Fig. 7.
Mechanisms of sodium channel loss-of-function in Brugada syndrome, progressive cardiac conduction disease, and sick sinus syndrome. a Decreased sarcolemmal expression of Nav1.5 due to premature degradation of mutant channel proteins by the quality control system in the endoplasmic reticulum. b Delayed activation of cardiac sodium channels (red circles). c Earlier inactivation of cardiac sodium channels (red circles)