Atrial fibrillation after coronary artery bypass surgery: association with changes in G protein levels in mononuclear leukocytes
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Atrial fibrillation (AFib) is a frequent complication of coronary artery bypass grafting (CABG). Its cause, however, is unknown. As the adrenergic system is involved in some types of AFib, we hypothesized that a change in guanine nucleotide-binding protein (G protein) expression plays a role in the development of post-CABG AFib. In 28 patients undergoing CABG surgery, the Gsα/Giαratio (stimulatory/inhibitory G protein α) at the protein (Western blotting) and mRNA (reverse transcription polymerase chain reaction) levels was measured before and after surgery. As a suitable test system allowing multiple analysis mononuclear leukocytes (MNL) were chosen. The perioperative change of the Gsα/Giαratio of protein and mRNA was significantly different in patients who subsequently developed AFib (eight patients) and in patients who did not (20 patients; P<0.01 and <0.001, respectively). On average, the protein Gsα/Giαratio decreased from 1.79±1.13 (mean±SD) to 1.32±0.69 in patients without AFib (P=0.1, n.s.) whereas a significant increase from 0.86±0.44 to 1.62±0.65 (P<0.01) was observed in patients subsequently developing AFib. The mRNA Gsα/Giαratio decreased significantly from 0.53±0.24 to 0.36±0.11 in patients without AFib (P<0.01) whereas a significant increase from 0.31±0.14 to 0.47±0.13 was observed in those who subsequently developed AFib (P<0.05). These results indicate that an increase of the Gsα/Giαratio in MNL is associated with AFib after CABG surgery and possibly may be used as a prognostic indicator of this complication.
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