Cardiac alternans and intracellular calcium cycling.

摘要: Cardiac alternans refers to a condition in which there is periodic beat-to-beat oscillation electrical activity and the strength of cardiac muscle contraction at constant heart rate. Clinically, occurs settings that are typical for arrhythmias has been causally linked these conditions. At cellular level, defined as alternations amplitude (mechanical alternans), action potential duration (APD; or APD alternans) Ca(2+) transient (Ca(2+) alternans). The cause multifactorial; however, always originate from disturbances bidirectional coupling between membrane voltage (Vm ) intracellular calcium ([Ca(2+) ]i ). Bidirectional fact that, cells, Vm depolarization generation potentials elevation [Ca(2+) required (a process referred excitation-contraction coupling); conversely, changes control because important currents dependent. Evidence mounting ultimately caused by signalling. Herein we review how two key factors cycling, namely release internal stores capability clearing cytosol after each beat, determine conditions under occurs. contributions -handling proteins (i.e. surface channels, ion pumps transporters channels) discussed.