The etiology and implications of dense cavitary "photopenia" on myocardial perfusion scintigraphy.

Dense cavitary ''photopenia'' was observed on 21 of 200 consecutive stress perfusion scintigrams. A prominent finding in many cases, it sometimes occupied only a portion of the region overlying the ventricular cavity, was often seen in some projections and not others, and was frequently adjacent to myocardial perfusion defects. To distinguish an etiology among reduced cavitary radioactivity, relatively increased background radioactivity, or reduced radioactivity in overlying myocardium, quantitative analysis of cavitary, lung and myocardial radioactivity was performed in patients with dense cavitary ''photopenia,'' with and without lung uptake, and compared with results from studies showing increased lung uptake without cavitary photopenia and with normal studies. The results showed that dense cavitary photopenia was related to reduced radioactivity in overlying myocardium. Correlative imaging studies performed with echocardiography and contrast ventriculography confirmed this relationship to myocardial scar in 15 of 21 patients in whom associated akinesis or dyskinesis was seen. Hence, dense cavitary photopenia on stress perfusion scintigraphy is due to a dense myocardial perfusion abnormality, and is often indicative of related scar and an associated severe contraction abnormality.