Focal areas of gap junction uncoupling in chimeric mice significantly increased spontaneous arrhythmic events compared to controls (P<0.01), but did not support sustained ventricular tachyarrhythmias.
Does focal gap junction uncoupling increase the frequency of spontaneous and inducible arrhythmias in a mouse model?
Focal areas of gap junction uncoupling in the myocardium increase the likelihood of arrhythmic triggers, but widespread uncoupling is required to support sustained arrhythmias.
p-value: p=<0.01
Genetic studies in the mouse have demonstrated that conditional cardiac-restricted loss of connexin43 (Cx43), the major ventricular gap junction protein, is highly arrhythmogenic. However, whether more focal gap junction remodeling, as is commonly seen in acquired cardiomyopathies, influences the propensity for arrhythmogenesis is not known. We examined electrophysiological properties and the frequency of spontaneous and inducible arrhythmias in genetically engineered chimeric mice derived from injection of Cx43-deficient embryonic stem cells into wild-type recipient blastocysts. Chimeric mice had numerous well-circumscribed microscopic Cx43-negative foci in their hearts, comprising approximately 15% of the total surface area as determined by immunohistochemical analysis. Systolic function in the chimeric mice was significantly depressed as measured echocardiographically (19.0% decline in fractional shortening compared with controls, P < 0.05) and by invasive hemodynamics (17.6% reduction in change of pressure over time, P < 0.01). Chimeras had significantly more spontaneous arrhythmic events than controls (P < 0.01), including frequent runs of nonsustained ventricular tachycardia in some of the chimeric mice. However, in contrast to mice with conditional cardiac-resricted loss of Cx43 in the heart, no sustained ventricular tachyarrhythmias were observed. We conclude that focal areas of uncoupling in the myocardium increase the likelihood of arrhythmic triggers, but more widespread uncoupling is required to support sustained arrhythmias.
Gutstein et al. (Sat,) conducted a other in Arrhythmogenesis and focal gap junction remodeling. Focal gap junction uncoupling (Cx43-deficient chimeric mice) vs. Wild-type controls was evaluated on Spontaneous arrhythmic events (p=<0.01). Focal areas of gap junction uncoupling in chimeric mice significantly increased spontaneous arrhythmic events compared to controls (P<0.01), but did not support sustained ventricular tachyarrhythmias.