ROCK1 and atrial fibrillation: However, the expression of ROCK1 in the non-myolytic left atrial myocytes of the MR AF patients did not significantly differ from the expression of ROCK1 in the non-myolytic left atrial myocytes of the normal control subjects (1303403.2 ± 257033.5 vs. 1248082.3 ± 50698.5, p = 0.815).