William Elias

Sources of variability for doppler color flow mapping of regurgitant jets in an animal model of mitral regurgitation

To determine whether Doppler color flow mapping could be used to quantify changing levels of regurgitant flow and define the technical variables that influence the size of color flow images of regurgitant jets, nine stable hemodynamic states of mitral insufficiency were studied in four open chest sheep with regurgitant orifices of known size. The magnitude of mitral regurgitation was altered by phenylephrine infusion. Several technical variables, including the type of color flow instrument (Irex Aloka 880 versus Toshiba SSH65A), transducer frequency, pulse repetition frequency and gain level, were studied. Significant increases in the color flow area, but not in color jet width measurements, were seen after phenylephrine infusion for each regurgitant orifice. For matched levels of mitral regurgitation, an increase in gain resulted in a 125% increase in color flow area. An increase in the pulse repetition and transducer frequencies resulted in a 36% reduction and a 28% increase in color flow area, respectively. Jet area for matched regurgitant volumes was larger on the Toshiba compared with the Aloka instrument (5.2 +/- 3.1 versus 3.2 +/- 1.2 cm2, p less than 0.05). Color flow imaging of mitral regurgitant jets is dependent on various technical factors and the magnitude of regurgitation. Once these are standardized for a given patient, the measurement of color flow jet area may provide a means of making serial estimates of the severity of mitral insufficiency.

Closure of the ductus arteriosus and mechanics of breathing in preterm infants after surfactant replacement therapy.

ABSTRACT: Treatment of premature infants with exogenous surfactant is thought to increase the incidence of the patent ductus arteriosus (PDA) due to improved mechanics of breathing and the resultant reduced pulmonary vascular resistance. As part of a prospective, blinded, controlled study of human amniotic fluid-derived surfactant, we assessed the time of closure of the PDA, defined by Doppler echocardiographic studies, performed at 6-h intervals, and the mechanics of breathing at 6, 18, and 30 h of age in 61 infants (gestational age, 25-29 wk, and birth wt, 450-1580 g). All infants had respiratory distress syndrome as confirmed by immature surfactant phospholipid profiles determined on either amniotic fluid and/or tracheal aspirate analysis, and chest radiograph, and all had a PDA at 6 h of age. Surfactant treatment was associated with more frequent clinically determined need for treatment of the PDA, but did not prolong the patency of the ductus in infants with spontaneous closure or in those requiring treatment with indomethacin. Infants with spontaneous closure of the PDA had significantly higher dynamic lung compliances and lower oxygen requirements and were treated with lower mean airway pressures than those requiring PDA treatment, although their arterial blood gas status was the same. The dynamic lung compliance of infants with right to left ductal shunting was significantly lower than those with left to right shunting at 6 and 18 h but was not different thereafter. This study suggests that the maturity of the ductus arteriosus, reflected by its tendency to close spontaneously, parallels the maturity of the lungs, reflected by their mechanical stability, and that ductal closing is not significantly altered by surfactant therapy.

Cine magnetic resonance imaging and color Doppler flow mapping displays of flow velocity, spatial acceleration, and jet formation: A comparative in vitro study

To study the effects of flow acceleration and high-velocity jets on the display characteristics of cine magnetic resonance imaging compared with color Doppler flow mapping, a custom-designed in vitro flow model was developed. This model consisted of a funnel segment tapering to an orifice (0.78 cm2) that leads into a confined receiving chamber with a second, discrete orifice (0.78 cm2) at its distal end. Cine magnetic resonance images obtained at varying flow rates (1.5 to 27.2 L/min) demonstrated loss of signal intensity throughout the tapering zone of spatial acceleration and a small zone of more marked signal loss immediately proximal to the second orifice (always < 50% of the signal intensity within the tapering funnel zone) associated with more rapid spatial acceleration. A formed jet was imaged distal to the first orifice, and the turbulence area surrounding the laminar central jet core correlated well with flow rate (r = 0.98), as did the distance from the orifice to the subsequent onset of flow relaminarization (r = 0.96). A turbulent spray area was always seen distal to the second, discrete orifice. Comparative observations with color Doppler flow mapping and continuous wave Doppler demonstrated that signal intensity on cine magnetic resonance imaging is reduced by both spatial acceleration, and the high-velocity and turbulent jets associated with obstructive and regurgitant lesions. In vitro evaluation of cine magnetic resonance imaging allows comparative observations to be made about the flow characteristics of cine magnetic resonance imaging and color Doppler flow mapping and provides a more rational basis for the interpretation of cine magnetic resonance imaging in the clinical setting.

Correlation of patent ductus arteriosus shunting with plasma atrial natriuretic factor concentration in preterm infants with respiratory distress syndrome

ABSTRACT: The concentration of plasma atrial natriuretic factor (ANF) and the mechanism for its secretion were investigated in 17 preterm infants with respiratory distress. Their mean gestational age was 29 wk and wt 1250 g. The infants were followed during the first week of life by sequential Doppler ultrasound studies. Ductal openness versus closure and amount of ductal flow were correlated with plasma ANF concentrations. In a subset of 10 infants, sequential Doppler color flow mapping was used to quantify the ductal flow. During the first 72 h, plasma ANF was high, 361 pg/mL; it decreased to 96 pg/mL by the end of the 1st wk. The ANF level was significantly higher when the ductus was open than closed (393 versus 123 pg/mL, p < 0.05). In patients with open ductus and bidirectional foramen ovale shunting (n = 3) ANF was 567 pg/mL and in those with left-to-right shunt 355 pg/mL (n 15, NS). The left atrial size, i.e. the left atrial to aortic root ratio, correlated with the amount of ductal shunting (r = 0.63, p < 0.01) and with ANF concentration (r = 0.46, p < 0.02). The correlation of ANF values and the magnitude of left-to-right ductal shunting assessed by color flow mapping was highly significant (r = 0.66, p < 0.001). In these patients, the elevation of ANF is reflective of ductal flow.

Noninvasive Doppler color flow mapping for detection of anomalous origin of the left coronary artery from the pulmonary artery and for evaluation of surgical repair

Anomalous origin of the left coronary artery from the pulmonary artery is a rare but important cause of congestive heart failure in infancy and of sudden death at all ages. Diagnosis is often missed when based solely on physical examination and noninvasive methods. A 4 year old patient is presented in whom mitral regurgitation was noted by a referring physician and an anomalous left coronary artery was found by Doppler color flow mapping upon referral and verified at cardiac catheterization. Doppler color flow mapping was also used intraoperatively using a gas-sterilized transducer to further clarify the hemodynamics and assess the surgical result. After creation of an intrapulmonary artery tunnel from the ostium of the left coronary artery to the aorta, anterograde coronary artery flow and absence of a residual left to right pulmonary artery shunt were verified during surgery by Doppler flow mapping. Postoperatively, residual mitral regurgitation and patency of the left coronary artery graft have been followed up serially by Doppler flow mapping. Therefore, Doppler color flow mapping is useful in the diagnosis and intraoperative and postoperative management of this important and potentially life-threatening abnormality.

Reptilian Echocardiography: Insights into Ontogeny and Phylogeny?

We describe the echocardiographic findings in a large reptile‐the carpet python. If ontogeny recapitulates phylogeny, the study of reptilian hearts may provide insights into human cardiac development. In addition, the reptilian heart has unique structural and physiological adaptations that may broaden our perspective on evolutionary cardiac adaptation.

Two-Dimensional Doppler Color Flow Mapping for Detecting Atrial and Ventricular Septal Defects: Studies in Animal Models and in the Clinical Setting

Two-dimensional Doppler echocardiography is an established and useful technique for imaging, localizing, and providing prognostic information related to ventricular septal defect (VSD) and atrial septal defect (ASD)—as well as for providing estimates of volume flow and pulmonary to systemic flow ratios (QP: QS). The Doppler technique, however, has not yet been widely applied systematically for the identification of defects that are too small to image—or for characterization of flow patterns across the ventricular septum or the atrial septum.

Two‐Dimensional Doppler Color Flow Mapping for Detecting Atrial and Ventricular Septal Defects

In experimental studies in six dogs as well as in clinical studies in eleven patients with atrial septal defect and 27 patients with ventricular septal defect, the diagnostic usefulness of color Doppler echocardiography in detection of small septal defects and multiple defects was analyzed. The study showed that atrial or ventricular septal defects with a size of 2.5 to 3 mm or more, which eluded detection with two-dimensional echocardiography, were easily identified with the color Doppler method. Additionally, multiple defects were reliably demonstrated. In atrial septal defects, according to the results of this study, the shunt area in the color Doppler image enables a semiquantitative estimation of the shunt volume.

Successful surgical closure of an arterial duct in 18 children in a third world country

OBJECTIVES To perform surgical closure of a clinically significant arterial duct on children in a third world country. BACKGROUND An arterial duct is one of the most common congenital cardiac defects. Large arterial ducts can cause significant pulmonary overcirculation, causing symptoms of congestive cardiac failure, ultimately resulting in premature death. Closure of an arterial duct is usually curative, allowing for a normal quality of life and expectancy. In western countries, arterial duct closure in children is usually performed by deployment of a device through a catheter-based approach, replacing previous surgical approaches. In third world countries, there is limited access to the necessary resources for performing catheter-based closure of an arterial duct. Consequently, children with an arterial duct in a third world country may only receive palliative care, can be markedly symptomatic, and often do not survive to adulthood. METHODS We assembled a team of 11 healthcare workers with extensive experience in the medical and surgical management of children with congenital cardiac disease. In all, 21 patients with a history of an arterial duct were screened by performing a comprehensive history, physical, and echocardiogram at the Angkor Hospital for Children in Siem Reap, Cambodia. RESULTS A total of 18 children (eight male and ten female), ranging in age from 10 months to 14 years, were deemed suitable to undergo surgery. All patients were symptomatic, and the arterial ducts ranged in size from 4 to 15 millimetres. Surgical closure was performed using two clips, and in four cases with the largest arterial duct, sutures were also placed. All patients had successful closure without any significant complications, and were able to be discharged home within 2 days of surgery. Of note, four children with arterial ducts died in the 5 months before our arrival. CONCLUSION Surgical closure of an arterial duct can be performed safely and effectively by an experienced paediatric cardiothoracic surgical team on children in a third world country. We hope that our experience will inspire others to perform similar missions throughout the world.