Intracoronary Adenosine Dose-Response Relationship With Hyperemia

OBJECTIVES The present study sought to establish the dosage of intracoronary (IC) adenosine associated with minimal side effects and above which no further increase in flow can be expected. BACKGROUND Despite the widespread adoption of IC adenosine in clinical practice, no wide-ranging, dose-response study has been conducted. A recurring debate still exists regarding its optimal dose. METHODS In 30 patients, Doppler-derived flow velocity measurements were obtained in 10 right coronary arteries (RCAs) and 20 left coronary arteries (LCAs) free of stenoses>20% in diameter. Flow velocity was measured at baseline and after 8 ml bolus administrations of arterial blood, saline, contrast medium, and 9 escalating doses of adenosine (4 to 500 mu g). The hyperemic value was expressed in percent of the maximum flow velocity reached in a given artery (Q/Q(max,) %). RESULTS Q/Q(max) did not increase significantly beyond dosages of 60 mu g for the RCA and 160 mu g for LCA. Heart rate did not change, whereas mean arterial blood pressure decreased by a maximum of 7% (p < 0.05) after bolus injections of IC adenosine. The incidence of transient A-V blocks was 40% after injection of 100 mu g in the RCA and was 15% after injection of 200 mu g in the LCA. The duration of the plateau reached 12 +/- 13 s after injection of 100 mu g in the RCA and 21 +/- 6 s after the injection of 200 mu g in the LCA. A progressive prolongation of the time needed to return to baseline was observed. Hyperemic response after injection of 8 ml of contrast medium reached 65 +/- 36% of that achieved after injection of 200 mu g of adenosine. CONCLUSIONS This wide-ranging, dose-response study indicates that an IC adenosine bolus injection of 100 mu g in the RCA and 200 mu g in the LCA induces maximum hyperemia while being associated with minimal side effects. (C) 2015 by the American College of Cardiology Foundation.