Estimated mean flow resistance increase during coronary artery catheterization.

The purpose of this investigation is to examine the influence of the presence and size of the catheter on the measurement of mean pressure drop and, thus, flow resistance in coronary vessels. Relatively large mean translesional pressure gradients have been reported, but they may be due to obstruction effects. To evaluate this hypothesis, analytical flow modeling coupled with in vitro experimental evidence was used to estimate mean flow resistance increases due to the presence of a catheter in a proximal vessel for concentric and eccentric catheter configurations. For an angioplasty catheter, over the relative range of catheter size to coronary vessel size (di/d(o)) from 0.3 to 0.7 (which is currently being used clinically), the flow resistance increased by a large factor of 3-33 for the concentric configuration. For smaller infusion catheters, the flow resistance increase was less, although still appreciable. Very small angioplasty guidewire also leads to sizeable increases in flow resistance. Effects of catheter eccentricity also indicated substantial increases in flow resistance, although the magnitude was less. These initial results might be used by clinicians to obtain rough estimates of actual mean pressure gradients in vivo in relatively straight proximal segments of artery from values measured with catheters. Since catheters are used so widely clinically, these initial results may be useful also for other vessels in the vascular system where the mean flow is describable by the Poiseuille relation. Whereas there is reasonable confidence in the flow modeling methodology, hemodynamic data are needed to evaluate the actual magnitude of the effects of obstruction in vivo.