One of the commonest, as well as one of the most interesting, varieties of cardiac irregularity is that known as auricular fibrillation. In this condition the auricles, instead of contracting rhythmically, are thrown into a state of tremulousness involving small bundles of fibrils.
The walls of the auricle stand in the diastolic position; systole, either complete or partial, is never accomplished; the wall, as a whole, is stationary, but careful examination of the muscle reveals an extremely active condition; it appears to be alive with movement; rapid, minute and constant twitchings or undulatory movements are observed in a multitude of small areas upon its surface (Lewis).
The result, usually, is a rapid and extremely irregular pulse. From the turmoil in the auricles a shower of impulses passes down the bundle of His into the ventricles. The weakest of these impulses fail to affect the ventricles. The stronger ones, occurring
TAUSSIG AE. COMPLETE AND PERMANENT HEART-BLOCK FOLLOWING THE USE OF DIGITALIS IN AURICULAR FIBRILLATION. Arch Intern Med (Chic). 1912;X(4):335-342. doi:10.1001/archinte.1912.00060220040005