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Background: The advertised catheter sheath introducer (CSI) size, the internal diameter (ID), defines the maximum size of medical devices that can pass through it. However, the outer diameter (OD) determines the risk of vascular injury, varies considerably between manufacturers, and is not advertised. The highest risk of vascular injury is in infants less than one year of age and 3 - 6Fr CSIs are typically used.

Methods: The OD of 3, 3.3, 4, 5, and 6F CSIs (5 of each size) from different manufacturers were measured using a Mitutoyo Digital Micrometer. CSIs were measured with the dilator in place. Three authors measured the OD at the mid- and proximal portions (3 readings at each site) and were blinded to the other authors’ measurements. Continuous variables are reported as mean ± SD. Mid and proximal measurements were compared using an independent samples T test. Cronbach’s alpha and Intraclass Correlation Coefficient were used to measure the agreement for measurements between authors. Significance was set at P < .05.

Results: Based on our study there are significant differences in the OD of CSIs among manufacturers, and these are not advertised. There was no difference in the diameter of the CSI at the mid-point or proximally (P < .05). The intra-rater and inter-rater reliability were excellent (Cronbach’s Alpha 1.0 and Intraclass correlation coefficient 1.0). CSIs developed for transradial catheterization had the smallest OD when compared to traditional CSI (1F, 0.33 mm smaller). The OD of CSIs by Terumo Interventional Systems were on average 0.5F (0.17 mm) smaller than those from other manufacturers. The OD of the 4F transradial CSI by Merit Medical (Prelude IDeal, 1.610 ± 0.006 mm) is essentially the same as the OD of the 3F Elite HV Braun Interventional Systems (1.644 ± 0.016 mm), 3.3Fr PediaVascular (1.635 ± 0.005 mm) CSIs.

Conclusions: A smaller CSI does not guarantee a smaller OD. The OD of the 4F transradial CSI is the same as the OD of the 3Fr and 3.3Fr CSI. The “smaller” CSIs also require use of specially designed 3F catheters and 0.030-inch guidewire. On the other hand, the 4F CSI has the same OD but offers access to a wider assortment of well-established, commonly stocked, and cheaper 4F diagnostic and interventional tools. This is achieved without increasing the risk of vascular injury and may also help reduce catheterization laboratory inventory in the era of cost containment.


Cardiology | Pediatrics


Presented at Midwest Pediatric Cardiology Society Annual Meeting 2019. Kansas City, Missouri. Awarded “Best Fellow Oral Presentation.”

Presented at CHOP Cardiology 2019: 22nd Annual Update on Pediatric and Congenital Cardiovascular Disease. Huntington Beach, California.

Choosing Catheter Sheath Introducers in Infants-Information You Are Not Provided but Should Have!