Discussion:
In this case report, we have demonstrated successful cardiac resynchronisation using His-bundle pacing in a patient with Scimitar syndrome with subsequent improvement in the patient’s heart failure symptoms. Utilization of integrated image modalities using CARTOSEG™ and CARTOUNIVU™ software helped us to achieve successful cardiac resynchronization despite the difficult anatomy with respect to the cardiac chambers as well as the CS tributaries. To the best of our knowledge, our case is the first description of His-CRT implantation in Scimitar syndrome with image integration tools.
Image integration using three-dimensional electro-anatomical mapping systems was crucial for understanding the Scimitar syndrome complex cardiac anatomy given the right lung hypoplasia and right sided dextroposition of the heart1 , and in advancing the lead to the key cardiac landmarks. In our patient, L-transposition of great arteries (L-TGA) and left sided valvular abnormalities were specifically ruled out.
The use of CARTOSEG™ and CARTOUNIVU™ image integration modules has previously been shown to reduce fluoroscopy time and procedural complications.2 In our case, planning with CARTOSEG™ allowed orientation to the inter-ventricular septum in unconventional fluoroscopic views. Predefining and integrating the location of the His-bundle potentially reduced the procedural time.
Cardiac resynchronization with His-bundle pacing (His-CRT) is evolving rapidly as a viable strategy and as an alternative to the LV lead implanted through the CS (conventional CRT).3, 4 This has added a new dimension to patients where placement of an LV lead may be technically challenging as in our case. It is possible to correct the focal and proximal LBBB at the level of the His conduction system by pacing distal to the block as shown in our case.
In congenital heart diseases, the perceived difficulties of His-bundle pacing are related either to the cardiac malrotation as observed in our case or due to varied positions of the AV node conduction axis. Nevertheless, His-bundle pacing for complete heart block has been achieved in congenital anomalous hearts like in persistent left superior vena cava (LSVC) 5, dextrocardia 6, Ebstein’s anomaly 7 and in L-TGA 8. In a recent case series of patients with intraventricular conduction defects and L-TGA, His-bundle pacing was preferred over conventional CRT given the CS may be impossible to reach without compromise to procedural success rates and subsequent functional improvements.9As the technology evolves, we will expect successful His-bundle pacing in all ranges of congenital heart diseases. The extent and duration of the desired reverse remodelling of the LV remains to be seen in our case.