In which condition are A waves on a CVP tracing absent?

In atrial fibrillation, A waves on a central venous pressure (CVP) tracing are absent due to the disorganized electrical activity in the atria. In this condition, the atria do not contract effectively, which means there is no coordinated atrial contraction to produce the A wave that reflects right atrial pressure changes during atrial systole. Instead of having clear A waves corresponding to atrial contraction, the tracing may show a more erratic pattern that corresponds to the irregular rhythm of atrial fibrillation.

In contrast, conditions such as tricuspid regurgitation and pulmonary hypertension may still show A waves, though they may be altered in size or morphology due to the pathological states affecting right atrial pressure dynamics. Chronic obstructive pulmonary disease can influence venous return and right heart function, potentially affecting A wave appearance but does not inherently cause their absence. Therefore, in the context of atrial fibrillation, the absence of A waves in the CVP tracing is a distinctive feature directly related to the irregular atrial activity rather than the other listed conditions.