Table 1.
Affected ion channels | Na+ current reduction (via PKC and c-Src, also via abnormal splicing) ⇒ reduction in conduction velocity |
KATP inhibition ⇒ repolarization abnormality | |
NCX activation ⇒ increasing inward current and facilitating afterdepolarization | |
I to, I Kr, I Ks inhibition ⇒ abnormal repolarization | |
Increase in inward Ca++ current (direct or via CaMKII activation) ⇒ facilitating afterdepolarization | |
Increase in late Na+current ⇒ facilitating afterdepolarization | |
| |
Effect on intracellular Ca++ handling | Impairment of SERCA ⇒ increase intracellular Ca++ levels ⇒ facilitating afterdepolarization |
Affecting RyR receptor (via CaMKII activation) ⇒ leakiness of SR ⇒ increase intracellular Ca++ levels ⇒ facilitating afterdepolarization | |
| |
Effect on myocyte-myocyte coupling | Affecting assembling of Cx43 at gap junctions ⇒ reduction in conduction velocity |
| |
Effect on extracellular matrix | Activating fibrotic process (via TGF-β) ⇒ reduction in conduction velocity and impaired myocyte-myocyte coupling due to collagen deposition |
CaMKII: Ca2+/calmodulin-dependent protein kinases II; Cx43: connexin 43; NCX: Na+/Ca2+ exchanger; RyR: ryanodine receptor; SERCA: sarco-/endoplasmic reticulum Ca++ - ATPase; TGF-β: Transforming Growth Factor-β.