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Alterations in the transmural gradient of ventricular repolarization with different pacing sites in normal and heart failure canines

WANG Tao¹, PANG Zhan-Qi¹, LIN Xue-Qi¹, SONG Bo-Wen¹, LI Zhuo-Ran¹, LI Shi-Jun^1,2, XIA Yun-Long^1,*

¹Department of Cardiology, Dalian Municipal Central Hospital Affiliated of Dalian Medical University, Dalian 116033, China；²First Affiliated Hospital of Dalian Medical University, Dalian 116011, China

Abstract

Alterations of the transmural gradient of repolarization may contribute to the increase of transmural dispersion of repolarization and ventricular arrhythmias. The transmural gradient of repolarization may play an important role in sudden death associated with left ventricular epicardial pacing. To investigate the changes of transmural gradient dispersion of ventricular repolarization with different pacing sites in heart failure (HF) canines, 8 mongrel dogs were randomized into healthy group and HF group (n = 4). We mapped the monophasic action potential duration (MAPD) in the subendocardial, subepicardial and mid-myocardial layers of the left ventricle (LV) in canines of healthy and HF groups during right atrium (RA) pacing, right ventricular apical endocardial (RVEndo) pacing, left ventricular lateral epicardial (LVEpi) pacing and biventricular (Biv) pacing respectively. The results showed that in the healthy group, the MAPDs were significantly different among the three layers during RA pacing (all P < 0.05). The MAPD was longer in the mid-myocardial layer compared with those in the subepicardial and subendocardial layers during RVEndo, LVEpi or Biv pacing (P < 0.05). However, there was no significant difference in MAPD between the subendocardial and subepicardial layers during RVEndo, LVEpi or Biv pacing (P > 0.05). In the HF group, the MAPDs in all three layers were prolonged compared with those in the same locations in the healthy group (all P < 0.05). However, there were no differences in MAPD among the three layers during RA, RVEndo, LVEpi or Biv pacing (all P > 0.05). By MAP recording with our new mapping electrode, we found a transmural MAPD gradient among the three layers of the LV during RA pacing and the gradient between the subendocardial and subepicardial layers vanished during RVEndo, LVEpi or Biv pacing in healthy dogs. In contrast, there was no transmural MAPD gradient during RA, RVEndo, LVEpi or Biv pacing in HF dogs. These results are helpful to understand the mechanism of ventricular arrhythmias in patients with HF.

Key words: Heart failure; monophasic action potential; repolarization; transmural gradient; pacing

Received: 2019-09-24　　Accepted: 2020-03-03

Corresponding author: 夏云龙　　E-mail: yunlong_xia@126.com

DOI: 10.13294/j.aps.2020.0047

Citing This Article：

WANG Tao, PANG Zhan-Qi, LIN Xue-Qi, SONG Bo-Wen, LI Zhuo-Ran, LI Shi-Jun, XIA Yun-Long. Alterations in the transmural gradient of ventricular repolarization with different pacing sites in normal and heart failure canines. Acta Physiol Sin 2020; 72 (4): 419-425