Spiral Activation of Superior Vena Cava: The Utility of Ultra-high-resolution Mapping for Caval Isolation.

Little is known about the manner in which the superior vena cava (SVC) is activated during sinus rhythm (SR).To assess the manner of caval activation with ultra-high-density mapping system (Ryhthmia™) and its utility for SVC isolation.Forty atrial fibrillation (AF) patients (55±12 years, paroxysmal AF in 23) who underwent SVC mapping with Ryhthmia™ were studied. The location of the sinus node (SN), phrenic nerve (PN) and caval activation manner during SR were analyzed. The SVC was isolated by radiofrequency applications at the electrical connections, shown as breakthroughs on Rhythmia™.The SN location varied widely (lateral/posterior/anterior: 60%/8%/32%), while the PN mostly located in the lateral segment (lateral/anterior: 82%/18%). In 36 patients who underwent SVC isolation, the mean number of breakthroughs was 2.5±0.8. The first breakthrough predominantly located in the anterior aspect (anterior/septal/posterior/lateral: 78%/14%/5%/3%), and the atrial activation was conducted superiorly and clockwise from the SN (referred to as "spiral activation") in 32(89%) patients. The mean rotation angle from the SN to the first breakthrough was 79±41°. In addition, 10(25%) patients showed the SN within the SVC. Although radiofrequency applications were needed at the PN capture site in 31% of patients, the SVC was successfully isolated without any complications in all patients.The SN location showed great heterogeneity, however, the atrial activation predominantly showed a clockwise spiral form. This is the first report to use ultra-high-resolution mapping to demonstrate the manner of spiral activation, which is useful for the safe and efficient isolation of the SVC.