Direct intracoronary evidence of collateral steal in humans

Coronary steal is defined as a fall in blood flow toward a certain vascular region in favor of another area during arteriolar vasodilatation, ie, a coronary flow velocity reserve (CFVR) <1. The purpose of this study was to determine the frequency of steal in patients with a wide range of collateral supply to a vascular area of interest and to assess whether steal is associated with the amount of collateral flow.

One hundred patients 57+/-9 years old with a coronary artery stenosis to be dilated were examined with intracoronary (IC) Doppler guidewires. IC adenosine-induced CFVR<1 obtained distal to the stenosis was defined as steal. An index for collateral flow was determined by positioning the Doppler guidewire in the collateral-dependent vessel distal to the stenosis and measuring the flow velocity time integral during (Vi(occl), cm) and after (Vi(ø-occl)) balloon occlusion. Vi(occl)/Vi(ø-occl) was determined without and with intravenous adenosine (140 microg x kg(-1) x min(-1)). Coronary steal occurred in 10 of 100 patients. Patients with steal showed superior collaterals compared with those without steal: Vi(occl)/Vi(ø-occl)=0.65+/-0.24 in patients with steal versus 0.29+/-0.18 in those without steal (P=.0001). In all patients with steal, there was a reduction in collateral flow during intravenous adenosine-induced hyperemia, whereas in the majority (70%) of patients without steal, collateral flow increased or remained unchanged during hyperemia.

Coronary steal assessed by intracoronary Doppler flow velocity measurements occurs in 10% of patients with a wide range of coronary collaterals to the vascular area from which blood flow is redistributed. There is a direct association between the presence of steal away from and the amount of collateral flow toward the region under investigation. Collateral flow to the vascular region studied decreases during adenosine-induced hyperemia, which indicates a mechanism of steal via the extensive collaterals.