Low coronary microcirculatory resistance associated with profound hypotension during intravenous adenosine infusion: implications for the functional assessment of coronary stenoses.

Background: Intravenous adenosine infusion produces coronary and systemic vasodilatation, generally leading to systemic hypotension. However, adenosine-induced hypotension during stable hyperemia is heterogeneous, and its relevance to coronary stenoses assessment with fractional flow reserve (FFR) remains largely unknown.

Methods And Results: FFR, coronary flow reserve, and index of microcirculatory resistance were measured in 93 stenosed arteries (79 patients). Clinical and intracoronary measurements were analyzed among tertiles of the percentage degree of adenosine-induced hypotension, defined as follows: %ΔP(a)=-[100-(hyperemic aortic pressure×100/baseline aortic pressure)]. Overall, %ΔP(a) was -13.6±12.0%. Body mass index was associated with %ΔP(a) (r=0.258; P=0.025) and obesity, an independent predictor of profound adenosine-induced hypotension (tertile 3 of %ΔP(a); odds ratio, 3.95 [95% confidence interval, 1.48-10.54]; P=0.006). %ΔP(a) was associated with index of microcirculatory resistance (ρ=0.311; P=0.002), coronary flow reserve (r=-0.246; P=0.017), and marginally with FFR (r=0.203; P=0.051). However, index of microcirculatory resistance (β=0.003; P<0.001) and not %ΔP(a) (β=-0.001; P=0.564) was a predictor of FFR. Compared with tertiles 1 and 2 of %ΔP(a) (n=62 [66.6%]), stenoses assessed during profound adenosine-induced hypotension (n=31 [33.3%]) had lower index of microcirculatory resistance (12.4 [8.6-22.7] versus 20 [15.8-35.5]; P=0.001) and FFR values (0.77±0.13 versus 0.83±0.12; P=0.021), as well as a nonsignificant increase in coronary flow reserve (2.5±1.1 versus 2.2±0.87; P=0.170).

Conclusions: The modification of systemic blood pressure during intravenous adenosine infusion is related to hyperemic microcirculatory resistance in the heart. Profound adenosine-induced hypotension is associated with obesity, lower coronary microcirculatory resistance, and lower FFR values.