Pecho/diagnóstico , Angina de Pecho/fisiopatología , Vasos Coronarios , Electrocardiografía Ambulatoria , Prueba de Esfuerzo , Sistema de Conducción Cardíaco/fisiopatología , Actividades Cotidianas , Adulto , Anciano , Angiografía Coronaria , Femenino , Hemodinámica , Humanos , Masculino , Persona de Mediana EdadRESUMEN
To evaluate whether the ischemic threshold has a circadian rhythm in patients with syndrome X, we analyzed 90 episodes of ST depression detected on 24-hour Holter recordings of 12 such patients. Ischemic threshold was considered as heart rate (HR) at 1 mm ST depression. To correct for differences in basal HR among patients, however, the ischemic threshold was also calculated as a normalized index of HR at 1 mm ST depression: [(HR at 1 mm ST-24-hour modal HR)/24-hour modal HR]-100. Mean hourly values of both absolute and normalized HRs at 1 mm ST depression were obtained by grouping and averaging respective values of all episodes detected in every hour of the day in all patients. Chronobiologic analysis was performed by single cosinor method. A significant circadian rhythm was found for HR (mesor 76 beats/min, amplitude 10 beats/min, acrophase at 2:16 P.M., p < 0.001), number of episodes of ST depression (mesor 3.75, amplitude 2.9, acrophase at 2:45 P.M., p < 0.001) and cumulative time of ischemia, with a high correlation of distributions. Episodes of ST depression showed a double peak initially in the morning, and again in the afternoon. Both raw and normalized values of HR at 1 mm ST depression also had a significant circadian variation in ischemic threshold, which was lower in the night and early morning hours, progressively increased until the first afternoon hours, and subsequently decreased in the evening.(ABSTRACT TRUNCATED AT 250 WORDS)
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Ritmo Circadiano , Angina Microvascular/fisiopatología , Isquemia Miocárdica/fisiopatología , Análisis de Varianza , Electrocardiografía Ambulatoria/instrumentación , Electrocardiografía Ambulatoria/métodos , Electrocardiografía Ambulatoria/estadística & datos numéricos , Femenino , Hemodinámica , Humanos , Análisis de los Mínimos Cuadrados , Masculino , Angina Microvascular/diagnóstico , Persona de Mediana Edad , Isquemia Miocárdica/diagnóstico , Estadísticas no ParamétricasRESUMEN
BACKGROUND: Sublingual nitrates are much more effective in relieving angina pectoris in patients with coronary artery disease than in patients with syndrome X, but it is not known whether their effect on exercise tolerance is also different in these two groups of patients. METHODS AND RESULTS: Treadmill exercise testing was performed before and after administration of sublingual isosorbide dinitrate (ISDN, 5 mg) in 18 patients with syndrome X (effort angina and normal coronaries, group X) and in 33 patients with documented coronary artery disease (group C). As a selection criterion, all patients had ST-segment depression > or = 1 mm on the control exercise test. Compared with the control test, the main differences in the two groups observed during the exercise test after administration of ISDN were (1) heart rate at 1-mm ST-segment depression was higher (126 +/- 25 versus 104 +/- 15 beats per minute [bpm], P < .01) in group C, whereas it was not different (125 +/- 15 versus 126 +/- 16 beats per minute) in group X; (2) the rate-pressure product at 1-mm ST-segment depression, the time to 1-mm ST-segment depression, and the exercise duration were significantly improved in group C (P < .01 for all) but were worsened in group X (18,047 +/- 4159 versus 20,535 +/- 4507 bpm . mm Hg, P = .014; 268 +/- 312 versus 429 +/- 214 seconds, P < .01; 494 +/- 279 versus 622 +/- 194 seconds, P = .013, respectively); (3) a normalization of the ECG (no ST-segment depression) was obtained in 10 patients (30%) of group C but in only 1 (5%) of group X (P < .01); (4) angina was prevented in 10 of 19 patients of group C but in no patient of group X (P < .01). CONCLUSIONS: In patients presenting with anginal chest pain, the effects of sublingual nitrates on exercise testing appear to be clinically useful to distinguish patients with coronary artery stenoses from patients with syndrome X. Indeed, worsening of exercise tolerance is highly predictive of normal coronary arteries. Furthermore, the failure of nitrates to improve exercise tolerance in patients with syndrome X suggests that a deficiency in coronary prearteriolar nitric oxide production is unlikely to play a key role in the pathophysiology of the syndrome.