View metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Elsevier - Publisher Connector 120S JACC Vol. 5, No. 1 January 1985: 120S-7S Radionuclide Angiocardiography in Children S. T. TREVES, MD, JANE NEWBERGER, MD, ROGER HURWITZ, MD Boston, Massachusetts Clinical use of radiotracer techniques in pediatric car• radiation dose to the patient. The development of ul• diology is increasing. Three basic methods being em· trashort-lived radionuclides (such as iridium-191m with ployed are first pass radionuclide angiocardiography, a half-life of only 5 seconds), improvements in nuclear gated blood pool scanning and myocardial perfusion imaging instrumentation and numerical analysis should scintigraphy. These methods are rapid, safe and accu• contribute to a further utilization of these methods. rate. They are minimally invasive and result in a low (J Am Coil Cardiol1985,'5:120S-7S) Three radionuclide methods are being applied in the field fining certain venous abnormalities, such as vena caval ob• of pediatric cardiology. These are first pass radionuclide struction. There is great potential for further improvement angiocardiography, gated blood pool scanning and myo• of this technique, including the introduction of ultrashort• cardial perfusion scintigraphy. Over the past few years, lived radionuclides and advances in instrumentation. Ultra• there has been further progress and experience, both in the short-lived radionuclides, such as iridium-191m, render this technology and clinical applications of these radionuclide technique even safer because they result in a significant techniques in children. These methods provide information reduction in radiation absorbed dose to patients and permit on cardiovascular dynamics, intra- and extracardiac shunts, more convenient and precise interventional testing. Recent anatomy, myocardial function, myocardial perfusion and improvements of gamma camera design allow better spatial chamber size and output. As radionuclide methods are safe, resolution and improved performance at the high count rates accurate, rapid and minimally invasive, they continue to that occur in first pass radionuclide angiocardiography. gain acceptance among pediatric cardiologists. In this re• Detection and quantitation of shunts are probably the view, we will discuss the clinical applications and meth• most frequent indications for radionuclide angiocardiogra• odology of first pass radionuclide angiocardiography and phy in children. Results are accurate when compared with gated blood pool scanning in children. Myocardial imaging those from more invasive techniques, and are more con• is discussed elsewhere in this issue. sistent than results from most other noninvasive techniques. Radionuclide angiocardiography provides a means to ac• curately and serially monitor hemodynamic changes and can Radionuclide Angiocardiography help select those patients who need additional invasive pro• Clinical Applications cedures. In our institution, shunt quantitation by radio• nuclide angiocardiography has supplanted cardiac catheter• Radionuclide angiocardiography is performed in a few ization in the preoperative evaluation of some patients with minutes and it can be done on an outpatient basis or at the atrial septal defect. Other patients have been discharged bedside. It is a safe, accurate and relatively noninvasive from further cardiac care on the basis of radionuclide eval• method. Results are available within a few minutes after uation. Children ofall ages, including premature infants and the examination. children immediately after surgery, can be evaluated easily Quantitation of left to right shunting is highly reliable with these methods (2). by first pass radionuclide angiocardiography (I). This tech• Radionuclide angiocardiography is useful in the diag• nique also provides rapid and accurate estimation of right nosis of residual defects or patch detachment, as in atrial and left ventricular ejection fraction and may assist in de- septal defect, ventricular septal defect or patent ductus ar• teriosus. After the Mustard operation, radionuclide angio• From the Children's Hospital, Harvard Medical School, Boston, cardiography shows a characteristic pattern in the absence Massachusetts. of defects. This technique can detect residual defects, vena Address for reprints: S. T. Treves, MD, Director, Division of Nuclear Medicine, Children's Hospital, Harvard Medical School, 300 Longwood caval obstruction and collateral circulation and also can Avenue, Boston, Massachusetts 02115. measure ventricular performance (3). © 1985 by the American College of Cardiology 0735-1097/85/$3.30 JACC Vol. 5, NO.1 TREVES ET AL. 121S January 1985:120S-7S RADIONUCLIDE ANGIOGRAPHY Recently, we used first pass radionuclide angiocardiog• effect of adriamycin and other chemotherapeutic agents on raphy after the arterial switch operation in children with cardiac function is also being studied with this technique. transposition of the great vessels. In such patients, radio• nuclide angiocardiography is useful in demonstrating right Methods and left ventricular function, myocardial perfusion and the Radiopharmaceuticals. Technetium-99m. Technetium• presence of shunts. In some of these patients, radionuclide 99m as sodium pertechnetate is the most commonly em• angiocardiography demonstrates nearly normal features. In ployed radiotracer in first pass radionuclide angiocardiog• others, myocardial ischemia, infarction and ventricular dys• raphy. It has a physical half-life of 6 hours, and during its function can be detected. decay emits a gamma ray of 140 keY. Intravascular indi• Measurement ofleft to right shunting in premature infants cators, such as technetium-99m labeled to human serum with patent ductus arteriosus can be made while the patient albumin or to red blood cells, are used if the first pass study is in the neonatal intensive care unit using mobile equip• is performed just before a gated blood pool scan. Any other ment, and can be accomplished without interrupting their technetium-99m-Iabeled radiopharmaceutical (except rna• care. In these small infants, it is possible to diagnose spon• croaggregated albumin) may be used for this study provided taneous medical or surgical ductal closure. Radionuclide that the administered activity is adequate. Technetium-99m angiocardiography can also be used in these patients after diethylenetriamine pentaacetic acid (DTPA) may be used to surgery to detect additional, previously undiagnosed left to reduce body background in serial studies. The usual dose right shunts or surgical failure (4,5). of technetium-99m for first pass radionuclide angiocardiog• We have found that iridium-191m radionuclide angio• raphy is 200 /Lei/kg body weight, with a minimal dose of cardiography can be used reliably in the detection of left to 2 to 3 mCL The radiotracer must be in a volume of 1 ml right shunting in infants. In nine such patients, there was or less to permit the intravenous administration of a rapid good agreement in the measurement of left to right shunting and compact bolus. The whole body radiation absorbed dose with catheterization and iridium-191 m angiocardiography for technetium-99m pertechnetate ranges from 0.110 rad in (r= 0.90) (6). infants to 0.182 rad in adults. The target organ (the organ Patients with ventricular septal defects and pulmonary receiving the most radiation) in the case of pertechnetate is hypertension can also be evaluated with first pass radio• the bowel, with an absorbed dose ranging from 1.3 rads in nuclide angiocardiography to help assess their suitability for infants to 2.8 rads in adult patients (5). surgery. Studies are performed first with the patient breath• Iridium-191m. In recent years, we introduced iridium• ing room air, and again after breathing an athmosphere rich 191m, a tracer with a physical half-life of only 5 seconds, in oxygen. Increasing left to right shunt flow after breathing for first pass radionuclide angiocardiography (11). This ra• oxygen indicates pulmonary vascular reactivity and, if of diotracer is produced from an osmium-191~ iridium-191m sufficient magnitude, suggests that the patient is a candidate radionuclide generator. Osmium-191, the parent radio• for surgical correction. Unchanged left to right shunting nuclide, has a physical half-life of 16 days. The radionuclide after breathing oxygen suggests fixed changes in the pul• generator can deliver multiple doses of iridium-191 m for 1 monary vasculature and a less favorable prognosis if the to 2 weeks. Advantages of iridium-191 m include a very low ventricular septal defect is closed (7). radiation absorbed dose to patients, the capacity for repeated Adult patients with a clinical question of left to right studies within a short interval with negligible background shunting through an atrial septal defect may be evaluated radiation and the ability to administer greater amounts of with first pass radionuclide angiocardiography. Some of activity than with technetium-99m. This radiotracer has been these patients are asymptomatic, and a heart murmur is used in detection and quantitation of shunts, estimation of discovered on a routine physical examination. Other patients right and left ventricular ejection fraction and venography. in this group present with increasing dyspnea with excercise. We used iridium-191m to examine more than 150 patients In most cases, the diagnosis of left to right shunting or its ranging from premature infants to patients 60 years of age. absence can be