Segmental Arteriography in Pulmonary Embolism

FOR THE PAST several years we have pursued with vigor the arteriographic investigation of pulmonary emboli and have chanced upon a number of features not previously described or poorly documented. Demonstration of these features is largely attributable to the use of segmental pulmonary injections, as well as the sometime application of bronchial arteriography, in the study of embolism. Arteriographic manifestations of pulmonary embolism include arterial occlusions, stenoses, and filling defects (5). Indirect signs such as slowed flow and regional disparities in vascularity are associated but less reliable findings. These manifestations are readily apparent when emboli involve major pulmonary branches. However, embolic involvement of small pulmonary branches, 0.5 to several millimeters in diameter, usually occurs in pulmonary embolism (11). Indeed, emboli may be lodged exclusively in such small branches. These emboli cause the same fundamental arteriographic manifestations as large vessel emboli, but segmental arteriography is required for precise demonstration. Furthermore, segmental injections may demonstrate embolic sequelae which have otherwise escaped in vivo detection. Technic Segmental arteriography refers to the selective injection of contrast medium into pulmonary branches which supply a pulmonary segment or lobe. These injections might also be termed super-selective or subwedge, but the immodesty of the former term and the inaccuracy of the latter prompt acceptance of “segmental” as the preferred designation. Although pulmonary arteriography is one of the oldest angiographic procedures, the technic has not kept pace with angiographic developments elsewhere in the body. While selectivity is pursued in catheterizing most vessels, it seems to be generally assumed that adequate pulmonary arteriograms may be obtained with main pulmonary artery injections. Although such injections offer a decided improvement over the intravenous route, main pulmonary artery injections do not provide clear visualization of small peripheral vessels because: (a) there is marked dilution of contrast medium during cardiac systole, (b) there is obscuration of detail by overlapping of vessels, and (c) blood flow is diverted from areas of emboli. Segmental arteriography overcomes these disadvantages. Of singular importance, it enables diversion of contrast medium into, rather than away from, areas of greatest embolic obstruction. Our technic routinely incorporates segmental arteriography and is performed in the following manner. A large woven nylon side-hole catheter, usually a No. 8 Eppendorf,3 is passed via antecubital cut-down into the pulmonary artery, and pulmonary artery pressure is recorded. If the pressure is not markedly elevated,40–50 ml of 75 per cent Hypaque or equivalent is injected at the rate of 25 ml per second, and serial anteroposterior films of the chest are obtained.