RESUMEN
The aim of this intravascular ultrasound study was to compare the type and the degree of vessel remodeling in proximal and distal de novo lesions within the same coronary artery in patients with stable angina pectoris. Seventy-six de novo coronary artery lesions in 38 coronary arteries of 38 patients were imaged by intravascular ultrasound. The vessel area (VA) within the external elastic lamina and the lumen area (LA) were measured, and the wall area (VA-LA) was calculated at the lesion site, and the proximal and distal reference sites. The VA ratio was defined as (lesion VA/average of the proximal and distal reference VAs) to represent the degree of vessel remodeling. The proximal coronary segments showed compensatory enlargement more often (68% vs 29%, p < 0.01) than the distal segments, and the VA ratio at the lesion site was significantly larger (1.1 +/- 0.3 vs 1.0 +/- 0.2, p <0 .01) in proximal segments than in distal segments. The type of coronary remodeling was discordant in 61% and concordant in only 39% of coronary arteries between the proximal and distal segments. The type of coronary remodeling of proximal and distal coronary lesions was inhomogeneous, even within the same vessel. Proximal coronary segments showed more prominent compensatory enlargement than distal segments, which have a similar degree of luminal narrowings.
Asunto(s)
Angina de Pecho/diagnóstico por imagen , Enfermedad de la Arteria Coronaria/diagnóstico por imagen , Ultrasonografía Intervencional , Adulto , Anciano , Anciano de 80 o más Años , Análisis de Varianza , Angina de Pecho/patología , Enfermedad de la Arteria Coronaria/patología , Vasos Coronarios/diagnóstico por imagen , Vasos Coronarios/patología , Humanos , Procesamiento de Imagen Asistido por Computador , Masculino , Persona de Mediana Edad , Análisis de RegresiónRESUMEN
OBJECTIVES: To validate intravascular ultrasound (IVUS) measurements for differentiating functionally significant from nonsignificant coronary stenosis. BACKGROUND: To date, there are no validated criteria for the definition of a flow-limiting coronary artery stenosis by IVUS. METHODS: Preinterventional IVUS imaging (30-MHz imaging catheter) of 70 de novo coronary lesions was performed. The lesion lumen area and three IVUS-derived stenosis indixes comparing lesion lumen area with the lesion external elastic lamina (EEL) area, the mean reference lumen area and the mean reference EEL area were compared with the results of stress myocardial perfusion imaging. RESULTS: The lesion lumen area and three IVUS-derived stenosis indexes showed sensitivities and specificities ranging between 80% and 90% using stress myocardial perfusion imaging as the gold standard. The lesion lumen area < or =4 mm2 is a simple and highly accurate criterion for significant coronary narrowing. CONCLUSIONS: Quantitative IVUS indices can be reliably used for identifying significant epicardial coronary artery stenoses.
Asunto(s)
Enfermedad Coronaria/diagnóstico por imagen , Tomografía Computarizada de Emisión de Fotón Único/métodos , Ultrasonografía Intervencional , Anciano , Angiografía Coronaria , Prueba de Esfuerzo , Femenino , Humanos , Masculino , Perfusión , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , Índice de Severidad de la EnfermedadRESUMEN
Norepinephrine (NE) (2.5 micrograms/kg/min) was administered to 5-week-old male Sprague Dawley rats by subcutaneous osmotic mini pumps for 14 days to generate an in vivo cardiac hypertrophy model and the responses with respect to aging examined. In the model, ventricles were significantly hypertrophied without myocardial necrosis and without significant increases in heart rate or blood pressure; the beta adrenergic system was down-regulated. In 37-week-old rats receiving 1.0 microgram/kg/min NE, there was a tendency towards heart failure, and myocardial necrosis and interstitial fibrosis were revealed by histological examinations. The density of beta adrenergic receptors and adenylyl cyclase activity was lower in the older rats. The excess stimulation of adrenergic receptors caused severe cardiac injury in old rats regardless of down regulation of beta adrenergic receptors.
Asunto(s)
Envejecimiento/fisiología , Cardiomegalia/fisiopatología , Norepinefrina/farmacología , Animales , Presión Sanguínea , Frecuencia Cardíaca , Masculino , Ratas , Ratas Sprague-Dawley , Sistema Nervioso Simpático/fisiopatologíaRESUMEN
BACKGROUND: Prolonged asystole is sometimes an extreme manifestation of neurally mediated syncope. HYPOTHESIS: To investigate the mechanism of head-up tilt testing-induced prolonged (life-threatening) cardiac asystole, we measured temporal changes in frequency domain heart rate variability indices in 25 patients with syncope of undetermined etiology. METHODS: Head-up tilt testing (80 degrees) was performed in 25 patients for up to 40 min or until asystole or syncope occurred. Three patients (Group 1; 37 +/- 13 years, 1 man 2 women) had an episode of prolonged cardiac asystole (> or = 10 s) during testing, necessitating cardiopulmonary resuscitation. Syncope, but no asystole, was induced in 10 patients (Group 2; 48 +/- 31 years, 6 men, 4 women), and 12 patients (Group 3; 55 +/- 20 years, 5 men, 7 women) failed to show asystole or syncope during testing. Power spectra of low (0.04-0.15 Hz) and high (0.15-0.40 Hz) frequency, and total (0.01-1.00 Hz) frequency spectra were measured in consecutive 2 min segments throughout the test. RESULTS: Maximally changed values in heart rate, systolic blood pressure, and heart rate variability indices during testing were compared among the three groups (maximally changed values did not include the values during tilt-induced symptoms). High frequency spectra in Groups 2 and 3, but not in Group 1, decreased during the test. High frequency spectra, low frequency spectra, and total spectra in Group 1 were significantly higher than those in Groups 2 and 3 during testing. In Group 1 patients, findings at test-induced asystole were consistent with exaggerated sympathetic and concurrent persistent parasympathetic activity. CONCLUSION: Unusual autonomic responses to orthostatic stress can cause prolonged asystole, and this autonomic nerve dysregulation may relate to asystolic episodes associated with cardiovascular collapse.
Asunto(s)
Sistema Nervioso Autónomo/fisiopatología , Paro Cardíaco/fisiopatología , Pruebas de Mesa Inclinada , Adulto , Presión Sanguínea , Reanimación Cardiopulmonar , Femenino , Paro Cardíaco/etiología , Frecuencia Cardíaca , Humanos , Masculino , Persona de Mediana Edad , Síncope/etiología , Síncope/fisiopatología , Nervio Vago/fisiopatologíaRESUMEN
Isoproterenol was continuously administered to rats at a rate of 2.5 microg/kg/min for 7 days via subcutaneously implanted osmotic minipumps. This treatment induced cardiac hypertrophy with increases in heart rate and systolic blood pressure. Beta-adrenoceptor (beta-AR) density decreased in hypertrophied hearts, but the affinity for 125I-cyanopindolol did not change. The beta-AR density decrease did not accompany the change in expression of beta1-AR mRNA. In hypertrophied hearts, adenylyl cyclase activities in the steady state, and stimulated with isoproterenol, forskolin, and manganese, decreased but there was no change in the expression of adenylyl cyclase type V mRNA. The results suggest that beta-AR downregulation and adenylyl cyclase desensitization in isoproterenol-induced cardiac hypertrophy are caused by post-transcriptional changes.