392 - Intravascular-ECG Guided Umbilical Venous Catheter Placement: An Observational Trial (NeoNav Study) to Assess P-wave Characteristics

Poster Number: 392
Publication Number: 392.134

Christiane Theda, Royal Women's Hospital, Melbourne, Parkville, Victoria, Australia; Mubin Yousuf, Royal Women's Hospital, Brunswick West, Victoria, Australia; Shing Yue Sheung, The Royal Women's Hospital, Melbourne, Victoria, Australia; Katerina P. Barons, Deakin University, Melbourne, Victoria, Australia; Alexander Newton, Royal Women's Hospital, Melbourne, Victoria, Australia; Andreas Pflaumer, The Royal Children's Hospital, Parkville/Melbourne, Victoria, Australia

Background: Umbilical venous catheters (UVCs) are widely used for central vascular access in newborns. After placement, imaging is used for tip confirmation; adjustments add procedure time and patient stress. Intravascular electrocardiography (IV-ECG) guided UVC placement has been described but is not widely adopted. It uses P-wave characteristics to determine UVC tip location. Wu et al (J Paed Child Health 2020 56:716) describe P-wave changes depending on tip location: (1) tall/sharp P-wave, tip high in atrium, (2) biphasic P-wave, middle of atrium, (3) negative or absent P-wave, low atrium and cavoatrial junction (Figure 1).

Objective: Compare P-wave characteristics of IV-ECG with three different UVC tip positions as determined by anteroposterior x-rays: (A) UVC "high", > 1 cm above diaphragm, (B) UVC in a "correct" position (diaphragm +/- 1 cm) (C) UVC “low”, > 1 cm below diaphragm.

Design/Methods: We recruited 50 newborns and obtained 380 IV-ECG recordings at UVC placement, while in-situ and at removal. IV-ECGs were obtained through saline filled UVCs with a Johans Adapter; signals were processed by an analog-digital converter and custom software. P-waves were categorized as "positive”, “zero”, “negative” or “biphasic” (either +/- or -/+) by the software and reviewed by a blinded researcher. P-waves were “unidentifiable” when neither software nor reviewers were able to categorize them. UVC tip position on x-ray was assessed while blinded to IV-ECG features.

Results: UVC tip on x-ray was "high" (n=75), "correct" (n=186) or "low" (n=119), Figure 2. A positive or biphasic IV-ECG P-wave indicated the UVC was "high". The biphasic P-wave at high locations started with a positive deflection (+/-). A negative P-wave reliably indicated that the UVC tip was “correct”. Biphasic P-waves seen at a "correct" position were -/+. Positive P-waves are typically associated with a "high" UVCs but can be present at “correct" or "low" positions (with lower voltage). A "zero" P-wave is found with "correct" and "low" positions. The P-wave characteristics were difficult to assign in 37% of recordings.Conclusion(s): With 50 participants and 380 recordings our study is markedly larger than previously published work. The IV-ECG P-wave allows for assessment of tip position with some overlap between groups; signal quality varies, limiting the method at this time. Further work to optimize signal quality, evaluate utility of other ECG characteristics and develop analysis algorithms will allow this method to become a new standard of care for precise UVC placement; enhancing safety and reducing radiation and procedure times.
Figure 1: Intravascular ECG P-wave characteristics compared to umbilical catheter position on imagingThe P-wave is positive or biphasic when the catheter tip is in the superior vena cava (SVC) or high in the right atrium; it becomes negative or disappears when the tip is in the low atrium or at the cavoatrial junction (as per literature).
Figure 2: Comparison of P-wave characteristics with umbilical catheter tip position on x-ray (NeoNav Study results)Positive and biphasic (+/-) P-waves are seen with catheter tips "too high", negative and biphasic (-/+) p-waves are seen with "correct" position. At a "too low" position, P-wave characteristics are often difficult to identify or the P-wave has disappeared. There is some overlap between groups.