Purpose: To investigate the regional development of LVS and its influence on LA conduction.
Methods: 70 patients with persistent AF underwent high-density voltage mapping of the LA in sinus rhythm prior to pulmonary vein isolation. LVS was defined as regions displaying <0.5 mV, <1.0 mV or <1.5 mV bipolar voltage. A 10-segment model of the LA served to investigate the regional distribution of LVS. The impact of LVS on LA conduction was evaluated using LA activation time (LAT) at mapping and P-wave at digitized-amplified (40 mm/mV, 200 mm/s) 12-lead ECG. An algorithm using the derived ECG-parameters was developed and tested in a validation cohort of 90 patients with no history of AF.
Results: A high variation of LVS was observed between patients at all three cutoff-values defining low-voltage (1.4 cm2 to >50 cm2). With increasing overall LVS, the antero-septal region was affected first, followed by the roof and finally the posterior parts of the LA. Significant LVS antero-septally was sufficient to induce marked prolongation of the p-wave (130 ms in control vs 186 ms with antero-septal LVA, p<0.0001). Advanced interatrial block (IAB) due to impaired conduction through the Bachmann-bundle which is located antero-septally was frequent once significant LVS in this region developped (2.9% in control vs 49% in antero-septal LVS, p<0.0001). While patients with IAB in general had longer p-wave duration and more overall LVS (144 ms/ 12.9 cm2 in control vs 193 ms/ 38.1 cm2 in IAB, p=<0.0001/<0.0001), we identified a subgroup in whom a late-terminal positive deflection in lead I was the only ECG-marker of severe LVS of the anteroseptal and posteroinferior LA. An algorithm based on these observations including p-wave duration and presence of IAB or late-terminal deflection in lead I identified three degrees of expected LVS with increasing risk to develop AF in the validation cohort (see figure, p<0.0001).
Conclusions: LVS in persistent AF begins in the antero-septal region of the LA, where it affects conduction through the Bachmann-bundle. Careful analysis of the amplified p-wave for duration, IAB and presence of late-terminal deflection in lead I can identify patients at risk for future AF.