SIGNIFICANCE OF DIPYRIDAMOLE-INDUCED TRANSIENT DILATION OF THE LEFT-VENTRICLE DURING TL-201 SCINTIGRAPHY IN SUSPECTED CORONARY-ARTERY DISEASE

The occurrence and significance of transient dilation of the left ventricle during dipyridamole stress-redistribution thallium-201 scintigraphy was studied in 73 patients who underwent both dipyridamole thallium-201 study and coronary angiography. Transient dilation ratio was calculated from planar anterior images by dividing the computer-derived left ventricular area on the initial image by that of the 4-hour image. In 11 patients with normal coronary arteriograms or <50% coronary stenosis, the transient dilation ratio was 0.98 ± 0.046. An abnormal transient dilation ratio was defined as ≥1.12, representing ≥3 standard deviations above the mean normal value. When the 15 patients with an abnormal ratio were compared with the 58 with a normal ratio, the former group had a significantly higher frequency of 3 critical (≥90%) coronary stenoses (33 vs 5%), higher prevalence of collaterals (67 vs 24%), more extensive myocardial reversible defects by planar (71 vs 10%) or by single-photon emission computed tomography (87.5 vs 35%) imaging and a higher incidence of dipyridamole-induced anginal chest pain (53 vs 22%). No significant difference between the 2 groups was noted with respect to age, gender, prior myocardial infarction, single or double critical coronary stenosis, dipyridamole-induced ischemic electrocardiographic response and increased lung uptake. An abnormal transient dilation ratio of ≥1.12 was a specific marker of multivessel (87%) or 3-vessel (85%) critical coronary artery disease. Left ventricular transient dilation observed during dipyridamole thallium-201 scintigraphy is a marker of extensive myocardial ischemia caused by under-lying extensive critical coronary stenosis and thus may be termed "transient ischemic dilation.". © 1990.