Connexin40 knockout mice exhibited significantly slower conduction velocity in the right bundle branch compared to wild-type mice (43.7 vs 74.5 cm/s; P<0.01).
Connexin40 knockout mice exhibit significant conduction defects in the specialized conduction system, demonstrating the critical role of gap junctions in cardiac impulse propagation.
Absolute Event Rate: 43.7% vs 74.5%
p-value: p=<0.01
Connexin40 (Cx40) is a major gap junction protein that is expressed in the His-Purkinje system and thought to be a critical determinant of cell-to-cell communication and conduction of electrical impulses. Video maps of the ventricular epicardium and the proximal segment of the right bundle branch (RBB) were obtained using a high-speed CCD camera while simultaneously recording volume-conducted ECGs. In Cx40(-/-) mice, the PR interval was prolonged (47.4+/-1.4 in wild-type WT n=6 and 57.5+/-2.8 in Cx40(-/-) n=6; P<0.01). WT ventricular epicardial activation was characterized by focused breakthroughs that originated first on the right ventricle (RV) and then the left ventricle (LV). In Cx40(-/-) hearts, the RV breakthrough occurred after the LV breakthrough. Additionally, Cx40(-/-) mice showed RV breakthrough times that were significantly delayed with respect to QRS complex onset (3.7+/-0.7 ms in WT n=6 and 6.5+/-0.7 ms in Cx40(-/-) n=6; P<0.01), whereas LV breakthrough times did not change. Conduction velocity measurements from optical mapping of the RBB revealed slow conduction in Cx40(-/-) mice (74.5+/-3 cm/s in WT n=7 and 43.7+/-6 cm/s in Cx40(-/-) n=7; P<0.01). In addition, simultaneous ECG records demonstrated significant delays in Cx40(-/-) RBB activation time with respect to P time (P-RBB time; 41.6+/-1.9 ms in WT n=7 and 55.1+/-1.3 ms in n=7; P<0.01). These data represent the first direct demonstration of conduction defects in the specialized conduction system of Cx40(-/-) mice and provide new insight into the role of gap junctions in cardiac impulse propagation.
Tamaddon et al. (2000) studied Connexin40 knockout (n=14). Connexin40 knockout vs. Wild-type mice was evaluated on Conduction velocity of the right bundle branch (p=<0.01). Connexin40 knockout mice exhibited significantly slower conduction velocity in the right bundle branch compared to wild-type mice (43.7 vs 74.5 cm/s; P<0.01).