RESUMEN
Recent data from our laboratory have shown that patients with the indeterminate form of Chagas' disease can have impairment of left ventricular contractility, as evaluated by the slope of the left ventricle end-systolic pressure-dimension relationship. We also showed that Chagas' disease patients with minimal baseline wall motion abnormalities detected by two-dimensional echocardiography have more intense contractility impairment when compared to patients with the indeterminate form of the disease without this abnormality. The prognostic implications of these findings have not been established. We evaluated 59 patients (37-76 years, mean = 55 years) with different clinical forms of Chagas' disease, who had normal left ventricular global systolic function at baseline (57.6 +/- 6.9%) and who had at least one additional echo during clinical follow-up (0.4-17.6; mean 4.6 years). Group 1 consisted of 14 patients with minor baseline left ventricle wall motion abnormalities and group 2 consisted of 45 patients without these abnormalities. During follow-up, global left ventricle systolic function deterioration was observed in 10 group 1 patients (71.4%) and in only 10 group 2 patients (22.2%; P < 0.005). Age and duration of follow-up were not independent determinants of left ventricular function deterioration in these patients. The present data indicate that mild segmental left ventricular wall motion abnormalities are associated with worsening of systolic function in Chagas' disease patients who have normal baseline global systolic performance.
Asunto(s)
Enfermedad de Chagas/fisiopatología , Contracción Miocárdica/fisiología , Disfunción Ventricular Izquierda/fisiopatología , Adulto , Anciano , Cardiomiopatía Chagásica/diagnóstico por imagen , Cardiomiopatía Chagásica/fisiopatología , Enfermedad Crónica , Ecocardiografía , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Pronóstico , Índice de Severidad de la Enfermedad , Disfunción Ventricular Izquierda/diagnóstico por imagenRESUMEN
The present study describes an auxiliary tool in the diagnosis of left ventricular (LV) segmental wall motion (WM) abnormalities based on color-coded echocardiographic WM images. An artificial neural network (ANN) was developed and validated for grading LV segmental WM using data from color kinesis (CK) images, a technique developed to display the timing and magnitude of global and regional WM in real time. We evaluated 21 normal subjects and 20 patients with LVWM abnormalities revealed by two-dimensional echocardiography. CK images were obtained in two sets of viewing planes. A method was developed to analyze CK images, providing quantitation of fractional area change in each of the 16 LV segments. Two experienced observers analyzed LVWM from two-dimensional images and scored them as: 1) normal, 2) mild hypokinesia, 3) moderate hypokinesia, 4) severe hypokinesia, 5) akinesia, and 6) dyskinesia. Based on expert analysis of 10 normal subjects and 10 patients, we trained a multilayer perceptron ANN using a back-propagation algorithm to provide automated grading of LVWM, and this ANN was then tested in the remaining subjects. Excellent concordance between expert and ANN analysis was shown by ROC curve analysis, with measured area under the curve of 0.975. An excellent correlation was also obtained for global LV segmental WM index by expert and ANN analysis (R2 = 0.99). In conclusion, ANN showed high accuracy for automated semi-quantitative grading of WM based on CK images. This technique can be an important aid, improving diagnostic accuracy and reducing inter-observer variability in scoring segmental LVWM.
Asunto(s)
Ecocardiografía/métodos , Hipertrofia Ventricular Izquierda/diagnóstico por imagen , Interpretación de Imagen Asistida por Computador/métodos , Redes Neurales de la Computación , Disfunción Ventricular Izquierda/diagnóstico por imagen , Adulto , Anciano , Estudios de Casos y Controles , Femenino , Humanos , Modelos Lineales , Masculino , Persona de Mediana Edad , Curva ROC , Índice de Severidad de la EnfermedadRESUMEN
PURPOSE: Weaning failure and prolonged mechanical ventilation are associated with increased morbidity, cost of care, and high mortality rates. In the last few years, cardiac performance has been recognized as a common etiology of weaning failure, and growing evidence suggests that left ventricular diastolic dysfunction is a key factor that determines weaning outcomes. Therefore, we performed a systematic review and a meta-analysis to evaluate whether diastolic dysfunction in the critically ill patient subjected to mechanical ventilation is an independent predictor of weaning failure. MATERIALS AND METHODS: We searched MEDLINE, EMBASE, Cochrane Central Register of Controlled Trials, LILACS, Google Scholar, and ClinicalTrials.gov from inception to September 2014, along with conferences proceeding from January 2005 through September 2014, and included Observational Studies and Randomized Clinical Trials evaluating predictors of weaning failure. RESULTS: Ten studies were included in the systematic review; and 7, in the meta-analysis (6 observational studies and 1 randomized controlled trial). Patients who developed weaning failure had a higher E/e' ratio when compared with those who did not (mean difference, 2.65; 95% confidence interval, 0.52-4.79; P= .01); however, there was no difference in the E/A ratio (mean difference, 0.07; 95% confidence interval, -0.04 to 0.18; P= .22). Both the E/e' and E/A ratios were associated with weaning-induced pulmonary edema at the end of a spontaneous breathing trial. CONCLUSION: A higher E/e' ratio is significantly associated with weaning failure, although a high heterogeneity of diastolic dysfunction criteria and different clinical scenarios limit additional conclusions linking diastolic dysfunction with weaning failure.
Asunto(s)
Edema Pulmonar/epidemiología , Respiración Artificial , Desconexión del Ventilador/métodos , Disfunción Ventricular Izquierda/epidemiología , Enfermedad Crítica , Diástole/fisiología , Humanos , Factores de Riesgo , Insuficiencia del Tratamiento , Disfunción Ventricular Izquierda/fisiopatologíaRESUMEN
There are limited data on the potential influence of blood viscosity on the quantification of valvular regurgitation by color Doppler in the clinical setting. This study was designed to evaluate the effects of blood viscosity on jet dimensions and the proximal flow convergence (proximal isovelocity surface area, PISA) method of estimating valvular insufficiency severity. We used an in vitro flow model filled with human blood at varying hematocrits (15%, 35%, and 55%) and blood viscosity (blood/water viscosity: 2.6, 4.8, 9.1) in which jets were driven through a known orifice (16 mm(2)) into a 110-mL compliant receiving chamber (compliance: 2.2 mL/mm Hg) by a power injection pump. Blood injections (2 and 4 mL) at flow rates of 4, 6, 8, 10, and 12 mL/s were performed. Proximal flow convergence and spatial distribution of jets were imaged by a 3.5-MHz transducer. Pressure and volume in the flow model were kept constant before each injection. Ultrasound settings were the same for all experiments. Jet area decreased significantly with increasing blood viscosity, but the difference in jet dimensions was much larger for lower than for higher flow rates and for highest blood viscosity. Estimation of flow rate by the PISA method was not significantly influenced by blood viscosity. Blood viscosity has a major influence in jet area, especially for lower flow rates, but did not change significantly the grading of regurgitation by the PISA method. Thus this factor should be considered for determining the method of choice when quantification of valvular regurgitation is performed in patients with anemia or polycythemia.
Asunto(s)
Viscosidad Sanguínea , Circulación Coronaria , Ecocardiografía Doppler en Color , Insuficiencia de la Válvula Mitral/diagnóstico por imagen , Modelos Cardiovasculares , Ecocardiografía Doppler en Color/métodos , Hematócrito , HumanosRESUMEN
Pericardial cysts are not common and rarely cause symptoms. We report a unique case of a 15-year-old male patient with cardiac tamponade clinically diagnosed who was referred for echocardiography. Transthoracic echocardiography revealed, in addition to a large pericardial effusion associated with echocardiographic signs of cardiac tamponade, an 8 x 5 cm echofree image suggesting a pericardial cyst adjacent to the right atrium. Immediately after pericardiocentesis, yielding a serosanguinous liquid, the patient showed striking clinical improvement and echocardiography demonstrated minimal pericardial effusion with persistence of the cystic image. At surgery a pericardial cyst containing a sanguinous fluid was found and the pathologic findings were consistent with hematic pericardial cyst. Thus echocardiography played a fundamental role for the diagnosis and treatment of the rare complication of a pericardial cyst documented in this patient.
Asunto(s)
Taponamiento Cardíaco/etiología , Quiste Mediastínico/complicaciones , Adolescente , Taponamiento Cardíaco/diagnóstico por imagen , Ecocardiografía , Humanos , Masculino , Quiste Mediastínico/diagnóstico por imagen , Derrame Pericárdico/diagnóstico por imagen , Derrame Pericárdico/etiología , PuncionesRESUMEN
To compare the sensitivity of dipyridamole, dobutamine and pacing stress echocardiography for the detection of myocardial ischemia we produced a physiologically significant stenosis in the left circumflex artery of 14 open-chest dogs (range: 50 to 89% reduction in luminal diameter). In each study, dobutamine (5 to 40 microg kg(-1) min(-1) in 3-min stages) and pacing (20 bpm increments, each 2 min, up to 260 bpm) were performed randomly, and then followed by dipyridamole (up to 0.84 mg/kg over 10 min). The positivity of stress echocardiography tests was quantitatively determined by a significant (P<0.05) reduction of or failure to increase absolute and percent systolic wall thickening in the stenotic artery supplied wall, as compared to the opposite wall (areas related to the left anterior descending artery). Systolic and diastolic frozen images were analyzed off-line by two blinded observers in the control and stress conditions. The results showed that 1) the sensitivity of dobutamine, dipyridamole and pacing stress tests was 57, 57 and 36%, respectively; 2) in animals with positive tests, the mean percent change of wall thickening in left ventricular ischemic segments was larger in the pacing (-19 +/- 11%) and dipyridamole (-18 +/- 16%) tests as compared to dobutamine (-9 +/- 6%) (P = 0.05), but a similar mean reduction of wall thickening was observed when this variable was normalized to a control left ventricular segment (area related to the left anterior descending artery) (pacing: -16 +/- 7%; dipyridamole: -25 +/- 16%; dobutamine: -26 +/- 10%; not significant), and 3) a significant correlation was observed between magnitude of coronary stenosis and left ventricular segmental dysfunction induced by ischemia in dogs submitted to positive stress tests. We conclude that the dobutamine and dipyridamole stress tests showed identical sensitivities for the detection of myocardial ischemia in this one-vessel disease animal model with a wide range of left circumflex artery stenosis. The pacing stress test was less sensitive, but the difference was not statistically significant. The magnitude of segmental left ventricular dysfunction induced by ischemia was similar in all stress tests evaluated.
Asunto(s)
Cardiotónicos , Dipiridamol , Dobutamina , Isquemia Miocárdica/diagnóstico por imagen , Vasodilatadores , Animales , Estimulación Cardíaca Artificial , Enfermedad Coronaria/diagnóstico por imagen , Modelos Animales de Enfermedad , Perros , Ecocardiografía/métodos , Femenino , Modelos Lineales , Masculino , Sensibilidad y Especificidad , Índice de Severidad de la EnfermedadRESUMEN
A pulsatile pressure-flow model was developed for in vitro quantitative color Doppler flow mapping studies of valvular regurgitation. The flow through the system was generated by a piston which was driven by stepper motors controlled by a computer. The piston was connected to acrylic chambers designed to simulate "ventricular" and "atrial" heart chambers. Inside the "ventricular" chamber, a prosthetic heart valve was placed at the inflow connection with the "atrial" chamber while another prosthetic valve was positioned at the outflow connection with flexible tubes, elastic balloons and a reservoir arranged to mimic the peripheral circulation. The flow model was filled with a 0.25% corn starch/water suspension to improve Doppler imaging. A continuous flow pump transferred the liquid from the peripheral reservoir to another one connected to the "atrial" chamber. The dimensions of the flow model were designed to permit adequate imaging by Doppler echocardiography. Acoustic windows allowed placement of transducers distal and perpendicular to the valves, so that the ultrasound beam could be positioned parallel to the valvular flow. Strain-gauge and electromagnetic transducers were used for measurements of pressure and flow in different segments of the system. The flow model was also designed to fit different sizes and types of prosthetic valves. This pulsatile flow model was able to generate pressure and flow in the physiological human range, with independent adjustment of pulse duration and rate as well as of stroke volume. This model mimics flow profiles observed in patients with regurgitant prosthetic valves.
Asunto(s)
Ecocardiografía Doppler en Color , Enfermedades de las Válvulas Cardíacas/diagnóstico por imagen , Prótesis Valvulares Cardíacas , Modelos Cardiovasculares , Flujo Pulsátil , Presión Sanguínea , Atrios Cardíacos , Humanos , Falla de PrótesisRESUMEN
Invasive and noninvasive methods used to evaluate ventricular function in Chagas's disease are reviewed. The traditional indices of overall ventricular performance reflect the interaction of preload, contractility, afterload and heart rate. Therefore, they are unable to distinguish changes in contractility from modifications of loading conditions. The role of ventricular function as a predictor of mortality in chronic Chagas' heart disease is discussed. Ventricular function abnormalities in patients with indeterminate and digestive forms of Chagas' disease are especially emphasized. Finally, the evidence of early impairment of diastolic performance in digestive forms of Chagas' disease are especially emphasized. Finally, the evidence of early impairment of diastolic performance in patients with Chagas' disease is presented.
Asunto(s)
Cardiomiopatía Chagásica/fisiopatología , Función Ventricular/fisiología , Cardiomiopatía Chagásica/diagnóstico , Enfermedad Crónica , Pruebas de Función Cardíaca , Humanos , Pronóstico , Análisis de Regresión , Presión VentricularRESUMEN
Woman, 42 years-old, receiving immunosuppressive therapy for a lymphoma, presented reagudization of Chagas' disease, from its indeterminate phase. Intense inflammatory visceral aggression, due to extensive intracellular proliferation of the Trypanosoma cruzi, was the likely mechanism for acute myocarditis leading to severe right ventricular failure. Antiparasite chemotherapy was effective in the control of visceral involvement and for the remission of cardiac failure. The clinical course in this case is compatible with the hypothesis of early right ventricular damage in Chagas' disease.
Asunto(s)
Cardiomiopatía Chagásica/complicaciones , Disfunción Ventricular Derecha/etiología , Adulto , Cardiomiopatía Chagásica/diagnóstico por imagen , Ecocardiografía Doppler , Femenino , Insuficiencia Cardíaca/diagnóstico por imagen , Insuficiencia Cardíaca/etiología , Humanos , Disfunción Ventricular Derecha/diagnóstico por imagenRESUMEN
The case of a neonate in heart failure with the classical signs of coarctation of the aorta is described. Two dimension and Doppler echocardiography ruled out coarctation of the aorta and an abdominal ultrasonography detected a large thrombotic formation in the abdominal aorta, confirmed at necropsy.
Asunto(s)
Aorta Abdominal , Coartación Aórtica/diagnóstico por imagen , Insuficiencia Cardíaca/complicaciones , Trombosis/diagnóstico por imagen , Coartación Aórtica/complicaciones , Diagnóstico Diferencial , Humanos , Recién Nacido , Masculino , Trombosis/complicaciones , UltrasonografíaRESUMEN
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.
Asunto(s)
Cardiomiopatía Dilatada/fisiopatología , Insuficiencia Cardíaca/fisiopatología , Hemodinámica , Complicaciones Cardiovasculares del Embarazo/fisiopatología , Adolescente , Adulto , Femenino , Ventrículos Cardíacos/fisiopatología , Humanos , Periodo Posparto/fisiología , Embarazo , Tercer Trimestre del Embarazo/fisiologíaRESUMEN
Functional pulmonary atresia is a relatively rare clinical condition usually associated with Ebstein's malformation, tricuspid valve dysplasia, Uhl's anomaly, or transient myocardial ischemia with severe tricuspid regurgitation. The occurrence of functional pulmonary atresia associated with transient tricuspid regurgitation in a newborn with an anatomically normal heart is even more uncommon. We describe a case in which color Doppler flow mapping played an essential role in diagnosis and follow-up of this clinical condition in a newborn who had normal intracardiac anatomy.
Asunto(s)
Atresia Pulmonar/diagnóstico , Diagnóstico Diferencial , Ecocardiografía Doppler en Color , Ventrículos Cardíacos/diagnóstico por imagen , Ventrículos Cardíacos/patología , Humanos , Recién Nacido , Masculino , Válvula Pulmonar/diagnóstico por imagen , Válvula Pulmonar/patología , Insuficiencia de la Válvula Pulmonar/diagnóstico , Insuficiencia de la Válvula Tricúspide/diagnósticoRESUMEN
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.
Asunto(s)
Gasto Cardíaco , Cardiomiopatías/fisiopatología , Cardiomiopatía Dilatada/fisiopatología , Complicaciones Cardiovasculares del Embarazo/fisiopatología , Trastornos Puerperales/fisiopatología , Adulto , Femenino , Humanos , Embarazo , Tercer Trimestre del Embarazo , Volumen Sistólico , Resistencia Vascular , Función Ventricular Izquierda , Función Ventricular DerechaRESUMEN
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.
Asunto(s)
Arritmia Sinusal/fisiopatología , Corazón/fisiopatología , Prolapso de la Válvula Mitral/fisiopatología , Sistema Nervioso Parasimpático/fisiopatología , Mecánica Respiratoria , Sistema Nervioso Simpático/fisiopatología , Adulto , Aerobiosis/fisiología , Umbral Anaerobio/fisiología , Ejercicio Físico/fisiología , Corazón/fisiología , Humanos , Masculino , Sistema Nervioso Parasimpático/fisiología , Descanso/fisiología , Sistema Nervioso Simpático/fisiologíaRESUMEN
The present study describes an auxiliary tool in the diagnosis of left ventricular (LV) segmental wall motion (WM) abnormalities based on color-coded echocardiographic WM images. An artificial neural network (ANN) was developed and validated for grading LV segmental WM using data from color kinesis (CK) images, a technique developed to display the timing and magnitude of global and regional WM in real time. We evaluated 21 normal subjects and 20 patients with LVWM abnormalities revealed by two-dimensional echocardiography. CK images were obtained in two sets of viewing planes. A method was developed to analyze CK images, providing quantitation of fractional area change in each of the 16 LV segments. Two experienced observers analyzed LVWM from two-dimensional images and scored them as: 1) normal, 2) mild hypokinesia, 3) moderate hypokinesia, 4) severe hypokinesia, 5) akinesia, and 6) dyskinesia. Based on expert analysis of 10 normal subjects and 10 patients, we trained a multilayer perceptron ANN using a back-propagation algorithm to provide automated grading of LVWM, and this ANN was then tested in the remaining subjects. Excellent concordance between expert and ANN analysis was shown by ROC curve analysis, with measured area under the curve of 0.975. An excellent correlation was also obtained for global LV segmental WM index by expert and ANN analysis (R² = 0.99). In conclusion, ANN showed high accuracy for automated semi-quantitative grading of WM based on CK images. This technique can be an important aid, improving diagnostic accuracy and reducing inter-observer variability in scoring segmental LVWM.
Asunto(s)
Humanos , Masculino , Femenino , Adulto , Persona de Mediana Edad , Ecocardiografía/métodos , Hipertrofia Ventricular Izquierda , Interpretación de Imagen Asistida por Computador/métodos , Redes Neurales de la Computación , Disfunción Ventricular Izquierda , Estudios de Casos y Controles , Modelos Lineales , Curva ROC , Índice de Severidad de la EnfermedadRESUMEN
Recent data from our laboratory have shown that patients with the indeterminate form of Chagas' disease can have impairment of left ventricular contractility, as evaluated by the slope of the left ventricle end-systolic pressure-dimension relationship. We also showed that Chagas' disease patients with minimal baseline wall motion abnormalities detected by two-dimensional echocardiography have more intense contractility impairment when compared to patients with the indeterminate form of the disease without this abnormality. The prognostic implications of these findings have not been established. We evaluated 59 patients (37-76 years, mean = 55 years) with different clinical forms of Chagas' disease, who had normal left ventricular global systolic function at baseline (57.6 ± 6.9 percent) and who had at least one additional echo during clinical follow-up (0.4-17.6; mean 4.6 years). Group 1 consisted of 14 patients with minor baseline left ventricle wall motion abnormalities and group 2 consisted of 45 patients without these abnormalities. During follow-up, global left ventricle systolic function deterioration was observed in 10 group 1 patients (71.4 percent) and in only 10 group 2 patients (22.2 percent; P < 0.005). Age and duration of follow-up were not independent determinants of left ventricular function deterioration in these patients. The present data indicate that mild segmental left ventricular wall motion abnormalities are associated with worsening of systolic function in Chagas' disease patients who have normal baseline global systolic performance.
Asunto(s)
Adulto , Anciano , Femenino , Humanos , Masculino , Persona de Mediana Edad , Enfermedad de Chagas/fisiopatología , Contracción Miocárdica/fisiología , Disfunción Ventricular Izquierda/fisiopatología , Enfermedad Crónica , Cardiomiopatía Chagásica/fisiopatología , Cardiomiopatía Chagásica , Ecocardiografía , Estudios de Seguimiento , Pronóstico , Índice de Severidad de la Enfermedad , Disfunción Ventricular IzquierdaRESUMEN
A pulsatile pressure-flow model was developed for in vitro quantitative color Doppler flow mapping studies of valvular regurgitation. The flow through the system was generated by a piston which was driven by stepper motors controlled by a computer. The piston was connected to acrylic chambers designed to simulate "ventricular" and "atrial" heart chambers. Inside the "ventricular" chamber, a prosthetic heart valve was placed at the inflow connection with the "atrial" chamber while another prosthetic valve was positioned at the outflow connection with flexible tubes, elastic balloons and a reservoir arranged to mimic the peripheral circulation. The flow model was filled with a 0.25 per cent corn starch/water suspension to improve Doppler imaging. A continuous flow pump transferred the liquid from the peripheral reservoir to another one connected to the "atrial" chamber. The dimensions of the flow model were designed to permit adequate imaging by Doppler echocardiography. Acoustic windows allowed placement of transducers distal and perpendicular to the valves, so that the ultrasound beam could be positioned parallel to the valvular flow. Strain-gauge and electromagnetic transducers were used for measurements of pressure and flow in different segments of the system. The flow model was also designed to fit different sizes and types of prosthetic valves. This pulsatile flow model was able to generate pressure and flow in the physiological human range, with independent adjustment of pulse duration and rate as well as of stroke volume. This model mimics flow profiles observed in patients with regurgitant prosthetic valves.
Asunto(s)
Humanos , Ecocardiografía Doppler en Color , Enfermedades de las Válvulas Cardíacas , Prótesis Valvulares Cardíacas , Modelos Cardiovasculares , Flujo Pulsátil , Presión Sanguínea , Atrios CardíacosRESUMEN
To compare the sensitivity of dipyridamole, dobutamine and pacing stress echocardiography for the detection of myocardial ischemia we produced a physiologically significant stenosis in the left circumflex artery of 14 open-chest dogs (range: 50 to 89 percent reduction in luminal diameter). In each study, dobutamine (5 to 40 æg kg-1 min-1 in 3-min stages) and pacing (20 bpm increments, each 2 min, up to 260 bpm) were performed randomly, and then followed by dipyridamole (up to 0.84 mg/kg over 10 min). The positivity of stress echocardiography tests was quantitatively determined by a significant (P<0.05) reduction of or failure to increase absolute and percent systolic wall thickening in the stenotic artery supplied wall, as compared to the opposite wall (areas related to the left anterior descending artery). Systolic and diastolic frozen images were analyzed off-line by two blinded observers in the control and stress conditions. The results showed that 1) the sensitivity of dobutamine, dipyridamole and pacing stress tests was 57, 57 and 36 percent, respectively; 2) in animals with positive tests, the mean percent change of wall thickening in left ventricular ischemic segments was larger in the pacing (-19 Ý 11 percent) and dipyridamole (-18 Ý 16 percent) tests as compared to dobutamine (-9 Ý 6 percent) (P = 0.05), but a similar mean reduction of wall thickening was observed when this variable was normalized to a control left ventricular segment (area related to the left anterior descending artery) (pacing: -16 Ý 7 percent; dipyridamole: -25 Ý 16 percent; dobutamine: -26 Ý 10 percent; not significant), and 3) a significant correlation was observed between magnitude of coronary stenosis and left ventricular segmental dysfunction induced by ischemia in dogs submitted to positive stress tests. We conclude that the dobutamine and dipyridamole stress tests showed identical sensitivities for the detection of myocardial ischemia in this one-vessel disease animal model with a wide range of left circumflex artery stenosis. The pacing stress test was less sensitive, but the difference was not statistically significant. The magnitude of segmental left ventricular dysfunction induced by ischemia was similar in all stress tests evaluated