Ottawa – A key drug used to perform tests on the heart is in low supply in Canada is in short supply. The antiplatelet medication, called dipyridamole, is used to artificially relax arteries in the heart and dilate blood vessels so doctors can monitor blood flow through the heart muscle during a stress test. It is used on those who cannot exercise for the test due to mobility challenges, or those who have cardiovascular problems. The tests are also known as myocardial perfusion scans. So this meaning patients will have to wait a bit longer to see if they have heart problem.