Validation of the Frequency Spectra Obtained from the Noncontact Unipolar Electrograms During Atrial Fibrillation


  • This study was supported in part by a research grant and software from St. Jude Medical.

  • Manuscript received 15 February 2007; Revised manuscript received 14 June 2007; Accepted for publication 15 June 2007.

Address for correspondence: Shih-Ann Chen, M.D., Division of Cardiology, Taipei Veterans General Hospital, 201 Sec. 2, Shih-Pai Road, Taipei, Taiwan. Fax: 886-2-2873-5656; E-mail:


Introduction: Noncontact mapping (NCM) can record virtual unipolar electrograms (Egs) from multiple sites simultaneously; therefore, it has the potential to perform simultaneous frequency mapping during atrial fibrillation (AF). The aim of this study was to validate the frequency spectra of the noncontact unipolar Egs in both atria.

Methods: This study enrolled 12 patients (age = 61 ± 16 years) with paroxysmal or persistent AF who underwent catheter ablation guided by NCM. Noncontact and contact unipolar Egs were recorded simultaneously. The cross-correlation of the Eg morphology, activation time difference of the time-domain signals, and resultant frequency spectra were compared via dominant frequency (DF) and magnitude-squared coherence (MSC).

Results: A total of 159 sites were analyzed during AF. The variables that independently predicted a higher correlation between the contact and noncontact electrogram morphology were a smaller activation timing difference P < 0.01), smaller distance of the mapping sites to the array center (P = 0.01), and higher atrial voltage (P = 0.03). However, the average MSC of the frequency band within the physiologic range of AF (2 to 15 Hz) was only affected by the activation timing difference (P = 0.002). The DF value between the contact and noncontact unipolar signals correlated well with each other throughout the right atria and left atria in 94% of the mapping sites (r = 0.87, P < 0.001).

Conclusion: The accuracy of the noncontact unipolar Eg morphology decreased when the mapping sites harbored a smaller atrial voltage and longer distance to the array center. The DF difference between the contact and noncontact unipolar Eg was not affected by the distance to the array center.