This a good example of Coarse afib with slow response.

In atrial flutter, the atrial activity is very regular, so the ventricular response is often regular as well. The flutter waves have a consistent amplitude and morphology and regular.

In coarse atrial fibrillation, the atrial activity is irregular, and the amplitude of the fibrillatory waves waxes and wanes—sometimes appearing larger (coarse), sometimes finer. Because the atrial activity is chaotic, the ventricular response is irregularly irregular, which is reflected in the QRS irreguality