Evaluation of Intravenous Versus Intracoronary Adenosine in Coronary Reactivity Testing

Coronary flow reserve (CFR) and index of microcirculatory resistance (IMR) obtained through coronary bolus thermodilution are used to assess and treat patients with angina and no obstructive coronary artery disease. Previous studies demonstrate comparable results assessing epicardial ischemia by fractional flow reserve using intravenous (IV) or intracoronary (IC) adenosine. It is unknown if there is a similarity between IC and IV hyperemia with adenosine when performing coronary reactivity testing (CRT). We reviewed CRT data and baseline demographics in a cohort of patients who underwent CRT for ischemia and no obstructive coronary artery disease. We evaluated CFR and IMR in patients whereby maximal hyperemia was obtained by both IC and IV means using linear regression, one-way analysis of variance, Wilcoxon, and Bland-Altman analysis. We assessed 62 patients with a median age of 60.5 years (50 to 67), and 72% were females. The average CFR with IC adenosine was 3.12 (2.31 to 4.06) and 2.71 (2.0 to 3.88) with IV adenosine, with an R² value of 0.50 (p <0.0001). The average IMR with IC adenosine was 28.23 (16.24 to 50.72) and 22.27 (14.79 to 37.0) with IV adenosine, with an R² value of 0.33 (p <0.0001). Average intra-method variability between IC and IV adenosine was nonsignificant (p = 0.31 for CFR and p = 0.55 for IMR). Bland-Altman analysis showed reasonable agreement between IV and IC adenosine for CFR and IMR with slightly higher values using IC adenosine. Therefore, in CRT with bolus thermodilution, CFR and IMR values obtained with IC adenosine correlate well with those obtained with IV adenosine. This presents a potential alternative to IV adenosine for bolus thermodilution CRT.