Discussions

Fenestration creation across a Fontan baffle is often required for various indications in a failing Fontan system.^{Reference Kreutzer, Graziano, Stapleton and Rome6} The traditional use of the Brockenbrough needle has been the gold standard for Fontan baffle puncture and can be achieved in routine practice as demonstrated in several studies.^{Reference Rupp, Schieke and Kerst7,Reference El-Said, Ing and Grifka8} Conversely, Fontan baffle puncture can be difficult and challenging in a chronic and unyielding calcified lateral tunnel or extra-cardiac Fontan conduit. This study has demonstrated the effective use of radiofrequency energy via surgical electrocautery system for Fontan baffle puncture in creating Fontan fenestration in all attempted patients without any complications.

Recent advances have allowed the use of radiofrequency perforating energy delivered through a radiofrequency generator and NRG trans-septal needle (Baylis medical company) for trans-septal puncture. Studies have shown clinical utility in performing TSP in native and complex atrial septal tissue.^{Reference Esch, Triedman, Cecchin, Alexander and Walsh14} However, this system is relatively ineffective in a tough calcified conduit as the tip is delicate and the needle bends and fractures on manual pressure as noted in patient #15 (Fig 5). The use of radiofrequency energy via surgical electrocautery was described earlier by Bidart et al.^{Reference Bidart, Vaseghi and Cesario11} Several studies have demonstrated clinical usefulness and simplicity in using this technique for various indications. In adults with complex atrial septum due to fibrosis or compliant septum requiring multiple re-intervention for an electrophysiology study, this technique was used successfully for trans-septal puncture in several series.^{Reference Bidart, Vaseghi and Cesario11,Reference Elayi, Gurley, Di Sessa and Kakavand12} Similarly, we have described our early experience using this technique for trans-septal puncture in a diagnostic, interventional, and electrophysiology procedures primarily in children and adults with CHD (n = 55).^{Reference Gowda, Qureshi and Turner13}

Apart from the use of radiofrequency energy, several alternative techniques have been described for Fontan baffle puncture and fenestration creation. A few case series have reported successful creation of pulmonary artery to atrial roof communication and placement of a covered stent in a Diabolo fashion.^{Reference Aldoss and Divekar15,Reference Mehta, Jones and De Giovanni16} Casdonte et.al., described a novel approach of using the SafeSept trans-septal guide wire and a snare controlled Diabolo-shaped covered stent placement across the Fontan fenestration in one patient.^{Reference Casadonte, Wax and Gossett10} The use of a snare in controlling the desired central waist is a good technique and may be utilised under certain circumstances as described by several series.^{Reference Aldoss and Divekar15,Reference Stümper, Gewillig and Vettukattil17} We have not used the snare technique to deliver stents to any of our patients. We have however relied on natural tissue and Goretex tube resistance to create the desired central waist and target O₂ saturations to determine the final size of the central waist. Rupp et al., in a relatively larger series of 19 patients, demonstrated the effective use of the traditional Brockenbrough needle for Fontan baffle puncture and gradual balloon dilation to advance the sheath. They have predominantly used pre-mounted stents leaving a central waist due to natural resistance of the Goretex conduit to create a Diabolo-shaped stent. A majority of their patients (n = 16) had Fontan fenestration creation <1 month following the Fontan procedure. In comparison, our group included patients with older lateral tunnel and extra-cardiac conduits. The Fontan baffle puncture were futile in several patients using the traditional Brockenbrough needle despite multiple attempts. Our study highlights the use of radiofrequency energy through a surgical electrocautery blade that facilitated Fontan baffle puncture in calcified conduits (Table 1). In addition, it allowed controlled needle advancement in complex conduit anatomy with associated adjacent delicate structures (Figs 2 and 6) and avoided procedural injury. In relatively fresh Fontan conduits, advancing the dilator and sheath carefully following Fontan baffle puncture are generally effective in contrast to older calcified non-yielding conduits. Similar to Rupp et al., we have also adopted a smaller balloon dilation technique following Fontan baffle puncture and prefer advancing the sheath as the balloon is deflated to facilitate smooth sheath advancement and its position in the venous atrium. In our practice, we have exclusively used bare metal stent or pre-mounted stent instead of a covered stent. There has been no evidence of bleeding, extravasation, or pericardial effusion in the space between the conduit and the atrial wall, likely due to fibrosis and scarring post-surgery.

The mechanism of radiofrequency perforating energy use through surgical electrocautery involved delivering high energy and low power radiofrequency waves in short bursts that resulted in a localised increase in temperature (100 °C). The intracellular water vaporise causing disruption of the cell membrane.^{Reference Bidart, Vaseghi and Cesario11,Reference Veldtman, Wilson and Peirone18} This approach has been adopted for trans-septal puncture across native atrial septal tissue for various indications as demonstrated in several studies.^{Reference Bidart, Vaseghi and Cesario11–Reference Gowda, Qureshi and Turner13} The biophysical properties of PTFE in general would not favour the use of radiofrequency energy to cause an effective penetration.^{Reference Esch, Triedman, Cecchin, Alexander and Walsh14,Reference Veldtman, Wilson and Peirone18} Nevertheless, it has been postulated that radiofrequency energy facilitates the penetration of the endothelial cells on either side of the PTFE and additional mechanical force on the needle to puncture the Goretex material.^{Reference Esch, Triedman, Cecchin, Alexander and Walsh14} This observation was supported by several reports including our earlier and current experience.^{Reference Bidart, Vaseghi and Cesario11,Reference Gowda, Qureshi and Turner13,Reference Esch, Triedman, Cecchin, Alexander and Walsh14} In contrast to native atrial tissue, Fontan baffle puncture of a chronic extra-cardiac conduit can be extremely difficult. We were unable to puncture the heavily calcified lateral tunnel conduit using the traditional trans-septal needle approach. Several attempts delivering radiofrequency energy using the Baylis NRG needle were also ineffective as the needle was not sturdy, causing it to bend and fracture. Ultimately, Fontan baffle puncture was performed using high radiofrequency energy (25–50 W) through surgical electrocautery tip and persistent mechanical force (Fig 5). The trans-septal needle in this technique gets localised to a specific selected spot on initial application of radiofrequency energy. The stiffness of the traditional Brockenbrough system, sustained manual force with simultaneous radiofrequency energy application allowed steady slow advancement of the needle across the Fontan baffle to the atrium with minimal or absent needle displacement. This is the major advantage of this technique compared to all other approaches especially in a chronic heavily calcified baffle. We also found this technique to be useful in patients with bilateral femoral venous occlusion. Alternate venous access using trans-hepatic, right, and left internal jugular vein approach were used in five patients (Table 1). The ability to perform Fontan baffle puncture from the internal jugular approach or left femoral venous approach can be challenging using traditional techniques due to an unfavourable conduit configuration and concern for trans-septal needle to slide from the preferred position on manual force, and we hypothesise that using radiofrequency energy via electrocautery facilitated Fontan baffle puncture in patients in whom those access routes were used (Fig 3). In patients with a complex anatomy and delicate adjacent structures, it is essential to perform Fontan baffle puncture with minimum needle dislocation and controlled puncture to prevent injury. In a complex patient with extra-cardiac Fontan baffle with a restrictive native atrial septum, we were able to perform Fontan baffle puncture and maneuver the trans-septal needle at the desired site across the Fontan baffle, followed by a second puncture across the centre of the atrial septum for the placement of a large atrial septal stent (Fig 2). Similarly, Fontan baffle puncture was achieved in the pre-determined inferior portion of the extra-cardiac conduit to access and occlude major veno-venous collaterals using vascular plugs in two patients (Fig 4). In another patient, Fontan baffle puncture was cautiously performed with negligible needle displacement and manual force due to the close proximity of the atrial appendage (Fig 6). Fontan baffles are prone to chronic and sub-acute clot/thrombus formation, and we strongly recommend trans-esophageal echocardiography evaluation to identify any thrombus prior to Fontan baffle puncture. In addition, we need to be mindful of other sources of thrombus and clots, including char formation post-EP ablation, clots in the atrium and atrial appendage, and dislodged plastic particles from excoriation of the dilator when advancing the needle.^{Reference Greenstein, Passman, Lin and Knight19} These complications can be mitigated with procedural and post-procedure anticoagulation, antiplatelet therapy, continuous flushing, and using stylet to advance the needle within the dilator.