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

A waves on a central venous pressure (CVP) tracing represent the pressure changes associated with atrial contraction, specifically the contraction of the right atrium. In the presence of atrial fibrillation, the normal coordinated contraction of the atria is disrupted. This arrhythmia is characterized by chaotic electrical activity in the atria, leading to ineffective contractions, which significantly reduces or eliminates the A wave on CVP tracings.

In contrast, conditions such as right ventricular hypertrophy, tricuspid regurgitation, and mitral stenosis do not inherently affect the atrial contraction in such a way that would result in the absence of A waves. In these conditions, the right atrium may still contract, generating A waves, albeit possibly with altered morphology or amplitude due to the associated pressures and volumes. Therefore, it's the disruption of normal atrial function in atrial fibrillation that specifically leads to the absence of A waves on the CVP tracing.