Journal of the American College of Cardiology
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J. Am. Coll. Cardiol. · Jan 1996
Effect of ligation of patent ductus arteriosus on left ventricular performance and its determinants in premature neonates.
The purpose of this study was to determine in preterm newborn infants the effects of ductal ligation on ventricular performance and its determinants: preload, afterload and contractility. ⋯ Ventricular performance is higher in premature infants with than in those without patent ductus arteriosus because afterload is lower in the former group. Although ductal ligation increases blood pressure and systemic resistance, wall stress and ventricular performance are maintained. Our results suggest that the premature newborn maintains ventricular performance during stress, at least in part, by manipulating afterload.
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J. Am. Coll. Cardiol. · Jan 1996
Comparative StudyA new Doppler method for quantification of volumetric flow: in vivo validation using color Doppler.
This study was designed to assess the accuracy of a new Doppler method for quantification of volumetric flow in vivo. ⋯ The method showed close agreement with thermodilution and MRI for assessment of volumetric flow in vivo. It is therefore a noninvasive method with potential applications for cardiac output measurement and for quantification of volumetric flow of valvular insufficiency and restrictive lesions.
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J. Am. Coll. Cardiol. · Jan 1996
Clinical TrialDiurnal pattern of QTc interval: how long is prolonged? Possible relation to circadian triggers of cardiovascular events.
This study sought to evaluate the range and variability of the QT and corrected QT (QTc) intervals over 24 h and to assess their pattern and relation to heart rate variability. ⋯ The maximal QTc interval over 24 h in normal subjects is longer than heretofore thought. Both QT and QTc intervals are longer during sleep. The QTc interval and QTc variability reach a peak shortly after awakening, which may reflect increased autonomic instability during early waking hours, and the time of the peak value corresponds in time to the period of reported increased vulnerability to ventricular tachycardia and sudden cardiac death. These findings have implications regarding the definition of QT prolongation and its use in predicting arrhythmias and sudden death.
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J. Am. Coll. Cardiol. · Jan 1996
Clinical TrialDiagnosis of ascending aortic dissection by transesophageal echocardiography: utility of M-mode in recognizing artifacts.
This study sought to assess the reliability of biplanar transesophageal echocardiography in the diagnosis of ascending aortic dissection and to test the utility of M-mode information in the differential diagnosis of ascending aortic ultrasound artifacts and intimal flap images. ⋯ Biplanar transesophageal echocardiography permits reliable diagnosis of ascending aortic dissection. Ultrasound artifacts are common, but assessment of the location and mobility of intraluminal images by M-mode echocardiography definitely improves diagnostic accuracy.
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J. Am. Coll. Cardiol. · Jan 1996
Clinical TrialA potential clinical method for calculating transmural left ventricular filling pressure during positive end-expiratory pressure ventilation: an intraoperative study in humans.
This study sought to investigate whether right atrial pressure could be used to estimate pericardial pressure during positive end-expiratory pressure (PEEP). ⋯ The present observations suggest that right atrial pressure may be used to estimate changes in pericardial pressure with PEEP and that pulmonary capillary wedge pressure minus right atrial pressure is a potentially clinically useful approximation of transmural filling pressure.