A lumen sizing workhorse guidewire for peripheral vasculature: two functions in one device.

OBJECTIVES: Ideally, guidewires used during peripheral vasculature (PV) interventions could serve both as a therapy delivery platform and a diagnostic tool for real-time vessel sizing (2-in-1 function). BACKGROUND: Vascular imaging modalities, like intravascular ultrasound (IVUS), used during lower PV interventions, can improve outcomes versus angiographic assessment alone, but are rarely used due to added time, cost, and required clinical training/interpretation. METHODS: A 0.035″ bodied 0.035″ conductance guidewire (CGW) is described here as a vascular navigation and diagnostic real-time PV sizing tool. When attached to a console, the CGW creates a safe, electric field to determine vascular size through simultaneous voltage measurements. RESULTS: The CGW showed functionality as a workhorse guidewire on the bench (torqueability and trackability equivalent to a Wholey guidewire) and in vivo (over-the-wire stent deployment in domestic swine and first-in-man study with no major adverse events). Validation of CGW sizing versus the true diameter and IVUS was completed in 4-10 mm diameter phantoms on the bench and in swine and showed virtually no bias with excellent repeatability and accuracy (i.e., CGW repeatability: swine phantom bias = 0.03 ± 0.09 mm (1.3% error). CGW vs. true diameter: in vivo bias = 0.14 ± 0.15 mm (2.7% error). IVUS vs. true diameter: swine phantom bias = 0.01 ± 0.36 mm (4.7% error). CCW vs. IVUS: swine phantom bias = 0.13 ± 0.26 mm (3.8% error)). CONCLUSIONS: Real-time, accurate, and safe PV dimension assessment and therapy-delivery (2-in-1 function) is possible using a novel workhorse 0.035″ bodied CGW.

Accurate nonfluoroscopic guidance and tip location of peripherally inserted central catheters using a conductance guidewire system.

BACKGROUND: Bedside placement of peripherally inserted central catheters (PICCs) may result in navigation to undesirable locations, such as the contralateral innominate or jugular vein, instead of the superior vena cava or right atrium. Although some guidance and tip location tools exist, they have inherent limitations because of reliance on physiological measures (eg, chest landmarks, electrocardiogram, etc), instead of anatomical assessment (ie, geometric changes in the vasculature). In this study, an accurate, anatomically based, non-X-ray guidance tool placed on a novel 0.035" conductance guidewire (CGW) is validated for PICC navigation and tip location. METHODS: The CGW system uses electrical conductance recordings to assess changes in vessel cross-sectional area to guide navigation of the PICC tip. Conductance rises and oscillates when going in the correct direction to the superior vena cava/right atrium, but drops when going in the incorrect direction away from the heart. Bench and in vivo studies in six swine were used to confirm the accuracy and repeatability of the PICC placement at various anatomical locations. The PICC tip location was confirmed by direct visualization vs the desired location. RESULTS: CGW PICC guidance was highly accurate and repeatable with virtually no difference between actual and desired catheter tip location. The difference between the CGW PICC location vs the desired target was -0.07 ± 0.07 cm (6.6% error) on the bench and 0.04 ± 0.10 cm (5% error) in vivo. No complications or adverse events occurred during CGW usage. CONCLUSIONS: The CGW provides an anatomically based, reproducible, and clinically significant method for PICC navigation and tip location that can improve accuracy, decrease the wait time prior to therapy delivery, decrease cost, and minimize the need for X-ray. These findings warrant clinical evaluation of this navigation tool for PICC line placement.

Reduction of right ventricular pacing in patients with sinus node dysfunction using an enhanced search AV algorithm.

BACKGROUND: Dual chamber pacing typically results in a high percentage of ventricular pacing. A number of studies have been conducted suggesting detrimental effects of ventricular desynchronization produced by long-term RV pacing. Pacemaker algorithms that extend the AV interval to uncover intrinsic AV conduction have been utilized to reduce ventricular pacing. These algorithms are often limited to AV intervals below 250 ms limiting the ventricular pacing reduction. We hypothesized that by allowing AV intervals to extend beyond 300 ms, a marked reduction in RV pacing can be achieved. METHODS: A total of 30 patients (17 men, mean age 71 +/- 9) with standard Brady indications, and implanted with a Medtronic Kappa 700 pacemaker, were randomized to 2-week treatments with default Search AV (KSAV) parameters or Enhanced Search AV (ESAV) parameters. The Enhanced Search AV algorithm included the capability for continuous adjustment of AV delays and the ability to auto disable in patients with persistent AV block. RESULTS: Among patients with intact AV conduction, percent VP was greater in KSAV versus ESAV (70 +/- 40% vs 19 +/- 28%, P < 0.001). In patients with persistent AV block, the algorithm suspended appropriately and there was no significant change in the percent VP between both arms of the study. In 18/22 patients, percent VP was reduced below 40%. CONCLUSIONS: Substantial reduction in ventricular pacing can be achieved by allowing the AV interval parameters to extend beyond 300 ms using the ESAV algorithm. In patients with AV block, ESAV suspended and patients were paced at their nominal settings.