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Figure 1 Instrumentation of Dogs and Set-Up During Catheterization

The left circumflex artery is instrumented by a perivascular (perivasc) flow probe and occluder. A 2.8-F infusion catheter is advanced over a 0.014-inch pressure/temperature (temp) sensor-tipped guidewire through a Y-connector (Y₁) and positioned with its tip just proximal to the flow probe and occluder. The infusion catheter is connected to an infusion pump by a second Y-connector (Y₂), enabling continuous infusion of saline at room temperature (8 to 25 ml/min). The sensor-tipped guidewire is connected to the interface (Radi-Analyzer) as routinely done in coronary pressure measurement, and distal coronary pressure (P_d) and temperature (T) are displayed on the interface. The aortic pressure (P_a), measured at the tip of the guiding catheter, is recorded by a regular pressure transducer and displayed on the interface. (Inset) Set-up in humans was identical to that in dogs, with the exception of the perivascular flow probe and occluder. The tip of the infusion catheter is positioned proximal to the stenosis (if present) and with its side holes in a segment without major side branches.