OBJECTIVETo discuss the role of calcium-overloading in initiation and maintenance of atrial fibrillation (AF).

METHODSThe right atrial appendages were obtained from 14 patients with AF and 12 patients with sinus rhythm. The mRNA expression of proteins influencing the calcium homeostasis was measured by semi-quantitative reverse transcription-polymerase chain reaction (RT-PCR) and normalized to the mRNA level of glyceraldehyde-3- phosphate dehydrogenase. The left atrial diameter (LAD), mitral valvular area (MVOA), and systolic pulmonary arterial pressure were obtained by echocardiography before surgery.

RESULTSCompared to sinus rhythm group, the mRNA levels of L-type calcium channel alc, sarcoplasmic reticulum (SR), calcium adenosine triphosphatase (Ca2+ -ATPase), and ryanodine receptor type-2 (R(Y) R2) were significantly decreased (P < 0.01); the mRNA level of inositol triphosphate receptor type-1 (IP3R1) was significantly increased (P < 0.05). No changes in the mRNA expression of phospholamban and calsequestrin were observed between two groups (P > 0.05). Correlations were found between MVOA and mRNA levels of LVDC-Calc, SR Ca2+ -ATPase (r = 0.719, P = 0.004; r = 0.625, P = 0.017). The mRNA level of SR Ca2+ -ATPase was negatively correlated with LAD (r = -0.573, P = 0.032).

CONCLUSIONSCalcium loading may be responsible for the occurrence and maintenance of AF, and abnormal regulation in the mRNA expression may be the molecular mechanism of intracellular Ca2+ overload. The progressive nature of AF involves structural change.

Arrhythmia, Sinus ; metabolism ; Atrial Fibrillation ; metabolism ; pathology ; Calcium ; metabolism ; Calcium Channels ; biosynthesis ; genetics ; Calcium-Binding Proteins ; biosynthesis ; genetics ; Calcium-Transporting ATPases ; biosynthesis ; genetics ; Chronic Disease ; Heart Atria ; metabolism ; pathology ; Humans ; Mitral Valve ; pathology ; Myocardium ; metabolism ; RNA, Messenger ; biosynthesis