Richard A. Humes

Regression equations for calculation of z scores of cardiac structures in a large cohort of healthy infants, children, and adolescents: an echocardiographic study.

BACKGROUND Decision making in the care of pediatric patients with congenital and acquired heart disease remains reliant on detailed measurements of cardiac structures using 2-dimensional echocardiography. Calculated z scores are often used to normalize these measurements to the patients body size. Existing normal data in the literature are limited by small sample size, small numbers of measured cardiac structures, and inadequate data for the calculation of z scores. Accordingly, we sought to develop normative data in a large pediatric cohort using modern echocardiographic equipment from which z scores could be calculated. METHODS Two-dimensional and M-mode echocardiography was performed in 782 patients ranging in age from 1 day to 18 years. Measurements were made of 21 individual cardiac structures. Regression equations were derived to relate the size of the various cardiac structures to body surface area. Data are presented graphically, and regression equations are derived relating cardiac dimension to body surface area. CONCLUSION The presented data will allow the calculation of z scores for echocardiographically measured cardiac structures. This information will be valuable for clinicians caring for infants and children with known or suspected cardiac disease.

Spontaneous regression of cardiac rhabdomyoma

Abstract Multiple cardiac rhabdomyomas in a neonate with tuberous sclerosis were first described by Von Recklinghausen in 1862. These hamartomas are the cardiac tumors most frequently encountered during infancy and childhood. Rhabdomyomas account for 45% of primary heart tumors in children and represent 53% of primary benign childhood cardiac tumors. 1 Approximately 30% of patients with tuberous sclerosis have cardiac rhabdomyomas. 2 Their natural history is unclear because most reviews on this subject are based on autopsy data. The prognosis for cardiac rhabdomyomas is believed to be grim because of reported fatality rates of 53% by the first week of life and 78% by 1 year of age. 2,3 With widespread use of echocardiography in pediatrics during the last 2 decades, it has become clear that rhabdomyomas result in a wide spectrum of clinical manifestations, ranging from a total absence of symptoms to intrauterine or sudden postnatal death. Also reported are hydrops fetalis, dysrhythmias, inflow or outflow obstruction, congestive heart failure and possibly cerebral embolization. Histologic examination of these masses in 1923 was suggestive of spontaneous regression. 4 Isolated clinical reports of spontaneous regression have recently appeared. 5 We now describe a series of 5 infants with tuberous sclerosis who had close documentation of the size of their 13 tumors.

Myocardial flow reserve in patients with a systemic right ventricle after atrial switch repair

OBJECTIVES The purpose of this study was to assess myocardial blood flow (MBF) and flow reserve in systemic right ventricles (RV) in long-term survivors of the Mustard operation. BACKGROUND There is a high prevalence of systemic RV dysfunction and impaired exercise performance in long-term survivors of the Mustard operation. A mismatch between myocardial blood supply and systemic ventricular work demand has been proposed as a potential mechanism. METHODS We assessed MBF at rest and during intravenous adenosine hyperemia in 11 long-term survivors of a Mustard repair (age 18+/-5 years, median age at repair 0.7 years, follow-up after repair 17+/-5 years) and 13 healthy control subjects (age 23+/-7 years), using N-13 ammonia and positron emission tomography imaging. RESULTS There was no difference in basal MBF between the systemic RV of survivors of the Mustard operation and the systemic left ventricle (LV) of healthy control subjects (0.80+/-0.19 vs. 0.74+/-0.15 ml/g/min, respectively, p = NS). However, the hyperemic flows were significantly lower in systemic RVs than they were in systemic LVs (2.34+/-0.0.69 vs. 3.44+/-0.62 ml/g/min respectively, p < 0.01). As a result, myocardial flow reserve was lower in systemic RVs than it was in systemic LVs (2.93+/-0.63 vs. 4.74+/-1.09, respectively, p < 0.01). CONCLUSIONS Myocardial flow reserve is impaired in systemic RVs in survivors of the Mustard operation. This may contribute to systemic ventricular dysfunction in these patients.

A Systematic Approach to Prenatal Diagnosis of Transposition of the Great Arteries Using 4-Dimensional Ultrasonography With Spatiotemporal Image Correlation

patiotemporal image correlation (STIC) is a recent technological advance in ultrasonographic imaging that allows dynamic multiplanar slicing and surface rendering of the fetal heart.1–5 In a previous study, a technique was developed to systematically visualize the outflow tracts from volume data sets acquired with STIC.3,4 The addition of color and power Doppler imaging to STIC technology made it possible to dynamically display rendered views of the outflow tracts with minimal manipulation of the volume data set.5 Prenatal diagnosis of transposition of the great arteries (TGA) is associated with a significant reduction in both preoperative and postoperative mortality, a decrease in the rate of metabolic acidosis and multiorgan failure during the neonatal period, reduced need for ventilatory support, and shorter hospitalization time.6,7 Unfortunately, prenatal detection rates for TGA have been low in most of the studies published to date.8–15 Among the reasons for failure to prenatally detect most cases of TGA are the absence of risk factors to identify a target population for screening and the need to systematically examine the outflow tracts to establish the diagnosis.6,16 Despite recommendations by scientific societies such as the American Institute of Ultrasound in Medicine to extend the basic fetal cardiac examination to include visualization of the outflow tracts whenever technically feasible,17 this examination remains a technical challenge for many sonographers.6,18 Four-dimensional volume data set acquisition followed by a systematic approach to image the outflow tracts may reduce the operator dependency of prenatal ultrasonography. Volume acquisition is still operator dependent with current commercially available technology. However, once a good-quality volume data set is acquired, the outflow tracts can be systematically imaged by following algorithms developed for gray scale,3,4 color, or power Doppler5 imaging. It is anticipated that algorithms developed to image specific cardiac structures with 3or 4-dimensional volume data sets may eventually become automated by computer software (automated multiplanar imaging).19 Received April 22, 2004, from the Department of Obstetrics and Gynecology, Wayne State University, Detroit, Michigan USA (L.F.G., B.B., M.C.T.); Perinatology Research Branch, National Institute of Child Health and Human Development, National Institutes of Health, Department of Health and Human Services, Bethesda, Maryland USA (L.F.G., J.E., R.R.); Division of Fetal Imaging, William Beaumont Hospital, Royal Oak, Michigan USA (W.L.); and Division of Cardiology, Children’s Hospital of Michigan, Wayne State University, Detroit, Michigan USA (R.H.). Revision requested May 24, 2004. Revised manuscript accepted for publication June 1, 2004. Address correspondence and reprint requests to Roberto Romero, MD, Perinatology Research Branch, National Institute of Child Health and Human Development, Department of Obstetrics and Gynecology, Wayne State University/Hutzel Hospital, 4707 St Antoine Blvd, Detroit MI 48201 USA. E-mail: warfiela@mail.nih.gov. Abbreviations STIC, spatiotemporal image correlation; TGA, transposition of the great arteries

Augmented norepinephrine and renin output in response to maximal exercise in hypertensive coarctectomy patients

To evaluate a possible neural or renal contribution to the hypertension that occurs in some patients following coarctation of aorta repair, 35 patients underwent graded bicycle exercise with serial measurements of plasma norepinephrine concentrations and plasma renin activity. Sixteen patients with coarctectomy who had systolic or diastolic hypertension at peak exercise were compared with 19 normotensive patients with coarctectomy. The average time interval between coarctation repair and study was significantly longer (p less than 0.05) in the hypertensive group than in the normotensive patients (12.8 +/- 4.8 versus 8.7 +/- 2.2 years). The heart rate response to exercise was similar for both patient groups. The systolic blood pressure in the hypertensive group was higher than in the normotensive group at rest in the supine and upright positions and at 5 minutes of recovery, in addition to peak exercise, and the diastolic blood pressure was increased at peak exercise. Plasma norepinephrine concentrations were significantly higher at peak exercise and during recovery in the hypertensive group than in the normotensive patients. Plasma renin activity was also significantly higher in the hypertensive group at peak exercise. These data suggest that patients with coarctectomy who have a hypertensive response to exercise have an augmented sympathetic nervous system output and increased plasma renin activity that may lead to peripheral vasoconstriction at peak exercise and that may contribute to the development of their hypertension.

Aortic root dilation after the Ross procedure.

This study evaluated changes in neoaortic root geometry in patients who underwent the Ross procedure. Serial postoperative echocardiographic measurements of the neoaortic root indexed to the square root of body surface area (centimeters divided by meters) were obtained from 30 patients (age range 3.1 to 31.4 years) and compared with paired preoperative and immediate postoperative values. Normal aortic root diameter Z scores were derived from root dimensions obtained from 217 healthy controls. Compared with preoperative values, an immediate stretch of the neoaortic versus pulmonary root (annulus and sinuses of valsalva) was observed at a mean follow-up period of 1 week. Additional aortic annular dilation from baseline prehospital discharge values was observed at 2 to 12 months (baseline vs follow-up annulus Z score: 1.4 vs 2.6, p <0.01, n = 16) and at 16 to 33 months follow-up (0.8 vs 2.0, p <0.05, n = 12). In a similar fashion, there was additional enlargement of the aortic sinus from its stretched state at hospital discharge at 2 to 12 months (baseline vs follow-up sinus Z score: 2.0 vs 3.3, p <0.01, n = 17) and at 16 to 33 months (1.7 vs 3.0, p <0.01, n = 13). There were no differences in root size between 2 to 12 and 16 to 33 months after surgery. There was a decrease in left ventricular size with no alteration in blood pressure or degree of aortic valve regurgitation. Thus, aortic root dilation occurs up to the first year after the Ross procedure but does not appear to progress beyond this time.

The Role of Chronotropic Impairment During Exercise After the Mustard Operation

To better understand the role of chronotropic impairment on exercise performance after the atrial switch (Mustard) operation, 20 patients who had undergone this operation for uncomplicated d-transposition of the great arteries exercised to maximal volition using a 1 min incremental treadmill protocol. Heart rate, oxygen consumption, carbon dioxide production and minute ventilation were monitored continuously. Two-dimensional echocardiograms were obtained before testing to calculate the right ventricular inflow volume indexed to body surface area. All patients achieved maximal aerobic capacity based on their ventilatory patterns and respiratory exchange ratio. Maximal heart rate was reduced (175 beats/min; 87% of predicted for age) and maximal oxygen consumption was decreased (31 ml/kg per min; 75% of predicted for age and gender). There was no correlation between maximal oxygen consumption and maximal heart rate. Right ventricular volume index, however, had a significant inverse correlation with maximal heart rate (r = -0.62, p less than 0.005). There was no correlation between right ventricular volume index and heart rate at rest. These results suggest that decreased maximal oxygen consumption in patients after the Mustard procedure is not a result of chronotropic impairment. Right ventricular dilation may be a compensatory response to chronotropic impairment.

Enhanced resting left ventricular filling in patients with successful coarctation repair and exercise-induced hypertension

M-mode and Doppler echocardiographic analyses of left ventricular (LV) shortening and filling were performed in 50 patients who underwent coarctectomy (median follow-up 9.5 years) and in 16 athletes in a control group before an exercise stress test with upright bicycle ergometry was performed. Thirty-two of 50 patients and 18 of 50 patients had a normotensive and hypertensive response to exercise, respectively. Preexercise echocardiographic data were compared among the control, normotensive, and hypertensive patient groups. LV peak filling rates (dD/dt, diastole) were increased in the hypertensive group (18.3 +/- 3.5) compared with those in the normotensive group (14.4 +/- 3.2; p < 0.001) and the control group (13.6 +/- 2.8; p < 0.001). LV shortening was enhanced in the coarctectomy group compared with that in the control group. A higher aortic isthmus Doppler gradient at peak exercise was not found in the hypertensive group compared with that in the normotensive group. Therefore patients with successful coarctectomy in childhood have enhanced LV shortening and relaxation at rest. Demonstration of enhanced LV peak filling rates may help identify patients at risk for exercise-induced hypertension.

Pressure Recovery in Pediatric Aortic Valve Stenosis

This study was designed to evaluate the phenomenon of pressure recovery in pediatric patients with aortic stenosis and also to evaluate how observed differences between catheter and Doppler gradients can be predicted by Doppler echocardiography. Doppler measurements of aortic valve stenosis gradients are known to overestimate observed gradients in the catheterization laboratory. Pressure recovery has been shown to be a contributing factor to this discrepancy. However, the clinical relevance of correcting Doppler gradients using the pressure recovery equation has not been evaluated in the pediatric population. Simultaneously obtained catheter and Doppler gradients were studied in 14 patients (range, 0.03–18 years; mean, 4.1 years) with aortic valve stenosis. A total of 23 data points were measured because 9 patients underwent balloon valvuloplasty and had both a pre- and a post-balloon valvuloplasty data point in the study. The catheter gradients were then compared to peak, mean, and pressure recovery corrected Doppler gradients. Pressure recovery was calculated using a previously validated equation. As expected, measured echocardiographic continuous-wave peak Doppler gradients overestimated the observed catheter gradients (range, 16–93 mmHg; mean, 43 mmHg). The continuous-wave peak Doppler gradients, mean, and pressure recovery adjusted gradients were equally as good in correlating the observed catheter gradients to those obtained by Doppler echocardiography (r = 0.92). However, pressure recovery corrected Doppler gradients were in better agreement with catheter gradients than echocardiographic mean or peak Doppler gradients (95% limit of agreement: −9 to 19 mmHg for pressure recovery corrected gradients, −30 to 11 mmHg for mean Doppler gradients, and 2–83 mmHg for peak Doppler gradients). Measured continuous-wave peak Doppler gradients consistently overestimated catheter gradients. The noted differences may be predicted using the pressure recovery equation. Pressure recovery is a significant factor in children with aortic valve stenosis.

CT Artifact Mimicking Pulmonary Embolism in a Patient with Single Ventricle

A 16-year-old male with known tricuspid atresia-type IB, who had previously undergone a lateral tunnel Fontan palliation presenting with chest pain, was referred to our hospital with massive pulmonary embolism (PE) based on computed tomography (CT) scan findings of a filling defect in the area of the superior vena cava (SVC) and pulmonary arteries with a SVC clot (Fig. 1). The CT scan was performed on a two-slice Siemens/Emotion Duo Isovue 300 scanner with standard protocol for PE with deep vein thrombosis. At our hospital, the patient’s CT scan was reviewed by experienced pediatric radiologists who concurred with the findings. He underwent a cardiac catheterization that revealed normal Fontan hemodynamics. The angiograms revealed a widely patent lateral tunnel and SVC communication to the pulmonary arteries, with no filling defects within the SVC, lateral tunnel, or branch pulmonary arteries (Fig. 2). The distal pulmonary arteries and pulmonary venous return appeared normal. The patient was discharged the next day in stable clinical condition with a diagnosis of noncardiac chest pain. Fontan palliation is a multiple-stage surgical reconstruction culminating in diversion of systemic venous return to the pulmonary arteries, which is performed in the setting of single ventricle physiology. Central venous (3%– 16%) and intracardiac (17%–20%) thromboses are a major cause of morbidity and mortality after Fontan palliation (both early and late) [1]. Low-velocity and nonlaminar flow patterns in the Fontan circuit, atrial arrhythmias, abnormal liver functions, protein-losing enteropathy, and coagulation abnormalities have been described as etiologic factors causing thromboembolism [2]. Until recently pulmonary angiography has been the ‘‘gold standard’’ for diagnosing PE, but it is not readily available, is invasive, and delivers a high radiation dose. CT is evolving as the test of choice for diagnosing PE. Single-slice CT exceeds 95% sensitivity and specificity for detection of emboli in the main, lobar, and segmental pulmonary arteries; however, it is unable to reliably detect emboli limited to subsegmental or smaller vessels [3]. Multidetector (MD) CT has improved the sensitivity and specificity of detection not only of PE, but also of indirect signs of detection of PE and alternative diagnoses; MDCT has also reduced acquisition times, reduced respiratory and cardiac motion artifacts, and is noninvasive. In one study MDCT had an accuracy of 91% in the depiction of suspected acute PE when conventional pulmonary angiography was used as the reference standard [4]. The factors leading to misdiagnosis of PE on a CT scan include patientrelated, technical, anatomical, and pathologic factors [5]. Gadolium-enhanced magnetic resonance angiography is a noninvasive technique that involves no ionizing or iodinated contrast agent and has a good sensitivity and specificity to provide the correct diagnosis [3]. This case illustrates that the sluggish, nonpulsatile, lowvelocity blood flow seen in the Fontan circuit can cause misdiagnosis of PE on a CT scan. In the setting of a single ventricle physiology, MDCT, with particular attention to optimizing scanning technique, contrast injections, and understanding the physiology and anatomy, can be diagnostic. However, there have been no data available suggesting that MDCT protocols need to be revised for patients with sluggish, low-velocity blood flow as seen in the Fontan circuit. If these modalities are unavailable, H. R. Singh (&) T. J. Forbes R. A. Humes Division of Cardiology, The Carman and Ann Adams Department of Pediatrics, Children’s Hospital of Michigan, Wayne State University School of Medicine, 3901 Beaubien Street, Detroit, MI 48201, USA e-mail: hsingh6@dmc.org