Ultrasound myocardial tissue characterization by integrated backscatter in children treated with anthracyclines.

The objective of our study was to evaluate integrated backscatter (IBS) measurement, an ultrasound method of myocardial tissue characterization, in children receiving cardiotoxic anthracyclines for malignancy. Myocardial injury is known to diminish the normal cyclic variation of IBS (CVIBS) during the cardiac cycle. We used a cross-sectional, case-controlled study of children receiving anthracyclines and serial, prospective observation in a subgroup of children. The study took place in a university-affiliated, tertiary referral center for pediatric cardiology and oncology. Children undergoing routine echocardiograms before, during, and after anthracycline treatment participated in this study. Children evaluated in the cardiology clinic for innocent murmurs participated as controls. There was no intervention. CVIBS was measured using specialized echocardiographic software which quantitates the intensity of backscattered echoes returning from myocardial cells within a user-defined region of interest. Standard echocardiographic measures of left ventricular function were also made. The results indicated that abnormal CVIBS was prevalent during anthracycline treatment (17%) and at late follow-up (20%). In serial studies, CVIBS decreased in all children after anthracycline treatment. Anthracycline dose and time since last dose did not predict which children would have abnormalities of left ventricular function or of CVIBS. This report provides preliminary evidence that CVIBS may be a useful supplement to the noninvasive, echocardiographic assessment of the heart during anthracycline treatment in children.

New Doppler techniques for the evaluation of regurgitant and shunt volumes.

The aim of this review is to highlight some relatively new applications of Doppler echocardiography in children. Recent observations of flow dynamics through a restricted orifice have revealed that flow through an opening converges toward the orifice in a series of proximal isovelocity hemispheric surfaces. The flow convergence region can be demonstrated by Doppler echocardiography as a color mosaic on the ventricular side of the mitral valve in the presence of mitral regurgitation and on the left-ventricular side of a ventricular septal defect with left-to-right shunting. The continuity principle dictates that regurgitant flow rate can be calculated as the product of the hemispheric surface area of the flow convergence region and the velocity at that hemispheric surface. Using this principle, investigators have made quantitative flow measurements of mitral regurgitation, ventricular septal defect flow and aortic regurgitation. These studies demonstrate that this new technique of noninvasive quantification has the potential of providing direct measures of regurgitant and shunt flow. However, further validation in the pediatric population is needed before it can be incorporated into routine clinical practice.

A retrospective review of the role of transesophageal echocardiography in aortic and cardiac trauma in a level I Pediatric Trauma Center.

This study examined the role of transesophageal echocardiography in blunt aortic and cardiac trauma in a Pediatric Level I Trauma Center. In a > 5-year retrospective review, we identified 10 children with blunt cardiac (n = 4; tricuspid valve in two; mitral valve in one; aortic valve in one) and aortic (n = 6; aortic rupture in five, subintimal flap in one) trauma. Diagnosis of the cardiac injuries was made with transthoracic echocardiography, with transesophageal echocardiography providing additional anatomic detail and postoperative assessment in three of four children who required surgical intervention. Diagnosis of the aortic injuries was made with transesophageal echocardiography in five of six patients; one patient underwent aortography before transfer. Transesophageal echocardiography also identified depressed myocardial function in one child and aided in surgical management of the five aortic ruptures. In blunt chest trauma, transesophageal echocardiography provides accurate evaluation of cardiovascular structure and function and guides operative repair.

Cyclic variation of integrated ultrasound backscatter: normal and abnormal myocardial patterns in children.

Cyclic variation of integrated backscatter (CVIBS) is altered in adults with myocardial infarction, allograft rejection, and cardiomyopathy. Its utility in children has not been tested. We studied 99 normal subjects: 16 fetuses, 13 newborns, 47 children, and 23 teenagers. Fifteen children with cardiomyopathy (13 dilated and two infiltrative) were studied to define abnormal CVIBS. CVIBS was measured in the anterior septum and the left ventricular posterior wall from a two-dimensional ultrasound image with an acoustic densitometry software package. CVIBS was similar in the anterior septum (3.7 +/- 1.9 dB) and the posterior wall (4.1 +/- 2.4 dB) of all children after birth. CVIBS was significantly lower in the fetus (septum: 2.8 +/- 1.6 dB) and in children with cardiomyopathy (septum: 0.6 +/- 1.6 dB, dilated; -1.2 +/- 4.2 dB, infiltrative; p < 0.01). Four children, studied after recovery from cardiomyopathy, had diminished CVIBS despite the return of normal systolic function. The pattern and extent of CVIBS in children is similar to that of adults. CVIBS is diminished in children with cardiomyopathy.

Indications for echocardiography in the diagnosis of infective endocarditis in children.

The role of transthoracic echocardiography as a diagnostic tool in children suspected of having infective endocarditis (IE) has not been defined. We hypothesized that echocardiography is only useful in children in whom there is high clinical suspicion of IE based on physical examination findings or persistently positive blood cultures. Echocardiographic reports and medical records of all inpatients (n = 133) from 1990 to 1992 who underwent echocardiography for suspected IE were reviewed. Fifty-nine of the 133 patients (44%) identified had either persistently positive blood cultures (n = 48), physical examination findings of IE (n = 20), or both (n = 9). The echocardiogram was positive in 7 of these patients (12%) and negative in all 74 patients without positive physical findings or positive blood cultures (p = 0.003). A new or changing precordial murmur, embolic phenomena, congestive heart failure, mechanical ventilation, and positive blood cultures were predictive of positive echocardiograms for IE by univariate analysis. The presence of fever, immune deficiency, and central lines, alone or in combination, was not predictive of a positive echocardiogram. In the absence of physical findings or persistently positive blood cultures, echocardiography is a low-yield study and is unlikely to aid in the diagnosis of IE in children.

Role of echocardiography in the diagnosis and surgical management of accessory mitral valve tissue causing left ventricular outflow tract obstruction.

We report an unusual case of left ventricular outflow tract obstruction caused by accessory mitral valve tissue. This case illustrates the importance of transthoracic echocardiography in preoperative evaluation and the usefulness of transesophageal echocardiography for intraoperative assessment. If the accessory mitral valve has no functional significance it may be surgically excised, thereby relieving the outflow tract obstruction.

A simplified method for calculating wall stress in infants and children.

Measurement of the end-systolic wall stress-mean velocity of circumferential fiber-shortening relation, a load-independent measure of contractility, has enabled cardiologists to assess ventricular function under various loading conditions and at different heart rates. Unfortunately, it is time-consuming and difficult to perform in routine pediatric practice. Because a close relationship was noted between end-systolic pressure and mean blood pressure, we estimated wall stress by mean blood pressure in 115 patients. There was an excellent correlation between end-systolic blood pressure and mean arterial pressure (r = 0.84) and end-systolic wall stress and mean systolic wall stress (r = 0.98). The difference in mean blood pressure was 5.1 mm Hg (95% confidence interval-10.5 to 20.6 mm Hg), and the difference in mean wall stress was 2.7 gm/cm2 (95% confidence interval-2.0 to 3.8 gm/cm2). More important, substitution of mean blood pressure for end-systolic pressure allowed accurate identification of patients with normal contractility (55/56) and abnormal contractility (57/59).

Mechanisms of change in cardiac performance in infants undergoing extracorporeal membrane oxygenation.

OBJECTIVE: To determine whether changes in cardiac performance observed in infants early during extracorporeal membrane oxygenation are due to the underlying disease process, the partial bypass procedure, changes in cardiac loading conditions, or due to a direct myocardial effect of hypoxia-reoxygenation. DESIGN: Consecutive case series. PATIENTS: Infants with meconium aspiration syndrome were studied at the end of their extracorporeal membrane oxygenation course (veno-arterial, n = 12; veno-venous, n = 8), after lung compliance and pulmonary arterial pressure returned toward normal and they were ready to have extracorporeal membrane oxygenation discontinued. INTERVENTIONS: Heart rate, mean arterial blood pressure, and load-dependent indices, and a load-independent index of cardiac performance were measured at increasing bypass flow rates (25, 50, 75, 100, 125 mL/kg/min). MEASUREMENTS AND MAIN RESULTS: Heart rate, mean arterial blood pressure, and load-dependent indices of cardiac performance (left ventricular shortening fraction and stroke volume) were normal at 25 mL/kg/min bypass flow rate and did not change significantly with increasing bypass flow rates. The load-independent index of performance was within the normal range for infants and did not change significantly with increasing bypass flow rates. CONCLUSIONS: The previously described decreases in cardiac performance during extracorporeal membrane oxygenation are not due to the underlying disease process or the bypass procedure but are due to changes in loading conditions during partial bypass.

Routine use of transesophageal echocardiography and color flow imaging in the evaluation and treatment of children with congenital heart disease.

We reviewed our experience with transesophageal echocardiography (TEE) and color flow imaging in 157 consecutive patients with known or suspected heart disease to ascertain the impact of this technology on patient care. TEE was performed for diagnostic purposes (22/157), during interventional cardiac catheterizations (13/157), and during operative procedures (122/157). Diagnostic studies were performed after transthoracic echocardiography (TTE) in 21 of 22 patients. TEE was performed because TTE was inconclusive (15/21) or failed to provide sufficient detail of an abnormality (6/21). TEE detected an abnormality in 6 of 15 inconclusive TTEs. TEE was helpful during interventional cardiac catheterizations, particularly during umbrella closure of septal defects and in patients with complex venous and atrial anatomy undergoing transseptal puncture. TEE studies performed before cardiac operations significantly changed the diagnosis in only 5 of 122 (4%) patients, but the information changed the surgical approach in 4 of 5 of these patients. Postoperative TEE assessment more frequently changed care and resulted in further surgical management in 9 of 122 (7%) or a change in medical management in 6 of 122 (5%) patients. TEE was discontinued because of complications before studies were completed in only 4 of 157 (3%) patients. TEE and color flow imaging is a useful adjunct to care of children with known or suspected congenital heart disease.

Congenital diaphragmatic hernia: long-term outcome in neonates treated with extracorporeal membrane oxygenation.

As more infants with congenital diaphragmatic hernia (CDH) survive with extracorporeal membrane oxygenation (ECMO), it seems prudent to detail the longterm outcome in these medically complex infants. Eighteen children with CDH-treated with postoperative ECMO were recruited for participation in this study. The mean duration of ECMO was 193 hours (range 82 to 493 hours), mean time to extubation after ECMO was 142 hours (range 34 to 312 hours), and median duration of hospitalization was 46 days (range 30 to 181 days). Of the 18 infants, 4 (22%) were discharged home requiring oxygen therapy. At follow-up the notable findings were a high incidence of gastroesophageal reflux and failure to thrive. At both 1 and 2 years of age, 50% of infants were at less than the 5th percentile for weight. At 1 and 2 years of age, 39% and 21%, respectively, were at less than the 5th percentile for weight/length ratio. A total of 16 children (89%) had clinical evidence of reflux, and 8 (44%) were discharged home on a regimen of nasogastric feedings. Reherniation occurred in 4 children (22%) and was more frequent when a patch was used. An electrocardiogram showed right ventricular hypertrophy in 6 (43%); oxygen saturation by pulse oximetry was > 95% in all children, and pulmonary artery pressure was estimated by Doppler echocardiography to be normal in 12 of 14 children examined. The neurodevelopmental outcome (Bayley Scales or Stanford-Binet scale) at 1 to 4 years of age was not dissimilar from that of other ECMO-treated children. Given the severity of illness in the neonatal period, the general health and development of children with CDH surviving after ECMO are good. Surprisingly few children have long-term respiratory complications related to pulmonary hypoplasia. Follow-up in the first few years should be aimed at aggressive nutritional intervention to prevent the growth failure that appears to be prevalent in these children.

Diagnosis of anomalous left coronary artery by Doppler color flow mapping: distinction from other causes of dilated cardiomyopathy.

BACKGROUND: Anomalous origin of the left coronary artery from the pulmonary trunk is difficult to diagnose reliably by two-dimensional echocardiography. Therefore, Doppler color flow mapping was tested in 29 patients with dilated cardiomyopathy or anomalous left coronary artery, or both. METHODS AND RESULTS: All patients with anomalous left coronary artery (10 patients) or dilated cardiomyopathy (27 patients) (excluding those with other known causes for cardiomyopathy) examined between January 1988 and May 1991 were identified. The direction of flow in the three main segments of the left coronary system was determined by Doppler color flow mapping. In all 10 patients with anomalous left coronary artery, flow mapping demonstrated an abnormal jet from the left coronary artery into the pulmonary trunk and retrograde flow in at least two segments of the left coronary system. The diagnosis was confirmed in all 10 patients at operation. Doppler color flow mapping, performed in 19 of the 27 patients with dilated cardiomyopathy, demonstrated anterograde flow in at least one segment of the left coronary system in 16 of the 19 patients; flow direction was not determined in the other 3 patients. Coronary artery anatomy was confirmed by aortic root or left ventricular angiography in 14 patients and at autopsy in 1 patient and was not directly confirmed in 4 patients. Left ventricular function spontaneously improved to normal in three of the latter four patients, a clinical course not consistent with anomalous left coronary artery. The left coronary artery appeared to arise from the aortic root by two-dimensional echocardiographic imaging alone in all patients with dilated cardiomyopathy and in 5 of 10 patients with anomalous left coronary artery (50% false negative diagnoses). CONCLUSIONS: Detection of an abnormal jet into the pulmonary trunk and retrograde flow in the left coronary system by Doppler color flow mapping is reliable for diagnosing anomalous left coronary artery whereas two-dimensional echocardiographic imaging alone is often inconclusive or misleading. Determining flow direction in the left coronary system in patients with dilated cardiomyopathy is useful for excluding anomalous left coronary artery but is technically more difficult to document in this condition than in anomalous left coronary artery.

Tetralogy of Fallot. The spectrum of severity in a regional study, 1981-1985.

The combined medical and surgical mortality rate for 125 infants with tetralogy of Fallot registered in the Baltimore-Washington Infant Study from 1981 to 1985 was 28% (mean age at follow-up for living infants, 40 months). Despite early diagnosis and successful early repair in many infants, significant risk factors for death included pulmonary atresia, major additional cardiac anomalies, major noncardiac malformations, low birth weight, and prematurity. There is a wide spectrum of severity, ranging from infants with isolated tetralogy and no risk factors who have an excellent prognosis to infants with three or more risk factors and a high probability of neonatal death. Further treatment advances will improve outcome in some, but not all, infants. A regional all-inclusive study of a specific cardiac defect can define research and treatment challenges not obvious from selected clinical series.

Cardiac performance in infants referred for extracorporeal membrane oxygenation.

We performed cardiac evaluations in 59 infants referred for severe lung disease to determine whether cardiac performance was impaired in those requiring extracorporeal membrane oxygenation (ECMO). Infants were divided into two groups: group 1 (n = 25) received conventional therapy and group 2 (n = 34) received ECMO therapy after meeting established criteria. Ventilatory and oxygenation indexes and estimates of right ventricular systolic pressure were measured. Load-dependent and load-independent echocardiographic indexes of cardiac performance were also measured. The infants in the two groups had similar diagnoses, age, weight, inotropic support, ventilator and oxygenation indexes on admission, and survival. Heart rate and estimates of preload and afterload were similar in the two groups. Ventricular shortening fraction was 36.1 +/- 7.6% in group 1 and 40.5 +/- 8.8% in group 2 (p value was not significant). Velocity of circumferential fiber shortening (VCF/sec) was 1.41 +/- 0.35 in group 1 and 1.58 +/- 0.39 in group 2 (p value was not significant). The relationship between wall stress and ventricular shortening was similar in the two groups. There were no differences in cardiac output. Pulmonary artery pressure was estimated to be 56 +/- 13 mm Hg in group 1 and 63 +/- 10 mm Hg in group 2 (p = 0.017). Thus no significant differences were found in load-dependent or load-independent measures of cardiac performance in infants with severe lung disease treated with ECMO or conventional therapy. We conclude that cardiac failure is not the primary cause of clinical deterioration in infants with severe lung disease who require ECMO therapy.