Impact of catheter size on reliability of quantitative coronary angiographic measurements (comparison of 4Fr and 6Fr catheters).

To evaluate the feasibility of catheter down sizing for QCA, the reliability of a 4Fr catheter as a calibration device was evaluated. Repeated coronary angiograms of 9 lesions were obtained using 4Fr and 6Fr catheters under otherwise identical conditions. The calibration factor was measured 10 times by 4Fr and 6Fr catheters. QCA measurements including minimal lumen diameter (MLD), interpolated normal reference (Int N), percent diameter stenosis (%DS), and lesion length (LL) were performed by two technicians twice with a 3-month interval. The intraobserver and interobserver variability of each parameter was evaluated using intraclass correlation coefficients (ICCs). Mean of mean SD of calibration factor was significantly larger in 4Fr than in 6Fr in 9 lesions. The mean of mean coefficient of variance was significantly larger in 4Fr catheters vs in 6Fr catheters. A 6Fr catheter showed excellent reliability for both intraobserver and interobserver variability in MLD, Int N, %DS, and LL. In contrast, 4Fr showed that reliability in intraobserver variability depended on the analyst. Although reliability of interobserver variability in Int N measured by the 4Fr catheter was >0.80, the value was less than that by the 6Fr catheter. Taking these results into consideration, 4Fr catheters are less reliable than 6Fr catheters when measuring QCA data especially for follow-up data that need most accurate measurements of MLD and %DS. It would be better to use a 6Fr catheter to evaluate QCA measurements such as acute gain, late loss, restenosis rate, and device size.