Author + information
- Fahad S. Almehmadi, MD, MPHa,b,∗ (, )
- Jason D. Roberts, MD, MASa,
- Lorne J. Gula, MDa,
- Mouhannad M. Sadek, MDc,
- Imane El Hajjaji, MDa,
- Allan C. Skanes, MDa,
- Jaimie Manlucu, MDa,
- Raymond Yee, MDa,
- Anthony S. Tang, MDa,
- Peter Leong-Sit, MDa and
- George J. Klein, MDa
- aLondon Heart Rhythm Program, Western University, London, Ontario, Canada
- bKing Faisal Cardiac Center, King Saud bin Abdulaziz University for Health Sciences, Jeddah, Saudi Arabia
- cOttawa Heart Institute, University of Ottawa, Ottawa, Ontario, Canada
- ↵∗Address for Correspondence:
Dr. Fahad Almehmadi, King Saud bin Abdulaziz University for Health Sciences, Jeddah, 22384, Saudi Arabia.
Objectives This study sought to identify minimum threshold values below which conduction over the atrioventricular (AV) node would be unexpected.
Background Para-Hisian pacing is used to evaluate for the presence of a septal accessory pathway (AP); however, threshold values to differentiate nodal from AP conduction are unknown.
Methods The authors performed high- and low-output para-Hisian pacing during sinus rhythm to capture the His and para-Hisian ventricular myocardium (H+V) and para-Hisian ventricular myocardium (V) alone, respectively. The change in stimulation (stim)-to-atrial electrogram interval after loss of His bundle capture in patients with (AP+) and without (AP−) a septal AP was evaluated. Stim-to-proximal coronary sinus (PCS) and stim-to-high right atrium (HRA) intervals were measured and within-patient differences (△) for V and H+V capture were calculated.
Results A total of 23 AP+ and 45 AP− patients were evaluated. The difference in stimulus to earliest atrial signal in the high right atrial catheter seen with the loss of His bundle capture (△-Stim-HRA) (21 ms; interquartile range [IQR] 3 to 43 ms vs. 64 ms; IQR: 56 to 73 ms; p < 0.001) and difference in stimulus to earliest atrial signal in the proximal coronary sinus catheter seen with the loss of His Bundle capture (△-stim-PCS) (11 ms; IQR: 0 to 30 ms vs. 61 ms; IQR 52 to 72 ms; p < 0.001) were shorter in AP+ patients. The shortest △-stim-PCS and △-stim-HRA in AP− patients were 37 ms and 32 ms, respectively, whereas the longest corresponding intervals in AP+ patients were 51 ms and 75 ms, respectively.
Conclusions A △-stim-PCS <37 ms or △-stim-HRA <32 ms confirmed the presence of a septal AP, whereas a value >51 ms for △-stim-PCS or >75 ms for △-stim-HRA excluded it. Alternatively, the minimum △-stim-PCS with loss of His capture compatible with AV nodal conduction in isolation was 37 ms, and a △-stim-PCS >51 ms effectively ruled out the presence of a septal AP.
Dr. Manlucu has been a consultant to Medtronic, Biosense Webster, and Baylis Medical. Dr. Tang has received a research grant. All other authors have reported that they have no relationships relevant to the contents of this paper to disclose.
The authors attest they are in compliance with human studies committees and animal welfare regulations of the authors’ institutions and Food and Drug Administration guidelines, including patient consent where appropriate. For more information, visit the JACC: Clinical Electrophysiology author instructions page.
Preliminary work was presented as a poster presentation at the 39th Heart Rhythm Society (HRS) meeting held on May 2018 and at the Annual Canadian Cardiovascular Society meeting held on October 2018.
- Received March 10, 2020.
- Revision received May 5, 2020.
- Accepted May 7, 2020.
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