Comparison of 3- versus 6-minute infusions of adenosine in thallium-201 myocardial perfusion imaging.

Adenosine thallium stress testing has a demonstrated utility in the detection of coronary artery disease. The optimal dose for diagnostic efficacy with minimal side effects has not been critically evaluated. A randomized 3- and 6-minute infusion of adenosine (140 micrograms/kg/min) was performed in 11 subjects. Subjects reported more side effects during the 6-minute infusion protocol (p < 0.05). Hemodynamic changes were not different during either infusion duration. All dysrhythmias began within 2 minutes and therefore the duration of the infusion did not influence their occurrence. Segmental comparison of the stress images demonstrated an 89% agreement. Delayed scans demonstrated a 79% agreement. There was a higher incidence of redistribution following the 6-minute infusion (p = 0.014). We conclude that when side effects necessitate the discontinuation of a 6-minute adenosine infusion, a diagnostic test can still be achieved if 2 to 3 minutes of adenosine have been administered before the thallium injection; however, the amount of viable myocardium may be underestimated.