The peripherally inserted central catheter (PICC) is a very commonly used medical device. As PICCs are peripherally inserted, the catheter needs to be guided from its insertion point to the central venous system. Currently, this is done using fluoroscopy-guided insertion (FGT), blind technique (BT), or electrocardiogram (ECG) based techniques.

Fluoroscopy-guided insertion uses x-ray fluoroscopy and is considered the gold standard (1–3). By design, this technique needs dedicated infrastructure and technology. The BT is insertion with no guidance and is the most popular, as it can be used bedside with no special technology (4).

More recently, ECG-based techniques that rely on the modification of an intracavitary ECG signal to position the catheter tip optimally in the central vein have been developed (5). The use of these techniques is spreading among non-radiologic users, with a global use of 62% (6).

This manuscript aims to review the rationale for optimal positioning of the catheter tip in the superior vena cava (SVC) and describes the current technologies of ECG-based techniques and their respective advantages and limitations.

In order not to miss a major information, this narrative review integers at least the articles retrieved from Pubmed with the simplified research equation.

Search: (”Catheterization, Peripheral”[Mesh]) AND “Electrocardiography”[Mesh] Filters: English, from 2008–2022.

Peripherally inserted central catheters has always inspired numerous discussions of complications such as occlusion, infection, and thrombosis (7).

Among these issues, it is known that positioning an internal catheter tip distant from the cavo-atrial junction (CAJ) makes the catheter more likely to undergo internal repositioning and venous thrombosis. As the distance from the catheter tip to the CAJ is the single and strong predictor of central thrombosis and tip repositioning (8), an optimal central tip position is mandatory. This is of particular importance in the pediatric population where blind placements may only reach a 40% of correct positioning (9, 10). Ensuring the central positioning of the catheter has been demonstrated to reduce the risk of PICC-related thrombosis by about 40% (11).

An intracardiac tip position too far from the CAJ may also be a source of unwanted events such as cardiac arrhythmias (tachycardia or bradycardia) due to direct irritation of the right atrium or ventricle (12–14), which is potentially lethal. Catheter placement more than 3–5 cm beyond the CAJ should thus be avoided (12, 15, 16).

According to the distance from the tip to the CAJ, the PICC positions can be classified into three types (Figure 1A) (4).

The electrocardiogram localization technology relies on the use of Lead II’s complex of Einthoven’s Triangle in order to obtain the maximal P-wave signal [limb electrodes at the right arm (RA) and left leg (LL)] (17).

This surface tracing serves as reference and is compared to the same tracing seen in intracavitary through the PICC tip, which is used as an electrode.

The P-wave varies between the two tracing reaching its highest value at the CAJ.

The operator will therefore be able to find the position of the catheter related to the maximum height of the P-wave.

Peripherally inserted central catheters are not a uniform product, there are a lot of subtle and less subtle variations on PICC design that deserve to be addressed.

The actual catheters can be differentiated based on their material which is mostly polyurethane (PUR) but also silicone.

They may also be differentiated by the location of the cut to adjust their length. Some catheters are trimmed on their “free end side” which is the proximal part of the catheter, closer to the hearth. While other are trimmed on their outer part, near to the hub, which is the distal part of the catheter.

The distal catheter part may also vary regarding its design. It may be straight, i.e., with the same French size on the whole catheter or it may be “reverse tapered” which consists in a gradual augmentation of the French catheter size in the last centimeters of the catheter (generally 2 more French size in 5–8 centimeters length).

Some catheters are non-valved while others are valved this permits aspiration with negative pressure, infusion with positive pressure and a closed system with neutral pressure.

Among these, the strongest point of attention is the trim point which further determines the technique of insertion.

At insertion point the reverse tapered catheter is designed to give kinking resistance as well as participate to a better hemostasis which is a rather interesting property.

However, Itkin et al. (19), in a randomized study addressing straight and tapered devices, mentioned no statistical difference regarding safety endpoints such as post-procedure bleeding rates and thrombosis incidence. No other comparison point exists, as theirs is the only such study.

Technique A presents the interesting possibility of integrating valves in the hub side, making clamping unnecessary. The valve is bidirectional, opening inwardly during infusion and outwardly during aspiration; this minimizes occlusion rates due to blood reflux in the catheter and subsequent clotting, by 20% (20, 40). Two more recent RCT tried to address the effect of valve technology on occlusion rate with no advantages of valved vs. non-valved PICC, however both have interrupted for other reasons (21, 41).

Also, cutting the open end (technique A) results in the loss of some of the manufactured smooth and round catheter tip (42). This introduction of “roughness” is of no importance in technique B but may have some clinical repercussions, such as an increased risk of thrombosis or infection, with technique A (43). However no studies have addressed the problem of PICC tip roughness and thrombosis or infections.

Intuitively, it makes sense that a rough catheter tip may not be ideal. Another option exists, combining technique B and a distally (inner) valved closed tip. This catheter configuration seems similar to an outer valve in regard to occlusion rates (44). The only device with a distal valve is made out of silicone (which is probably the only way to have an inner valve) whereas most of the other actual devices are made of PUR.

The complication rates of silicone and PUR devices are apparently similar, though it is difficult to thoroughly address this point due to a lacunar specification of post-care informations in studies (39).

It exists no points of comparison between ECG devices, in that way ECG technologies will be discussed relative to other techniques.

Considering liquid transmission, saline has half the conductivity of sodium bicarbonate (NaHCO₃), (respective impedances are 200,000 and 100,000 Ω). When it is needed to enhance the ECG signal capacity, an hypertonic solution may be effective, Capasso et al. (55) used a 4% saline which has an impedance of is 77,000 Ω, similar to that of NaHCO₃ (56). Regarding wire transmission, high conductivity is characteristic of metals. Enhancing saline concentration enhances the conductivity but care must be taken in the ability of kidneys to excrete sodium (in newborns this capacity is low) (57).

Despite this, the analysis was markedly lacking in evidence because the retained studies were only quasi-experimental in design. Moreover, the included studies concern mostly central venous catheters (CVC) such as port, jugular CVC, or tunneled CVC. More powerful trials oriented to PICCs should be run.

Stenosis and obstructions are rather uncommon (3%) in populations without catheter history but may rise to 7.5% in populations with central catheterization history (58). In these cases, mapping the SVC system through venography is a necessary step for a successful guidance procedure as well as for endoluminal interventions such as balloon angioplasty. As well, resistance during the passage of the catheter with extravascular wire tracking indicates venous perforation risk (59) and also necessitates cartography through venography (60).

These elements may clearly be considered a limiting factor of ECG technologies. Fluoroscopy permits a direct tract visualization which is greatly useful in identifying the right venous pathway which may be challenging to identify through indirect ECG visualization (61). Arterial pathway may also not be highlighted through indirect ECG guidance (62).

At the same time, the scope of use of ECG guidance is constantly increasing in connection with clinical research and former limits of the system may be alleviated. Even if active magnetic device such as ventricular assist device are still problematic for ECG guidance (63), concomitant indwelling central catheters has been proved not to affect tip positioning (64). Also it has been showed that patients presenting abnormal surface ECG such as atrial fibrillation may be successfully managed through the use of ECG guidance (65). This technique may also be supplemented by the “bubble test.” In correct placed PICCs, it consists in ultrasound visualization of micro-bubbles in the right atrium (subcostal four chamber view) within 2 s after injection of saline–air mixture (66).

Considering secondary malposition diagnosis (tip migration after an initial adequate central positioning). Saline ECCG technology allows the following of the inserted tip in a way as effective as diagnostic CRX (67) and bedside repositioning through P-Wave morphology control after each repositioning maneuvers (arm abduction, high flow flush technique, patient mobilization) (68).

What precision can be reached under ECG is a frequent subject of controversy between users who are more for the use of FX technology or more for the use of ECG technology (2, 3, 28). What is undeniable is that ECG is clearly superior to blind insertion techniques (69, 70).

On one hand, ECG is especially interesting for premature infants as accumulated radiation dose may manifest years after exposure (71). On the other hand, in order to reach the same degree of central tip precision under ECG as under fluoroscopy, accommodations regarding the insertion point should be acknowledged.

The first kind of concession (technique A) is related to the length of catheter needed to ensure the capacity to observe the P-wave modifications (P-wave maximal amplitude in the absence of initial deflection) and by this means to position the catheter at the CAJ. Operators may need up to 2 cm of extra catheter length (72) while Elli put forward a 3.8 cm discrepancy between ECG measure and cutaneous landmark (73); ultimately, these leeway centimeters will reverberate at the insertion point (30) and may have uncertain repercussions (74).

The second type of concession is related to the disturbances caused by the device at the insertion point. These disturbances are either intravascular or extravascular.

Should the device be reverse tapered to ensure better hemostasis (technique A), its increase in diameter (toward the hub) may be as high as 2F, with potential associated bloodstream perturbations (75).

The different advantages and limits of PICC devices classified by technique and transmission medium are summarized in Table 1. Table 2 summarizes different commercially available catheters classified by technique and valve presence.

In practical use, a PICC and ECG can be combined in multiple ways, depending on the device’s trim point, material, valve position, and transmission medium, according to the operator’s choices. From a strategic point of view, the ECG-guided PICC is an effective alternative oriented toward undelayed patient management and optimized workflow, although it lacks some strengths that are needed in complex situations.

SQ: conceptualization, critical review, editing of the draft, and decision to submit for publication. GG: preparation, visualization, data presentation, writing the initial draft, editing of the draft, and creation of the published work. Both authors contributed to the article and approved the submitted version.

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

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