This document discusses pressure changes that can occur during coronary angiography, specifically damping and ventricularization. Damping is defined as a significant decrease in pressure at the coronary ostium when the catheter is placed, accompanied by the disappearance of pressure waveforms, suggesting no antegrade flow. Ventricularization occurs when blood circulates within a coronary artery like a closed system, deforming the aortic pressure waveform. The document emphasizes the importance of the operator recognizing abnormal pressure changes to avoid complications, and provides solutions like catheter replacement or intracoronary nitroglycerin to address issues.