4.1 The tip positions of PICCs implanted via lower limb veins in adult patients and associated ECG changes

Malpositioned tip, deep and shallow catheter tip can directly lead to complications, such as venous thrombosis, arrhythmia, and pericardial tamponade (Zhang et al., 2014). In such cases, the catheter position should be readjusted. A characteristic high-amplitude P wave indicates that the catheter tip has traveled through the right atrium from the inferior vena cava to the junction of the superior vena cava and the right atrium. This suggests that the catheter tip was positioned too deep. The catheter was withdrawn until the P waves became consistent with the body surface ECG, indicating that the catheter tip was in the upper part of the inferior vena cava and did not enter the right atrium (Zhou et al., 2017; Weber et al., 2020).

The results of this study revealed that all the FICC tips inserted into adult patients were located below the diaphragm in the inferior vena cava. Negative, Biphasic, and high-amplitude P waves did not appear in 47.1% of the patients during the FICC insertion procedure. An abdominal X-ray revealed that the FICC tips were located in the inferior vena cava, far from the diaphragm. This may be due to the FICCs’ limitations of being cut primarily at the front end as well as the large landmark measurement error, which often led to the catheter length being too short. Furthermore, as the adult inferior vena cava is longer than the superior vena cava, the catheter tip may not have reached the inferior vena cava above the diaphragm and the right atrium even if all the cut catheters were inserted. Therefore, there were no changes in the P-wave characteristics.

During FICC insertion in the remaining 52.9% of the patients, negative and biphasic P waves, and positive high-amplitude P waves appeared in the patient ECGs. Abdominal X-rays showed that, although the tip of the catheter was located in the inferior vena cava below the diaphragm, it was close to the diaphragm level. Although abdominal X-rays revealed no malpositioned tips in any patients, and the tips were all confirmed to be located in the inferior vena cava, the changes in the P-wave shapes and amplitudes revealed that the tip positions were close to the caval–atrial junction. Though there were no data supporting, the QRS seems to increase in amplitude while approaching the heart. This was an interesting trend.

This study found that intracavitary ECG technology can assist the positioning of PICC tips inserted via the lower limb veins in adult patients. This finding is significant in terms of providing greater clinical guidance for this procedure. Traditional PICC tip positioning uses abdominal X-rays after catheter insertion. If the tip is malpositioned after insertion, readjustment is necessary. This introduces the risk of infection and adjustment failure. The use of ECGs for procedure guidance is significant for preventing tip malposition and achieving proper positioning during FICC insertion in adult patients.

The main limitation of this study was that limited by the technical and equipment conditions, our hospital uses abdominal X-ray for positioning, not subcostal ultrasound, which was also the way adopted by many hospitals in China. Furthermore, sample size expansion in any future research is necessary. Limited by the technical and equipment conditions, our hospital uses abdominal X-ray for positioning, which is also the way adopted by many hospitals in China.