We have used two prototype fiberoptic angioscopes to visualize the interior of the right heart and pulmonary arteries to aid in the detection and localization of chronic pulmonary emboli, a difficult disease to diagnose with standardly available imaging techniques. The initial prototype was shorter, wider, and had less distal flexibility than the newer prototype. The initial prototype was used in eight patients and the angioscopic examination led to a change in the diagnosis in four. It also allowed more accurate localization of chronic emboli which aided the surgical approach in five patients. Use of this instrument was limited, however, because its diameter was too large to always permit insertion through the external jugular vein. The newer prototype is both longer and narrower allowing access through either the external jugular or an antecubital (arm) vein. This instrument has been used in two patients. In the first access was gained through the antecubital route when the external jugular was found to be inadequate. This patient could not have undergone angioscopy with the earlier prototype. Both instruments achieve good visualization. The earlier prototype is easier to manipu-late through the right heart, but more difficult to guide through the branching pulmonary arteries; the newer prototype is more difficult to guide through the heart because of the stiffness of its bundle, but easier to manipulate through branching arteries because of the greater flexibility of its distal tip.
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