Identification of the fossa ovalis by voltage mapping using a high-density mapping catheter

FUNDING ACKNOWLEDGEMENTS: Type of funding sources: None. INTRODUCTION: Transseptal puncture (TP) is routinely performed under fluoroscopy and/or echocardiography guidance. Additional methods to localize the fossa ovalis (FO) may decrease radiation exposure, as well as periprocedural risk. In the recent years, high-density mapping (HDM) catheters have been used for mapping and ablation of left atrial (LA) arrhythmias. PURPOSE: The aim of this study is to determine whether a HDM catheter can reliably identify the specific FO electrogram (EGM) patterns. METHODS: During atrial fibrillation (AF) ablation, a voltage map of the right-sided atrial septum was created using a HDM catheter (Pentaray, Biosense Webster, USA, spacing 2-6-2 mm). The location of the FO was identified by transesophageal echocardiogram and fluoroscopy guidance prior to TP. At the end of the procedure, a 3D phantom was created during catheter retrieval from the left to the right atrium through the TP. Post ablation analysis was done to evaluate whether the HDM catheter was able to record EGM characteristics of the FO. RESULTS: Fifteen patients were included (male 63%, mean age 61.2±11.7 y. o.); 80% of the cases were in sinus rhythm, 53% had a normal LA size, and the mean CHADS2-VA2SC score was 1.5 ± 1.6. One patent fossa ovalis and one septal pouch of the left atrium were seen. In all patients, an area of low voltage could be identified in the vicinity of the transseptal puncture. In 74%, the location of transseptal puncture was inside of the area of low voltage. The mean voltage value of this area was 0.6 ± 0.3 mV, whereas the mean voltage value of the myocardium surrounding the "low voltage area" was 4.3 ± 2.1 mV (P<0.01). The surface of the low voltage could be best demarcated using a scale from 0.05 -1.5 mV with an area measured at 3.8 ± 2.6 cm2 [Figure 1]. At other voltage scales, the FO surface demonstrated smaller areas of low voltage (scale/surface [mV/cm2] : 0.05-0.5/ 0.8 ± 1.3; 0.05-1.0/2.2 ± 1.8; 0.5-1.0/2.3±1.6). In 63%, fractionated potentials were recorded in the area of the FO [Figure 1]. CONCLUSIONS: Based on its EGM characteristics, the fossa ovalis can be accurately localized with a high-density mapping catheter. This finding will certainly help to implement radiation free procedure particularly when echocardiographic modalities are not available. Figure 1: Mapping of the region of the fossa ovalis with a high density mapping catheter revealed an area of low voltage with fractionnated electrogram. Fossa ovalis was identified by transseptal puncture. TP: phantom of the catheters, CS: coronary sinus, H: His, IVC: inferior vena cava, SVC: superior vena cava, * fractionnated electrogram [Figure: see text]