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Commentary |
1 Department of Radiology, JT N370, University of Alabama Hospitals, 619 South 19th St., Birmingham, AL 35233.
Received November 2, 2005; accepted after revision November 11, 2005.
Each month the American Journal of Roentgenology will republish
online one of the 100 most-cited articles from its first century. A
corresponding commentary in the print journal by a contemporary radiologist
will provide a current perspective. For a full list of these articles, see
page 3 of the January 2006 issue of the AJR or go to
www.ajronline.org.
Keywords: cardiac imaging • contrast media • MRI
The article "Visualization of the Chambers of the Heart, the Pulmonary Circulation, and the Great Blood Vessels in Man" by George P. Robb and Israel Steinberg in the January 1939 issue of AJR [1] is a true classic and considered a landmark publication in the evolution of cardiac imaging. Because many readers of this commentary on the article may not be aware of the status of the radiology at the time the article was written, a few words about that era will be helpful in realizing the significance and implications of the article's findings.
By the early 1930s, when Robb was an associate in internal medicine at Harvard University, the science of radiology was modestly advanced. Contrast roentgenography of the gastrointestinal tract, urinary tract, gallbladder, and bronchial tree was established. Lipiodol (iodized oil, Guerbet) was invented, and myelography and pneumoencephalography were not rare. Peripheral arteriography was introduced by Dos Santos et al. [2] after the success of carotid arteriography by Moniz [3] in 1927. Werner Forssmann [4] had succeeded in passing a rubber ureteric catheter through his own upper extremity vein into the right atrium (1929), and he also performed pulmonary angiography in animals (1931) [5]; however, attempts at injection of contrast media through such rubber catheters to show cardiovascular structures were unsuccessful. Angiography through direct puncture of the cardiac chambers and aorta in 1935 [6] and catheter aortography showing coronary arteries in animals in 1933 [7] were attempted, but none was a practical clinical technique.
Any attempt at performing cardiac angiography in humans was limited by the available choice of contrast media (safety and comfort limiting the volume needed to overcome the effects of dilution); injectors (to inject contrast medium fast enough to maintain adequate bolus); and filming devices (to time accurately the filming or obtain more than one view). Robb trained in the laboratories of Herman Blum gart and Soma Weiss at Harvard University in the methods of determining circulation time, first by indicator dyes and later from clinical signs after venous injection of chemicals. They developed and perfected measurement of arm vein to pulmonary circulation time after IV injection of ether [8] and arm to carotid sinus circulation time after injection of cyanide solution [9]. Robb subsequently moved to New York, where he met one of his former residents, Israel Steinberg, who was working in the radiology department at Bellevue Hospital. In 1936, the two began animal experiments in visualizing cardiac chambers via venous injections of contrast media.
Unknown to them, Augustin Castellanos, a pediatrician in Havana, Cuba, also had similar ideas about cardiac angiography and faced similar problems when studying adult patients. He had better luck in achieving satisfactory opacification of the right heart chambers through IV injections in children with congenital heart disease because of the smaller size of his subjects. Castellanos et al. presented their findings about cardiac angiography of interventricular communications and pulmonary stenosis to the Havana Society for Clinical Research in 1937 [10].
The method used by Robb and Steinberg in adults consisted of two essential parts: "the injection of enough radiopaque substance into the blood entering the heart to make the chambers and important thoracic blood vessels opaque to the roentgen ray during the first circulation; and the making of the roentgenograms of these structures at the time of maximum opacification" [1]. The innovations that overcame the previous inability to visualize the cardiac chambers and great vessels in the adults included "[use of] 70% solution of Diodrast [iodopyracet, Winthrop], adequate dosage, rapid IV injection, accurate determination of the time for exposure, and proper positioning during roentgenography" [1]. The manuscript is elegantly written, with great attention to even minute procedural detail: "The stopcock with the needle attached is grasped in the right hand between the index and middle fingers in front and the thumb behind" [1].The degree of rotation for each oblique position, determined by fluoroscopy, was measured with an angle meter or a revolving stool designed for this procedure. After loading the syringe used for injection with warmed 70% Diodrast, approximately 20 mL of blood was slowly withdrawn into the syringe, forming a layer above the Diodrast column. When the entire volume of liquid in the syringe was injected rapidly while the patient was inhaling (to reduce the intrathoracic pressure, facilitating rapid injection), the column of the blood above the contrast medium acted as the modern-day saline flush. The exposures were made 1-2 sec less than the measured ether time for visualization of the right heart and cyanide time for the left ventricle and the ascending aorta. The pulmonary circulation was visualized in 75 of 79 attempts, and one or both ventricular chambers were visualized in 68 of 76 attempts for "cardiac study."
These results were first presented to the Section on Pharmacology and Therapeutics at the 89th annual session of the American Medical Association in June 1938, and a few weeks later at the 39th annual meeting of ARRS in Atlantic City, New Jersey. The dramatic nature of the findings was so startling that many of the physicians attending the meetings were unconvinced. Steinberg's wife, sitting among them as a spectator, heard many annoyed remarks from the neighboring audience: "This is not true. They are lying" [11].
Undoubtedly, Robb and Steinberg showed the feasibility and safety of contrast visualization of cardiac chambers and thoracic vessels. With great prescience they also described the technical improvements that could be made to their technique—all of which have come to pass, culminating in modern-day cardiac imaging. Those improvements include: (1) synchronization of heartbeat and radiographic exposure—ECG-gated imaging techniques including earlier superimposition of ECG tracing on cine angiograms and more recent nuclear cardiologic techniques, cardiac MRI, and MDCT; (2) cardiac measurement and mensuration—manual and computer-aided techniques; (3) rapid serial roentgenography or cineroentgenography—rapid film changers [12] and cineangiography [13]; (4) simultaneous roentgenography in frontal and lateral projections and volumetric measurements—biplane radiography [14], biplane cineangiography [15], and 3D imaging; (5) safer contrast media—ameliorating adverse effects, and allowing use of larger volumes; (6) newer contrast agents including low and isoosmolar agents; (7) simplification of injection techniques, achieved by catheter angiography [16, 17], and pressure injectors [10, 18].
When one studies the evolution of cardiac imaging from 1939, the developments concentrated on superior visualization of the chambers and vessels by selective angiography (achieved by antegrade [17, 19] and retrograde [20] catheter techniques) and rapid filming. For several decades, IV angiocardiography was forsaken, eclipsed by selective catheter angiography. This began changing slowly with the advent of digital subtraction angiography, pioneered by researchers in the 1970s [21, 22]. This technique was used primarily to visualize arterial structures after IV contrast material injection. Its application to cardiac imaging did not gain popularity because echocardiography and nuclear cardiology made noninvasive imaging of the cardiac chambers practical, and IV digital subtraction angiography was not suitable for coronary artery imaging. However, the advent of cardiac MRI and MDCT has completed the circle, rejuvenating the concept of cardiac (and even coronary artery) imaging after IV injection of contrast agents. It is fascinating to note the similarities between the Robb and Steinberg techniques and modern coronary CT angiography using MDCT: use of large volumes of contrast medium, rapid IV injection complemented by saline flush, determination of timing of the initiation of the scan, multiplanar imaging achieved by 3D image reconstruction. The limitations faced by those investigators nearly seven decades ago, attaining sufficient concentration of contrast medium and accurate timing of the image acquisition, remain the same.
In 1939, Robb and Steinberg stated, "Visualization of the chambers of the heart, pulmonary circulation, and the great vessels in man is safe and practical. It opens up a new field for the study of the anatomy and the physiology of the circulation" [1]. Their pioneering work opened the frontiers of cardiac diagnosis and surgery. In the new millennium when cardiovascular disease accounts for nearly half of the deaths in the developed world, the combination of the same techniques and the power of computers is beginning to offer new possibilities for noninvasive cardiac imaging.
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