(Hellenic Journal of Cardiology) HJC ñ 341 Hell J Cardiol 46: 341-347, 2005 D ipyridamole (DIP) is a vasodilatory substance which is widely used to perform pharmacological stress tests, almost always in combination with oth- er imaging techniques, such as myocardial perfusion imaging (MPI) and, less common- ly, echocardiography. Pharmacological stress- ing is necessary when investigating patients who have a reduced capability to perform exer- cise. This may be either due to physical limi- tations, such as musculoskeletal or neuro- logical problems or poor general physical condition, or the result of drug therapy that prevents the attainment of an adequate dou- ble product with treadmill exercise, such as the use of ‚-adrenoceptor antagonists. The mechanism of action of DIP is via the blockade of cell membrane transport of adenosine, thus raising the extracellular le- vels of adenosine, which in turn raises cAMP levels and calcium uptake in coronary smooth muscle cells, leading to coronary vasodila- tion. 1,2 This dilation leads to a three- to five- fold increase in coronary blood flow in heal- thy coronary arteries with no stenoses or damaged endothelium. In abnormal arter- ies, the failure to dilate leads to increased vascular resistance of those vessels and pref- erential blood flow through the normally di- lated arteries. This heterogeneity of blood flow reserve causes relative ischaemia of the myocardium supplied by the stenosed or abnormal coronary arteries and is referred to as coronary steal. 2-5 One of the advanta- ges of DIP is that it does not cause tachycar- dia and has no positive inotropic effects; thus it has no significant effect on myocar- dial oxygen demand and consumption. 2,3 The relative ischaemia induced by DIP is usually clinically silent. However, on occa- sion, it may be expressed clinically as angina pectoris or as ST segment depression on the patient’s electrocardiogram, as has been not- ed in 6-34% of patients undergoing DIP phar- macological stressing. 6 The aim of this review is to examine the significance of DIP-induced ST segment de- pression and to explore its possible diagnos- tic and prognostic implications. What is the significance of ST depression after DIP infusion in the investigation of patients with suspected or known coronary artery disease? The relative ischaemia caused by DIP, as mentioned previously, is due to the devel- opment of myocardial flow heterogeneity and coronary steal. The phenomenon of coronary steal occurs when coronary flow to a stenosed artery is preferentially diverted upon vasodilator administration, via collat- eral vessels that supply that particular terri- tory, to a territory supplied by the artery from which the collaterals have originated. This is due to the fall in resistance in the non-ste- ST Changes in Dipyridamole Pharmacological Stress Testing: Do They Have Diagnostic or Prognostic Significance? ATHANASSIOS ANTONOPOULOS 1 , KALLIOPI GALANOPOULOU 2 1 Department of Cardiology, 7 th IKA Hospital, 2 Department of Cardiology, 1 st IKA Hospital, Athens, Greece Manuscript received: December 17, 2004; Accepted: May 17, 2005. Address: Athanassios Antonopoulos 59 Alexandras Avenue, 11474 Athens, Greece e-mail: a-anton@otenet.gr Key words: Dipyridamole, ST depression, prognosis, diagnosis. Review Article Review Article