Scintiangiocardiography in children. Rapid sequence visualization of the heart and great vessels after intravenous injection of radionuclide

Radionuclide angiography: as diagnostic method for Wilms' tumor with direct extension into the heart

Radioisotope angiography may be used as an initial study in Wilms' tumor. We report a patient who had a total nephrectomy but then had severe cardiovascular complications. These led to open heart surgery and removal of a tumor lodged in the right atrium. Radioisotope angiography, performed two weeks earlier, showed a "cold" image on the anterior wall of the right ventricle. This finding was later confirmed by other studies and finally at the time of a second operation. The purpose of this paper is to discuss the different methods employed in this case, to emphasize the risks attributed to each, and finally to suggest the use of non-invasive studies such as radioisotope angiography as a practical method of study in infancy.

Radionuclide quantitation of right-to-left intracardiac shunts in children

A simple, noninvasive method for measurement of right-to-left intracardiac shunts would enhance the management of patients with congenital heart disease. This study describes application of data processing techniques used previously in dye-indicator curves to data recorded during the initial transit of radioactive bolus through the central circulation. Radionuclide angiocardiograms were performed in 20 children, mean age 30 months, immediately after cardiac catheterization for congenital heart disease. The radionuclide data recorded over the carotid artery were used to replace arterial sampling required for dye indicators, and forward triangles were fitted to calculate the right-to-left shunt in an approach similar to that of Wood for indicator-dilution curves. Ten of the children had right-to-left shunts by Fick and radionuclide measurement, and 10 of the children with septal defects had no right-to-left shunt by either technique. Both the radionuclide and Fick measurements correlated well (r = 0.95). Therefore, radionuclide angiocardiographic data may be used for accurate calculation of right-to-left shunts in small children, eliminating the need for arterial sampling.

Radionuclide angiography in congenital heart disease

Cardiac nuclear imaging (radionuclide angiography, electrocardiographic gated ventriculography and myocardial scintigraphy) provides structural and functional information simultaneously. This method extracts accurate quantitation of cardiovascular hemodynamics and unique information regarding myocardial perfusion. It is a reliable and relatively simple and atraumatic technique because the only discomfort to the patient is a simple intravenous injection. These studies are carried out rapidly in out- or inpatients. Radionuclide angiography is ideal also to assess the effect of exercise, oxygen or drugs on cardiac function. The radiation exposure associated with current nuclear imaging is within the range of common radiographic procedures and many times lower than that of cardiac catheterization. The use of newer radionuclides such as iridium-191m with a physical half-life of 4.96 seconds will result in a dramatic decrease in the radiation exposure to patients undergoing radionuclide angiography. Also, newer and smaller computerized gamma cameras will provide studies of improved spatial resolution and accuracy. The future of pediatric applications of cardiac nuclear imaging is bright.

Quantitative radionuclide angiocardiography

This study introduces a new method for calculating actual left ventricular volumes and cardiac output from data recorded during a single transit of a radionuclide bolus through the heart, and describes in detail current radionuclide angiocardiography methodology. A group of 64 healthy adults with a wide age range were studied to define the normal range of hemodynamic parameters determined by the technique. The normal radionuclide cardiac index averaged 3.25 +/- 0.75 liters/min/m2, the end-diastolic volume index was 62 +/- 16 ml/m2, the stroke volume index was 40 +/- 9 ml/m2, and the ejection fraction was 0.66 +/- 0.07. Radionuclide angiocardiograms were performed in patients undergoing cardiac catheterization to validate the measurements. In 33 patients studied by both techniques on the same day, a close correlation was documented for measurement of ejection fraction (r = 0.89) and end-diastolic volume (r = 0.89). Determination of the linear regression equation for the end-diastolic volumes obtained by the two methods (EDVcath = 1.26 x EDVRN - 7.56) permitted correction of end-diastolic volume and provided an approach for calculation of stroke volume and cardiac output. To validate the method of volumetric cardiac output calculation, 33 simultaneous radionuclide and indocyanine green dye determinations of cardiac output were performed in 18 normal young adults and correlated closely over a range of 4-17 liters/min (r = 0.94). These independent comparisons of radionuclide measurements with two separate methods document that initial transit radionuclide angiocardiography accurately assesses left ventricular function.

Detection and quantitation of cardiovascular shunts with commonly available radionuclides

Detection and quantitation of shunts can be done accurately, rapidly, and safely using radionuclide techniques. The most frequent use of radionuclides in the evaluation of shunts is first-pass radionuclide angiography for the detection and quantitation of left-to-right shunts. Thallium-201 myocardial scintigraphy is useful in the evaluation of right ventricular overload secondary to left-to-right shunting. Radionuclide angiography has applications for premature and newborn infants with patent ductus arteriosus and respiratory distress, older children with unexplained heart murmur, and in the postoperative evaluation of patients undergoing cardiovascular surgery.

First-pass radionuclide assessment of right and left ventricular performance in patients with cardiac and pulmonary disease

First-pass radionuclide angiocardiography allows noninvasive determination of right and left ventricular performance from a single study. Analysis is made from the high frequency components of the regional radionuclide time-activity curves. Both regional and global ventricular performance can be assessed at rest and during exercise. Sequential studies can be performed to evaluate therapeutic interventions. This technique has been applied in a broad spectrum of patients with cardiac and pulmonary disease and has been shown to have major clinical impact.

Qualitative radionuclide angiocardiography in the diagnosis of corrected transposition

Seven patients with corrected transposition were studied by qualitative radionuclide angiocardiography. In four patients with situs solitus with apex on the left, the pulmonary artery was in a medial and posterior position, to the right of the aorta, with its root attached to the morphological left ventricle positioned on the right. The aorta arose from the ventricle placed on the left and had an anterior position. The ventricle located on the right has a triangular shape. In the case of situs solitus with dextroversion, the pulmonary artery was to the right of the aorta and had a right-to-left direction. The ventricle placed on the right was ovoid. In one single case of situs inversus with levoversion, the pulmonary artery was on the left, emerging from the morphological left ventricle placed on the left, and was ovoid in shape, while the aorta was on the right arising from the morphological right ventricle. In one case of situs inversus with dextrocardia, atrioventricular relationships were the same as in levoversion but the apex was on the right and the morphological left ventricle was triangular. Qualitative radionuclide angiocardiography is a simple and non-invasive method for obtaining morphological data for the precise diagnosis of corrected transposition.

Noninvasive detection and quantification of left-to-right shunts in children using oxygen-15 labeled carbon dioxide

A method for the detection and quantification of left-to-right intracardiac shunts is described which utilizes a single breath inhalation of oxygen-15 labeled carbon dioxide (C15O2). The inhaled gas rapidly crosses the alveolar membrane and the oxygen-15 label is exchanged through the carbonate cycle to form oxygen-15 labeled water within the pulmonary capillary blood. Pulmonary indicator clearance curves are measured by external scintillation probes. A simplified method of shunt flow quantification was developed from indicator dilution principles and used for the analysis of the clearance curves. Inhalation studies were performed with 62 children on the day prior to cardiac catheterization. The presence or absence of left-to-right shunt was confirmed by contrast angiography in all cases. Twenty-six children were found to have no shunts by C15O2 inhalation, oximetry or angiography. Of the 36 with shunts, 34 were detected by C15O2. Two of these were designated as equivocal because they were considered to be less than the threshold of definitive detection by C15O2 (having Qp/Qs less than 1.2); 32 were positive and there were two false negatives with small ventricular septal defects. There were no false positives by C15O2. The correlation coefficient between C15O2 and oximetry values of shunt flow for those patients with proven shunts was 0.82.

Radionuclide angiocardiographic measurement of left ventricular volume and ejection fraction

In recent years a number of different radionuclidic techniques have been developed to measure left ventricular volume and ejection fraction. Area-measurement concepts have been applied to static and electrocardiographically gated radionuclidic images which have resulted in accurate measurement of left ventricular end-diastolic volume (LVEDV) and ejection fraction (LVEF). Gated (end-diastolic and end-systolic) image analysis has also proven capable of detecting regional left ventricular wallmotion abnormalities in patients with coronary disease. Time-activity curves can be extracted from left ventricular images, and several dynamic techniques have been developed and have also resulted in accurate measurement of LVEDV and LVEF. Radionuclide methods are currently available which are accurate and atraumatic and consequently applicable to the serial study of patients with heart disease. In particular, several of these radionuclide methods are relatively inexpensive and should be able to be performed in most hospitals.

Nontraumatic determination of left ventricular ejection fraction by radionuclide angiocardiography

Previous reports have suggested that left ventricular ejection fraction can be assessed by recording the passage of peripherally administered radioactive bolus through the heart. The accuracy and validity of this technique were examined in 20 patients undergoing diagnostic cardiac catheterization. 99m-Tc-human serum albumin was injected via a central venous catheter into the superior vena cava and precordial activity recorded with a gamma scintillation camera interfaced to a small digital computer. A computer program was designed to generate time-activity curves from the left ventricular blood pool and to calculate left ventricular ejection fractions from the cyclic fluctuations of the left ventricular time-activity curve which correspond to left ventricular volume changes during each cardiac cycle. The results correlated well with those obtained by biplane cineangiocardiography (r equals 0.94) and indicated that the technique should allow accurate and reproducible determination of left ventricular ejection fraction. The findings, however, demonstrated that the time-activity curve must be generated from a region-of-interest which fits the left ventricular blood pool precisely and must be corrected for contributions arising from noncardiac background structures. This nontraumatic and potentially noninvasive technique appears particularly useful for serial evaluation of the acutely ill patient and for follow-up studies in nonhospitalized patients.

Quantitation of left-to-right cardiac shunts with radionuclide angiography

A quantitative radionuclide angiogram technique using an intravenous injection of technetium-99m (Tc-99m) pertechnetate is described for quantitation of left-to-right shunts in the central circulation. Data analysis assumes exponential indicator clearance from normal cardiac chambers by dilution. A late prolongation of tracer disappearance compared to the initial clearance rate indicates an abnormally early return of indicator to the cardiac chamber. Patients with left-to-right shunts demonstrate prolonged clearance of radioactivity from all cardiac chambers distal to the site of shunt. The magnitude of curve distortion is quantitatively related to the size of shunt, and counts recorded from the right lung are used for shunt quantitation. Quadratic regression analysis of data from 21 patients with left-to-right shunts and eight normal subjects demonstrated a correlation coefficient of 0.951 between measurements of left-to-right shunts by the radionuclide and by the Fick method. Observations on 14 patients with aortic or mitral valve disease revealed this method of shunt evaluation to be of limited value in the presence of severe cardiac valvular disease. However, the method permits detection of left-to-right shunts that are too small to be diagnosed by the Fick method and accurately quantitates shunts which are not at either extreme in size and flow. This technique appears to be potentially useful for the initial diagnosis and serial evaluation of patients with these disorders.

Pediatric radiocardioangiography. Shunt diagnosis

On the basis of a comparison of the shunt diagnoses in 73 radiocardioangiographic examinations with those from cardiac catheterization supplemented by operation and/or autopsy findings, it is shown that an intravenous injection of 99m technetium pertechnetate with subsequent evaluation using a scintillation camera and computerized regional time-activity curves is very accurate for the qualitative diagnosis of both left-to-right and right-to-left shunts down to the order of 1.2:1. The advantages of the method are: (1) it is quick (5-10 min for the patient, 20-30 min for the further processing and evaluation); (2) it is safe (extremely low radiation exposure enabling repeated examinations); (3) it is effortless for the patient (thus well suited for use in critically ill patients); and (4) it is applicable with the same accuracy in all age groups (including very young infants and neonates). Thus, the RCG is a promising method for ambulatory diagnosis of questionable heart disease, for the precatheterization workup, and for repeated follow-up studies, i.e. postoperative patients.

Further applications of scintillation scanning technics to the diagnosis and management of infants and children with congenital heart disease

Radionuclide angiography provides a reliable and extremely rapid technic for assessing the physiologic and pathologic features of cardiovascular malformations. Eighty-six infants and children and seven adults have been studied after intravenous infusion of 99m technetium with a scintillation camera coupled to a computer-tape storage system. Pulmonary vascular isotope-dilution curves detected the presence or absence of left-to-right intra- or extracardiac shunts with great sensitivity. Therefore, the method has especially widespread applicability in the distinction between organic and innocent heart murmurs, in the evaluation of postoperative patients, and in the assessment of the natural course of selected, specific malformations. Moreover, also without resorting to cardiac catheterization, scintillation scanning is capable of defining great artery orientation and position, cardiac chamber position, approximate chamber volumes, and the distribution of pulmonary arterial blood flow. The method described is technically simple, without known risk, is easily applicable to large numbers of patients, and provides clinically important information concerning many forms of congenital heart disease.

Determination of the site, extent, and significance of regional ventricular dysfunction during acute myocardial infarction

Infarct site, extent, and the degree of associated asynergy are major determinants of the hemodynamic consequences of myocardial infarction. Although conventional electrocardiography and vectorcardiography are routinely employed in assessing the location and size of infarction, they are relatively nonspecific. The newer techniques of high-frequency electrocardiography and isopotential mapping offer promise but have yet to undergo systematic evaluation. A rough measure of the extent of infarction is obtained from serum enzyme measurements. However, they furnish no information with regard to localization.

The region of infarction may be detected by precordial scanning following the intravenous or intracoronary injection of a radioisotope. The infarct may be revealed as an area of decreased perfusion (cold spot) or as an area to which a specific radioactive label is bound (hot spot). With the availability of newer radionuclides such as 43 potassium and the use of computer techniques, a more precise means of localizing and quantifying myocardial infarction may become available.

Optimal definition of asynergy is obtained with contrast angiography. However, the risk of this procedure has limited its use, to date, in acute myocardial infarction. Apex- and kinetocardiography, chest X-ray, and fluoroscopy often suggest regional ventricular dysfunction, but these techniques are not sufficiently specific. Newer noninvasive methods for objectively evaluating regional ventricular dysfunction are ECG-gated cardiac scintiphotography and radarkymography. With ECG-gated scintiphotography, end-diastolic and end-systolic cardiac isotope images are obtained following intravenous injection of 99m technetium-albumin. From these images, assessment of asynergy and extent and location of infarct can be made. With radarkymography, heart-wall motion is assessed and quantitated by tracking segments of the cardiac silhouette visualized on a cinefluorogram. These techniques are ideally suited to the acutely ill patient. Echocardiography is another noninvasive technique with potential application to the study of asynergy. However, at present, only posterior-wall motion can be measured.

At the time of surgery regions of infarction may be localized by means of chemical indicators (fluoroscein), isotope techniques, or epicardial electrocardiographic mapping. Recently much has been learned about the hemodynamics of myocardial infarction. Through the use of the techniques described, further insight into regional ventricular abnormality and extent and localization of myocardial infarction could be obtained. With this information better approaches to therapy and prognosis could be developed.

Many students of the coronary circulation must have noted that the ventricular zone affected by ligating a large coronary branch not only appears cyanotic and dilated, but that it seems to alter in its mode of contraction. The detailed and sequential changes in contraction are not easily followed by the unaided eye and so far have not been recorded myographically. The reasons for this were the lack of an adequate and suitable myograph and a technique for the application of one to a limited ventricular surface so that records obtained represent, at least reasonably well, changes in muscle length and not predominantly artifacts due to position changes, thrusts and vibrations of the vigorously beating ventricle. 1

Nuclear angiocardiography in the diagnosis of congenital heart disease in infants

Nuclear angiocardiography with a gamma camera, a pinhole collimator, and 99m Tc pertechnetate was performed on 43 children aged 3 years or less, including 10 neonates. Twenty-six children had congenital heart disease, which was confirmed at cardiac catheterization; the rest had no structural cardiac anomaly. Use of the pinhole collimator allowed magnification of cardiac images, with enhancement of resolution. Sensitivity was improved by positioning the pinhole 14 cm rather than 19 cm from the crystal of the gamma camera. Anterior and left lateral angiocardiograms were obtained with both 35-mm images at 0.3-sec intervals and cine-images at 18 frames/sec.

Abnormalities in origin, size, and position of the great arteries, in chamber configurations, and in the time and course of activity in right and left heart, lungs, and great vessels were used to assist in identification of anomalies such as transposition of the great arteries, pulmonary atresia with intact ventricular septum, truncus arteriosus, and aortic atresia. 99m Tc in a dose of 18.5 mCi/M 2 of body area was used and produced whole-body and gonadal radiation doses less than 1 rad. The low risk and simplicity of the technic make it promising as a screening procedure and as an adjunct to cardiac catheterization for cyanosed infants.