An in vitro study of the hemodynamic effects of catheter injections.

The injection jet from a catheter has been shown to elevate distal pressure and flow. These disturbances in flow present a problem for the application of digital arteriography to measure physiologic flow. The authors used an in vitro model to determine the primary factors responsible for the increases in distal flow with the goal that these disturbances might be estimated and minimized. Experiments were performed to evaluate the importance of the cross-sectional area of the catheter and vessel, the importance of absolute vessel flow, and the importance of distal resistance. A lumped resistance model predicted the flow changes to within 3% of the preinjection vessel flow. In the model system the elevation of distal flow in percent was equal to (the injection rate divided by the tube flow rate) multiplied by (the proximal resistance divided by the total resistance) multiplied by 100. Because the resistance ratio generally is small, injections at physiologic flow rates should produce acceptably small increases in distal flow. The use of a large diameter catheter or the presence of a proximal stenotic lesion would increase the ratio.