Yasumi Uchida, MD
274 pp. Armond, NY: Futura; 2001. $80.00. ISBN 0-87993-478-6
“Always the laws of light are the same, but the modes and degrees of seeing vary.”
— Henry David Thoreau
The impetus for the development of instrumentation that permitted visual inspection of structures within the heart in the early part of the 20th century was the hope of treating mitral stenosis without interrupting blood flow. Early cardioscopes consisted of a metal tube with lenses and a light bulb, which were similar in concept to the first endoscope used by Kussmal (Fribourg 1868) to examine the esophagus of a sword swallower. In some cardioscopes, a blade was incorporated for commissurotomy. Despite promising experimental studies, the first attempt to perform cardioscopy in a patient with mitral stenosis in 1926 was unsuccessful. The opacity of blood to light represented a major problem that led to numerous modifications, such as the use of saline injections and transparent balloons.
Displacement of blood within coronary arteries with a crystalloid solution is far simpler than within cardiac chambers. And dramatic improvements in the miniaturization of coherent fiberoptic bundles permitted placement of angioscopes within coronary vessels, as my colleagues, notably John Marais, and I demonstrated in the early 1980s. The potential for coupling laser plaque ablation to angioscopes thereafter generated considerable interest and perhaps peaked with the concept of computer-controlled on-line plaque recognition by spectral analysis and laser energy delivery through each member of a fiberoptic bundle. However, such “Star Wars” therapies did not prove practical clinically.
For nearly 2 decades, Dr Yasumi Uchida investigated the more realistic use of fiberscopes as diagnostic tools in cardiology. Within his newly published book, Coronary Angioscopy, many previously unpublished images obtained during hundreds of clinical procedures performed by the author are provided. In part I, “Clinical Application of Percutaneous Coronary Angioscopy,” which represents the majority of the book, there are 17 chapters ranging from the history of angioscopy to histological correlations and angioscopic classification of plaque and thrombus pathology. Just as a single cineframe cannot show the full potential of an angiogram, videoframes from an angioscopic procedure do not do justice to the wealth of information available in the videotape. Nevertheless, many of the angioscopic images are spectacular, and the range of coronary pathology covered will provide readers with an excellent resource on the subject.
Uchida and coworkers, as well as numerous other groups, have used angioscopy to provide unique insights into the pathophysiology of acute coronary syndromes and the response to interventional therapies. The images and their interpretation in Uchida’s book represent a basic observational approach that is necessary before posing rigorous hypotheses. Inspection of coronary pathology in living humans has confirmed post mortem studies, which determined the importance of thrombus in patients with unstable angina and acute myocardial infarction and the vulnerability of yellow plaques to rupture. Perhaps the real power of angioscopy is fully realized when dynamic changes in coronary pathology are observed over time. For example, in Chapter 9, angioscopy revealed the fine structure of the growth of fibrin strands superimposed on a small thrombus adjacent to the injured luminal surface. Such strands provide scaffolding for the incorporation of more erythrocytes and the propagation of thrombus growth. The interaction of flow patterns and devices such as guidewires and stents on thrombus formation is likewise revealed. Numerous other interesting observations, such as the disappearance of erythrocytes from small thrombi during saline flushes, leaving only white fibrin threads, are shown. After thrombolysis, a frosty glass-like appearance on the luminal surface may indicate the preexistence of a red, erythrocyte-rich thrombus.
The ability to visualize the pattern of uptake of vital dyes, such as Evans blue dye, by angioscopy, as shown by Uchida in various tissues, is another unique and useful aspect of the procedure. Evans blue has an affinity for fibrin and regions of increased endothelial permeability. As a result, otherwise unapparent injury to the endothelial lining layer during even simple passage of a guidewire is recognizable. A “cotton candy” appearance of a lesion is characteristic angioscopically of a fibrin-rich white thrombus, which is distinguished from white plaque after staining with Evans blue. In one patient, Evans blue dye staining of a yellow plaque was shown to be prevented by 6 months of treatment with a lipid-lowering agent. This single study demonstrates the potential utility of the use of vital dyes during angioscopy for studying the efficacy of medical therapy in stabilizing atheromatous plaques. Unfortunately, Evans blue, which was used many years ago for densitometric cardiac output measurements, was abandoned clinically in the United States in favor of indocyanine green because of the potential concern of the mutagenicity of diazo compounds. Thus, Uchida’s clinical observations with this dye are particularly valuable. Other agents, such as fluorescent porphyrins, might also be used to study lesion characteristics, such as the rapidity of plaque growth, but much basic work will be necessary before clinical utility can be realized.
Many angioscopic findings are likely to have important prognostic implications. In Chapter 12, for example, the occurrence rate of acute coronary syndromes in patients with glistening yellow plaques was much greater than that for patients with either white plaques and nonglistening yellow plaques. Other groups have confirmed the unstable nature of yellow plaques, as well as the poorer prognosis of patients in whom thrombus is present at the time of angioplasty.
Angioscopy is a more invasive procedure, of course, than angiography. It will be important, therefore, in future studies to show that this procedure improves patient outcome, whether by altering medical therapy or by guiding an intervention. The risk of complications in Uchida’s series is quite low (1.6%), but it is likely to be higher if used by less skilled interventionists. Continued miniaturization of the fiberoptic bundle will help reduce the small chance of mechanical injury, and other advances may enhance the information obtained. A disadvantage of this technique compared with intravascular ultrasound has been the lack of quantitative information obtained with angioscopy. As noted by Uchida, however, quantitative colorimetric analysis to aid discrimination of thrombus and plaque composition has recently been described by others. Moreover, with the use of a “lightwire,” which projects a ring of light onto the luminal surface, we demonstrated that angioscopy can be used to quantify luminal dimensions with greater precision than any other technique.
It is a testimony to Uchida’s extensive work with angioscopy that all images were obtained by the author and colleagues. Indeed, if the work of other groups had been included, in terms of images and their interpretation as well as technical considerations, a second volume would have been required. For readers seeking a comprehensive dissertation on coronary angioscopy, the relatively small fraction of the several hundred references on the subject cited or discussed in the book will probably not suffice.
In Part II of the book, cardioscopy systems used by the author and associates are described, and many interesting images are provided. For example, the potential use of cardioscopy to evaluate the adequacy of blood flow to the left ventricle by the color of trabeculae (eg, pale or white is consistent with a reduction in flow) is described. The cardioscopic appearance of the endocardial surface of the left ventricle in patients with various myocardial diseases (eg, myocarditis, endocardial fibroelastosis, amyloidosis) may likewise be informative. Detection of thrombi within the heart and pulmonary arteries represents another interesting application. However, the use of fiberscopes to distinguish internal compromise of luminal dimensions by chronic pulmonary emboli from extrinsic compression associated with other causes, as shown by Deborah Shure and her colleagues by their pioneering studies initiated in 1980, is not discussed. As for coronary angioscopy, whether the benefits of the information obtained outweigh the risk associated with cardioscopy (1% in Uchida’s laboratory) will require formal, long-term studies.
In summary, I highly recommend this interesting book for interventionists and those interested in coronary pathology. The technical advice regarding the performance of angioscopic procedures should be tempered by a knowledge of regulatory differences between countries.