Optimal duration of adenosine infusion for the assessment of coronary flow reserve

Background: Adenosine intravenous infusion is used to evaluate Coronary Flow Reserve (CFR) in patients with coronary artery disease. However, the proposed duration of adenosine infusion ranges from 90 seconds to 5 minutes. Therefore the optimal duration of Adenosine infusion to obtain maximal vasodilator effect still remains uncertain. Aim: Purpose of this study was to define the optimal duration of adenosine intravenous (iv) infusion to elicit maximal coronary hyperemic effect. Materials and Methods: We consecutively enrolled 101 patients between June 2009 and May 2011. The mean age was 53±11 years (64% male, 36% female), and ejection fraction (EF) was 59±13%. All patients underwent blood flow velocity Doppler recording in the distal left anterior descending coronary artery (LAD) at baseline and during adenosine iv infusion via a pump at the dosage of 0.14 mg/Kg/min over 5 minutes. Coronary blood flow velocity in LAD was continuously recorded by a well-validated non invasive approach: enhanced transthoracic Color-guided Pulsed-Wave Doppler recording. The time to maximal hyperaemic effect was obtained by activating a built-in chronometer at the starting of adenosine infusion. Results: We found that the peak effect occurred at 72 ± 32 seconds (see histogram). The peak effect occurred within 90 sec in 80 pts (66%) and after 90 sec in 46 pts (34%). In no pt, peak hyperaemic effect took place beyond 3 minutes. In addition in the vast majority of cases (90%) the maximal vasodilatatory effect was reached before the tachycardic phase of adenosine effect. Conclusions: The results of this study seem to indicate that the optimal duration of adenosine infusion to evaluate CFR should be at least 3 minutes.