Effect of nifedipine on dipyridamole thallium-201 myocardial scintigraphy.

The effect of a calcium antagonist drug, nifedipine, on dipyridamole thallium-201 images was assessed in 10 angina patients with positive dipyridamole test. Two dipyridamole thallium-201 tests were performed, the first in basal conditions, the second after administration of 20 mg nifedipine. After dipyridamole, heart rate and double product increased respectively from 68.0 +/- 8.2 to 94.7 +/- 11.5 beats/min (p less than 0.01) and from 9459.5 +/- 1800.2 to 12,770.0 +/- 1864.7 mmHg X beats/min (p less than 0.01). Dipyridamole when infused after nifedipine induced an increase in heart rate from 74.2 +/- 7.16 to 88.8 +/- 5.6 beats/min (p less than 0.01) and in double product from 9650.5 +/- 1348.0 to 11,399.0 +/- 1146 mmHg X beats/min (p less than 0.05). Systolic and diastolic blood pressures were unmodified during the two studies. Segment scores were comparable before and after nifedipine. Thus, nifedipine does not worsen thallium-201 myocardial images obtained during dipyridamole infusion, therefore, this test could provide an alternative to exercise thallium-201 in patients receiving calcium antagonist drugs.