Atrial systole significantly contributes to the arterial pulse. In ectopic beats, without preceding atrial systole, the arterial pressure pulse is significantly diminished. Wherein the ventricular diastolic interval is not disturbed, as seen in nodal rhythm with atrioventricular (A-V) dissociation or in complete A-V block, the amplitude of the arterial pulse is significantly influenced by the presence or absence of effective atrial systole.
Lamb LE. Atrial Contraction Influence on the Arterial Pulse Wave. Arch Intern Med. 1968;121(4):328-331. doi:10.1001/archinte.1968.03640040022004