Premature atrial contractions, or PACs, are when the top part of the heart (atrium) contracts before making a complete beat. With PVCs, the bottom part of the heart (ventricle) contracts too early.
Both conditions can cause similar symptoms, especially a feeling of fluttering in the heart. While PVCs increase your risk of cardiomyopathy, PACs likely don’t. That’s according to a 2019 study that also found PACs to be associated with a higher risk of developing more severe arrhythmias, like atrial fibrillation or supraventricular tachycardia.